How Exercise Reduces Risk of Alzheimer’s Disease

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By Tanya Thakur, MBBS

Alzheimer’s disease (AD) is one of the most devastating illnesses among older adults. The disease not only degrades memories but also affects one’s independence and takes a toll on family members.

AD is a progressive neurodegenerative disorder caused by the accumulation of abnormal misfolded protein deposits in the brain, including beta-amyloid plaques, tau tangles, and Hirano bodies. These deposits disrupt normal neuronal function, leading to the gradual loss of memory, cognitive skills, and, eventually, the ability to carry out daily activities.

AD is the most common cause of dementia, accounting for approximately 60 to 80 percent of cases. Presently, an estimated 6.7 million individuals in the U.S. have AD. In 2019, Alzheimer’s was ranked as the sixth leading cause of mortality among individuals aged 65 and above. Notably, between 2000 and 2019, while fatalities from stroke, heart disease, and HIV declined, deaths related to Alzheimer’s increased by more than 140 percent.

Even though scientists are working toward curing AD, we can take preventative measures by incorporating healthy habits, such as regular exercise, into our routine.

“It is a common misconception that we have minimal control over our risk of developing Alzheimer’s disease. However, nearly half of the Alzheimer’s cases could have been prevented or delayed by modifiable factors, including lifestyle changes,” says Sarita Khemani, MD, Clinical Associate Professor of Medicine and Neurosurgery Hospitalist at Stanford University. “Therefore, we should do everything in our power to incorporate healthy lifestyle habits as early as possible.”

The Link Between Exercise and Alzheimer’s Disease

There are many things we can do to reduce our risk of developing dementia. Several research studies have concluded that physical activity is one of the best ways to reduce risk significantly. For example, after analyzing 16 studies on exercise and dementia, the Alzheimer’s Society found that regular exercise reduces the risk of developing dementia by 28 percent and, specifically, AD by 45 percent.

The connection between the brain and aerobic exercise is likely due to neuroplasticity, which is the brain’s ability to adapt and form new neural connections or strengthen the existing ones. During aerobic exercise, our brain expresses cAMP response element binding (CREB) proteins that influence the transcription of synaptic genes, including those encoding for brain-derived neurotrophic factor (BDNF). BDNF supports neurogenesis (the formation of new neuron cells), neuroprotection, and angiogenesis (the formation of new blood vessels). BDNF also increases the volume of gray matter and the hippocampus (the site of memory in the brain).

Physical activity also serves as a potent modulator of other health risk factors, including hypertension, hypercholesterolemia, and insulin resistance, all of which increase the risk of developing dementia. Vascular damage caused by atherosclerosis can accelerate the cognitive decline associated with AD due to reduced blood and oxygen flow to the brain, leading to hypoxia of neural cells.

“Brain changes associated with Alzheimer’s begin approximately 20 years before symptoms appear,” says Dr. Khemani. “Exercise stands out as one of the most effective strategies for prevention, offering a low-cost, non-pharmacological, and low-risk option accessible to everyone.”

The Best Exercises to Prevent Alzheimer’s

While aerobic exercise increases BDNF levels, resistance exercises, such as lifting weights, are thought to have a greater influence on insulin-like growth factor-1 (IGF-1) levels. IGF-1 is a hormone that manages the effects of growth hormone in the body and is essential for promoting cognitive abilities.

Because aerobic and resistance exercises elicit different neurophysiological changes, studies have indicated that combining both modalities can enhance exercise-induced neuroplasticity to a greater extent than either modality alone.

For example, one study compared the effects of combined aerobic and strength training, aerobic exercise alone, and no exercise on cognitive function among dementia patients. After nine weeks, the combined exercise regimen yielded the most pronounced results across cognitive domains. Also, the observed gains in both motor and cognitive areas regressed towards baseline levels more than two months post-intervention, meaning it is essential to exercise regularly to sustain its neurological benefits.

Regarding the type of aerobic exercise most effective for AD prevention, Dr. Khemani recommends incorporating sprint intervals into our workouts. “We encourage our patients to engage in moderate-intensity exercises incorporating some high-intensity interval training, if possible, as these activities have been shown to be more impactful for Alzheimer’s prevention than light exercise alone,” she says.

 

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Jumping into the Ice Bath Trend! Mental Health Benefits of Cold Water Immersion

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By Maya Shetty, BS

Key Takeaways

  • Research shows that cold water immersion (CWI) may improve mental health by increasing endorphin and norepinephrine levels. 
  • CWI may also improve resilience to stress by decreasing cortisol levels.
  • CWI can be adapted to meet different wellness goals, whether for immediate relief or long-term mental health benefits.
    • For individuals seeking a quick boost in mood, daily cold water face immersions and occasional full-body plunges might be beneficial.
    • For those aiming for long-lasting benefits such as lowered cortisol levels, enhanced mood regulation, and increased resilience to stress, research shows that consistent full-body CWI may be beneficial.

Have you ever considered how taking a cold plunge might affect your mental state? Beyond the initial shock, CWI is proving to have profound effects on brain health and mental well-being. Initially popular as a recovery technique among athletes, it has now evolved into a bold wellness practice for those seeking to enhance their overall health. This practice, which involves plunging into cold water (roughly 10-15°C, 50-60°F), has ignited significant research interest, and emerging studies now suggest that CWI can improve mood, decrease stress, and potentially slow the progression of neurodegenerative diseases.

“I personally do cold water immersion and find it to be an immensely rejuvenating activity,” says Stanford Psychiatrist, Vanika Chawla, MD, member of the Lifestyle Medicine Cognitive Enhancement pillar.

CWI can take many forms, each involving its own protocol and equipment. The most common forms include:

  • Ice Baths: Traditionally utilized by athletes for recovery after intense physical activity, ice baths require submerging the body up to the neck in ice-cold water. Also known as cold plunging, this practice generally lasts only a few minutes and involves limited movement.
  • Cold Showers: A more accessible form of CWI, taking cold showers can offer many of the same benefits as ice baths but are easier to incorporate into daily routines.
  • Open Water Swimming: This active form of CWI involves swimming in cold rivers, lakes, or oceans, allowing for longer exposure times to the cold.
  • Cryotherapy Chambers: Though they do not involve water, cryotherapy chambers expose the body to extremely cold air temperatures for brief periods, stimulating a physiological response similar to that achieved through water immersion.

Choosing the type, temperature, and duration of CWI depends on your cold tolerance and the resources available to you. It is generally recommended to aim for a temperature that feels uncomfortable but still safe (no colder than 10°C, 50°F). If you have any form of access to cold water, whether it be a lake, a river, or your home shower and bathtub, you can participate in CWI and begin to explore its benefits.

Can Cold Water Plunges Improve Mental Health?

While the idea of diving into extremely  cold water seems unappealing to most, recent studies have shown that CWI offers emotional benefits. In 2021, researchers recruited undergraduate students to take a 20-minute dip in chilly sea water (13.6°C, 56.5°F) and report their emotions before and after using a Profile of Mood States questionnaire. Compared to controls, the students who engaged in CWI experienced a shift in mood, noting a significant decrease in negative emotions like tension, anger, depression, fatigue, and confusion. Moreover, they experienced boosts in positive emotions such as vigor and self-esteem. Further research involving thirty-three adults new to cold-water swimming highlighted similar benefits. After immersing in a cold bath (20°C, 68°F) for just five minutes, participants reported feeling more active, alert, attentive, proud, and inspired.

These studies, which utilize self-reported questionnaires, indicate that cold-water immersion may significantly enhance mood and overall psychological well-being. It appears to activate traits associated with increased motivation and vitality, while simultaneously diminishing feelings of distress and nervousness. 

How to Lower Cortisol Levels Naturally

CWI presents a unique stimulus for the body, prompting significant shifts in its hormonal stress response, particularly involving cortisol, a key regulator of stress. Unlike other stress hormones such as noradrenaline, cortisol levels remain relatively unchanged during the initial shock of cold water. Research highlights an intriguing aspect of cortisol dynamics: while levels do not significantly change during CWI, they significantly decrease afterward.

For example, a study concluded that a one-hour CWI session, whether in thermoneutral (32°C, 90°F), cooler (20°C, 68°F), or cold (14°C, 57°F) water, did not lead to an increase in blood cortisol concentrations. Instead, cortisol levels tended to decrease across all temperatures tested and remained below initial levels an hour after immersion. These findings suggest that cortisol production is not significantly activated by CWI, contrary to what might be expected under typical stress conditions. In fact, CWI may have potent stress-modulating effects. Further research indicates that cortisol levels remain considerably lower for up to three hours after just 15 minutes of CWI (10°C, 50°F). This pattern of response reveals a sophisticated regulatory mechanism, suggesting that CWI can effectively diminish feelings of stress following a session.

CWI may have the potential to modify our body’s stress response to stressors in everyday life. In a study where participants engaged in winter swimming (water 0-2°C, 32-36°F) for twenty seconds or cryotherapy (-110°C, -166°F) for two minutes, three times a week for twelve weeks, the body adapted remarkably. After just four weeks, participants showed significantly lower cortisol levels post-exposure, with levels continuing to drop in the following weeks. This adaptation contrasted with the noradrenaline response, which remained consistent even as the body became accustomed to the cold stress. This reduced cortisol response not only diminished the stress perceived from cold but also potentially enhanced the body’s capacity to manage other stressors more effectively. 

The main take away from this study is that by reducing cortisol production in response to repeated cold exposure, participants might also release less cortisol in response to other stressors in everyday life, thus fostering a more resilient physiological state over time.

“Resilience is the ability to adapt to life’s stressors and adversities,” says Dr. Chawla. “The body and mind are interconnected, therefore greater physiological resilience may lead to greater psychological resilience as well.”

How Cold Water Immersion Impacts the Brain

CWI has been scientifically observed to influence brain function, affecting mood, stress response, and potentially brain health through several mechanisms. The immediate physiological response triggered by CWI is largely due to the dramatic change in temperature. A dense concentration of cold receptors in the skin detects this change, leading to a surge of electrical impulses from peripheral nerve endings to the brain. This intense stimulation activates various neural pathways, initiating a cascade of chemical responses designed to help the body manage and adapt to the stressor.

During the initial shock of CWI, the body experiences stress and discomfort due to the sudden drop in temperature. To counteract this, endorphins, the body’s natural pain relievers, are released. These endorphins not only reduce pain but also enhance feelings of well-being, akin to the “runner’s high” that often occurs in other physically demanding or stressful situations. 

CWI also activates the sympathetic nervous system (SNS), which controls our “fight-or-flight” responses. This activation leads to a significant increase in noradrenaline (also known as norepinephrine), an excitatory neurotransmitter that not only helps manage stress but also boosts energy and focus. The surge in noradrenaline increases blood flow to the brain, potentially causing feelings of euphoria.

These two neurotransmitters play complementary roles. While norepinephrine prepares the body to handle acute stress by enhancing alertness and readiness, endorphins work to soothe pain and promote a positive mood. This dual response helps individuals cope with the immediate impacts of cold exposure more comfortably and can make the experience of cold water immersion more tolerable–and potentially even rewarding.

Regarding whether CWI has long-term positive effects on the brain, research indicates inconsistent results with respect to the increase of endorphin levels. It is possible that not everyone experiences this endorphin response to CWI, and among those who do, the effect may diminish over time, as the body becomes accustomed to the cold exposure. On the contrary, the increase in noradrenaline continues with each session of CWI, even after the body has adapted after months of regular practice. 

These findings underscore the potential of CWI to be used as a reliable tool for improving energy, focus, and mood. These findings also point to the potential of CWI to be used in the treatment of neurological conditions that involve low noradrenaline, including anxiety and depression. However, more research is needed to understand if CWI has long-term effects on emotional well-being outside the water.

Also, CWI may improve brain function through the release of cold-shock proteins, which are produced by the body in response to cold conditions. Animal studies reveal that proteins like RNA binding protein (RBM3) play a crucial role in repairing and regenerating nerve cell connections after they’ve been exposed to cold. Additionally, studies have demonstrated that over-expressing RBM3 can help prevent neuronal connection loss in mice with neurodegenerative diseases. Although there is limited evidence in humans, these findings in mice suggest that regular CWI could potentially boost the expression of such beneficial proteins in humans, offering protection against or slowing the progression of neurodegenerative diseases by preserving and reinforcing neural connections. 

Reaction to Cold Water: Full-Body vs. Facial Immersion

Physiological responses to CWI differ significantly based on whether the exposure is to the full body or just the face. Full-body immersion exposes a significant surface area to cold, inducing thermal stress that can substantially lower skin and core body temperatures. This extensive exposure activates the sympathetic nervous system, which in turn triggers a release of neurotransmitters and hormones that drive the stress response. Consequently, this leads to vasoconstriction, an increased heart rate, and a heightened metabolic rate, all of which help preserve body heat and maintain core temperature.

In contrast, immersing just the face in cold water activates parasympathetic activity, which is responsible for “rest and digest” functions in the body. This effect is likely due to the mammalian diving reflex—an evolutionary adaptation that optimizes respiration and conserves oxygen by preferentially directing oxygen to vital organs. The diving reflex is mediated by the vagus nerve, which activates the parasympathetic system and releases a sense of calm. The trigeminal nerve in the face also plays a crucial role when stimulated by cold, sending signals that further enhance parasympathetic output, decreasing heart rate, and boosting digestive activity. 

These differences highlight how CWI can be strategically used to target specific physiological responses and therapeutic outcomes, depending on whether the exposure is localized to the face or involves the entire body.

“I sometimes recommend facial cold water immersion to my patients as part of the T in TIPP skills to help people with emotion regulation. TIPP stands for temperature, intense exercise, progressive muscle relaxation, and paced breathing,” says Dr. Chawla. “These skills involve changing your body chemistry to shift emotions. Some people find brief facial immersion in cold water or taking a cold shower to be helpful in shifting their body chemistry and thereby shifting their emotional state.” 

Safety Considerations

CWI can offer several health benefits, but it’s essential to approach this practice with caution due to potential risks. One of the most obvious risks is hypothermia, as immersing in cold water significantly drops body temperature. To prevent hypothermia, limit immersion time to no more than 10 minutes. 

Furthermore, it is important to understand the cold shock response. Entering cold water suddenly can trigger an involuntary gasp reflex followed by hyperventilation. Hyperventilation increases the risk of drowning (especially in open water plunging) and can also lead to arrhythmias or even a heart attack, particularly in those with underlying heart issues. To better manage the cold shock response, it’s advised to enter the water slowly, allowing your body to adjust to the temperature gradually. 

It is also important to never swim alone regardless of your swimming strength or experience. Having a partner ensures that help is readily available in case of an emergency, such as cramps, sudden illness, or difficulty in the water.

Finally, remember to allow your body to gradually acclimatize to whatever CWI technique you choose. If you are a beginner, begin with shorter durations (2 minutes) in warmer water (roughly 20°C, 68°F), progressively moving to colder temperatures with longer durations as your body adapts.

“This intervention is not for everyone. It’s important for people to consider what works best for their individual needs,” says Chawla. “If you are going to try CWI, be mindful of how it impacts your mind and body and incorporate the activity into your routine accordingly.”

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How Exercise Improves Microbiome Health (and Vice Versa)

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By Mary Grace Descourouez, MS, NBC-HWC 

The human gastrointestinal tract is home to trillions of microorganisms that create the gut microbiome. The gut is where the body digests and absorbs nutrients from our food and, therefore, where we get our energy to perform daily human functions. Microbiota are microorganisms in the gut microbiome that help the body harvest energy, fight pathogens, and regulate immunity. Having a high diversity of microbiota helps us to process food effectively, providing the substrates and nutrients needed to keep us going throughout the day. Therefore, it is crucial to make lifestyle choices that promote a healthy and diverse microbiome.

Many people know that a nutrient-rich diet contributes to a healthy microbiome, however, research shows that movement and exercise may also have a positive effect, and, inversely, a healthy microbiome may improve athletic performance.

“It is a relatively new field, but available studies suggest a bidirectional relationship between performance and the health of the microbiome,” says Anne Friedlander, PhD, Exercise Physiologist and Assistant Director of Stanford Lifestyle Medicine. “People who are more active have a healthier and more diverse microbiome, and that, in turn, provides the person with the nutrients required to enhance physical and cognitive performance. It is a mutually beneficial relationship.” 

How Exercise Improves the Microbiome

Movement and exercise have many benefits on our overall health, including positive effects on the microbiome. Studies show that athletes have a more diverse microbiome composition than non-athletes. Microbiome diversity is important because it helps make our food’s nutrients more bioavailable for optimal functioning of the body.

Another study found that active women were associated with high microbiome diversity compared to sedentary women. Specifically, researchers found that consistent physical activity increased the amount of 11 genera of “good” bacteria, including Bifidobacterium spp, Roseburia hominis, Akkermansia muciniphila, and Faecalibacterium prausnitzii. 

How the Microbiome Improves Athletic Performance

Just as exercise positively impacts the microbiome, emerging research shows that microbiome health may also play a part in enhancing exercise performance.

For example, a 2019 study showed that a specific gut microbiota in marathon runners may have enhanced their athletic performance on race day.  In this study, researchers collected fecal samples from the runners before and after the marathon and compared them to microbiota of non-runners. The “good” bacteria Veillonella emerged as the most common in the runners, especially post marathon. Veillonella is a bacterial strain that converts exercise-induced lactate into propionate, which is a natural enzymatic process known to enhance athletic performance.

Researchers then put the Veillonella bacteria from the marathon runners into lab mice who underwent a treadmill exertion test to investigate the hypothesis that this bacterial strain enhances athletic performance. The results showed the mice improved performance by 13 percent after inoculation. This study is one of the first to infer that a healthy microbiome could enhance athletic performance.

“We have a long way to go to fully understand the complex system that involves the microbiome and athletic performance, but the early data look promising regarding gut health and exercise,” says Dr. Friedlander.  “Exercise, along with eating fermented foods and fiber, is a great place to start if you want to improve your gut health and overall health.”

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Probiotics, Prebiotics, and Postbiotics: What Are They and Why Are They Important?

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By Maya Shetty, BS

Key Takeaways:

  • Probiotic and prebiotic supplements lack substantial scientific evidence that they promote microbiome health. 
  • Rather than taking supplements, experts recommend eating fermented foods (probiotics) to promote microbiome diversity and fibrous foods (prebiotics) to feed and sustain “good” bacteria in the gut.  
  • Recommended fermented foods (probiotics): 
    • Fermented vegetables: kimchi, sauerkraut, and certain pickled vegetables
    • Fermented dairy: yogurt, cottage cheese, kefir, and certain cheeses
    • Fermented soy: tempeh and miso
  • Recommended high-fiber foods (prebiotics):
    • Legumes: lentils, chickpeas, black beans, and kidney beans
    • Seeds: chia seeds, flaxseeds, pumpkin seeds, and sunflower seeds
    • Whole grains: quinoa, brown rice, oats, and barley
    • Nuts: almonds, walnuts, pistachios, and pecans
    • Vegetables: broccoli, Brussels sprouts, artichokes, carrots, and sweet potatoes
    • Fruits: apples, pears, berries (raspberries, blueberries, strawberries), and bananas
  • Postbiotics, the byproduct of probiotic and prebiotic activity, not only reduce the risk of chronic diseases and support brain health, but also offer anti-inflammatory and beneficial metabolic effects.

Within our bodies, there exists a bustling community that often goes unnoticed but plays a pivotal role in our well-being—the microbiome. Understanding the impact of the microbiome on our health is not just a scientific curiosity, it’s a crucial aspect of our health that underscores our body’s complex equilibrium. Through continuous negotiations, our body and microbiome engage in a symbiotic relationship—a dynamic exchange where we provide our microbiome with nourishment and “good” inhabitants, and in return, it synthesizes beneficial compounds to support our health.

“We are, in essence, walking ecosystems. Our health is intimately connected to the trillions of bacteria, viruses, and fungi that make up this community,” says Sean Spencer, MD, PhD, Gastroenterologist and Physician Scientist at Stanford University.

The microbiome actively participates in various bodily functions, from aiding digestion and nutrient absorption to eliminating toxins and synthesizing vitamins and amino acids.

“The influence of our microbiome extends far beyond the confines of the digestive system, reaching major body systems like the immune system, metabolism, and the central nervous system,” states Rachele Pojednic, PhD, Stanford University  nutrition and exercise scientist.

While the definition of a healthy microbiome remains unclear, the majority of studies find that high microbiome diversity is linked to better health outcomes. “A healthy microbiome is one that is equipped to process a diverse array of dietary fiber to produce  health-promoting compounds for our body,” states Dr. Spencer. “Low microbiome diversity is linked to various health conditions, including diabetes and obesity and likely has reduced fiber-degrading potential and lower production of health promoting compounds.”

A recent study revealed that the average Californian has a microbiome that contains 277 microbial species, a stark contrast to the average of 730 found in non-industrialized populations. This finding aligns with a mounting body of evidence suggesting that modern lifestyles and Westernized diets have significantly depleted the essential diversity of our gut microbiome.

Therefore, many individuals have sought ways to manipulate their microbiome and increase its diversity via supplementation. Commonly referred to as probiotics and prebiotics, these supplements have surged in popularity, achieving sales of $35 billion in 2015 and projected to reach $65 billion by the end of 2024.

Despite their widespread use, there is significant confusion about what they are, where to find the best ones, and what they can and can’t do. Regardless, experts say the most powerful and beneficial sources for all your biotic needs are often overlooked (hint: they are in your refrigerator).

What Are Probiotics and Why are They Important?

Probiotics are live microorganisms that are consumed for health benefits and typically found in fermented foods like yogurt, kimchi, and sauerkraut. They play a crucial role in supporting our gut by introducing beneficial bacteria to our microbiome community. Simultaneously, they reduce the proliferation of harmful bacteria by constraining their available space for growth.

Upon hearing the term “probiotics,” many individuals associate it with the supplement pills that have long been advertised to improve digestive health. However, these supplements are not recommended over food, as they can displace favorable microbial residents in the gut.

“The doses of microbes found in supplements are overly potent, with billions to trillions of microbes, far exceeding the amounts in fermented foods, which contain hundreds of thousands to millions,” states Dr. Pojednic. “In this context, more is not better; natural sources provide a gentler, more physiologically effective way to support your microbiome.”

Another problem with probiotic supplements is they are created under the assumptions that the same bacteria strains are beneficial to everyone. But research indicates that microbiota composition and function varies significantly among individuals. What benefits one person may not necessarily work for another, and the scientific community is yet to develop the means to tailor probiotic prescriptions on an individual basis. Moreover, most beneficial gut bacteria that promote health are not yet available in probiotic supplement form.

“While healthy microbiomes may display certain shared characteristics, such as diversity, the specific types of bacteria that truly confer benefits remain unclear. Therefore, the limited selection of bacterial strains found in probiotic supplements may not be what your gut needs,” states Dr. Spencer.

Rather than taking probiotic supplements, Spencer and Pojednic recommend increasing the intake of probiotics by consuming fermented foods. Furthermore, fermented foods contain metabolic byproducts and other signaling molecules that probiotic supplements alone do not. Growing evidence suggests these metabolites confer additional health benefits and may aid the colonization of beneficial bacteria in our gut.

Fermented foods have been associated with enhancing microbiome diversity and overall health in several studies. A notable study was conducted at Stanford University, where participants adhered to a diet rich in fermented foods. Following a ten-week regimen of daily intake of five servings of fermented foods, participants demonstrated increased microbiota diversity and a notable reduction in inflammation in the body.

Dr. Spencer highlights this intriguing correlation, stating, “As the diversity of participants’ gut microbiome increased, there was a simultaneous decrease in various markers of inflammation, emphasizing the beneficial impact of fermented foods on overall health.”

“It’s important to remember that not all fermented foods have probiotic properties. When identifying probiotic foods, look on the labels for terms like ‘live cultures’ or ‘active cultures.’ Additionally, look for foods in the refrigerated section of the grocery store,” states Dr. Pojednic.

Should I Take Probiotics After Antibiotics?

A popular strategy to mitigate the depletion of one’s microbiota following antibiotics is to take probiotic supplements. However, a study revealed that probiotic supplements could unintentionally impede the normal recovery of the microbiota by displacing beneficial microbes in the gut. Participants who received the probiotic supplement took more than five months for their microbiome to recover, in contrast to those who received a placebo, whose microbiome returned to normal within three weeks. These findings suggest that taking probiotic supplements after antibiotic treatment did not help balance the microbiome; in fact, these supplements impaired its recovery.

“When this trial came out a few years ago, it created a paradigm shift in the field by showing that taking probiotics after antibiotics may actually delay the recovery of your microbiome,” states Dr. Spencer. “Now, I spend a lot of my time in GI clinics convincing people not to take probiotic supplements after antibiotics.”

While probiotic supplements are often used to alleviate symptoms linked to gastrointestinal conditions, such as irritable bowel syndrome and diarrhea, the American Gastroenterological Association does not recommend probiotics for the treatment of any adult gastrointestinal conditions outside of pouchitis. In any case, it’s advisable to consult with a physician before incorporating a probiotic supplement into one’s routine.

“As of now, there are very few probiotic supplements that have strong evidence of their beneficial effect in treating gastrointestinal disease,” states Dr. Spencer. “Nevertheless, this landscape is evolving quickly with ongoing research and advancements in probiotics. I’m hopeful that the next generation of probiotics will target GI disease more effectively.”

What Are Prebiotics and Why are They Important?

After establishing a diverse and healthy microbiome (by consuming a variety of probiotic foods), it becomes crucial to actively sustain it. What you eat directly fuels your microbiome community and determines which microbes will flourish and which will parish in the competitive landscape of your gut.

Prebiotics are nutrients that foster the growth and proliferation of beneficial bacteria in the gut, ultimately contributing to overall gut health. The main prebiotics our microbiome thrives on are known as microbiota-accessible carbohydrates (MACs), commonly referred to as dietary fiber. These complex carbohydrates, found in fruits, vegetables, whole grains, legumes, and other plant materials, resist our body’s degradation and absorption processes. This digestive resistance allows them to reach the colon still intact, providing a feast for our gut bacteria.

For individuals consuming diets high in sugar, fat, and protein, but lacking in dietary fiber, these macronutrients will break down and enter the bloodstream before reaching our colons. As a result, the typically diverse microbial community found in our colons will starve. Over time, the microbiome, in its quest for sustenance, may resort to consuming the gut’s protective mucus layer. This degradation can lead to a cascade of adverse effects, including inflammation within the gastrointestinal tract.

“Without the nourishment provided by fiber, the microbiome is left to fend for itself, potentially resulting in detrimental consequences for both its composition and the overall health of the gut,” states Dr. Spencer. “Eating prebiotic-containing foods is critical to sustain a healthy microbiome.”

In recent years, prebiotic supplements have gained popularity, however, our experts advise opting for fibrous foods over supplements to meet your microbiome’s probiotic requirements. This preference is rooted in the fact that foods offer a diverse array of fiber types, whereas supplements commonly feature a single type. The consumption of a singular fiber type restricts the nutritional support available to our microbiome, and can limit overall diversity that is crucial for a healthy microbiome. Moreover, fiber-rich foods offer various nutritional health benefits not found in supplements. Dr. Spencer suggests that if occasional supplement use is preferred to meet prebiotic needs, choosing supplements with a mix of fiber types is advisable. Nevertheless, opting for fiber-rich foods proves to be a more dependable and cost-effective source.

While more research is needed to fully understand the microbiome and how probiotics and prebiotics work in harmony, it’s reasonable to infer that the presence of one may enhance the function of the others. To promote microbiome diversity and a healthy gut, it’s essential for one’s diet to be a balanced combination of fermented foods (probiotics) and dietary fiber (prebiotics).

“My favorite breakfast is yogurt (a probiotic food) topped with berries and whole-grain granola (which are prebiotic foods). In one delicious meal, I fulfill all my biotic needs,” states Dr. Pojednic.

What Are Postbiotics and Why are They Important?

While many have heard of probiotics and prebiotics, the term postbiotics is relatively new. Postbiotics are the byproduct of probiotic and prebiotic activity. Essentially, they are the waste products left behind by the breakdown of fiber by the bacteria  in your microbiome.

These byproducts can be both beneficial and harmful to your health. The breakdown of fiber yields a treasure trove of beneficial postbiotics. Among these are essential elements such as vitamins, enzymes, amino acids, and short-chain fatty acids (SCFAs). One standout SCFA is butyrate, a superpower molecule throughout the body that plays a pivotal role in various aspects of health. Linked to a reduced risk of chronic diseases, butyrate also exhibits anti-inflammatory properties, supports brain health, and has beneficial metabolic effects.

Conversely, the breakdown of meat in the digestive process yields molecular byproducts such as choline and L-carnitine. In the microbiome, these compounds get broken down further into trimethylamine (TMA), which is subsequently absorbed by the circulatory system and oxidized in the liver to form trimethylamine N-oxide (TMAO). Elevated levels of TMAO have been associated with an increased risk of clot-related cardiovascular events. Intriguingly, a study conducted at Stanford suggests that refraining from meat consumption for eight weeks could potentially suppress the “bad” bacteria associated with TMA production when reintroducing meat into the diet, however, additional research is required to validate this hypothesis.

Postbiotic Supplements

While the concept of postbiotics is relatively new, the popularity of postbiotic supplements is on the rise. Butyrate supplements, for instance, are becoming increasingly common. It is essential to recognize that a deficiency in Butyrate might signify an underlying issue with one’s diet and digestive system, which a supplement alone may not rectify. The most effective strategy for boosting postbiotics involves embracing a diet rich in fermented food and fiber.

Take Home Message: Food is Better than Supplements

Compared to supplements, fermented and fibrous foods provide a diverse array of microorganisms that benefit your microbiome. Moreover, supplements miss out on the synergistic biotic combination of components found in whole meals. Research consistently underscores the pivotal role of diet in shaping the composition and function of a healthy gut microbiome, serving as the most comprehensive and research-backed biotic source.

“We have abundant data to demonstrate that food affects the microbiome. And while supplements certainly have their place–to address nutrient deficiencies and improve specific health outcomes–the evidence for the supplements widely marketed for benefiting the gut are limited at best,” states Dr. Pojednic. “To ensure your microbiome is getting the sustenance it needs, it is best to get your probiotics from fermented foods and prebiotics from high-fiber foods, which have the added bonus of numerous other health benefits.”

Another thing to consider is safety and efficacy of the supplements. Most supplements are loosely regulated by the FDA, meaning manufacturers don’t need to prove safety and efficacy. For this reason, it’s always better to get a nutrient or biotic source from food over supplementation unless it has been recommended by your physician or dietitian.

Most importantly, relying on biotic supplements cannot remedy the consequences of a poor diet. Long-term dietary habits play a pivotal role in the adaptability of the gut microbiome, with the consumption of diverse fermented and high-fiber foods being paramount. As our dietary habits evolve, so does the microbiome, adapting and diversifying to create a resilient and well-balanced ecosystem. In essence, the journey to a healthier gut extends beyond the allure of quick-fix supplements.

“While there is some regulation on manufacturing and marketing of supplements, enforcement is rare unless there is a well-documented negative health effect. Third party testing is key to ensuring you are consuming a safe product. Otherwise, you can fall prey to deceptive claims, mislabeled ingredients or possible contamination,” states Dr. Pojednic. “Safe, well studied supplements have their place, but we just aren’t there yet with these products.”

With ongoing advances in microbiome research, the future may hold more precise probiotic, prebiotic, and postbiotic interventions, potentially enhancing the effectiveness of supplements. However, the foundation of gut health remains deeply rooted in dietary habits, emphasizing the enduring value of natural, food-based approaches over supplementation.

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Microbiome Expert Sean Spencer, MD, PhD: On a Mission to Prove that Food is Medicine

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By Sharon Brock, MEd, MS

Sean Spencer, MD, PhD is a Gastroenterologist and Physician Scientist at Stanford University School of Medicine. Along with seeing patients in the clinic, Spencer conducts cutting-edge research on the microbiome in the Sonnenburg Lab. In his research, Spencer focuses on how nutrition affects the microbiome and the immune system, as well as how our diet can prevent and treat gastrointestinal disease and potentially increase longevity.

“There’s a clear association between the microbiome and healthy aging. Studies of centenarians show a different microbiome configuration and metabolite production compared to those with a shorter life span and unhealthy aging,” says Spencer. “The microbiome is a key aspect of lifestyle medicine because what we eat and how we exercise affects our microbiome composition.” 

 The Medical Path

 Growing up amidst the rich agricultural tradition in Madison, Wisconsin, Spencer learned from an early age the importance of nutritious food for optimal health. As an undergraduate at the University of Wisconsin, Spencer majored in medical microbiology and immunology, and knew since his sophomore year that he wanted to practice medicine.

“After taking a human physiology course, I just knew that learning as much as I could about the human body and using that knowledge to help people was the only thing I wanted to do,” says Spencer. “As an undergrad, I also discovered that I could conduct research while caring for patients, and that clarified my career path further.”

These career goals prompted Spencer to pursue an MD-PhD program in immunology at the University of Pennsylvania, which he completed in 2015.

“In graduate school, I realized how our diet has a profound impact on the microbiome, and can directly influence the immune system,” says Spencer. “You want to think of the three aspects [nutrition, microbiome, and immune system] at the three corners of a triangle. They each impact the other.”

After completing an internal medicine residency at the Harvard-affiliated Massachusetts General Hospital, Spencer came to Stanford in 2017 for a fellowship in gastroenterology (GI).

“I came to Stanford specifically to work with Justin Sonnenburg, so it was great to be accepted to both the GI clinical program and his lab,” says Spencer. “What I love most about Stanford are the people and the creativity. This focus on the microbiome and nutrition is unique to Stanford and I’m glad to be part of a community that thinks about lifestyle medicine in both research and clinical care.”

Living His Dream

For the last three years, Spencer has been a practicing, board-certified GI physician at Stanford Medicine and a researcher in one of the most prestigious microbiome labs in the country. Spencer lights up when he talks about his current research on the small intestine microbiome:

“Most microbiome studies look at poop, which represents the very end of the GI tract, but the small intestine is 20 feet long, and researchers have sampled almost none of it,” says Spencer. “We’ve developed a novel technology to sample and investigate the microbiota [bacteria] of the small intestinal microbiome, which has been a huge blank space for the longest time.”

The small intestine is where many nutrients, including glucose, are absorbed into the bloodstream. Since high glucose levels are linked to diabetes and obesity, Spencer believes this research will potentially lead to the development of therapies to be used alongside lifestyle medicine, to enhance its benefits, for individuals with these medical conditions.

Spencer also studies hormones in the small intestine, such as Glucagon-like peptide-1 (GLP-1), which is the hormone targeted in the popular weight-loss drugs Ozempic and Wegovy. “The new GLP-1-targeted medications are powerful and amazing drugs, but it’s important to recognize that we have the power to regulate these hormonal pathways with our diet and lifestyle choices,” he says.

Although his work in the lab is a source of fulfillment, Spencer also enjoys bringing his research findings directly to his patients as a GI physician. Spencer is able to offer this bench-to-bedside level of care since he attained both a medical degree and a PhD in immunology.  

“I’m most proud that I have the skillset to listen to patients and identify what they need clinically, and then do the research to fill in the gaps and conduct clinical trials to develop new therapies to help them,” says Spencer.

Looking to the Future

Spencer’s future plans are to work in a clinical setting where he can continue to see GI patients and perform clinical trials on nutrition-microbiome-immune research. Studies from the Sonnenburg lab he would like to continue are testing the anti-inflammatory effects of fermented foods, which help treat food allergies, and the mechanisms by which our diet, microbiome, and immune system impact each other.

Regarding patient care, Spencer takes a “food is medicine” approach and plans to conduct more research to back up that message. “My future goal is to perform research that reinforces the recommendations of lifestyle medicine; to build the evidence-base for types of food that promote a healthy microbiome and prevent and treat disease,” says Spencer. “This research will help us understand what aspects of food are critical for promoting health and wellness and has real potential to offer improved dietary advice and to help our patients promote health through what they eat.”

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Dr. Spencer’s Science-Based Smoothie for Gut Health

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By Maya Shetty, BS

In the complex world of gut health, finding straightforward solutions that effectively support the microbiome can be challenging. For this reason, Sean Spencer, MD, PhD, Gastroenterologist and Physician Scientist at Stanford University, created a meticulously engineered morning smoothie recipe to support his own gut health. Guided by his deep understanding of the gut’s delicate ecosystem, this smoothie is not just a meal but a strategic tool for fostering a flourishing microbiome.

Ingredients:

  • 1 cup spinach
  • ½ avocado
  • ½ apple
  • 1 tsp green banana flour
  • 1 tsp L-glutamine powder
  • 1 scoop (20 grams) pea protein powder
  • Top up with liquid of choice: water, coconut water, milk or nut milk (without additives)

Creating the Base

Dr. Spencer tailors his morning smoothie base with a focus on nutrient density and diversity, recommending a blend of apples, spinach, and avocado. Yet, he emphasizes the flexibility of the recipe to accommodate personal tastes and digestive responses. For those who find certain fruits, like apples, lead to bloating, Dr. Spencer says they can be easily substituted with other fruits like bananas or blueberries. 

“I find spinach, apple, and avocado make a tasty combination, yet the door is open to experiment with different fruits to achieve a healthy blend of nutrients and fiber,” he states.

Dr. Spencer points out the unique contribution of avocados to the smoothie. Unlike many fruits, avocados are rich in healthy fats, crucial for delivering steady energy throughout the day. Moreover, they are remarkably high in fiber, with half an avocado offering six to seven grams, making up about a quarter of the USDA’s daily recommended fiber intake. This dual benefit of avocados enhances the smoothie’s nutritional profile, making it a powerhouse of sustained energy and digestive health.

When it comes to liquid choices, almond milk is Dr. Spencer’s preferred option, but he notes the suitability of any type of milk or coconut water as long as it’s free from inflammatory additives, such as added sugars and thickeners, which can negatively impact the microbiome when consumed regularly. He also cautions against the deceptive practices of some brands that claim no added sugars while employing enzymes that convert complex carbohydrates into simple sugars (such as alpha-amylase added to oat milks), effectively sneaking in unwanted sugars.

“To ensure the healthiest choice for your microbiome, I recommend opting for products with short and simple ingredient lists,” he states.

Pea Protein Powder

Dr. Spencer chooses pea protein for its gentle impact on the digestive system and its impressive nutritional profile. It also boasts a comparable protein content to whey and includes all nine essential amino acids—vital nutrients your body is incapable of producing on its own.

Dr. Spencer advises that choosing the right protein powder for your gut is not about type, but rather additives. Most protein powders on the market, including pea protein, are formulated with emulsifiers. These additives, such as soy lecithin, cellulose gum, xanthan gum, guar gum, acacia gum, and polysorbate 80, are used to enhance the powder’s mixability in liquids. Despite their practical benefits, emulsifiers come with a downside–they’re notoriously harsh on the microbiome.

Recent research has shed light on the detrimental effects of common emulsifiers, revealing their capacity to directly alter the gut microbiota and incite inflammation. Such disruptions can compromise an otherwise healthy microbiome, underscoring the importance of choosing products wisely. A randomized controlled trial illuminated the extent of this impact, showing that the inclusion of emulsifiers in the diet over a mere 11-day period led to a noticeable decline in microbiome diversity and a reduction in the production of beneficial metabolic byproducts, or postbiotics.

Green Banana Flour (Resistant Starch)

Green banana flour enriches the microbiome with its high resistant starch content, a form of fiber with powerful benefits to the microbiome. Resistant starch has many health benefits and earns its name for its ability to bypass digestion in the small intestine, journeying instead to the large intestine. Here, it serves as a vital food source for beneficial gut bacteria, promoting a robust and healthy microbiome. The fermentation of resistant starch by these microbes results in the production of valuable postbiotics, such as short-chain fatty acids, essential for maintaining gut health. As bananas ripen they convert their starch to simple sugars, while the starch in green bananas remains intact, retaining its prebiotic properties. 

Dr. Spencer also mentions other fiber supplements like psyllium husk, which, although beneficial for digestion and adding moisture to bowel movements, does not serve as a fermentable food source for the microbiome. This distinction highlights the importance of choosing fibers that not only facilitate physical digestion but also actively contribute to the microbiome’s health.

“Other prebiotic supplements and sources exist. However, I choose to supplement with a resistant starch source because it has strong evidence that it is an accessible and fermentable source of fiber for microbiome,” he says.

While Dr. Spencer regularly uses green banana powder as a prebiotic supplement, he emphasizes the significance of incorporating a variety of fiber sources into one’s diet, noting this shouldn’t be the only fiber source in the day. 

“A diverse intake of fibers is crucial for a thriving microbiome, and I recommend consuming other prebiotic-rich foods such as potatoes, whole grains, beans, legumes, nuts, seeds, and a wide array of fruits and vegetables throughout the day,” he says.

L-Glutamine Powder

L-Glutamine offers a range of benefits for gut and microbiome health, such as reducing GI symptoms after morning workouts. It’s also recognized for its role in maintaining the integrity of the intestinal lining and reducing the inflammatory response during gut lining irritation. 

Furthermore, L-Glutamine serves as a vital energy source for the cells within the small intestine. This attribute is essential for maintaining intestinal health and addressing conditions where impaired intestinal barrier is present because it decreases gut permeability and reinforces the intestinal barrier.

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What is Fiber and Why is it Important for the Microbiome?

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By Sharon Brock, MEd, MS

Key Takeaways: 

  • Fiber promotes a healthy microbiome by feeding the “good” bacteria in the gastrointestinal tract.
  • Fiber is not broken down by the digestive organs but instead passes through the body to support healthy bowel movements.
  • 95% of Americans are deficient in fiber.
  • 19-38 grams of fiber per day is recommended and should be added to every meal.
  • Fiber is found in plant-based foods, particularly beans, nuts, fruits, and vegetables.
  • Fiber has many health benefits, including reducing risk of cardiovascular disease, type 2 diabetes, and several cancers.

Fiber not only helps us stay regular, but it also supports a healthy gut microbiome, which is crucial for overall health. Studies show that getting enough fiber strengthens the immune system, supports gut health, reduces inflammation and risk for heart disease, stroke, hypertension, obesity, Type 2 diabetes, and several cancers, including colon and breast cancer.

Although the Institute of Medicine recommends consuming 19-38 grams of fiber per day, national surveys show that 95 percent of Americans don’t consume enough fiber in their diets.

“The biggest thing I’ve learned in my nutrition research is that it’s very rare for people to consume sufficient fiber,” says Jessica Hope, Nurse Practitioner, and member of the Stanford Lifestyle Medicine nutrition pillar. “As a country, we aren’t deficient in protein; we are deficient in fiber. We need to spread awareness about this problem.”

What is Fiber, and What Does it Do?

Fiber is a type of carbohydrate that serves as a prebiotic, or food for the “good” bacteria in the gut, promoting a  healthy microbiome. Also, rather than being broken down by digestive organs, fiber passes through the body to support healthy bowel movements. There are two types of fiber: soluble and insoluble.

Soluble Fiber

Soluble fiber dissolves in water and creates a gel-like substance that slows the movement of food through the digestive tract. This slower digestion reduces blood sugar spikes, lowers blood cholesterol, and helps you to feel fuller longer.

Best food sources of soluble fiber include:

  • Legumes: Beans of all kinds, including kidney, black, pinto, white, lima, navy, chickpea; edamame; and peas
  • Oats
  • Tofu
  • Avocado
  • Brussels sprouts
  • Sweet potatoes
  • Broccoli
  • Pumpkin

Insoluble Fiber

Insoluble fiber (aka roughage) is found in the skin and structure of fruits and vegetables—it’s what makes these foods crunchy. Instead of dissolving in water, insoluble fiber attracts water into the stool, making it softer and easier to move through the digestive system. This promotes bowel-movement regularity and prevents constipation and hemorrhoids. Also, since these crunchy foods require more chewing, it takes longer to eat a fiber-rich meal, slowing down digestion and helping with portion control.

Best food sources of insoluble fiber include:

  • Whole wheat products, like 100% wholewheat bread and pasta
  • Oat bran and oatmeal
  • Legumes: Beans of all kinds, including kidney, black, pinto, white, lima, navy, chickpea; edamame; and peas
  • Berries: including blackberries, blueberries, raspberries, strawberries
  • Whole grains, including quinoa, rye, barley, amaranth, brown rice
  • Leafy greens, like kale and spinach
  • Vegetables, like broccoli, okra, radishes
  • Nuts, especially almonds and walnuts
  • Fruits with edible skins, like pears and apples
  • Avocados
  • Sunflower, flax, and chia seeds
  • Potatoes and sweet potatoes
  • Popcorn

Many plant-based foods offer both types of fiber. For example, the flesh of an apple has soluble fiber, and the skin contains insoluble fiber. Legumes and beans also offer both types of fiber.

“Grains don’t carry as many micronutrients as fruits, vegetables, nuts, or seeds,” says Hope. “There’s nothing wrong with getting your fiber from whole grains, they just don’t pack as much of a nutritional punch.”

Health Benefits of Fiber

Consuming adequate amounts of fiber is associated with a host of health benefits and disease prevention, such as:

Cardiovascular Health

Many studies show that beta-glucan, a soluble fiber found in oat and barley foods (such as cereals), reduces the amount of cholesterol in the blood. Lower cholesterol reduces the risks of atherosclerosis (hardening of the arteries) and high blood pressure.

Type 2 Diabetes

Soluble fiber (including beta-glucan) also slows down digestion and reduces sugar absorption into the bloodstream, which lowers overall body weight and the risk for type 2 diabetes.

“Americans eat so few beans compared to other cultures. I think that one of the reasons why we have more heart disease and diabetes in our country is because we don’t have many beans as a traditional part of our diet,” says Hope.

Microbiome Health and Stronger Immune System

The gut microbiome is the community of microorganisms found in the small and large intestine of the digestive tract. Fiber serves as a prebiotic, meaning it feeds the microbiota or “good” bacteria in the large intestine, allowing it to flourish and take up space. This strengthens the immune system in that all bacteria compete for surface area on the gut lining, so if enough space is occupied by “good” bacteria, the “bad” bacteria won’t have room to grow.

Also, when our microbiota consume fiber in the large intestine, they release acids that keep the colon healthy, such as short-chain fatty acid, butyric acid, acetic acid, and propionic acid.

“Microbiota in our gut need to eat just like we do, and when we eat, we are also feeding them. If we don’t feed them enough fiber, they will look around to see what else they can eat. Recent research is pointing toward the possibility that the circumstance referred to as ‘leaky gut’ occurs when microbiota are so starved they begin to eat the lining of our own intestine,” says Hope. “Of all the reasons to eat a lot of fiber, this is the main one for me.”

Anti-inflammation and Anti-Cancer Effects

Research also shows that fiber-rich foods reduce inflammation. One study showed barley increased the amount of butyric acid-producing bacteria in the gut, which is known to suppress excessive inflammatory responses.

Butyric acid has been shown to prevent the development of chronic disease and inhibit tumor cell proliferation, reducing the risk of several cancers, including colon, breast, esophageal, lung, and liver cancer.

Fiber and Longevity

In this epidemiologic study, there is a clear association between fiber consumption and reduction in all-cause mortality. The study shows that among those who consume between 20 to 30 grams of fiber per day, which is the recommended amount, there is a 10 to 20 percent reduction in death from any cause.

Easy Ways to Add Fiber to Your Diet

You can find fiber in most whole or minimally processed plant-based foods, including beans, whole grains, nuts, seeds, fruits, and vegetables.

Easy-to-make, fiber-rich meals:

  • Breakfast – berries with whole grain cereal or oatmeal; avocado toast on whole-grain bread
  • Lunch – leafy-green salad with beans or lentils and avocado
  • Snack – popcorn, whole fruit (eat the skin if possible), nuts (almonds, walnuts)
  • Dinner – quinoa or brown rice with sweet potatoes, broccoli, asparagus, carrots, and/or Brussels sprouts
  • Dessert – pumpkin pie

 Tips to get more fiber in your diet:

  • Eat whole fruits and vegetables instead of juicing—the pulp is the fiber!
  • Swap white rice, pasta, and bread with their brown or 100% wholewheat counterparts.
  • For protein, swap animal products, which contain no fiber, with beans and tofu.
  • If you find fresh produce spoils too quickly, frozen fruits and vegetables are just as nutritious.
  • Fiber supplements (such as ones with psyllium husk) help regulate bowel movements but don’t promote a healthy microbiome because they don’t feed the “good” bacteria. Therefore, it is recommended to consume daily fiber intake from food sources rather than supplements. 

How to Prevent Gas and Bloating from Eating Fiber

The microbiome is comprised of different kinds of bacteria that eat different types of fibrous foods. For example, some bacteria specifically digest black beans, other bacteria digest oats, while other bacteria digest kale. Hope explains that if someone who doesn’t eat black beans frequently suddenly consumes 25 grams of black beans in one day, they won’t have enough black-bean digesting bacteria in their gut, resulting in gas and bloating.

“To prevent gas and bloating, the keys are to drink lots of water and start slow when incorporating more fiber into your diet. The amount of fiber we eat should be just slightly more than the bacteria we already have in our guts are asking for,” says Hope. “People often say things like, ‘black beans don’t agree with me’ but that isn’t the case. They just don’t have enough of the bacteria that digest those beans. Rather than avoid black beans, they can incorporate them slowly into their diets, allowing time for that specific bacteria to multiply.”

Along with starting small to prevent digestive discomfort, Hope suggests experimenting with easy ways to increase the fiber of every single meal to make the habit sustainable. For example, this can be achieved by adding berries to your breakfast, beans to your lunch, and vegetables to your dinner.

According to research, if all Americans increased their fiber intake by 10 grams per day, the reduction in all-cause mortality would be profound, and everyone would be a little bit healthier.

“Along with being essential for your health, fibrous foods are delicious!,” says Hope. “The best way to increase fiber in your diet is to choose foods that you enjoy and add them, little by little, throughout the day. So, if you don’t like beans, perhaps you could start with apples and blueberries, and shop and plan to make these your go-to snack or dessert to develop this healthy habit.”

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Considerations When Choosing Supplements

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By Maya Shetty, BS

This blog is part of our Supplements newsletter. If you like this content, sign up to receive our monthly newsletter!

Key Takeaways: 

  • The supplement industry operates with minimal external oversight. Thus, it is critical for consumers to rigorously assess the actual need and proven efficacy of a supplement prior to its use.
  • Most supplement claims lack scientific evidence. Consumers should only consider supplements with solid scientific backing.
  • Opt for brands verified for purity and bioavailability by third-party organizations.
  • Supplements should supplement—not replace—a healthy diet and lifestyle. Emphasize whole foods, physical activity, and balanced health practices over seeking quick fixes.

In an era where every shelf in the wellness aisle promises a solution to your health concerns, supplements stand out as both suspects and saviors. The market is flooded with options: B12 promises to energize you, omega-3 asserts it will curb inflammation, vitamin C and zinc vow to enhance your immunity, and greens powders claim to do everything in between. With so many claims, it’s important to learn how to navigate the supplement world with a critical eye and an informed mind. Stanford Lifestyle Medicine Registered Dietician Marily Oppezzo, PhD, MS, RDN, DipACLM explains how to approach the supplement market and make informed choices for your health.

What is a Dietary Supplement?

Dietary supplements are ingestible products that contain “dietary ingredients” intended to supplement the diet, including vitamins, minerals, herbs, amino acids, fatty acids, live microbials, and protein powders, among many others. Navigating this expansive world requires an understanding of their nature and regulation—or lack thereof. Though many claim to be from natural sources, supplements are essentially laboratory-created entities designed to alter our physiology, underscoring the importance of approaching them with the same level of scrutiny as any medication.

“Just because a supplement is labeled as ‘natural’ or derived from natural sources doesn’t make it healthy, or even safe,” states Dr. Oppezzo. “This is particularly relevant when considering the unnaturally high concentrations [of the nutrient] often found in supplements.”

Despite their widespread use for health-related purposes, dietary supplements are in a regulatory gray area. When it comes to most supplements, the Federal Drug Administration (FDA) is not responsible for ensuring safety, efficacy, purity, or potency. These aspects are managed by the supplement manufacturers themselves (per the Dietary Supplement Health and Education Act of 1994). This means that supplements are exempt from the rigorous testing and validation process mandated for pharmaceuticals, with the FDA stepping in only if enough post-market reports indicate adverse effects. This regulatory gap makes it challenging for consumers to navigate the supplement aisle, emphasizing the importance of thorough evaluation when considering the necessity of a supplement.

Evaluating the Need for a Supplement

While many individuals view supplements as a way to meet their basic nutritional requirements or as a convenient method to optimize health, the reality is that there are relatively few situations where supplements have proven beneficial.

Before taking any supplement, Dr. Oppezzo recommends pausing to consider several key questions: 

  • What is my reason for believing I have a nutritional deficiency or need to take this supplement? Have I spoken to my doctor or taken a blood test to confirm this deficiency? Is there even a test to confirm this?
  • Has a credible source such as a Registered Dietitian or Doctor recommended this to me, or am I influenced by persuasive advertising?
  • What benefits do I expect to gain from taking this supplement? Is there any scientific evidence that this supplement will help me?

Of course, there are circumstances where supplementation can be beneficial. Age, certain medical conditions, and specific lifestyle choices can impact our body’s ability to absorb or synthesize vital nutrients. For instance, older adults might struggle to produce enough vitamin D or B-12 naturally. Athletes engaging in intense training may require additional iron or protein or calories to support their performance levels, while those following vegan or vegetarian diets might need nutrients less common in plant-based foods, such as B-12, omega-3 fatty acids, calcium, and vitamin D.

The most reliable way to determine your nutritional needs is through a professional consultation with a dietitian. This approach allows for a tailored assessment for needs, evaluation of evidence behind supplements you are interested in, and ongoing monitoring to adjust as necessary. 

Assessing Supplement Claims

A significant portion of supplement usage is driven by misconceptions and marketing rather than genuine need. “The wellness industry often races ahead of scientific validation, promoting products with claims that outpace the available evidence,” states Dr. Oppezzo. “They aren’t cutting edge, they are flying out way past the cliff of evidence.”

Addressing this challenge, Dr. Oppezzo encourages consumers to first look for any peer-reviewed studies backing the “need” or the claim of a supplement. Ideally, ask an expert to do this for you. 

While certain supplements, such as vitamin B12, are actually essential nutrients, supported by extensive research, others, like various greens powders and phytochemical blends, lack robust evidence demonstrating their effectiveness throughout the body. The absence of any regulation allows many products to make exaggerated claims without solid proof. As such, many supplement labels contain a hodgepodge of wellness buzzwords, such as “immune booster,” “supports gut health,” and “promotes health aging,” without any science to back up the claims.

Secondly, Dr. Oppezzo urges us to think about its bioavailability—the extent to which it can be absorbed and utilized by the body. Imagine being in the shoes of a supplement itself, considering all the gauntlets it has to pass to do the thing you think it will do and deliver the marketed effects.

Like any ingested substance, supplements are first broken down by the stomach, absorbed in the gut, processed in the liver, incorporated into the bloodstream, and then transported to organs and cells throughout the body. The critical question is whether the supplement can survive this journey in a form that retains its intended benefit and reaches the organ or cell where you think it will do its purported job.

“Let’s put essential vitamins and minerals aside for a moment. Even if there is evidence some supplement or chemical will do something if you dropped it on your cells in a test tube, you don’t know that this translates to your real live body. Further, you don’t even know if the supplement will even succeed at getting inside your body in the first place, let alone maintaining its original ‘active’ structure after it gets inside,” states Dr. Oppezzo.

It’s important to approach supplements with a healthy dose of skepticism and informed judgment. Not all supplements are inherently harmful; some can offer significant benefits when used appropriately. Yet, the decision to incorporate them into your health regimen should be made with careful consideration, guided by credible evidence and, when possible, professional advice. Once identifying the need for a supplement, Dr. Oppezzo recommends the following framework to decide the appropriate brand, dosage, and context for its consumption.

Framework for Choosing a Supplement

1. Assess the Safety and Efficacy

When it comes to supplements, third-party testing is a gold standard for ensuring product safety and efficacy. Organizations like ConsumerLab, US Pharmacopeia, and NSF International offer unbiased supplement evaluations, checking for purity, potency, and safety. Consumers can either check these websites to find a trustworthy supplement brand or look for products that bear their certifications. While some manufacturers conduct their own testing, third-party validation is preferable for an impartial review. Also, the supplement landscape is ever-changing, so checking for updates regularly is wise. 

However, it’s important to understand that these organizations do not directly test the efficacy and safety of supplements. This information can only be provided through clinical trials. According to Dr. Oppezzo, these organizations primarily verify the product has the amount that it claims on the bottle, has the supplement in at least a bioavailable form that can get absorbed into your body, and that it is free from high levels of known contaminants. 

2. Dosage Matters

The saying “more is better” is not necessarily true for supplements – or even essential nutrients. Both inadequate and excessive consumption of nutrients can have detrimental effects on health. Although the body is capable of excreting surplus nutrients, fat-soluble vitamins can accumulate in the body to toxic levels if consistently consumed in large amounts. On the other hand, overconsumption of water-soluble vitamins usually leads them to be excreted through urine, which is inefficient, costly, and known as “expensive urine.”

Therefore, it is crucial to adhere to recommended dietary allowances (RDAs) as a starting point and tailor intake based on individual responses. Importantly, consistently exceeding 100 percent of the RDA can result in nutrient imbalances. One example is selenium, a nutrient where both insufficient and excessive intake have been associated with hair loss. Ironically, many products marketed as “hair vitamins” contain selenium levels surpassing the RDA, potentially worsening the very issue they aim to remedy. 

3. Consider the Chemistry

The effectiveness of a supplement can also depend on its chemical form. For example, vitamins that are fat-soluble achieve maximum absorption when consumed simultaneously with a source of fat, such as a small portion of nuts. Additionally, the interaction between nutrients is important; for instance, copper and zinc compete for absorption, and an excess of one can lead to a deficiency in the other. Supplements can also have harmful interactions with certain pharmaceutical medications, so it is important to consult with healthcare providers before starting a new supplement. 

Another important consideration is the degradation of these compounds. For example, there is an oxidation potential of omega-3 and other fatty acid supplements. This means they have the potential to go “rancid” and lose their efficacy, especially when exposed to heat or open air. This vulnerability stems from the unsaturated nature of these fats, which contains double bonds in their molecular structure that are more reactive with oxygen. 

Indications of rancidity include a strong, fishy odor or an unpleasant taste in fatty acid supplements. Additionally, you can look for information on the peroxide value (PV), a common measure of its oxidation potential. This can be found on some supplement labels, as well third-party testing reports, such as NutraSource. Dr. Oppezzo recommends supplements with PV levels less than 8 mEq/kg.

Supplements Are Not Substitutes for a Healthy Diet

Regardless of whether supplements are part of your daily routine, it is important to remember supplements should be seen as supplemental and not taken at the cost of eating whole foods. While they can sometimes fill nutritional gaps, supplements should be distinct from other health behaviors, such as eating well and moving often.

Moreover, focusing on single ingredients or specific nutrients without considering the holistic picture can lead to misconceptions about what supplements can achieve. Just taking vitamin D, for instance, won’t fully address bone health if it’s not combined  with strength training and a calcium-rich diet.  Good health is about the synergy between multiple  health practices and how they complement each other.

“The allure of a quick fix or ‘magic pill’ is an enticing narrative in our fast-paced world, yet it’s important to remember that there is no replacement for a good diet and regular exercise,” states Dr. Oppezzo. “The foundation of healthy aging always has and always will be a direct result of the choices we make on a daily basis, which is what lifestyle medicine is all about.”

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Vitamin D: Benefits, Sources, Deficiency

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By Maya Shetty, BS

This blog is part of our Supplements newsletter. If you like this content, sign up to receive our monthly newsletter!

Key Takeaways: 

  • Vitamin D affects the health of bones and also plays a role in our muscles, immunity, and prevention of some diseases.
  • The most common form of vitamin D is synthesized in the skin after exposure to sunshine. Vitamin D can also be found in some foods naturally as well as supplements and fortified foods.
  • Vitamin D insufficiency is defined as less than 30 ng per mL of blood. Strive to maintain sufficient vitamin D levels through a balanced diet, sensible sun exposure, and supplementation as needed. 
  • When choosing a vitamin D supplement, D3 is recommended over D2, and should be combined with a fat (such as a handful of almonds or an Omega-3 supplement). You should not take more than 4,000 IU (100 mcg) per day due to the potential for toxicity unless recommended by a medical professional.

In a nation saturated with supplements, vitamin D commands the spotlight as one of the most widely taken across all age groups, second only to multivitamins. 

“Ever since vitamin D deficiency was found to be the root cause of rickets, we have long recognized its role in bone health. Now research is looking at this vitamin as a panacea for numerous ailments, from the common cold, to even cancer,” states Robert Oh, MD, MPH, Chief Wellness Officer of the VA Palo Alto Healthcare System. 

As ongoing research peels back the layers of complexity surrounding this vitamin, the scientific landscape becomes dynamic and subject to rigorous debate.

Where Does Vitamin D Come From?

Vitamin D distinguishes itself from other vitamins due to its unique ability to exist as both a dietary nutrient and as a hormone. Sourced from sunlight exposure, food, and supplements, this fat-soluble vitamin accumulates in the body’s fatty tissues and liver, available to be released as needed.

Sunlight

The primary source of vitamin D is the production that occurs in our skin from cholesterol precursors when exposed to the sun’s ultraviolet-B (UVB) rays, earning its nickname “the sunshine vitamin.” Considering the pivotal role sunlight plays in vitamin D production, daily exposure is beneficial.

Some plants and animals also possess the ability to synthesize vitamin D, contributing to the vitamin’s content in various foods and supplements. In plants, vitamin D is in the form D2 (ergocalciferol), while in animals, including humans, it is in the form D3 (cholecalciferol). Both forms are absorbable by humans; however, there is evidence suggesting that D3 has a more substantial and prolonged impact.

Food

High amounts of vitamin D3 are found in oily fishes such as salmon, mackerel, and sardines, whereas small amounts are found in eggs, red meat, and liver. 

Vitamin D2 is found in specific mushrooms, but its concentrations vary significantly based on exposure to light. Mushrooms, much like our skin, require sunlight for vitamin D production. “Since commercially available mushrooms are typically grown in dark conditions, they contain minimal amounts of vitamin D and organic mushrooms will contain almost none. Exposure to UV light through irradiation, which is not allowed in organic food production, will substantially increase conventional mushroom vitamin D content,” said Rachele Pojednic, PhD, Stanford University nutrition and exercise scientist.

Due to the limited natural food sources of vitamin D, many products, including breakfast cereals, dairy items, and plant-based milks, are fortified with vitamin D2 and D3. For a comprehensive list of vitamin D content in specific foods, refer to the U.S. Department of Agriculture (USDA) list categorized by nutrient content and food name.

Supplements

Vitamin D2 and D3 can be found in supplement form. Due to the potentially higher bioavailability, D3 supplements are typically recommended over D2. 

Dr. Pojednic emphasizes the importance of considering the fat-soluble nature of vitamin D when taking a supplement. “Vitamin D absorption, especially when consumed in concentrated doses, will be significantly enhanced when taken in conjunction with dietary fat, such as a handful of almonds or an omega-3 supplement,” she says.

When determining the appropriate vitamin D supplementation dosage, keep in mind that higher is not better. Toxic levels of vitamin D can arise from excessive supplement intake, a risk not associated with sunlight exposure due to the skin’s ability to self-regulate production. Therefore, Dr. Oh advises consulting with a physician or dietitian before taking high-dosage supplements. “Too much vitamin D can cause health issues, such as too high calcium levels or even kidney damage, so work with your care team if you are taking high doses of vitamin D,” he says.

Health Benefits of Vitamin D

Vitamin D is crucial for human health. While primarily recognized for its role in building strong bones, new findings suggest that this fat-soluble vitamin may exert a broader influence throughout the body. 

“We now know that the majority of organs and tissues in the body possess vitamin D receptors,” states Dr. Pojednic. “This finding suggests vitamin D has effects beyond the skeletal system, sparking considerable research in the potential benefits of vitamin D for multiple health conditions.”

A substantial portion of this research focuses on the effects of vitamin D supplements, rather than dietary and sunlight sources. However, this by no way means the benefits of vitamin D are found solely through supplementation. Additionally, it should be noted that many studies have not compared outcomes in individuals with sufficient versus deficient vitamin D blood levels, which make conclusions from many supplementation studies difficult to interpret.

Bone Health

Vitamin D stands as a key player in sustaining the structural integrity of our skeletal system by facilitating the absorption of calcium and phosphorus—the building blocks of our bones. Through the process of mineralization, these minerals are incorporated into our bones to maintain normal bone density. Inadequate vitamin D levels can result in insufficient mineralization, which can lead to weakened bones and conditions such as osteoporosis, as well as more severe disorders like rickets and osteomalacia. 

While the adverse effects of inadequate vitamin D on bone health are well-established, the evidence concerning the impacts of supplemental vitamin D over-and-above sufficient levels remains inconsistent.

In 2007, the US Agency for Healthcare Research and Quality synthesized the research on vitamin D and determined daily supplementation of vitamin D (≤ 800 IU) with calcium (≥ 500 mg) resulted in small increases in bone mineral density in older adults. 

There is additional evidence that suggests that vitamin D supplementation lowers the risk of fractures in institutionalized older adults (700-800 IU vitamin D) and female navy recruits (800 IU vitamin D and 2000 mg calcium). However, both groups were initially at a high risk of vitamin D deficiency, and their levels were likely insufficient to begin with.

 On the contrary, the largest vitamin D study to date, Vitamin D and Omega-3 Trial (VITAL), showed that daily supplementation of 2000 IU vitamin D did not reduce fracture risk in more than twenty-five thousand midlife and older adults who had sufficient vitamin D levels on average.

The current body of evidence indicates that vitamin D supplementation offers the most significant benefits for individuals with deficiencies. However, for those already meeting their vitamin D requirements, the benefits of additional supplementation are less clear. This suggests the need to approach vitamin D supplementation for bone health as a targeted strategy—aimed at maintaining sufficient levels rather than striving for excessively high, or supramaximal, levels. Such a focused approach ensures supplementation benefits those who need it, without unnecessary excess in those already meeting their vitamin D requirements.

Dr. Pojednic underscores the importance of a proactive approach, stating, “Ensuring sufficient intake of vitamin D and calcium serves as a foundational preventive measure to mitigate bone mineral loss and reduce the risk of osteoporosis later in life.” This strategy is particularly crucial early in life, as the foundation for peak bone mass, particularly for women, is established in our twenties. By achieving and maintaining optimal levels of vitamin D and calcium from a young age, individuals can maximize their bone strength and preserve it as they age.

Muscle Health

Our muscles need vitamin D to function and develop properly. Studies have established a correlation between deficient vitamin D levels and muscle weakness, pain, and atrophy. While the precise molecular mechanisms of vitamin D’s influence on skeletal muscle necessitate further investigation, cell culture studies indicate that vitamin D administration can alter cell pathways related to muscle contraction, cell proliferation, differentiation, growth, and inflammation.

An increasing body of research suggests a positive impact of high and low vitamin D supplementation on physical performance and injury prevention, particularly in vitamin D deficient adults and athletes. Research has identified a negative correlation between blood levels of vitamin D and biomarkers of muscle damage and inflammation, as well as number of injuries. 

“These findings indicate the potential of vitamin D as a supplement for aiding recovery in injured or overtrained athletes,” states Dr. Pojednic. “However, further research is required to determine the optimal dosages and interventions for effective recovery.”

It has also been hypothesized that vitamin D may reduce the risk of falls in older adults by enhancing muscle strength and coordination, thus improving balance and postural sway. An analysis of multiple studies indicates that daily vitamin D supplementation may decrease the risk of falls in older adults with low vitamin D levels. However, this protective effect was not observed in individuals with sufficient vitamin D levels, a conclusion supported by the VITAL trial, which administered 2,000 IU of vitamin D daily.

The current evidence regarding vitamin D and muscle health suggests that the benefits of supplemental vitamin D are, again, primarily observed in individuals deficient in the vitamin, mirroring patterns observed in bone health. However, it may also have some benefit for athletes and others struggling with muscle damage and recovery. Overall, more research is needed to understand the optimal level of vitamin D for muscle health and determine whether these levels exceed what is required for bone health.

Immune Function

Vitamin D plays a crucial role in immune health, demonstrating various effects on inflammation, autoimmune diseases, and infection rates. The VITAL study revealed that healthy individuals taking vitamin D (2,000 IU per day) were less likely to develop autoimmune diseases such as rheumatoid arthritis and psoriasis, with a 22 percent reduction in incidence over the five-year supplementation period. However, these protective effects were no longer evident after participants discontinued the vitamin D supplement. This implies that vitamin D needs to be consistently taken for long-term prevention.

In the context of respiratory health, a comprehensive meta-analysis demonstrated that daily or weekly vitamin D supplementation lowers the risk of upper respiratory tract infections, especially in very deficient individuals. During the COVID-19 pandemic, studies revealed that low serum levels are associated with a higher risk of COVID-19 infection.

These findings underscore the importance of maintaining optimal vitamin D levels for immune health and the long-term prevention of autoimmune and respiratory diseases. “Similar to muscle and bone health, supplemental vitamin D has the most consistent benefits among those with deficient levels at baseline,” states Dr. Oh. “However, the new findings suggest supplemental vitamin D may reduce autoimmune disease risk even in individuals with already sufficient vitamin D levels.” Therefore, further research is warranted to identify the optimal vitamin D level for sustaining long-term immune health.

Diabetes

Research has consistently found an inverse relationship between vitamin D blood levels and diabetes risk. Vitamin D deficiency may influence key biochemical pathways involved in the development of prediabetes and diabetes, impacting beta cell function in the pancreas and contributing to inflammation.

In a noteworthy observation from the Nurses Health study, women who regularly consumed higher daily doses of vitamin D (>800 IU) and calcium supplements (>1,200 mg) experienced a remarkable 33 percent lower risk of Type 2 Diabetes compared to those with lower doses (400 IU vitamin D, <600 mg Calcium).

Further evidence comes from randomized control trials, which have shown that the benefits of vitamin D supplementation are most pronounced in individuals with low levels of this nutrient. In a randomized clinical trial involving 2,000 adults with prediabetes, participants received daily high doses of vitamin D (4,000 IU) over two years. The study discovered a significant risk reduction for diabetes among those with severely low vitamin D levels. However, this beneficial effect was not observed in participants who already had sufficient levels of vitamin D.

Cancer and All-Cause Mortality

Epidemiological studies have revealed a connection between insufficient vitamin D levels and an increased risk of cancer and all-cause mortality, prompting significant research into the potential role of vitamin D in cancer prevention and overall longevity.

Laboratory studies showcase vitamin D’s ability to inhibit cancer cell growth, while epidemiologic investigations suggest that inadequate vitamin D levels correlate with a 30 to 50 percent increased risk of incident colon, prostate, and breast cancer, along with elevated mortality from these cancers. Despite these findings, clinical evidence remains mixed. The large-scale VITAL study reported a reduction in cancer-related deaths over five years of daily vitamin D supplementation (2,000 IU), but not a decrease in the risk of developing cancer. However, a recently published secondary analysis of the trial data revealed that participants taking the vitamin D supplement had a 20 percent lower likelihood of developing advanced cancer, defined as metastatic or fatal.

A review of several clinical trials further substantiated the link between low vitamin D levels and risk of mortality, more broadly showing a seven percent reduction in all-cause mortality with daily vitamin D supplementation (median dose 800 IU).

Many unknowns continue to surround vitamin D and its relation to cancer risk and overall mortality. “Significantly more research is needed to determine if low vitamin D levels are a risk factor for cancer and whether supplementation can impact overall longevity,” states Dr. Oh. “Nevertheless, the present data does suggest that individuals at risk for cancer may consider supplementing with vitamin D.”

How Much Vitamin D Do I Need?

There is controversy over the levels of vitamin D considered to be sufficient; however, it is widely acknowledged that 25-OH vitamin D levels below 30 ng per mL of blood (50 nmol/L) are insufficient to maintain bone health. 

Optimal levels of vitamin D vary among individuals based on factors such as age, race, metabolic differences, and physiological condition. Adding complexity to this understanding, Dr. Pojednic emphasizes that most vitamin D recommendations are based solely on bone health, and levels required to support other tissues may vary. As such, there is no universally accepted optimal vitamin D level for overall health.

Dr. Oh recommends optimizing natural sources of vitamin D first, such as averaging about 30 minutes in the sun most days, and including a few servings of vitamin D-rich foods in their diet. 

Dr. Pojednic adds that achieving these levels does not need to be a daily practice. “Since vitamin D is a fat-soluble vitamin, our fat cells can store excess for weeks. Therefore, it is more important to consider average sunlight exposure and vitamin D consumption rather than focusing on daily intakes,” she says.

Because vitamin D is stored in fat cells, excessive doses can build up to toxic levels, therefore taking high doses of vitamin D (i.e. more than 4,000 IU per day)  can be dangerous and should be avoided. Symptoms of vitamin D toxicity include weight loss, irregular heart beat, hardening of blood vessels and tissues due to increased blood levels of calcium, potentially leading to damage of the heart and kidneys.

Common Risk Factors for Vitamin D Deficiency

Although it seems easy to absorb 30 minutes of sunlight per day , vitamin D deficiency is common in the US. There are many factors to explain this, including limited geographical location, time outdoors, age-related changes, skin color, restrictive diets, and certain medical conditions. Those affected by these factors may need supplementation to ensure they meet their body’s vitamin D requirements.

1. Sun exposure

During the winter months, people who live in areas above 37 degrees north latitude, which includes cities such as San Francisco, Seattle, Denver, St. Louis, Philadelphia, New York, Boston, and Chicago, do not receive sufficient UVB exposure to produce the necessary amount of vitamin D.

“Vitamin D synthesis in our bodies occurs only at specific wavelengths,” explains Dr. Pojednic. “Thus, geographical location is an essential factor in determining the best way to maintain your vitamin D levels.”

Even people living in sunny areas can experience deficiency related to sun exposure. By spending significant time indoors or consistently wearing clothing that covers most of the body, our skin will not receive necessary exposure for optimal vitamin D synthesis. Moreover, while many believe they get sufficient sunlight through car or office windows, most windows filter out the UVB rays necessary for synthesis. 

Of course, there are many concerns surrounding direct sun exposure, most notably skin cancer. Using sunscreen and limiting sun exposure are still very important measures to protect the skin. While the role of sunscreen in contributing to low vitamin D levels is subject to debate, evidence indicates that the typical use of sunscreen does not significantly impact the body’s ability to produce vitamin D. This means that for most individuals, wearing sunscreen during exposure to sunlight still allows for the synthesis of vitamin D.

2. Age

The skin’s ability to produce vitamin D diminishes significantly with age, declining at an estimated rate of 13 percent per decade of life. Additionally, as we age, our body becomes less efficient in absorbing and utilizing vitamin D.

3. Skin color

Individuals with darker skin often exhibit lower blood levels of vitamin D likely due to the pigment melanin acting as a natural shade, reducing the production of vitamin D. Consequently, low vitamin D levels are particularly prevalent among Americans with darker skin tones. 

4. Diet

Individuals who cannot tolerate or choose not to consume milk, eggs, and fish, such as those with lactose intolerance or those adhering to a vegan diet, face an elevated risk of vitamin D deficiency. “The exclusion of these food sources, which are rich in vitamin D, makes it challenging for individuals in these groups to obtain sufficient levels of this nutrient from food alone,” states Dr. Pojednic.

5. Certain medical conditions

Individuals with inflammatory bowel diseases, such as ulcerative colitis, Crohn’s disease, celiac disease, and chronic pancreatitis may encounter difficulties in maintaining optimal vitamin D levels. This is because the absorption of vitamin D, a fat-soluble vitamin, is contingent on the digestive tract’s ability to absorb dietary fat, and inflammatory conditions within the tract can impede this process. Additionally, certain liver and kidney conditions may impair the metabolism and utilization of vitamin D within the body.

“Signs that your body may need more vitamin D than it is currently getting include bone pain, especially of your chest, shins and even overall chronic pain. For athletes, any bone stress injury like shin splints and poor healing stress fractures may indicate a vitamin D deficiency,” states Dr. Oh. “Finally if you have muscular weakness or pain, especially of your upper legs it would be reasonable to check your vitamin D levels with a blood test.”

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