In the world of health and wellness, vitamin D shines brightly, often referred to as the “sunshine vitamin.” This essential nutrient plays a role in numerous bodily functions, impacting everything from bone health to your immune system. The 2024 International Virtual Vitamin D Forum & Expert Panel Discussion shed light on the latest research and clinical applications of vitamin D, emphasizing its importance in maintaining optimal health and lowering disease risk.1
Vitamin D Deficiency Is a Global Problem
Despite its importance, vitamin D deficiency is a global concern. Dr. Michael Holick, a leading vitamin D researcher, highlighted the prevalence of this issue, emphasizing the need for increased awareness and action.
Data presented at the forum — including a study of more than 5,500 people attending routine health checkups at a Beijing hospital in which 87.1% had levels below 20 nanograms per milliliter (ng/mL)2 — show that a significant portion of the population has insufficient vitamin D levels. This deficiency has been linked to various health problems, including:
• Bone diseases — Vitamin D promotes calcium absorption, which is essential for strong bones. Severe deficiency can cause rickets in children and osteomalacia in adults. Holick presented research — a study of bone samples from 675 German adults who died in motor vehicle accidents3 — showing that even seemingly healthy individuals sometimes have evidence of osteomalacia, highlighting the subtle but significant impact of vitamin D deficiency on bone health.
• Immune system weakness — Vitamin D plays a role in immune function. Deficiency has been associated with an increased risk of infections, including respiratory illnesses.
Holick presented data, including his own study of more than 190,000 patients early in the pandemic, showing that vitamin D deficiency is associated with an increased risk of COVID-19 — a 54% higher risk of infection in that study — and with more severe outcomes.4 He also highlighted the role of vitamin D in supporting both innate and adaptive immunity, emphasizing its importance in overall immune health.
• Chronic diseases — Studies have linked vitamin D deficiency to an increased risk of chronic diseases such as heart disease, Type 2 diabetes, and certain types of cancer. Holick presented data from various studies showing a correlation between low vitamin D levels and an increased risk of these conditions.
Holick also addressed The Endocrine Society's updated guidelines on vitamin D, which have sparked debate among experts.
Rather than setting new intake targets, the guidelines rely on the existing recommended dietary allowance of 600 international units (IU) daily for adults up to age 70 years old and 800 IU for those over 70 years old, and suggest empiric supplementation only for specific groups, such as children and teens, adults 75 years and older, pregnant women, and people with high-risk prediabetes.
However, many experts argue that these recommendations are too low to achieve optimal vitamin D levels, especially for individuals with darker skin tones or those with limited sun exposure.
Dr. Sunil Wimalawansa, a clinician-scientist with over four decades of experience, added to the discussion by highlighting the concept of vitamin D as a "threshold nutrient." He explained that your body's response to vitamin D changes depending on the existing levels.
When someone is deficient, very small amounts of vitamin D may not produce a meaningful biological response until blood levels cross a certain threshold. But once levels approach sufficiency, the added benefit of extra vitamin D diminishes. This concept underscores the importance of individualizing vitamin D supplementation based on baseline levels and health goals.
Many Women Are Deficient in Vitamin D During Pregnancy
Vitamin D plays an important role during pregnancy, supporting both maternal and fetal health. Studies have linked adequate vitamin D levels during pregnancy to a lower risk of preeclampsia, preterm birth, and other complications — and even the 2024 Endocrine Society guidelines suggest empiric supplementation during pregnancy, citing its potential to lower these risks.5
Holick emphasized the importance of vitamin D supplementation for pregnant women, suggesting that higher doses than the standard recommendation are often necessary to achieve optimal levels — a decision best made with your health care provider.
Holick presented data from his research showing that a significant percentage of pregnant women, even those taking prenatal vitamins, are vitamin D deficient. In his hospital study, 73% of mothers and 80% of their newborns had levels below 20 ng/mL.6
He highlighted outcomes associated with this deficiency, including a higher risk of C-section in his own research7 and, in another study he cited, 60% fewer premature births among women whose levels were above 40 ng/mL.8 He also discussed research indicating that higher vitamin D levels during pregnancy are associated with a reduced risk of dental caries in infants.9
Vitamin D Linked to Reduced Cancer Risk and Brain Benefits
Dr. William Grant, a renowned vitamin D researcher, presented evidence linking vitamin D to a reduced risk of cancer. Studies he presented found that individuals with higher vitamin D levels have a lower risk of developing certain types of cancer, including colorectal and breast cancer. Grant interprets these findings as suggesting that vitamin D may play a meaningful role in lowering cancer risk.
Grant discussed the pioneering work of Cedric and Frank Garland, who first identified the link between UVB exposure and reduced cancer risk. He presented data from ecological studies showing a correlation between higher solar UVB levels and lower cancer mortality rates. Grant also highlighted the importance of considering vitamin D's impact on both cancer incidence and mortality.
In addition, Grant explained that the effect on incidence may be modest due to the influence of other risk factors — in the large VITAL trial, for example, 2,000 IU of vitamin D daily produced no significant reduction in cancer incidence overall but a significant 25% reduction in cancer mortality.10 Grant attributes this stronger effect on mortality to vitamin D's proposed role in reducing angiogenesis (formation of new blood vessels) and metastasis (spread of cancer).
Emerging research indicates that vitamin D also plays a role in brain health. Prospective cohort studies presented by Grant have linked higher vitamin D levels to a reduced risk of cognitive decline, dementia, Alzheimer's disease, and stroke.11,12 While the exact mechanisms are still being investigated, the findings suggest that maintaining adequate vitamin D levels may help support cognitive health as you age.
Grant highlighted the importance of considering the follow-up time in these studies, as longer follow-up periods may dilute the observed benefits. He suggested that vitamin D may have a more significant impact on brain health over shorter periods. Grant also discussed studies reporting significant improvements in measures of brain health after two to six months of vitamin D supplementation.13
Addressing Concerns About Vitamin D Safety and Toxicity
Vitamin D expert Wimalawansa addressed concerns about vitamin D safety and toxicity. He emphasized that vitamin D is generally safe when taken in appropriate doses, noting that reported complications from supplementation are extremely rare. However, excessive intake can lead to hypercalcemia, a condition characterized by high calcium levels in your blood.
Wimalawansa provided guidelines for safe vitamin D supplementation, emphasizing the importance of individualizing doses based on factors such as body weight, sun exposure and health conditions.
Wimalawansa clarified that vitamin D toxicity is exceedingly rare and usually occurs due to accidental ingestion of extremely high doses. He emphasized that diagnosing vitamin D toxicity requires more than just a high serum vitamin D level. Toxicity becomes possible above about 150 ng/mL, but it also requires high calcium in the blood and urine, suppressed parathyroid hormone, and clinical signs and symptoms of hypercalcemia, such as nausea, vomiting, dehydration, mental confusion, and heart rhythm problems.14
Wimalawansa further discussed contraindications. People who are hypersensitive to sunlight, such as those with lupus, should avoid direct sun exposure and may rely on vitamin D supplementation instead, under medical supervision.
By contrast, certain rare genetic disorders, such as Williams syndrome, and granulomatous diseases, such as sarcoidosis, increase sensitivity to vitamin D and call for caution with supplementation.15,16,17 He also addressed the question of whether additional calcium supplementation is necessary when taking vitamin D. He explained that when vitamin D levels are adequate, your body's ability to absorb calcium from your diet increases, making calcium supplementation typically unnecessary.
Your Immune System and Vitamin D — A Powerful Partnership
Dr. Aileen Burford-Mason, an immunologist, nutritionist, and independent research analyst, highlighted the role of vitamin D in immune function. She explained how vitamin D helps regulate your immune system, guarding against both underactivity and overactivity.
She also described adequate vitamin D levels as a vital part of fighting infections and controlling inflammation, and said it may help lower the risk of autoimmune diseases developing or progressing. However, she also stressed that vitamin D does not work alone.
Burford-Mason emphasized the importance of considering other nutrients, such as magnesium, which work in conjunction with vitamin D to support immune health. She discussed the two main components of your immune system: innate immunity and adaptive immunity and explained how vitamin D supports both branches of the immune system, helping your body fight off infections and maintain immune balance.
She also highlighted the importance of vitamin D in regulating the inflammatory response, helping the immune system switch off once its job is done, since prolonged, excessive inflammation can contribute to tissue damage and autoimmune disease.
Burford-Mason also presented data from randomized controlled trials on respiratory tract infections. In a 2010 trial in Japanese schoolchildren given a modest 1,200 IU of vitamin D daily over the winter months, about 11% of the vitamin D group developed influenza A, compared to nearly 19% of the placebo group.18
In another study, which was a meta-analysis of 25 randomized controlled trials, participants reported a 12% lower odds of developing at least one respiratory tract infection, with the greatest benefit in people who started out most deficient.19
For COVID-19, Burford-Mason cited a recent meta-analysis of 19 randomized controlled trials in COVID-19 patients reporting a 28% reduction in all-cause mortality with supplementation.20 She also discussed the VITAL trial finding of a 22% reduction in the development of autoimmune diseases among participants taking vitamin D,21 while emphasizing the need to assess each person's individual vitamin D status and to consider other nutrients that support immune function.
Clinical Applications of Vitamin D and Vitamin D Resistance
Dr. Richard Cheng, a physician specializing in antiaging and integrative cancer therapy, shared real-world examples from his clinical practice of how he uses vitamin D as part of a broader approach to health. He discussed the use of vitamin D in autoimmune diseases, metabolic disorders and even for antiaging purposes. Cheng emphasized the importance of a holistic approach, considering lifestyle factors such as diet, exercise and stress management in conjunction with vitamin D supplementation.
Cheng shared his personal experience using vitamin D in his practice, where he reports that he has not seen side effects in the patients he monitors. He described using high-dose vitamin D, alongside other nutrients and lifestyle measures, in patients with autoimmune conditions such as Hashimoto's and psoriasis, and said he has seen marked improvements, including normalized antibody levels in some cases.
Note that these are his own clinical observations rather than results from controlled trials, and doses at this level should only be used under the supervision of a physician who monitors your blood levels. Like Cheng stated, it’s important to monitor vitamin D levels and personalize treatment plans based on patient needs.*
Cheng discussed the concept of vitamin D resistance, in which some individuals require higher doses to achieve optimal levels. Various factors influence vitamin D's effectiveness, and he stressed the importance of addressing these factors through lifestyle modifications and targeted nutrient support, such as magnesium, to help vitamin D work as intended.
Factors that may contribute to vitamin D resistance include higher body weight, poor intestinal absorption (such as after bariatric surgery), certain medications such as anti-epileptic and antiretroviral drugs, and possibly genetic variations. Monitoring vitamin D levels and adjusting doses accordingly with your health care provider is therefore important.
*These findings are from research conducted in clinical settings. Results may not apply to all individuals.
The Power of the Sunshine Vitamin
The 2024 International Virtual Vitamin D Forum provided valuable insights into the latest research and clinical applications of vitamin D. The key takeaways include:
- Vitamin D deficiency is a global concern, impacting individuals of all ages and ethnicities.
- Maintaining adequate vitamin D levels is important for optimal health and has been linked to a lower risk of a wide range of conditions, from bone disorders to chronic illnesses.
- Vitamin D supplementation is generally safe when taken in recommended doses, but individual needs vary.
- Monitoring vitamin D levels is important, especially for individuals with specific health conditions or those taking higher doses.*
- A holistic approach, combining vitamin D supplementation when necessary with lifestyle factors such as diet, exercise and sun exposure, was the approach the panelists favored.
*Talk to your health care provider about whether this testing is appropriate for you.
Embracing Vitamin D for Better Health
The ideal way to raise your vitamin D levels is via safe sun exposure. Harnessing the sun's power for vitamin D production offers benefits far exceeding simple vitamin synthesis. Healthy sun exposure, reflected in robust vitamin D levels, is linked to numerous health advantages, including reduced cancer risk and enhanced longevity.
However, while sunlight is necessary for vitamin D and overall well-being, it demands careful management. The key is finding a balance between protection and reaping its rewards. If your diet includes significant amounts of seed oils, extra caution is warranted. These oils, rich in linoleic acid (LA), an omega-6 fatty acid, readily oxidize under ultraviolet light. This interaction on your skin is thought to initiate a cascade of breakdown products that may contribute to inflammation and DNA damage.
Therefore, if you consume seed oils, limit sun exposure to the gentler morning or late afternoon hours for four to six months while eliminating these oils from your diet. Individual characteristics also influence sun sensitivity, with skin color, determined by melanin, playing a pivotal role.
Melanin acts as a natural UV shield. Consequently, individuals with darker skin require more sun exposure to generate comparable vitamin D levels as those with lighter skin. This biological difference underscores the need for personalized sun strategies.
Body composition, particularly body fat percentage, is another important factor. Fat tissue stores fat-soluble substances, including oxidized seed oils. Individuals with higher body fat may experience prolonged risk even after dietary changes due to these stored oils. To assess your sun tolerance, especially if you consume seed oils, monitor your skin for redness or burning — a simple “sunburn test” that accounts for the season, your skin type and other factors.
The absence of pinkness suggests safe sun exposure. Avoiding sunburn, a clear indicator of overexposure and skin damage, is the goal. Reducing your body's LA stores may significantly lower your likelihood of sunburn and is thought to reduce your risk of skin cancer. However, vigilance remains essential, particularly during the transition. As you lower seed oil intake, avoid peak sunlight hours — typically the hours surrounding solar noon.
In most U.S. regions, this translates to avoiding direct sunlight from 11 a.m. to 3 p.m Gradually, as your body clears accumulated seed oils, safely increase sun exposure — once you've been off seed oils for four to six months, you can begin going into the sun around solar noon, which is the optimal time for sun exposure. Remember, individual responses vary, so observe your body's reactions during this process. If redness appears, seek shade immediately.
Strategies for Enhanced Sun Protection
If sun exposure is unavoidable before your body has fully cleared seed oils, consider protective measures. Astaxanthin, an antioxidant from marine sources, is a valuable ally. A daily intake of 12 milligrams may help bolster your skin's resistance to sun damage by neutralizing free radicals and reducing inflammation, providing added UV protection. Niacinamide cream (vitamin B3) is another beneficial tool.
Topical application has been studied for protection against UV-induced DNA damage and may help strengthen your skin barrier, enhancing resilience to sun stressors. Some people report noticeable improvements using niacinamide cream before sun exposure.
Overall, vitamin D is an essential nutrient that plays a role in maintaining optimal health, and research links adequate levels to a lower risk of disease. By embracing the sunshine vitamin, through a combination of sensible sun exposure and appropriate supplementation, you take a proactive step toward a healthier and more vibrant life.
This article is for informational purposes only and does not constitute medical advice. Consult a qualified health care provider before making changes to your health regimen.