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Vitamin D's Benefits For Your Brain, Depression, Immune Health & How to Get More

Vitamin D’s Benefits For Your Brain, Depression, Immune Health & How to Get More

January 29, 2016
Updated May 15, 2020

If you reside in the northern half of the United States, work indoors during the day, or generously apply sunscreen when outdoors, there is a good chance you are deficient in vitamin D. That pretty much amounts to anyone and everyone – even people you’d think are commonly in the sun like college and pro athletes.

Nutrition is everything to an athlete, but there’s become even more of an emphasis on it and with good reason. The importance of vitamin D deficiency cannot be overstated. Over 1 billion people worldwide across all ethnicities and age groups are estimated to be deficient[1].

Adequate vitamin D is required for bone synthesis, calcium balance, hormone production and immune function. If prolonged, vitamin D deficiency leads to serious bone mineralization abnormalities.

So it’s not just athletes that would benefit from some time in the sun or a few vitamin D pills, but certain teams and organizations have begun making sure their athletes have adequate vitamin D levels.

The training staff of teams like the Pittsburgh Steelers and Detroit Redwings believe vitamin D is able to keep their players on the field through its ability to support bone health and the immune system.

Sun Exposure and Vitamin D

Vitamin D's Benefits For Your Brain, Depression, Immune Health & How to Get More
Casual exposure to sunlight outside of winter months fulfills approximately 90% of vitamin D requirements for most people. However the amount of vitamin D produced from sunlight largely depends on several factors, including skin tone, age, and percentage of body fat.

Skin color is determined by the production and concentration of melanin, a light absorbing protein that evolved as a natural sunscreen. Fair skin contains relatively low melanin, and requires less exposure to UV light to produce a given amount of vitamin D when compared to darker skin.

For example, one study showed the a small dose of UVB light in fair skinned individuals resulted in a 50-fold increase in blood concentrations of vitamin D. The same dose of light exposure to the darkest skin type resulted in no increase in vitamin D production.

Body type also plays a role in levels of circulating vitamin D. Individuals with higher body fat percentages have more adipose tissue to deposit vitamin D, thereby removing it from the circulation and decreasing the quantity that reaches the target.

One study showed that obese individuals had 57% lower levels of vitamin D following UV exposure compared to non-obese subjects [2].

Sunscreen is an effective blocker of UVB and UVA radiation and not surprisingly will decrease vitamin D production. An SPF of 8 reduces vitamin D production by >95% and SPF 15 reduces production by >98%.

UV exposure clearly has both risks and benefits. The risk-benefit profile and the variability between ages and skin types continues to spur debate over general recommendations for sun exposure.

For example, the American Academy of Family Physicians and the American Academy of Dermatologists recommend complete sun avoidance with frequent application of sunscreen.

However recent recent studies criticize these recommendations, citing vitamin D deficiency as an unconsidered health hazard.

As the dawn of of personalized medicine approaches, it is likely that a combination of safe sun exposure and supplementation tailored to individuals will be the best strategy to obtain vitamin D.

Safe Sun Exposure

Generally, the best way to get vitamin D is to stand in the sun with as much of your skin exposed as legally possible. Sunlight strikes the skin convert a form of cholesterol into an inactive vitamin D precursor, so if you’re covered up with clothes or sunscreen, your body won’t be able to produce vitamin D.

However, there is an upper limit to how much vitamin D your body can produce in a day. Generally speaking, when your skin starts turning pink, it’s time to find some shade.

Unfortunately, if you live in the higher latitudes, you’re limited to the summer months to be able to get your vitamin D from the sun. Late spring and early fall may also work, but it’ll take longer due to the sun’s angle.

Nutrition and Supplementation

Vitamin D's Benefits For Your Brain, Depression, Immune Health & How to Get More
Very few foods contain high levels of vitamin D. Oily and fatty fish, such as salmon, swordfish and sardines have the highest vitamin D content. Fish supplements such as cod liver oil also contain high levels along with essential fatty acids.

Some argue that high vitamin A levels in cod liver oil is a risk for hypervitaminosis A. However, if you are an adult, you would have to be consuming excessive amounts of cod liver oil for years to reach toxic levels.

Arguably the safest and most direct method of obtaining adequate vitamin D is through consuming D3 supplements. According to groups like the Vitamin D Council, one should aim to supplement with 1000-5000 IU per day.

The absorption rate is approximately 80%, but according to researchers at Tufts University in Boston, a diet with greater monounsaturated fats than polyunsaturated fat can improve absorption[3].

The exact type of supplement also makes a difference. Vitamin D3 is highly preferred over vitamin D2, which is a yeast derivative product that is potentially toxic and ineffective when compared to D3.[4].

How much vitamin D we truly need is another ongoing debate amongst medical professionals and nutrition experts. The Institute of Medicine (IOM) recently tripled the recommended daily allowance to 600 IU with 4000 IU as a tolerable upper limit.

However many experts agree that this increase does not go far enough and even the IOM admits that 4000 IU per day is likely safe.

Although some foods are contain vitamin D, the total amount of vitamin D from food is low and the consumption of these foods is often infrequent. For the majority of people with low sun exposure during winter months, supplementation with vitamin D3 is vital.

Emerging Roles of Vitamin D

Vitamin D's Benefits For Your Brain, Depression, Immune Health & How to Get More
Research on vitamin D continues to discover new roles for the importance of this steroid hormone. Animal studies have provided insight to the distribution of vitamin D receptors throughout the brain and link the production of neurotransmitters to adequate circulating concentrations[2].

This research is supported by meta-analysis of human studies that showed low levels of vitamin D are associated with depression[5].

Furthermore, vitamin D has shown to be helpful in treating symptoms of Seasonal Affective Disorder (SAD) in adults and premenstrual syndrome in adolescents females [6-7]. The benefits of vitamin D supplementation clearly outweigh the risks.

A combination of safe sun exposure, consumption of oily fish, and the addition of vitamin D3 supplements will conservatively fulfill the needs for this nutritional component.

The array of biological activity throughout the human body, from bone strength to mood regulation, shows the dependency we have for this steroid hormone.


[1] Holick MF. Vitamin D deficiency. N Engl J Med. 2007. [2] Holick MF. Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. Am J Clin Nutr. 2004 [3] Niramitmahapanya S.Type of Dietary Fat Is Associated with the 25-Hydroxyvitamin D3 Increment in Response to Vitamin D Supplementation. J Clin Endocrinol Metab. 2011. [4] Bjelakovic G. Vitamin D supplementation for prevention of mortality in adults. Cochrane Database Syst Rev. 2014 [5] Eyles DW. Distribution of the vitamin D receptor and 1 alpha-hydroxylase in human brain. J Chem Neuroanat. 2005. [6] Anglin R., Samaan Z., Walter S., McDonald S. Vitamin D deficiency and depression in adults: systematic review and meta-analysis. British Journal of Psychiatry. 2013. [7] Tartagni M. Vitamin D Supplementation on Premenstrual Syndrome-Related Mood Disorders in Adolescents with Severe Hypovitaminosis D. J Pediatr Adolesc Gynecol. 2015.<
Onnit Research Team
The Onnit Research Team is comprised of medical professionals, researchers, and scientists interested in providing data-driven, actionable information.

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