Written by Emily Braatan | Reviewed by Adiana Castro, MS, RDN, CDN, CLT
The National Institutes of Health suggest that 10-15 minutes of sun exposure three times a week will provide the necessary amount of vitamin D production (but synthesis can be hindered by sunscreen, shade, and darker complexion).
Technology has explored the use of solar power in recent decades but, in a way, humans have always been walking solar panels. Vitamin D needs can be met through a combination of diet, supplementation and direct sunlight, making vitamin D a unique micronutrient. During exposure to sunlight, UV radiation causes a structural change in the skin’s 7-dehydrocholestrol, resulting in pre-vitamin D. Pre-vitamin D undergoes one hydroxylation reaction in the liver and a second in the kidneys before it is biologically active.
Vitamin D is essential to human development largely because of its relationship with calcium and phosphorous, which have an enormous effect on bone health. Vitamin D increases the uptake of both micronutrients by promoting their intestinal absorption and their reabsorption in the kidneys. Calcium and phosphorous contribute to bone mineralization, which is why vitamin D deficiency often presents as rickets in children or as osteoporosis in adults.
Some studies suggest the function of vitamin D may extend to inflammation and neurological health. A 2014 study by Zhang et al. looked at the role of gestational vitamin D deficiency on the health of rat offspring. The researchers compared rat pups from mothers who were fed a vitamin D-free diet during pregnancy with pups from mothers who had adequate vitamin D intake. The vitamin D-deficient pups exhibited significantly lower glucose tolerance, reduced insulin sensitivity, and increased prevalence of inflammatory biomarkers. The findings suggest that maternal vitamin D deficiency may form the basis for diabetes and inflammation in children.
A literature review published in the Annals of Pharmacotherapy drew on forty years of research in investigating the effect of vitamin D supplementation on the prevention and treatment of multiple sclerosis. The major finding was that vitamin D supplementation was associated with a 40% risk reduction of developing MS among animal models. The findings suggest supplementation may be therapeutic but human studies have been sparse and often involve various other supplements, which may confound the results.
Vitamin D deficiency is believed to be widespread in the U.S. due to limited dietary sources of the micronutrient as well as lack of sun exposure from outdoor physical activity. If interested in vitamin D supplementation, opt for the D3 form (cholecalciferol) over the D2 form (ergocalciferol) because it’s more efficient absorption and increased potency.
In 2010, the Institute of Medicine reevaluated vitamin D needs and set the Recommended Dietary Allowance at 600 international units (IU) of vitamin D per day (800 IU for individuals over the age of 70). Rich sources of Vitamin D include Cod Liver Oil, Fatty Fish, Mushrooms, Whole Egg and Liver.