Dr. Richard J. Ort, M.D.
Board Certified Dermatologist
Fellowship Trained - Harvard University
Vitamin D is a steroid hormone that plays many critical functions in our body. Vitamin D is needed to absorb calcium and phosphorous, which are essential for strong and healthy bones. Vitamin D can affect our immune system, cardiovascular health, cancer risk, brain function, and many other areas of our body. The two most important forms of Vitamine D are vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol).
Vitamin D can be obtained from our diet, from vitamin supplements, and from the sun! Very few foods are naturally good sources of vitamin D: mushrooms, fatty fish (salmon, tuna, sardines, mackerel), fish oils, and eggs. In the US, there are many vitamin D fortified foods such as milk, yogurt, juices, and cereals. Vitamin D supplements (D2 or D3) can be taken daily to supplement what we get from our diet.
Our skin can synthesize vitamin D (D3) when exposed to the sun. The sun's UVB rays convert a cholesterol-like compound in our body to vitamin D. Although the estimates are controversial, most experts agree that limited sun exposure can be helpful to make adequate vitamin D. A human requires 10-15 minutes of sun exposure at least twice a week on the face, arms, and hands, in bright sun, for adequate amounts of vitamin D3. However, longer exposure to the sun results in the extra vitamin supply being degraded as fast as it is generated!
The health risks of excessive UV exposure are significant, including accelerated skin aging and increased rates of skin cancer. The American Academy of Dermatology and the Skin Cancer Foundation caution against intentional exposure to the sun or artificial tanning UV light (tanning beds) due to the these risks. It is recommended that you obtain the recommended daily allowance (RDA) of Vitamin D through your diet and supplements, if necessary.
The RDA of vitamin D does vary by age:
Individuals who are concerned about not getting enough Vitamin D can have a blood test done to check their Vitamin D levels. Bottom line: Vitamin D is necessary for good health. Small amounts of sun exposure can be helpful, but it is safer to obtain your Vitamin D through diet and supplements rather than through sun exposure or tanning beds. Prolonged sun exposure will not produce more Vitamin D.