Most adults in the United States are not getting enough vitamin D, the “sunshine vitamin,” which is actually a fat-soluble hormone we need for bone health and protection against a number of serious diseases, including some forms of cancer.
Different types of vitamin D exist – two that are important for humans are vitamin D2 (ergocalciferol), produced by plants, and vitamin D3 (cholecalciferol), which is synthesized in human skin when it is exposed to sunlight. But it can be hard to get optimal sun exposure, particularly in northern latitudes during the dark winter months, and our dermatologist friends have made everyone so paranoid about sun exposure that most people use sunscreen all the time, and sunscreen blocks vitamin D synthesis.
In addition, as we get older our skin cannot synthesize vitamin D as efficiently as it did when we were young. In addition, the kidneys are less able to convert vitamin D to its active hormone form, making vitamin D deficiency common among the elderly. Add to that the difficulty in obtaining adequate amounts of vitamin D from food, and you can see why I recommend that everyone take 2,000 IU a day of vitamin D3, which appears to be better utilized by the body than D2.
Although current methods don't always yield accurate results, I also recommend that everyone get their vitamin D level tested. Look for results in the normal range, from 30.0 to 74.0 ng/mL of 25-hydroxy vitamin D (normal value ranges may vary slightly among different labs). If your levels are very low, your doctor will likely prescribe a period of more aggressive vitamin D supplementation.
– With Marti Lotman
Andrew Weil, M.D., is Founder and Director, Arizona Center for Integrative Medicine at the College of Medicine, University of Arizona, and Director of Integrative Health and Healing, Miraval Resort. He is a pioneer in the field of integrative medicine, which combines conventional medicine with alternative approaches. He received his medical degree from Harvard University.
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