Medicine for the Outdoors
Medicine for the Outdoors

Dr. Paul Auerbach is the world's leading outdoor health expert. His blog offers tips on outdoor safety and advice on how to handle wilderness emergencies.

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Sunlight and Vitamin D

Being in the outdoors has traditionally meant significant exposure to sunlight, and therefore to ultraviolet radiation, forms of which cause sunburn and skin cancers. It has long been taught that exposure to sunlight is necessary to maintain an adequate amount of vitamin D in the body. This concept has recently been challenged.

In November of 2008, the American Academy of Dermatology recommended "that an adequate amount of vitamin D should be obtained from a healthy diet that includes foods naturally rich in vitamin D, foods/beverages fortified with vitamin D, and/or vitamin D supplements; it should not be obtained from unprotected exposure to ultraviolet UV radiation."

The obvious reason why unprotected exposure should be avoided is to help reduce ultraviolet radiation-related cancers. In this modern age, where vitamin supplementation and a balanced diet are frequently possible, this makes great sense. For impoverished individuals, some afflicted by starvation, vitamin deficiencies (vitamin D deficiency can cause, among other problems, rickets) may preclude this approach.

Currently, the National Academy of Sciences has published guidelines for minimal intake levels of vitamin D, based upon age:

Birth to 13 years - 5 micrograms (mcg) = 200 International Units (IU)
14 to 50 years - 5 mcg (200 IU), including during pregnancy and lactation
51-70 years - 10 mcg (400 IU)
71+ years - 15 mcg (600 IU)

Risk factors for vitamin D deficiency include dark skin, elders, and photosensitive individuals. Such persons might need to take greater minimal amounts of vitamin D.

Many of us would benefit from rational vitamin and mineral supplementation, under the advice of a nutritionist or other informed health care practitioner.

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About the Author

Dr. Paul S. Auerbach is the world’s leading authority on wilderness medicine.