Sunshine vitamin stirs new debate

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By Ann Geracimos

A study reported this year by the British Association of Dermatologists showed that 83 percent of Australian dermatologists during winter 2006 had only the minimum amounts of vitamin D needed for good health, lower than that of elderly inpatients in a Melbourne hospital.

Dr. Holick acknowledged that sunlight does increase the risk of the milder nonmelanoma forms of skin cancer, but he said that's mainly because people falsely think using sunscreen will protect them and thus don't limit or moderate their time in the sun.

As for deadly melanoma, he said there is not an inevitable relationship to spending time in the sun, provided one doesn't regularly get sunburns.

"If you think about it, most melanomas occur on the least sun-exposed areas, and an occupation requiring sun exposure decreases the risk. It turns out when you put sunscreen on, you weren't protected from [the sun's ultraviolet radiation], which alters your immune system," he said.

Dr. David Heber, professor of medicine and director of the University of California at Los Angeles' Center for Human Nutrition, said that more complex factors may be at work in skin cancers and that dermatologists shouldn't be so dogmatic.

"We don't understand melanoma and its association with sun exposure," he said.

Vitamin D's main role is promoting the absorption of calcium and encouraging bone growth, the lack of which can cause a range of deformities and ailments. It also is essential for cell growth and an optimally functioning immune system.

A blood test can tell the level of vitamin D in a person's body, but primary care doctors have not always requested patients be tested.

"We used to think it was just appropriate for bones and teeth, and now we hear about [its importance to] the brain, heart and muscles," said Dr. Lipman, an endocrinologist.

Its lack "spans basically all chronic diseases," Dr. Holick said in an interview. "Every tissue and cell on the body has a vitamin D receptor, which means every cell needs D to function. ... It regulates bone health and increases the efficiency of the intestines to absorb the calcium that is critically important for nerve and muscle function. We now recognize most body tissues can activate vitamin D to regulate up to 2,000 genes."