Q: I read that vitamin D from sunlight prevents cancer. Are tanning beds even better?
Should I stop wearing sunscreen?
A: That question is the subject of heated discussions among dermatologists and medical researchers. Sunscreen and tanning bed manufacturers also have strong opinions, along with vitamin distributors and cancer awareness foundations.
Boston University’s Dr. Michael Holick created a firestorm among dermatologists in November 2007, when he published a book promoting the use of sunlight to combat vitamin D deficiency that he believes is epidemic in modern society.
Dr. Holick, an endocrinologist with a PhD in addition to his medical degree, is no heretic. His studies on vitamin D have pioneered treatments for chronic health conditions like psoriasis. But he has been criticized for his acceptance of six-figure funding from the tanning bed industry. He counters that sunscreen manufacturers have aggressively funded his detractors’ research.
The controversy stems from the behavior of vitamin D. A number of studies suggest an association with low levels of vitamin D and higher rates of breast, colon, and prostate cancer. Vitamin D may act as to slow the growth of blood vessels that “feed” a tumor. Vitamin D also appears to affect the immune system and is essential to the function of muscles.
There is conflicting evidence on the best way to achieve ideal levels of the vitamin, whether through diet, supplements or — this is the tricky part — ultraviolet rays.
Few foods naturally contain high levels of vitamin D. Fish are a good source, and commercially-available milk is supplemented in the United States. But there is a question whether typical American diets provide adequate vitamin D, or even what level constitutes “enough.”
When ultraviolet light from sun or tanning bulbs hits the skin, the body makes Vitamin D.
But sun exposure — particularly prolonged exposure leading to sunburns — has a clear relationship to the development of many common skin cancers. People with a family tendency are at even higher risk of the rare but potentially lethal melanoma-type skin cancers.
The issue becomes more complicated when taking into account the other effects of the vitamin, which is clearly effective in preventing osteoporosis. The impact of decreased bone fractures in those taking calcium/vitamin D supplements is weighed against the known increase in kidney stones and calcium-related complications.
Less medically relevant but of importance to many people is the fact that sun exposure causes skin damage and premature aging. Wrinkled, leathery skin in reformed sun worshippers has created a multi-billion dollar anti-aging industry.
So should you bake or take cover?
As usual, no one answer is a perfect fit. Maximum vitamin D production by the skin happens after a brief period of exposure — as few as two minutes for a fair-skinned person in the summer sun. Exposure to ultraviolet rays for 5-30 minutes no more than three times per week is adequate to achieve appropriate Vitamin D levels, a recommendation made by its greatest champion, Dr. Holick.
But before rushing out to the beach without a hat, keep in mind that even brief exposures, such as those from walking through a parking lot, “count” against this weekly recommendation. The amount of sunscreen needed to effectively block ultraviolet rays is more than what typical users apply. And because vitamin D is stored in fat, adequate summer exposure may supply winter needs.
So exercise caution and let moderation and personal risk factors be your guide. Sunburns are a clear signal that even if a little is good, a lot may not be better.