Research Suggests Need for Balance in Sunscreen Use
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In today's health news, we'll report on competing ways to prevent cancers. Evidence is mounting that vitamin D protects against a number of deadly cancers. It's one more benefit from a vitamin that's already believed to build strong bones. So researchers pretty much agree we need to get more of what's known as the sunshine vitamin. And that leads to a controversial possibility: that we might be smarter if we used less sunscreen. NPR's Patricia Neighmond reports.
PATRICIA NEIGHMOND reporting:
The most recent uproar started at a meeting of the American Association for Cancer Research. Doctors were already aware of a book by a dermatologist which touted the benefits of sun exposure without sunscreen in order to help the body make vitamin D. Then Harvard epidemiologist Ed Giovannucci gave a speech that said vitamin D might prevent more cancers than sunscreen does.
Mr. ED GIOVANNUCCI (Harvard): Just count the number of cancer deaths annually in the United States that might be related to vitamin D deficiency--and I emphasize might be--they outnumber skin cancer deaths 30:1.
NEIGHMOND: Every year, about 55,000 new cases of the most severe skin cancer, melanoma, are diagnosed, but that pales compared to the numbers of new cases of cancers which vitamin D might help prevent, including cancer of the colon, prostate, pancreas, esophagus, stomach and even breast.
Mr. GIOVANNUCCI: Vitamin D slows down cell proliferation. Vitamin D induces cell deaths of abnormal cells you actually want to die and not to keep developing, because they might develop toward cancer eventually. Vitamin D may even protect against some things that we would consider late stages of cancer, such as cells spreading, leaving the initial tumor and metastasizing to other tissues.
NEIGHMOND: Most researchers agree we need a lot more vitamin D than is now recommended by the federal government, but there aren't many foods which contain it. Fatty fish like sardines and salmon do. So does cod liver oil. Cereals and milk are fortified with it, and daily vitamins contain some vitamin D, but Giovannucci says it doesn't add up to very much.
Mr. GIOVANNUCCI: If someone goes sunbathing on the beach on a sunny day, in about 20 minutes or 30 minutes, that person could make up to 20,000 international units of vitamin D, and compare that with 100 international units that you get from a glass of milk. So you'd have to have like 200 glasses of milk a day to get that amount of vitamin D.
NEIGHMOND: Giovannucci says he's not suggesting people go to the beach and fry. He's just saying there may be a safe amount of sun. That's an idea which troubles the dermatology community. Stuart Lessin directs dermatology at the Fox-Chase Cancer Center in Philadelphia.
Mr. STUART LESSIN (Fox-Chase Cancer Center): There is clear evidence that ultraviolet light from the sun is a carcinogen, a cancer-causing substance. In fact, ultraviolet light is listed as one of the known carcinogens in humans.
NEIGHMOND: And the link is clear, says Lessin, between sunburns in childhood and later development of melanoma. Chronic tanning is known to cause a less severe form of skin cancer. The protective effects of vitamin D against a whole range of cancers is far less firmly established, and so Lessin says the message to avoid the sun is still critical.
Mr. LESSIN: You need to use sunscreen and protect yourself from the sun as best you can. If you know you're going to spend an extended period of time out in the sun, more than 10 to 15 minutes, then you should protect yourself from the sun. That is seeking shade and not sitting in the sun; that is wearing sun protective clothing, hats, sleeves, etc.; and using sunscreen. It's basically, you want to avoid a burn.
NEIGHMOND: The controversy over whether to use sunscreen less is largely irrelevant anyway, says Lessin, because most people don't put on enough sunscreen. The American Cancer Society says individuals on average get as little as 20 percent of the recommended coverage. In the meantime, researchers are looking forward to findings from ongoing clinical trials which will provide more definitive answers about the value of vitamin D in protecting against cancer. Those answers could help settle any questions about how much sunscreen people should use and how often. Patricia Neighmond, NPR News.