Catching rays? A few can do you good

For years we’ve been told to slather on sunscreen, wear hats and avoid the sun. Now, with new data on the benefits -- and widespread deficiency -- of vitamin D, some scientists and doctors say we may have gone overboard.

According to the American Cancer Society, more than 1 million people will be diagnosed with skin cancer this year, almost always because of too much sun. It’s no wonder that dermatologists and cancer specialists urge people to protect themselves.

But Dr. Michael Holick, a professor of medicine, physiology and biophysics at Boston University School of Medicine, believes shunning sunlight is a fool’s bargain: Although shade and sunscreen protect against common skin cancers, avoiding sun may increase the risk of much more serious diseases -- including cancers of the breast, colon and prostate -- by cutting off a natural way to make vitamin D. An SPF 8 sunscreen will reduce absorption of ultraviolet B rays by about 95%, and vitamin D production will drop by the same amount, he says.

Holick points out that most skin cancers are highly treatable and that the relationship between sunlight and the most dangerous form, malignant melanoma, is complex. Melanoma is most common in people who have had several blistering sunburns in childhood as opposed to steadier, less intense sun exposure.

Holick recommends “sensible sun exposure”: in general, 15 minutes of strong sunlight (without sunscreen) on the hands, face and arms three times a week. Fair-skinned people in sunny places may need even less time than that, he says.

Although some of his research is funded by the tanning industry, he says he doesn’t recommend tanning, either indoors or out. (People who use tanning beds should stay for only one-fourth to one-half of the time recommended by the manufacturer, he says.)

Some doctors already recommend sunshine. Dr. Robert Heaney, a professor of medicine at Omaha’s Creighton University who has conducted studies on vitamin D, recommends regular sun exposure along with 1,000 IU of vitamin D to his osteoporosis patients.

But such prescriptions don’t always sit well with dermatologists. “If people weren’t already getting enough sun, there wouldn’t be an epidemic of skin cancer,” says Dr. Barbara Gilchrest, chairwoman of the department of dermatology at Boston University School of Medicine.

Her “overwhelming opinion,” she says, is that people shouldn’t be seeking out sunlight or tanning beds to get more vitamin D. Furthermore, she believes most D researchers agree with her. “This is a manufactured debate,” she says. “The flames have been fanned by people with strong ties to the tanning industry.”

Gilchrest says Holick’s basic guidelines for sun exposure are reasonable, but she worries that many people won’t stop there. After 15 minutes (or less), the skin will stop making vitamin D, but the risk of cancer will continue to build, she says. She thinks that taking a supplement is much easier -- and safer -- than walking the fine line between a healthy glow and serious skin damage.

Anthony Norman, a professor of biochemistry at UC Riverside and a pioneer of vitamin D research, agrees that sunshine is a risky source of D. “There’s a good possibility that vitamin D is beneficial, but we don’t have to rely on UV rays to get it,” he says.

And last month, several medical groups including the American Cancer Society concluded that more research is needed before sun exposure recommendations can be made.

Dr. Len Lichtenfeld, the cancer society’s deputy chief medical officer, says that in some cases admonishments to avoid sun at all costs may have been overkill. But, he adds, even less severe forms of skin cancer “can require extensive surgery and are serious illnesses.”

And variable factors -- such as skin type, age, diet, latitude and sun intensity -- make safe, global recommendations very difficult, he says.

The new science of vitamin D has been “a bonanza” for the tanning industry, Gilchrest says. But, she notes, the vast majority of people who use tanning beds are active, fair-skinned young people -- a group not especially prone to vitamin D deficiency. These users also aren’t likely to give much thought to wrinkles and skin cancers that are still decades away.

“Unfortunately,” she says, “they may have to live with the downside for 40 years.”