We Pay When We Shun the Sun: Those Rays Provide Vitamin D, Which Cuts Risk of Certain Cancers, Studies Say.

By Alan Bavley, The Kansas City Star, Mo.

Jun. 6–After decades of worry about the damage too much sun can do to our skin, we may have gone too far, researchers say.

When we shun the sun — slathering ourselves with sunscreen or avoiding the outdoors — we also lose our biggest source of vitamin D. And in new research, including a report released Monday, scientists are finding that abundant doses of the sunshine vitamin drastically reduce the risks of breast, colon and prostate cancer.

Vitamin D even lowers the odds of developing autoimmune diseases such as multiple sclerosis and type I diabetes, some researchers say.

Our bodies produce their own vitamin D when exposed to the sun’s ultraviolet light. About 10 minutes a day in the summer is all that’s required, some scientists say, although with more than a million new cases of skin cancer each year, many dermatologists would cringe at even that amount.

But various experts say that as much as three-fourths of the U.S. population isn’t getting enough vitamin D. Our sedentary, indoor culture and conscientious use of sunscreens are contributing factors. For African-Americans, whose pigmentation reduces the effects of the sun, deficiency rates may be much higher.

Vitamin D deficiencies could pose a risk of the magnitude of smoking and contribute to about one-third of all cancer deaths, some researchers say.

The result is that up to 63,000 people a year in the U.S. may be dying prematurely from cancer due to insufficient vitamin D.

“The evidence is strong enough now we should be making changes to increase vitamin D intake,” said Cedric Garland, a researcher at the University of California, San Diego. “We need a lot more vitamin D than we ever imagined.”

Garland and his colleagues first noticed in the 1980s that risks for certain cancers appeared to be lower where winters were short and sunshine was abundant. They suggested a link to vitamin D.

Since that time research has burgeoned, with most of it strengthening links between vitamin D and cancer prevention:

–The American Cancer Society and several other health organizations have issued a statement acknowledging that vitamin D may reduce risks of some cancers and that people may not be getting enough to achieve the benefits.

–Researchers on Monday released the results of a major study suggesting that calcium and vitamin D supplements may lower the risk of breast cancer in women past menopause.

–A government panel will meet this week to review dietary guidelines for vitamin D and other nutrients.

Scientists have long recognized the key role vitamin D plays in the body’s ability to assimilate calcium to build bones.

But dietary guidelines were set relatively low, vitamin D proponents say, at 200 international units a day for most people. That’s about enough to prevent the crippling deficiency called rickets in children.

“It was just a guess, and they guessed badly,” said Bruce Hollis of the Medical University of South Carolina.

Only in the past decade have researchers been able to easily measure how much vitamin D is in people’s blood. What they discovered is startling.

Healthful blood levels of vitamin D may require 1,000 to 2,000 international units a day, what is now considered the maximum safe dose.

Getting that much vitamin D from fortified foods or multivitamin pills is practically impossible. Short of taking vitamin D supplements, the only way to get enough is through sun exposure, Hollis and other researchers say.

That advice has pitted vitamin D advocates against dermatologists who question the safety of spending any unprotected time in the sun.

In a statement last year, the American Academy of Dermatology Association said people should take supplements.

“Skin cancer is an epidemic in this country and recommending increased UV exposure with claims that sunlight somehow promotes good health is highly irresponsible,” said Vincent DeLeo, a Columbia University dermatologist.

Michael Holick, an endocrinologist at Boston University School of Medicine, was asked in 2004 to resign from the dermatology faculty after publishing a book, The UV Advantage, that advocated sun exposure.

“I don’t advocate tanning. I certainly don’t advocate sunburning,” Holick said. “But if you’re going to be outdoors, don’t always feel compelled to wear skin protection.”

The American Cancer Society says people should get their vitamin D through supplements and small amounts of sun exposure.

Laboratory research has shown that vitamin D promotes cancer prevention by causing cells to differentiate and specialize, rather than grow in aberrant ways into cancer cells.

“Probably what D does in the breast and maybe the prostate and colon is serve as a brake on cell growth,” said Carol Fabian, a breast cancer researcher at the University of Kansas Medical Center. “If we don’t have enough vitamin D, the normal braking system, the normal buffer isn’t there.”

While researchers are linking high vitamin D levels to cancer prevention, the benefits of vitamin D still haven’t been demonstrated by randomized trials. These studies would pit vitamin D against a placebo to see if it reduced illness or death over time.

One such study is the Women’s Health Initiative. The researchers gave about 18,000 women calcium and vitamin D supplements. A similar number got placebo pills. In a February report, the study found no difference in colon cancer risk between the two groups.

However, many women in the placebo group took the supplements on their own. Women in both groups who had high blood levels of vitamin D had lower cancer risks.

A second Women’s Health Initiative study on breast cancer released Monday found similar results. Overall, there was no difference in risk between women past menopause who received calcium and vitamin D supplements and those given a placebo over a seven-year period. But when researchers looked just at women who weren’t taking the supplements before the study started, the risk of developing breast cancer was reduced by 18 percent in the group taking calcium and vitamin D.

“The trial was not designed so we could easily define differences between the treatment and placebo groups,” said Fabian, who led a discussion of the findings Monday at the annual meeting in Atlanta of the American Society of Clinical Oncology.

“The bottom line is you won’t be able to see on your milk cartons or boxes of cereal that calcium and vitamin D can prevent breast cancer,” she said.

To reach Alan Bavley, call (816) 234-4858 or send e-mail to abavley@kcstar.com.

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Copyright (c) 2006, The Kansas City Star, Mo.

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