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Vitamin D May Protect Against Cancer

Researchers Say Supplements May Help Cut Risk of Breast, Colon Tumors
WebMD Health News
Reviewed by Louise Chang, MD

April 4, 2006 (Washington) -- At least half of American adults suffer from vitamin D deficiencies that place them at increased risk of cancer, researchers report.

The research suggests that taking at least 1,000 international units (IU) of vitamin D daily can slash the risk of breast, colon, and other cancers, says Cedric Garland, DrPH, of the University of California, San Diego.

His new study, presented here at the annual meeting of the American Association for Cancer Research, suggests that increasing intake of vitamin D can lower the chance of developing breast cancer by 10% to 50%.

Other research, also presented at the cancer meeting, suggests that consuming adequate amounts of vitamin D during adolescence and young adulthood is particularly important for lowering breast cancer risk.

Yet another study, also out today, suggests that consuming 1,500 IU of vitamin D can cut a man's risk of developing any cancer by almost one-fifth. Advances Against Colon CancerAdvances Against Colon Cancer

Diet Alone Doesn't Do the Job

Current recommendations call for people between the ages of 1 and 50 to consume 200 IU of vitamin D daily, with 400 IU recommended for those between the ages of 51 and 70. After age 70, 600 IU of vitamin D are recommended each day.

But given widespread vitamin D deficiency, those recommendations are way too low, Garland tells WebMD.

It's nearly impossible to get enough vitamin D in your diet alone, Garland says. An 8-ounce glass of milk contains only 100 IU of vitamin D. A serving of cereal has 20 IU.

By comparison, someone who spends 10 to 15 minutes in the sun on a sunny day without sunscreen can absorb 2,000 to 5,000 IU of vitamin D if 40% of the body is exposed, he says.

But come winter, supplements are really the only way to go, he says.

The Role of Supplements

Not all vitamin D supplements are created equal, Garland says.

Most use an old form -- D-2 -- that is far less potent than the more desirable D-3. Multivitamins typically contain only small amounts of D-2 and include vitamin A, which offsets many of vitamin D's benefits, he tells WebMD.

"It may be hard to find and expensive to find it, but you want to take vitamin D-3," Garland says. At the same time, researchers warn against taking large amounts of vitamin D without medical supervision. High doses can cause some side effects, including a dangerous buildup of calcium in the blood.

Garland's new analysis looked at breast cancer rates and vitamin D levels in 1,760 women. The women were divided into five groups depending on their blood levels of vitamin D.

Results showed that women with the highest blood levels of vitamin D were 50% less likely to develop breast cancer than those with the lowest levels. But very few women achieved that.

But even women in the second lowest quintile were 10% less likely to develop breast cancer than those with the lowest levels.

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