Study: Vitamin D Reduces Cancer Risk

The researchers intended to check mainly for the effects of calcium on bone health. Their interest in cancer risk was secondary.

But the lower cancer risk stood out. Only 13 women, or 3 percent, developed cancer over four years of calcium and vitamin D supplements. With calcium alone, 17 women, or 4 percent, got cancer. With dummy pills, cancer appeared in 20 women, or 7 percent.

That shows a 60 percent lower cancer risk over four years in the group taking both supplements, compared to patients taking placebos. And when the first-year cancers were excluded _ the ones mostly likely present before the study began _ the findings were stronger still: a 77 percent lower risk for the combo group.

While the calcium-only group lowered its four-year cancer risk by 47 percent compared to the untreated group, it did no better when early cancers were excluded. That suggests calcium alone may have done little in this experiment, the researchers said.

Experts reviewing the study focused on vitamin D as the powerful agent in the combo group, but it can't be ruled out that calcium might somehow amplify the effect of vitamin D.

While numbers were limited, these women developed a broad range of cancers, including disease of the breast, colon, lungs and blood. Dr. Michael Holick, of Boston University Medical Center, who sat on the professional panel that issued the 1997 guidelines for vitamin D, said this study shows that enough vitamin D "markedly reduces the risk of developing the most serious deadly cancers."

He supports raising the recommended amount of the vitamin and said 1,000 daily units of vitamin D3 would now be reasonable for most people.

On the other hand, Dr. Michael Thun of the American Cancer Society favors keeping the current recommendation of 200 to 600 IUs for now. And he cautioned that more than 2,000 units is viewed in the guidelines as potentially dangerous.

Joan Lappe, the study's lead researcher, said it "just adds to the great bunch of evidence that we need to have better vitamin D nutrition." Some foods carry the vitamin, like salmon, tuna and fortified milk, but diet accounts for little of the vitamin circulating in the body. Overexposure to the sun can cause skin cancer.

Still, people should consult their doctors before boosting their vitamin dosage, several experts also warned.

More study is needed to determine if the effects in this study hold true for large groups of people and men as well as women.

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On the Net:

Vitamin D fact sheet:

http://dietary-supplements.info.nih.gov/factsheets/vitamind.aspbold_off

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EDITOR'S NOTE _ Timberly Ross reported from Omaha. Jeff Donn reported from Boston.