One expert said the study is an important one. "This is the first paper looking at calcium, dairy products and all cancers combined," said Marji McCullough, strategic director of nutritional epidemiology at the American Cancer Society. The findings, she said, "were consistent with the previous literature."
For example, a controlled trial reported last year found no protective effect of calcium intake against breast cancer. The new report confirms that finding, and also finds that the nutrient offers no protective effect against prostate cancer.
The NCI study results "are consistent with guidelines for a healthy diet," McCullough said. "But it is important for people to understand that they shouldn't go overboard on calcium."
No additional protective effect was found for calcium intakes greater than 1,300 milligrams a day, according to the NCI study.
Current calcium recommendations are best met by dietary sources rather than supplements, McCullough added, in part because diet offers more than just calcium. "Calcium and vitamin D and are highly correlated in the diet, and it is difficult to isolate a single component," she said. "It may be that a combination of nutrients is important."
The combination of calcium of vitamin D is important, since vitamin D facilitates calcium's absorption by the digestive system. The skin makes vitamin D naturally through exposure to sunlight.
Another report in the same issue of the journal finds that that a combination of vitamins B6, B12 and folic acid appears to reduce the risk among women of age-related macular degeneration, a major cause of vision loss for older Americans.
A controlled trial including more than 5,400 women 40 and older found a 34 percent lower incidence of the eye disorder in women taking the vitamins compared to those taking an inactive placebo, said the report by researchers at Harvard Medical
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