April 21/Washington/The Hamilton Spectator -- Researchers at the Ponce School of Medicine in Puerto Rico reported that women who took calcium had a 40% lower risk of getting breast cancer, while those getting multivitamins showed a 30% reduction in risk.
The new findings, from a study of 744 women, were presented at a meeting of the American Association for Cancer Research in Washington.
The data contradicts results of a December 2008 trial that showed no reduction in cancer risk from vitamin supplements.
The scientists attributed the calcium benefit seen in the study to its effect on what they called DNA repair capacity -- the biological process by which cells patch up damaged DNA that otherwise may cause cancer.
The report suggests women may boost their cellular defences with dietary changes and long-term use of supplements, they said.
"The importance of this finding is that now we can monitor breast-cancer risk using DNA repair capacity," said Manuel Bayona, a professor of biostatistics and epidemiology at Ponce School of Medicine and an author of the paper.
"We believe that all women should be taking vitamins and supplements. Now we can tell if that regimen is really doing its work in reducing the risk."
A good analogy, Bayona said, is the management of heart disease. Just as doctors track patients' cholesterol and modify it with changes in diet or drugs, they could use blood tests to monitor the DNA repair ability of women at elevated risk for breast cancer and tweak it using dietary supplements.
A previous study in June 2007 in the American Journal of Clinical Nutrition found that women taking calcium and vitamin D showed a 60% reduction in cancer risk.
The relationship between vitamin supplements and cancer risk is more complicated.
Vitamins prevent and repair the cancer-causing damage done by free radicals, the highly reactive atoms that can wreak havoc on cells, according to Jaime Matta, a professor of pharmacology and toxicology at Ponce School of Medicine and a study coauthor.
However, recent research suggests that vitamin supplements have no protective power against cancer.
One study of 7,627 women in the Journal of the National Cancer Institute in 2008 found that women who took vitamins C and E and beta carotene had the same risk of cancer diagnosis and death as those who did not.
Research published in the Journal of the American Medical Association in 2009 showed that vitamin E may raise the risk of prostate cancer.
The new study was funded by the National Cancer Institute and the National Institutes of Health.
In followup research, Bayona and his fellow scientists will try to find the ideal daily vitamin regimen for women of varied ages.
From the April 26, 2010, Prepared Foods E-dition