The supposed colon cancer-preventing benefits of calcium and vitamin D supplements have been negated in a recent study in the New England Journal of Medicine.

The study details results of a 2,259-person study from 11 academic medical centers demonstrating that dietary supplementation with vitamin D and/or calcium after removal of pre-cancerous colorectal adenomas (aka polyps) does not reduce risk of developing future adenomas. Despite promising findings in models of the disease and in previous, smaller trials, the study offers strong evidence against the usefulness of these supplements in the prevention of future polyps.

Dennis J. Ahnen, MD, investigator at the University of Colorado Cancer Center and professor of gastroenterology at the Denver VA Medical Center, one of the paper’s co-authors, says:

“After a patient has colonic polyps removed it would be great to be able to offer a way for that patient to reduce his or her risk of developing future polyps or colorectal cancer. Unfortunately, this trial shows that taking vitamin D or calcium is probably not very useful in this setting."

In laboratory studies, vitamin D has been shown to slow the growth of cancer cells through inhibiting the growth of new blood vessels required to feed a cancer’s growth, and also by directly causing the death of cancer cells. In addition, vitamin D supplementation in mouse models of cancer lower the risk of developing the disease.

“This shows that what works in a dish and even what works in animal models doesn’t always work in humans,” Ahnen says.

The Similar was true of calcium supplementation. In population studies, people with higher calcium intake have lower incidence of colorectal cancer, and previous, smaller human trials have shown promise for calcium in the prevention of colorectal cancer.

“More work is required,” says Ahnen. “But at least in this setting, at this dose, with this population and measuring these outcomes, vitamin D and calcium supplementation did not appear useful."

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