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Colorectal cancer: calcium a key?

The prevention of colorectal cancer may rely on a twist on one of its possible causes--diet.

The cancer, which caused 60,000 U.S. deaths in 1985, has been linked to a high-fat diet. Now an analysis of people with early signs of colorectal cancer shows that calcium supplementation can return rapidly proliferating cells to normal within two or three months.

But the researchers who did the study, Martin Lipkin and Harold Newmark of Memorial Sloan-Kettering Cancer Center in New York City, caution that the work needs further verification before people start taking calcium en masse.

Lipkin and Newmark studied colon cells removed by biopsy from 10 people at high risk of colorectal cancer because of a positive family history. They found that the cells were dividing more rapidly than normal.

But within two to three months of starting calcium supplementation, new biopsies showed the cells looking more like cells from people at low risk of developing colorectal cancer. "The change is in the direction of healthy cells," says Newmark.

The current study shows that calcium supplementation -- in this case, 1.25 grams a day, about 1.5 times the recommended daily allowance -- can actually reverse an abnormal proliferative state, the researchers report in the Nov. 28 NEW ENGLAND JOURNAL OF MEDICINE.

The calcium connection has long been suspected. Colorectal cancer incidence is higher than normal among people drinking soft water, which is low in calcium (SN:9/21/85, p. 187), and people eating diets high in calcium and vitamin D have a lower-than-normal incidence of the cancer (SN:3/2/85, p. 141).

Previous work in animal systems showed that calcium binds fatty acids and bile acids, which are thought to induce cell proliferation. It may also inhibit cell proliferation directly, Newmark says.

While calcium in this dose range is not thought to have any ill effects, and is thought to limit hypertension and osteoporosis, larger studies are needed to see if the results hold and if there are any unexpected drawbacks to calcium supplementation, Newmark says.

Comments Cedric Garland of the University of California at San Diego, who has shown an epidemiologic link between colorectal cancer and low calcium intake, "It's a lot closer [to being proven], but it's still something we have to pursue a little more before we're positive. I think it shows we're absolutely on the right track."
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Author:Silberner, Joanne
Publication:Science News
Date:Dec 7, 1985
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