NEW YORK (Reuters Health) - In the Calcium Polyp Prevention Study, calcium supplementation reduced the risk of recurrent colorectal adenomas -- growths or polyps that can become cancerous - only in men with a low dietary ratio of calcium to magnesium.

"These results mean that designing a personalized diet/supplementation regimen that takes the ratio of both nutrients into account may be better than supplementing with only one or the other alone," Dr. Qi Dai from Vanderbilt University in Nashville told the American Association for Cancer Research's Seventh Annual International Conference on Frontiers in Cancer Prevention Research in Washington, D.C.

Calcium supplementation has been shown to inhibit the development of colorectal cancer although high calcium may simultaneously prevent the body from absorbing magnesium.

The Calcium Polyp Prevention Study tested whether calcium supplementation (1,000 milligrams daily for 4 years) could prevent colorectal adenoma recurrence. The study involved 930 men.

Dai and colleagues found that the dietary ratios of calcium to magnesium intake modified the effect of calcium treatment on adenoma recurrence.

According to the investigators, calcium supplementation reduced the risk of adenoma recurrence only if the dietary ratio of calcium to magnesium intake was low before treatment and remained low during treatment.

The risk of colorectal adenoma recurrence was reduced by 32 percent among men with baseline calcium to magnesium ratio below the median in comparison to no reduction at all for those above the median.

"These findings, if confirmed, may provide a new avenue for the personalized prevention of colorectal cancer," Dai and colleagues conclude.