A new study has determined that in order for calcium to have protective effects against colon cancer it may need to be combined with magnesium.
Past studies have linked both high magnesium and calcium levels to a reduced risk of colon cancer. However, researchers also have found that high calcium levels inhibit the absorption of magnesium, which may explain why, even though Americans have high calcium intake, they also have a higher incidence of colorectal cancer. Based on the results of a new study, researchers are beginning to believe that it’s the calcium to magnesium ratio that may offer an explanation for this occurrence.
In the new double-blind, placebo-controlled, randomized trial, presented at the Seventh Annual American Association for Cancer Research International Conference on Frontiers in Cancer Prevention Research, Vanderbilt University researchers gave 930 subjects 1,000 mg of calcium supplementation for 4 years. Participants underwent two follow-up colonoscopies, 1 year and 4 years after the study’s start to determine the incidence of colorectal cancer recurrence in the subjects. A validated food frequency questionnaire was given at study entry and year 4 to obtain information about the subjects’ usual diet over the previous year.
The study found that calcium supplementation reduced the risk of cancer recurrence only if the ratio of calcium to magnesium was low, and remained low during the intervention period. The researchers found that the risk of colorectal cancer recurrence was reduced by 32 percent among subjects with baseline calcium to magnesium ratio below the median. In subjects where this ratio was above the median, there was no reduction in the risk of colorectal cancer recurrence.
In summarizing the results, the study authors wrote, “We found that calcium supplementation reduced the risk of adenomas only among subjects with a low calcium:magnesium intake ratio. These findings, if confirmed, may provide a new avenue for the personalized prevention of colorectal cancer.”
Reference:
Dai Q, Baron J. Magnesium, calcium, and colorectal adenoma recurrence: Results from a randomized trial. Seventh Annual American Association for Cancer Research International Conference on Frontiers in Cancer Prevention Research, November 16 – 19, 2008, Abstract A62.