For every 100 milligram increase in intake of the mineral, the risk of colorectal cancer decreased by 12%, according to findings published in the American Journal of Clinical Nutrition.

However, the results were limited to overweight people, said the researchers, and may be related to effects of magnesium on insulin resistance and responses, which are thought to play a role in the development of tumors.

“The postulated role of magnesium in the causation of type-2 diabetes and increased risk of colorectal cancer seen in type 2 diabetes patients lend additional support for this mechanism.”

Diet

Dietary sources of magnesium include green, leafy vegetables, meats, starches, grains and nuts, and milk. Earlier dietary surveys show that a large portion of adults does not meet the RDA for magnesium (320 mg per day for women and 420 mg per day for men).

Recently, scientists from the Karolinska Institutet in Stockholm, Sweden reported that, data pooled from seven prospective studies revealed that, for every 100 mg per day increase in magnesium intake, the risk of stroke was reduced by about 9% (American Journal of Clinical Nutrition).

Colorectal cancer

The researchers analyzed data from a case-control study on benign colorectal tumors (adenomas) involving 768 cases and 709 control subjects. They also performed a meta-analysis of three colorectal adenoma studies and six colorectal cancer studies.

Results from the case-control study indicated that, for every 100 mg increase in magnesium intake, the risk of adenoma decreased by 19%, but only for overweight people over the age of 55.

In the meta-analysis, every 100 mg increase was associated with a 13% decrease in the risk of adenoma, and a 12% decrease in the risk colorectal cancer.

Limitations

Commenting on their findings, the researcher cautioned that there is only a small number of studies on the topic of magnesium and colorectal cancer, but the meta-analysis and case-control data indicated that the “consumption of magnesium-rich foods may be a new avenue to explore further in the search for cancer-prevention strategies”.

Source: American Journal of Clinical Nutrition
Published online ahead of print, doi: 10.3945/ajcn.111.030924
“Magnesium intake and colorectal tumor risk: a case-control study and meta-analysis”
Authors: P.A. Wark, R. Lau, T. Norat, E. Kampman