Calcium is usually linked to bone health. But a new study suggests it also has a role in preventing cancer, at least among women.

Summary

Calcium is important in bone health. A new survey shows that women who have a high intake of calcium have a lowered risk of cancer overall. And both men and women with high calcium intake have a reduced risk of certain types of digestive system cancers. It may be calcium itself, or other substances in calcium-rich dairy foods, which confer this protective effect.

Introduction

A high calcium intake though dairy foods and/or supplements is important in maintaining bone health, particularly as we get older and at higher risk of osteoporosis. Calcium is also important in reducing the risk of high blood pressure. Therefore, an intake of 1,200 milligrams a day is recommended which is obtainable through three cups a day of low-fat or fat-free dairy products. Previous research has suggested that maybe calcium can also protect against cancer, but results have been conflicting. The present study was therefore set up to uncover any such link.

What was done

Dr Yikyung Park and his colleagues at the National Cancer Institute analyzed data from nearly 300,000 men and nearly 200,000 women, all of whom were participants in the National Institutes of Health-AARP Diet and Health Study. They filled in a food frequency questionnaire, recording their intake of dairy, and other, foods, as well as any consumption of food supplements. This data was linked to the national cancer registry records of new cases of cancer.

What was found

Over an average of seven years follow up, there were 36,965 new cancer cases among the men and 16,605 among the women. In men, calcium intake was not linked to total cancer incidence. In women, incidence decreased with intakes of up to 1,300 milligrams per day. The men consuming the most calcium through food and supplements - up to 1,530 milligrams a day - had a 16 percent reduced risk of digestive cancer compared to those consuming the least calcium, at about 500 milligrams a day. For women, a similar effect was observed. The decrease in risk was most pronounced when it came to colorectal cancer. No effect of calcium was found for breast, prostate or any other kind of cancer except digestive.

What this study means

Calcium itself is known to reduce abnormal growth of cells of the gastrointestinal tract and the breast. It also binds onto bile and fatty acids which could otherwise damage the membrane of the large intestine. Dairy foods also contain vitamin D and conjugated linoleic acid and there is some evidence that they can protect against cancer too. Therefore, ensuring an adequate calcium intake may have added benefit to health over and above keeping the bones in good condition.

Source

Dairy food, calcium, and risk of cancer in the NIH-AARP diet and health study Archives of Internal Medicine Y. Park,  et al, Archives of Internal Medicine, February 2009, vol. 169, pp. 391--401