Women with higher intake of calcium appear to have a lower risk of cancer overall, and both men and women with high calcium intakes have lower risks of colorectal cancer and other cancers of the digestive system, according to a report in the February 23 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.
Calcium is known to benefit bone health, according to background information in the article. Because of this, the Institute of Medicine recommends 1,200 milligrams of calcium for adults age 50 and older, and the 2005 dietary guidelines for Americans recommend 3 cups per day of low-fat or fat-free dairy products. Studies of dairy products, calcium intake and cancer have revealed different results for different cancer sites.
Yikyung Park, Sc.D., of the National Cancer Institute, Bethesda, Md., and colleagues analyzed data from 293,907 men and 198,903 women who participated in the National Institutes of Health-AARP Diet and Health Study. Participants took a food frequency questionnaire when they enrolled in the study between 1995 and 1996, reporting how much and how often they consumed dairy and a wide variety of other foods and whether they took supplements. Their records were then linked with state cancer registries to identify new cases of cancer through 2003.
Over an average of 7 years of follow-up, 36,965 cancer cases were identified in men and 16,605 in women. Calcium intake was not associated with total cancer in men but was in women—the risk decreased in women with intake of up to 1,300 milligrams per day, after which no further risk reduction was observed.
"In both men and women, dairy food and calcium intakes were inversely associated with cancers of the digestive system," the authors write. The one-fifth of men who consumed the most calcium through food and supplements (about 1,530 milligrams per day) had a 16 percent lower risk of these types of cancer than the one-fifth who consumed the least (526 milligrams per day). For women, those in the top one-fifth of calcium consumption (1,881 milligrams per day) had a 23 percent lower risk than those in the bottom one-fifth (494 milligrams per day). The decreased risk was particularly pronounced for colorectal cancer. Calcium and dairy food intake was not associated with prostate cancer, breast cancer or cancer in any other anatomical system besides the digestive system.
"Dairy food, which is relatively high in potentially anticarcinogenic nutrients such as calcium, vitamin D and conjugated linoleic acid, has been postulated to protect against the development of colorectal and breast cancer," the authors write. Calcium has been shown to reduce abnormal growth and induce normal turnover among cells in the gastrointestinal tract and breast. In addition, it binds to bile and fatty acids, potentially reducing damage to the mucous membrane in the large intestine.
"In conclusion, our findings suggest that calcium intake consistent with current recommendations is associated with a lower risk of total cancer in women and cancers of the digestive system, especially colorectal cancer, in both men and women," the authors write.
(Arch Intern Med. 2009;169:391-401. Available pre-embargo to the media at www.jamamedia.org.)
Editor's Note: The study was funded by the Intramural Research Program of the National Cancer Institute, National Institutes of Health. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.
Archives of Internal Medicine