Calcium Intake Protects Against Cancer 

Calcium intake may protect against cancer, particularly gastrointestinal tract cancer, according to the results of a prospective study. Because people with diabetes are more prone to diabetes, it could be a positive approach to educate people the importance of calcium intake.

“Dairy food and calcium intakes have been hypothesized to play roles that differ among individual cancer sites, but the evidence has been limited and inconsistent,” write Yikyung Park, ScD, from the National Cancer Institute in Bethesda, Maryland, and colleagues. “Moreover, their effect on cancer in total is unclear.”

In the National Institutes of Health-AARP (formerly known as the American Association of Retired Persons) Diet and Health Study, the investigators evaluated the association of dairy food and calcium intakes with incidence of total cancer and cancer at individual sites. A food frequency questionnaire was used to determine intakes of dairy food and calcium from foods and supplements.

Linkage with state cancer registries allowed identification of incident cancer cases. Relative risks and 2-sided 95% confidence intervals (CIs) were determined with a Cox proportional hazard model.

During follow-up (average, 7 years), 36,965 cancer cases were identified in men and 16,605 in women. In men, calcium intake was not associated with total cancer. However, calcium intake was nonlinearly associated with total cancer in women, with the risk decreasing up to approximately 1300 mg/day but with no further risk reduction above those levels.

Dairy food and calcium intakes were inversely associated with cancers of the digestive system in both men and women. Multivariate relative risk for the highest quintile of total calcium vs the lowest was 0.84 in men (95% CI, 0.77 – 0.92) and 0.77 in women (95% CI, 0.69 – 0.91). This reduction in the risk for gastrointestinal tract cancer was especially prominent for colorectal cancer, and supplemental calcium intake was also inversely associated with the risk for colorectal cancer.

“Our study suggests that calcium intake is associated with a lower risk of total cancer and cancers of the digestive system, especially colorectal cancer,” the study authors write.

Limitations of this study include failure to examine whether associations with intakes of dairy food and calcium differed by tumor subtype or tumor aggressiveness of site-specific cancers, possible residual confounding by unknown or unmeasured risk factors, limited statistical power to examine an association for some low-incidence cancers, and diet evaluated only once at baseline.

“Nevertheless, our study is one of the first cohort studies to examine dairy food and calcium intakes in relation to total cancer as well as low-incidence cancers,” the study authors concluded. “Moreover, our prospective design avoids the recall and selection biases that can affect results from case-control studies.”

Practice Pearls:

• Current dietary guidelines recommend 1200 mg/day of calcium for adults 50 years and older and 3 cups per day of fat-free or low-fat dairy food according to the Institute of Medicine and the 2005 dietary guidelines for Americans, respectively.
• Calcium intake is associated with a lower risk for total cancer in women and cancers of the digestive system, especially colorectal cancer, in both men and women.

Arch Intern Med. Feb. 23,  2009;169:391-401.