According to a new study, calcium from diet and supplements is associated with reduced risk of colorectal cancer in a prospective cohort of women.

"We investigated the association between calcium intake and colorectal cancer in a prospective cohort of 45,354 women without a history of colorectal cancer who successfully completed a 62-item National Cancer Institute/Block food-frequency questionnaire. Women were followed for an average of 8.5 years, during which time 482 subjects developed colorectal cancer. We used Cox proportional hazards models, with age as the underlying time metric, to estimate risk of colorectal cancer," scientists in the U.S. report.

"Cut points between quintiles of energy-adjusted dietary calcium were 412, 529, 656 and 831mg/day," said Andrew Flood and collaborators at the University of Minnesota and the National Cancer Institute. "We created categories for calcium from supplements as follows: 0mg/day (n=25,441), 0 to 400mg/day (n=9,452), 401 to 800mg/day (n=4,176), and >800mg/day (n =6,285). Risk ratios and confidence intervals (95% CI) for increasing quintiles of dietary calcium relative to the lowest quintile were 0.79 (0.60-1.04), 0.77 (0.59-1.02), 0.78 (0.60-1.03), and 0.74 (0.56-0.98)(p=0.05)."

"For increasing categories of calcium from supplements, the risk ratios (and 95% CI) relative to no supplement use were 1.08 (0.87-1.34), 0.96 (0.70-1.32) and 0.76 (0.56-1.02)(p=0.09)," reported Flood and his colleagues. "Simultaneously high consumption of calcium from diet and calcium from supplements resulted in even further risk reduction, RR=0.54 (95% CI, 0.37-0.79) compared with low consumption of both sources of calcium. These data indicate that a difference of <400 to >800mg of calcium per day was associated with an approximately 25% reduction in risk of colorectal cancer, and this reduction in risk occurred regardless of the source of the calcium (i.e., diet or supplements)."

Flood and his coauthors published their study in Cancer Epidemiology Biomarkers and Prevention (“Calcium from Diet and Supplements is Associated with Reduced Risk of Colorectal Cancer in a Prospective Cohort of Women.” Cancer Epidem Biomarker Prev, 2005;14(1):126-132).

For additional information, contact Andrew Flood, Division of Epidemiology, University of Minnesota, 1300 South Second Street, Suite 300, Minneapolis, MN 55454.