The association of calcium and vitamin D, and colon and rectal cancer in Wisconsin women

Background Calcium and vitamin D have been hypothesized to reduce colorectal cancer risk. Epidemiological evidence, however, is mixed. Methods To explore those relationships, data were collected as part of a population-based, case-control study of colorectal cancer in Wisconsin women (678 controls, 348 colon and 164 rectal cancer cases). A semi-quantitative food frequency questionnaire was used to ascertain food and dietary supplement intake 2 years prior to interview. Logistic regression models were used to calculate odds ratios (OR). Results Higher levels of calcium intake were associated with reduced colon and rectal cancer risk. The following adjusted OR and 95% confidence intervals (CI) were observed, comparing the fifth quintile (based on control intake) with the first: colon cancer: OR = 0.6, 95% CI:0.4-1.0, P-trend: 0.03; rectal cancer: OR = 0.6, 95% CI:0.3-1.1, P-trend: 0.07. Similar relationships were observed for vitamin D intake, although OR were closer to the null value and did not always behave in a step-wise fashion (fifth quintile versus the first-colon cancer: OR = 0.7, 95% CI: 0.4-1.1, P-trend: 0.05; rectal cancer: OR = 0.8, 95% CI : 0.5-1.5, P-trend: 0.42). Conclusion These data support a protective association of calcium on colon and rectal canter risk.