Selected Dietary Micronutrients and the Risk of Right- and Left-Sided Colorectal Cancers: A Case-Control Study in Western Australia

PurposeContradictory results about the role of dietary factors in the causation of colorectal cancer (CRC) may partly be due to failure to discriminate between left- and right-sided CRC.MethodsWe undertook a population-based case-control study comparing 577 cases of left-sided CRC and 277 cases of right-sided CRC (n = 277) with 958 age- and sex-matched controls. Dietary exposure was measured using a food frequency questionnaire. Odds ratios (OR) were calculated across quintiles of dietary intakes of micronutrients, adjusting for potential confounders.ResultsCompared to those in the lowest quartiles of intake, we found a protective role of phosphorus on CRC particularly for right-sided cancers (Q5 OR = 0.66, 95% confidence interval [CI]: 0.52–1.02) and protective associations for iron and zinc were observed with left-sided cancers (Q5 OR = 0.78, 95% CI: 0.56–1.09 and Q5 OR = 0.65, 95% CI: 0.46–0.92, respectively). An increased risk of left-sided cancer, was observed for vitamin E (Q5 OR = 1.37, 95% CI: 0.97–1.96).ConclusionsAn increased risk of CRC was observed for vitamin E and decreased risks were seen for phosphorus, iron, and zinc. Differences in the risk of developing CRC according to subsite were observed for phosphorus and vitamin E.