Fish consumption and colorectal cancer risk: an evaluation based on a systematic review of epidemiologic evidence among the Japanese population

Objective: The association between fish consumption and colorectal cancer risk remains inconclusive. The present study systematically reviewed and meta-analyzed epidemiologic data on the association between fish consumption and colorectal cancer risk among Japanese.

Methods: Original data were obtained from MEDLINE searched using PubMed or from searches of the Ichushi database, complemented with manual searches. The associations were evaluated based on the strength of evidence, the magnitude of association and biologic plausibility. Meta-analysis was conducted according to the study design.

Results: Five cohort studies and 12 case-control studies were identified. Fish consumption was not significantly associated with colorectal, colon or rectal cancer risks. One cohort study showed a weak positive association with colorectal cancer, and another showed a weak inverse association with colon cancer in men and a moderate and weak inverse association with colon and rectal cancers in women. As regards case-control studies, four studies reported a weak inverse association, whereas one showed a weak positive association with colon cancer. Regarding rectal cancer, four case-control studies showed a weak inverse association, but two reported a weak-to-moderate positive association. The pooled relative risk/odds ratio (95% confidence interval) of colorectal cancer for the highest versus lowest category of fish consumption was 1.03 (0.89-1.18) and 0.84 (0.75-0.94) for cohort and case-control studies, respectively.

Conclusions: There was insufficient evidence to support an association between fish consumption and the risk of colorectal cancer among Japanese.