Foods and beverages and colorectal cancer risk: a systematic review and meta-analysis of cohort studies, an update of the evidence of the WCRF-AICR Continuous Update Project.

OBJECTIVE: As part of the World Cancer Research Fund International Continuous Update Project, we updated the systematic review and meta-analysis of prospective studies to quantify the dose-response between foods and beverages intake and colorectal cancer risk. DATA SOURCES: PubMed and several databases up to May 31 st 2015. STUDY SELECTION: Prospective studies reporting adjusted relative risk estimates for the association of specific food groups and beverages and risk of colorectal, colon and rectal cancer. DATA SYNTHESIS: Dose-response meta-analyses using random effect models to estimate summary relative risks (RRs). RESULTS: Results: 400 individual study estimates from 111 unique cohort studies were included. Overall, the risk increase of colorectal cancer is 12% for each 100g/day increase of red and processed meat intake (95%CI=4-21%, I2 =70%, pheterogeneity (ph)<0.01) and 7% for 10 g/day increase of ethanol intake in alcoholic drinks (95%CI=5-9%, I2 =25%, ph =  0.21). Colorectal cancer risk decrease in 17% for each 90g/day increase of whole grains (95%CI=11-21%, I2 =0%, ph =  0.30, 6 studies). For each 400 g/day increase of dairy products intake (95%CI=10-17%, I2 =18%, ph =  0.27, 10 studies). Inverse associations were also observed for vegetables intake (RR per 100 g/day =0.98 (95%CI=0.96-0.99, I2 =0%, ph =  0.48, 11 studies) and for fish intake (RR for 100g/day=0.89(95%CI=0.80-0.99, I2 =0%, ph =  0.52, 11 studies), that were weak for vegetables and driven by one study for fish. Intakes of fruits, coffee, tea, cheese, poultry and legumes were not associated with colorectal cancer risk. CONCLUSIONS: Our results reinforce the evidence that high intake of red and processed meat and alcohol increase the risk of colorectal cancer. Milk and whole grains may have a protective role against colorectal cancer. The evidence for vegetables and fish was less convincing.