Background and aims: To assess the relationships between food intake and colorectal cancer risk.
Methods: Systematic review of available prospective studies on dietary intake and colorectal cancer.
Results: Twelve out of 15 studies found no significant relationship between vegetable intake and colorectal cancer risk; also, 11 out of 14 studies found no relationship with fruit consumption. Conversely, the combined consumption of vegetables and fruit reduced colorectal cancer risk in three out of six studies, although the relationship was somewhat inconsistent between genders and anatomical localizations. Most studies found no relationship between cancer risk and red meat (15 in 20) or processed meat (seven out of 11) consumption; still, most of the reported relative risks were above unity, suggesting that high consumption of red or processed meat might increase colorectal cancer risk. The consumption of white meat, fish/seafood, dairy products, coffee or tea was mostly unrelated to colorectal cancer risk, although the consumption of smoked or salted fish actually increased risk.
Conclusions: The relationships between dietary intake and colorectal cancer risk might be less important than previously reported. The combined consumption of vegetables and fruit might be protective, whereas excessive consumption of meat or smoked/salted/processed food appears to be deleterious.