Fruit, vegetable intake linked to reduced colorectal cancer risk
MedWire News: Results from a meta-analysis suggest that increasing the amount of fruit and vegetables in the diet may reduce the risk for developing colorectal cancer, especially among individuals with a low level of intake.
"Although some caution is needed in interpreting the exact quantities and size of the risk estimates… our results indicate that there is a low threshold level of between 100 and 200 g/day that can reduce risk about 10%," say Dagfinn Aune (Imperial College London, UK) and co-authors.
The researchers identified 19 prospective studies reporting relative risk (RR) estimates of colorectal cancer associated with fruit and vegetable intake, providing evidence published up to May 2010.
Pooling data from 11 cohort studies to include 11,853 cases, the RR of developing colorectal cancer was 0.92 when looking at high versus low intake of both fruits and vegetables, calculated from the upper and lower ranges for intake in the studies.
Comparison of high versus low intake of fruit only (14 studies with 14,876 cases) revealed a significant inverse association with colorectal cancer (RR=0.90). Similar findings were observed for vegetable intake only (16 studies with 16,057 cases), with a corresponding RR of 0.91.
Linear dose-response analysis showed that intake of only vegetables was significantly associated with colorectal cancer risk per 100 g/day (RR=0.98). However, significant inverse associations emerged when the team used nonlinear models for fruits and vegetables.
Indeed, the analysis showed that most of the reduction in risk occurred when fruit intake was increased up to about 100 g per day. Higher intakes of fruit were associated with a further, but more modest decrease in colorectal cancer risk. Similarly, the greatest reduction in risk occurred with vegetable intakes between 100 and 200 g per day, with little evidence of a further reduction with higher intakes.
Importantly, the team found that the greatest reduction in colorectal cancer risk occurred when fruit and vegetable intake increased from very low initial levels.
Commenting on the findings, the team says that targeting individuals and populations with a low fruit and vegetable intake might be most effective for colorectal cancer prevention.
Writing in the journal Gastroenterology, the researchers conclude: "Further cohort studies are warranted to investigate specific types of fruit and vegetables, the impact of measurement errors on estimates, whether similar associations are found in non-White populations, and using biomarkers of fruit and vegetable intake."
By Ingrid Grasmo