Inconsistent findings from observational studies have continued the controversy over the effects of dietary fiber on colorectal cancer.
Dr Yikyung Park evaluated the association between dietary fiber intake and risk of colorectal cancer.
The researchers assessed 13 prospective cohort studies included in the Pooling Project of Prospective Studies of Diet and Cancer.
There were 725,628 men and women followed up for 6 to 20 years across studies.
Study- and sex-specific relative risks were estimated with the Cox proportional hazards model and were subsequently pooled using a random-effects model.
The main outcome measure was incident colorectal cancer.
During 6 to 20 years of follow-up across studies, 8081 colorectal cancer cases were identified.
|The relative risk for 30 or more g/d was 1|
|Journal of the American Medical Association|
The team compared the highest versus lowest study- and sex-specific quintile of dietary fiber intake.
A significant inverse association was found in the age-adjusted model.
However, the team observed that the association was attenuated and no longer statistically significant after adjusting for other risk factors.
In categorical analyses compared with dietary fiber intake of 10 to less than 15 g/d, the pooled multivariate relative risk was 1.2 for less than 10 g/d.
The researchers found that for 30 or more g/d the relative risk was 1.
Fiber intake from cereals, fruits, and vegetables was not associated with risk of colorectal cancer.
The pooled multivariate relative risks comparing the highest vs lowest study- and sex-specific quintile of dietary fiber intake were 1 for colon cancer.
The team noted that the relative risks comparing the highest vs lowest study- and sex-specific quintile of dietary fiber was 0.85 for rectal cancer.
Dr Park's team concluded, “In this large pooled analysis, dietary fiber intake was inversely associated with risk of colorectal cancer in age-adjusted analyses.”
“However, after accounting for other dietary risk factors, high dietary fiber intake was not associated with a reduced risk of colorectal cancer.”