Can dietary fiber help prevent colorectal cancer ?

The issue of whether dietary fiber can help prevent colorectal cancer has always been unclear, as studies have reached inconsistent results. Now a study from the Journal of the National Cancer Institute (Volume 102, page 614) suggests that the type of dietary assessment tools used in these studies might be to blame.

Researchers in the United Kingdom compared data from 579 people who developed colorectal cancer and 1,996 people who did not develop colorectal cancer. Some of the participants kept four-or seven-day food diaries in which they recorded what they ate, and others filled out a food frequency questionnaire detailing their usual diet.

In the food diary group, people who consumed 24 g of dietary fiber per day had a 30% lower risk of colorectal cancer than those who ate 10 g per day. This association remained even after the researchers adjusted for other risk factors such as age, physical activity, alcohol intake, and red meat consumption. However, the same analysis performed on the food frequency questionnaires did not find the same association.

Take-away message. Since food diaries are thought to be more accurate than food frequency questionnaires, this study supports the idea that higher dietary fiber intake can reduce colorectal cancer risk. Other studies using different parameters and assessment tools, such as food frequency questionnaires, may have reached inaccurate or inconclusive results.