Dietary Fibre, Whole Grains, And Risk Of Colorectal Cancer: Systematic Review And Dose-Response Meta-Analysis Of Prospective Studies, British Medical Journal, November 2011
"A high intake of dietary fibre, in particular cereal fibre and whole grains, was associated with a reduced risk of colorectal cancer."Interesting ... Fruits, vegetables, and beans were not as protective as whole grains:
"Our meta-analysis supports an inverse association between intake of dietary fibre, cereal fibre, and whole grains and risk of colorectal cancer, but we found no significant evidence for an association with intake of fibre from fruit, vegetables, or legumes."How much:
"Our results indicate a 10% reduction in risk of colorectal cancer for each 10 g/day intake of total dietary fibre and cereal fibre and a about a 20% reduction for each three servings (90 g/day) of whole grain daily, and further reductions with higher intake."What kind:
"Total whole grains included whole grain rye breads, whole grain breads, oatmeal, whole grain cereals, high fibre cereals, brown rice, and porridge."Dagfinn Aune, lead study author:
"The more of this fibre you eat the better it is. Even moderate amounts have some effect."That same BBC article said:
- Fibre And Whole Grains 'Reduce Bowel Cancer Risk,' BBC, November 10, 2011
"The lifetime risk of being diagnosed with colorectal cancer in the UK is estimated to be one in 14 (6.9%) for men, and one in 19 for women (5.4%)."Wow, those are some risks.
Update, November 17:
I'm adding a graph from the study and an excerpt from their "Mechanisms" paragraph. The graph shows a statistically significant and linear inverse association ... as fiber intake went up, cancer risk went down.
"... may decrease the risk of colorectal cancer by increasing stool bulk, diluting faecal carcinogens, and decreasing transit time, thus reducing the contact between carcinogens and the lining of the colorectum. In addition, bacterial fermentation of fibre results in the production of short chain fatty acids, which may have protective effects against colorectal cancer."These mechanisms aren't new to this blog, e.g. transit time and dilution. The interaction of fiber with colonic bacteria is notable. I saw this benefit with resistant starch too. (See Resistant Starch May Reduce Risk Of Colon Cancer.) Resistant starch isn't fiber per se; it's a vegetable starch that fails to get digested and ends up in the colon where bacteria feed upon it. I've written about it here.