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Title: Latest Evidence Links High-Fibre Diet With Reduced Colon Cancer Risk

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Lancet 2003;361:1491-95.
05/01/2003 07:01:00 PM
By Harvey McConnell

Consumption of dietary fibre, particularly from grains, cereals, and fruits, is associated with decreased risk of distal colon adenoma, according to the latest investigations in the United States and Europe. The US study is led by Dr Ulrike Peters and colleagues at the National Cancer Institute, Rockville, Maryland; the Connecticut School of Medicine, Farmington; University of Texas, MD Anderson Cancer Center, Houston; and University of Pittsburgh, Pennsylvania. It was carried out within the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, a randomised controlled trial designed to investigate methods for early detection of cancer. The researchers compared fibre intake among 33,971 members of the cohort who had sigmoidoscopy negative results for polyps, with 3,591 people who were found to have at least one histologically verified adenoma in the distal large bowel: descending colon, sigmoid colon, or rectum. More than 30 years ago, the late Dr Dennis Burkitt had noted the association of high dietary fibre intake with a low incidence of large bowel cancer in Africa. This current investigation was prompted by some recent studies suggesting no association between increased fibre intake and a reduced risk of colorectal cancer. Dr Peters and colleagues found that high intakes of dietary fibre were associated with a lower risk of colorectal adenoma, after adjustment for potential dietary and non-dietary risk factors. People in the highest quintile of dietary fibre intake had a 27% lower risk of adenoma than those in the lowest quintile. The inverse association was strongest for fibre from grains and cereals and from fruits. Risks were similar for advanced and non-advanced adenoma. Risk of rectal adenoma was not significantly associated with fibre intake. The protective association is independent of several dietary factors, including folate, a nutrient present in fruits and vegetables and which is of particular interest for colon carcinogenesis. "Nevertheless, fibre might also be a marker for unmeasured substances that have anti- carcinogenic effects and occur jointly with fibre, in particular fibre from fruits and grains," the clinicians said. The researchers conclude: "Whether fibre affects adenoma formation or subsequent persistence of the lesion (duration) is difficult to assess, however, finding an inverse association for small (non-advanced) adenoma suggests that high-fibre diet is protective from the earlier stages of adenoma formation." Similar results have been found in a large European study (see separate report).

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