Hard evidence on dietary fibre?

Findings from a massive European-based study published in this week's The Lancet (2003; 361: 1496-501)​​ suggest that a high fibre diet could considerably protect us against against colorectal cancer. The results dispute a mounting body of evidence that maintains dietary fibre has no such protective effect against colorectal cancer.

Researchers participating in the extensive study were reported as saying that people surveyed in previous studies were probably not eating enough fibre to show an effect on disease risk.

Sheila Bingham, head of the diet and cancer group at the British Medical Research Council's Dunn Human Nutrition Unit in Cambridge, England, was cited as saying that the research was the biggest study done on diet and cancer, and it suggested that if people who ate less than the recommended five portions of fruit and vegetables a day doubled their intake of fibre the risk of bowel cancer could be greatly reduced by 40 per cent.

Researchers from all over Europe examined the association between dietary fibre intake and incidence of colorectal cancer in 519 978 individuals aged 25-70 years taking part in the EPIC study, recruited from ten European countries. Participants completed a dietary questionnaire in 1992-98 and were followed up for cancer incidence.

Relative risk estimates were obtained from fibre intake, categorised by sex-specific, cohort-wide quintiles, and from linear models relating the hazard ratio to fibre intake expressed as a continuous variable.

The scientists report in The Lancet​ that they found dietary fibre in foods was inversely related to the incidence of large bowel cancer (adjusted relative risk 0·75 [95 per cent CI 0·59-0·95] for the highest versus lowest quintile of intake), the protective effect being greatest for the left side of the colon, and least for the rectum.

After calibration with more detailed dietary data, the adjusted relative risk for the highest versus lowest quintile of fibre from food intake was 0·58 (0·41-0·85). No food source of fibre was significantly more protective than others, and non-food supplement sources of fibre were not investigated, continue the scientists.

The findings, claim the researchers, indicate that people with a low average intake of dietary fibre could reduce the risk of colorectal cancer by a massive 40 per cent by simply doubling their total fibre intake from foods. Persuasive figures indeed.