Dietary fibre may not prevent bowel cancer
Press release issued: 30 April 2003
Eating a high fibre diet does not necessarily prevent bowel cancer, according to a new study published today in the International Journal of Epidemiology (IJE), edited in the Department of Social Medicine at the University of Bristol. However, such a diet may be good for preventing other chronic diseases, such as heart disease.
Researchers from the National Cancer Institute in the USA studied a cohort of 45,000 American women between the early 1970s and late 1990s. They looked at intake of sources of fibre (fruits, vegetables, beans and grains) in the women's diets and whether they had bowel cancer some years later.
The authors, led by Professor Volker Mai, found no evidence that the intake of dietary fibre was related to the incidence of bowel cancer.
This finding, and the apparently inconsistent findings of other studies in this area, may in part be explained by the difficulty of collecting accurate information on eating habits in these kinds of study. However, the authors also note that while these and other studies suggest that high fibre diets may not protect against bowel cancer, a high fibre diet may be good for preventing other chronic diseases, such as heart disease. There is no evidence that a high fibre diet is bad for health.
Bowel (or colorectal) cancer is the second most common cancer in England, accounting for 12 per cent of all cancer deaths, but less is known about bowel cancer than other forms of cancer and it does not gain as much public or political attention.
In the early 1970s it was suggested by the British surgeon Dr Denis Burkitt (1911-1993) that a high fibre diet might help to protect against bowel cancer, and a number of subsequent studies supported this. However, more recent and larger studies have reported no association between fibre intake and bowel cancer.
In a commentary on the American research paper, academics from the University of Bristol note how debate on the health effects of fibre - and specifically the benefits of wholemeal versus white bread - dates back to Hippocrates in the 5th century BC. Hippocrates believed that white bread was more nutritious.
They also point out that Burkitt's original work was based on geographical comparisons of Africa, Europe and the US. Although Burkitt observed that Africans had lower rates of bowel cancer and higher rates of fibre intake, they suggest that further work is needed to unravel exactly what aspects of African lifestyles actually protect people from bowel cancer.
Dr Debbie Lawlor of the Department of Social Medicine at Bristol University said: "It is interesting that this issue has been debated since ancient times and remarkable that the reasons Hippocrates gave for preferring white bread to wholemeal bread are similar, in some ways, to those used today to argue for the benefits of wholemeal bread and more fibre in the diet.
"Hippocrates recognised that wholemeal food passed through the bowel at a much quicker rate and was concerned that in doing so there would be less time for the body to absorb the food's nutritional content. Today rapid transit through the bowel - produced by a high fibre diet - is believed to have some benefit in reducing ingestion of some nutrients, such as cholesterol, that may be bad for health."
Paper: Volker Mai, Andrew Flood, Ulrike Peters, James V Lacey Jr, Catherine Schairer and Arthur Schatzkin. Dietary fibre and risk of colorectal cancer in the Breast Cancer Detection Demonstration Project (BCDDP) follow-up cohort IJE 2003, Vol 33, No 2 pp234-238.
Commentary: Debbie A Lawlor and Andy R Ness. Commentary: The rough world of nutritional epidemiology: does dietary fibre prevent large bowel cancer' IJE 2003, Vol 32, No 2 pp239-243.
The International Journal of Epidemiology is a key journal in the field of epidemiology and public health, published six times per year by Oxford University Press. It is edited at the Department of Social Medicine, University of Bristol, which is a leading centre for epidemiology, health services research and public health in the UK and was one of only three to be awarded the top 5* grade in the 2001 Research Assessment Exercise.