AICR Welcomes First Results from Largest Diet-Cancer Study Ever Undertaken

American Institute for Cancer Research
Friday, 2 May 2003

Diets High in Fiber Cut Risk of Colon Cancer Nearly in Half

The first results from the largest scientific study to ever investigate the links between diet and cancer risk are in, and they strongly support a role for dietary fiber in the prevention of colon cancer. Experts at the American Institute for Cancer Research (AICR) and the World Cancer Research Fund International (WCRF International) today welcomed these newly published findings, and expressed hope that they will help to clarify what has become to many a confusing and controversial issue.

Results from the European Prospective Investigation into Cancer (EPIC) study appear in the May 3 edition of the British journal The Lancet. Researchers tracked the diets of 519,978 subjects in ten European countries for an average of 4.5 years. They found that those subjects who ate the most dietary fiber (averaging 35 g/day) had their risk of colon cancer reduced by 40 percent, compared with subjects who ate the least fiber (averaging 15 g/day). The study focused strictly on dietary fiber, and did not investigate the effect of fiber supplements.

An American study published in the same issue of The Lancet used a different method but reached a similar conclusion. In this case-control study, researchers with the Prostate, Lung, Colorectal and Ovarian Cancer Screening project team (PLCO) compared the fiber intakes of 33,917 subjects without colon adenomas (non-malignant polyps) to 3,591 subjects with at least one polyp.

Those subjects who ate the most dietary fiber (more than 30 g/day) had their risk of polyps reduced by 20 percent, compared to those who ate the least (less than 15 g/day.)

Recent Studies Spark Confusion and Controversy

A 1997 expert panel report by AICR/WCRF concluded that there is convincing evidence that diets rich in dietary fiber (i.e., diets centered around a variety of fruits, vegetables, whole grains and beans) are linked to lower risk of several cancers, including colon cancer. In the past few years, some studies that have investigated the specific role of dietary fiber in colon cancer risk have found no protective association. These studies received a great deal of attention, and convinced many in the public to conclude that no link exists.

AICR experts have repeatedly urged caution in interpreting research results, and insist that any new scientific study can only add to the scientific debate, not close it. "Scientific consensus builds slowly, which is why it's always necessary to view new results in the context of what has gone before," said Ritva Butrum, Ph.D., AICR's Vice-President for Research.

Importantly, EPIC Study Examined Widely Divergent Diets

One factor that makes the EPIC study so unique in the field of diet-cancer research is the sheer number of subjects it is currently tracking – over half a million individuals, aged 24-75. Another, equally important strength of the project is its ability to compare the widely different diets of 10 European countries – Denmark, France, Germany, Greece, Italy, the Netherlands, Norway, Spain, Sweden and the UK. The enormous dietary variation among these countries means that diet-cancer associations are easier to identify.

Studies that investigate populations where there is little variation in the amount of fiber consumed, or in the kind of food that fiber comes from, have a more difficult time isolating links between fiber and disease risk.

Fiber-Rich Diets "Best Option for Reducing Colon Cancer Risk"

The debate on the existence of a fiber-colon cancer link continues. The authors of a paper appearing in the May 3 issue of the International Journal of Epidemiology (IJE) found no evidence that dietary fiber protected against colon cancer among a group of older women. The 45, 491 women, whose diets had been previously assessed in a breast cancer study, filled out follow-up dietary questionnaires over a period of 8 years.

When the authors compared subjects who ate the most dietary fiber (16.7g/day) to subjects who ate the least (7.1 g/day), the colon cancer rates of both groups were similar.

Dr. Butrum noted, however, that even those subjects who reported consuming the most fiber in the IJE study were eating amounts below the 20-35 g/day recommended by health experts for chronic disease prevention. In fact, the amount of dietary fiber eaten by the subjects in IJE study's "high-fiber" group was roughly equal to the amount eaten by subjects with the lowest fiber intake in both of the two Lancet studies.

In an editorial discussing the EPIC and PLCO studies, the Lancet concludes, "…eating a diet rich in plant foods, in the form of fruit, vegetables and whole-grain cereals probably remains the best option for reducing the risk of colon cancer, and for more general health protection."

AICR offers a free brochure called, "The Facts About Fiber" that explains more about the fiber-cancer link and offers advice about how to ease more fiber into the diet. Read "The Facts About Fiber"

For more information, or to contact American Institute for Cancer Research, see their website at: www.aicr.org