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Fiber intake and the reduced risk of colon cancer

Dietary fiber in food and protection against colorectal cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC): an observational study

Recent scientific studies have stirred up controversy regarding the role of fiber in reducing the risk of colon cancer. A well-publicized study published in 1999 known as the US Nurses Health Study found that increased consumption of fiber did not offer a protective effect against colon cancer (1). This finding, along with similar findings (2-4) contradicted the current belief that fiber provides a protective effect against colorectal cancer. Thus, several other studies attempted to replicate this finding and determine what, if any, effect fiber has on the prevention of colorectal cancer. One of these, the EPIC study (5), was conducted in Europe over a period of 6 years, and included subjects from 10 different countries. The results are summarized as follows:

• The study examined the effect of fiber intake on the incidence of colorectal cancer.
• Recruited participants from 10 countries, including Denmark , France , Germany , Greece , Italy , the Netherlands , Norway , Spain , Sweden , and the UK .
• 519,978 men and women aged 25-70 years took part in the study from 1992-1998.
• Participants completed dietary intake questionnaires during the study period, and afterwards study authors followed up to determine cancer incidence among the participants.
• Fiber intake was measured in quintiles with a range of 12.64 g to 31.91 g per day for women and 12.77 g to 35.61 g per day for men.

• Increased dietary fiber intake was associated with a reduced risk for colorectal cancer: for each quintile increase in fiber intake, they measured an 8% decrease in risk for colorectal cancer
• The study did not report a cut-off of how much fiber per day is most beneficial; however, since cancer risk decreases as fiber intake increases, even the lowest intake of fiber (12.6 g/day on average) was beneficial.

• The association was stronger for colon cancer than for rectal cancer

Notes:

• This study examined the effects of fiber in foods – not fiber from supplements or additives, so the findings may not apply to fiber attained from these sources.
• The EPIC study also did not examine whether one type of fiber was more protective than another, so they cannot yet claim that one type is more protective.

 

Why did previous studies find no association between fiber intake and colorectal cancer risk?

The EPIC study authors cited 2 main reasons for the previous findings:

1. In the US Nurses Study, participants did not consume as much fiber as those in the EPIC study – average daily fiber intake for the EPIC study ranged from 12.6 to 33.1 g per day, while for the Nurses Study, fiber intake ranged from 9.8 to 24.9 g per day. Fiber intake from cereals was even lower for the Nurses Study: 4.8 g per day in the highest intake group compared to 4.7 in the lowest intake group from the EPIC study.
2. Participants in the EPIC study were consuming fiber from a greater variety of sources than participants in the US Nurses Study.

For Further Consideration:

The EPIC study is the largest, most comprehensive study to date that has examined the relationship between fiber intake and risk of colorectal cancer – the strengths of this study include that it not only followed a large number of people, but also included a wide range of people based on age, geography, and cultural diversity. This strengthens the study results and appears to support the positive association between fiber intake and reduced colorectal cancer risk. Future studies however are needed to better elucidate what types of fiber are most beneficial, and in what form – cereals, whole grains, or fruits and vegetables. For now, follow the tips below, summarized from the EPIC study, to reduce your cancer risk.

Take Home Tips :

• Consume fiber on a regular basis
• Consume at least 25 grams of fiber daily
• To gain the maximum benefits associated with fiber consumption, individuals should start consuming high fiber diets early in life, however, it's never too late.
• Obtain fiber from a variety of sources – fruits, vegetables, whole grains, and cereals

References:

1. Alberts DS. Martínez ME, Roe DJ., et al. The Phoenix Colon Cancer Prevention Physicians' Network.. Lack of effect of a high-fiber cereal supplement on the recurrence of colorectal adenomas. N Engl J Med. 2000 ; , 342:1156-1162.

2. Fuchs CS., Giovannucci EL., Colditz GA., et al. Dietary fiber and the risk of colorectal cancer and adenoma in women. N Engl J Med . 1999; 340:169-176.

3. Schatzkin A, Lanza E, Corle D, Lance P, et al. Lack of effect of a low-fat, high-fiber diet on the recurrence of colorectal adenomas. N Engl J Med. 2000; 342:1149-1155.

4. Peters U, Sinha R, Chatterjee N, Subar, et al. Dietary fibre and colorectal adenoma in a colorectal cancer early detection programme. The Lancet . 2003; 361: 1491-1495.

5. Bingham, SA, Day, NE, Luben, R., et al. . Dietary fibre in food and protection against colorectal cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC): an observational study. The Lancet, 2003; 361:1496-1501.