HOME
Diet and Colon Cancer Information
Introduction
There are many conditions in Western industrialised societies today that were unheard of, or at least very rare, just a century ago. The same conditions are still unheard of in primitive peoples who do not have the 'benefits' of our knowledge. There is a very good reason for this: They eat what Nature intended; we don't. The diseases caused by our incorrect and unnatural diets are those featured on these pages.
Dietary causes:
Cereal fibre (bran)2: Fibre increases colon cancer
Animal studies have variably suggested that dietary fibre reduced risks, increased risks, or had no effect on bowel cancers. Epidemiological studies on humans have also found that intakes of dietary fibre are either protective, or to have no effect. There is also a growing scepticism in the USA that lack of fibre causes cancer; some studies have even suggested that a fibre-enhanced diet may increase the risk of colon cancer.[i]
It had been shown in the mid-1980s that dietary fibre increased the risk of colon cancers.[ii] In 1990 The British Nutrition Foundation admitted that the hypotheses that IBS, diverticulosis and colorectal cancer are caused by a deficiency of fibre had not been substantiated, neither had those that fibre might protect against diabetes, obesity and CHD.[iii] The Seventh King's Fund Forum on Cancer of The Colon and Rectum commented that 'cereal fibre does not offer protection against cancer'.[iv]
In 1995 Dr M Inoue and colleagues published an investigation of cancers at several colorectal subsites: ascending, transverse, descending, sigmoid, and rectum, within a Japanese hospital environment. They concluded that loose or soft faeces are a significant risk factor for cancer at these sites.[v] Bran loosens and softens faeces ? that's why it is recommended.
The following year Drs HS Wasan and RA Goodlad of the Imperial Cancer Research Fund showed that bran can increase the risk of colorectal cancers.[vi] 'Many carbohydrates', they say, 'can stimulate epithelial-cell proliferation throughout the gastrointestinal tract. They conclude: 'Until individual constituents of fibre have been shown to have, at the very least, a non-detrimental effect in prospective human trials, we urge that restraint should be shown in adding fibre supplements to foods, and that unsubstantiated health claims be restricted. . . . Specific dietary fibre supplements, embraced as nutriceuticals or functional foods, are an unknown and potentially damaging way to influence modern dietary habits of the general population.' This study spawned several critical letters. It comes as no surprise that half were from people connected with the breakfast cereal industry.[vii]
The results of a very large, long-term trial, published in 1999, also suggest that, contrary to popular belief, high dietary fibre intake does not protect against colorectal cancer.[viii] Researchers at Harvard Medical School and the Dana-Farber Cancer Institute, both in Boston, Massachusetts, studied 88,757 women over 16 years. They say: 'no significant association between fiber intake and the risk of colorectal adenoma was found'. But there was what they call an 'unexpected' finding, in that, according to their data, a high consumption of vegetable-derived fibre was actually 'associated with a significant increase (35%) in the risk of colorectal cancer'. They conclude 'Our data do not support the existence of an important protective effect of dietary fiber against colorectal cancer or adenoma'.
That fibre increased the risk of colon cancer was confirmed 6 years later by a large analysis of 17 studies of the effect of dietary fibre on colorectal cancer.[ix] Although the abstract of the study said that people with the highest intakes of fibre had a reduced risk of colon cancer, that was exactly the opposite of what the study data showed. Using the study's Table 3, dividing the number of cases of colorectal cancer by person-years of exposure, and multiplying by 10 to obtain number of cases per 10-person-years, since the mean study length was about 10 years, the effect was not a reduction in cancers as fibre intake increased but an increase. This is graphically illustrated in the graph below.
Lead researcher, Yikyung Park, said that 'There are more questions to be answered but clearly this adds to the growing body of evidence finding that high fiber intake does not lower the risk of colorectal cancer.'
References
[i]. Kritchevsky D. Fibre and cancer. in GV Vahouny and D Kritchevsky (eds). Dietary Fibre: Basic and Clinical Aspects. Plenum, NY. 1986. p427.
[ii]. Dietary studies of cancer of the large bowel in the animal model. In Vahouny GV, and D Kritchevsky (eds). Op cit. p 469
[iii]. Complex Carbohydrates in Foods: the Report of the British Nutrition Foundation's Task Force. The British Nutrition Foundation. Chapman & Hall, 1990.
[iv]. Cancer of The Colon and Rectum: the Seventh King's Fund Forum. London: King's Fund Centre, 1990.
[v]. Inoue M, et al. Subsite-specific risk factors for colorectal cancer: a hospital-based case-control study in Japan. Cancer Causes Control 1995; 6: 14-22.
[vi]. Wasan HS, Goodlad RA. Fibre-supplemented foods may damage your health. Lancet 1996; 348: 319-20.
[vii]. Various. Fibre and colorectal cancer. Lancet 1996; 348: 956-9.
[viii]. Fuchs CS, et al. Dietary Fiber and the Risk of Colorectal Cancer and Adenoma in Women. New Engl J Med 1999; 340: 169-176, 223-224.
[ix]. Park Y, et al. Dietary fiber intake and risk of colorectal cancer: a pooled analysis of prospective cohort studies. JAMA 2005; 294: 2849-2857.
Last updated 1 August 2008
