Fiber

In 1990 The British Nutrition Foundation admitted that the hypotheses that IBS, diverticulosis and colo-rectal cancer are caused by a deficiency of fibre had not been substantiated, neither havethose that fibre might protect against diabetes, obesity and CHD. 

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 The Seventh King's Fund Forum on Cancer of The Colon and Rectum agreed: 'TheForum commented that cereal fibre does not offer protection against cancer'.

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Cancer of The Colon and Rectum: the Seventh King's Fund Forum. London: King's Fund Centre, 1990. 

Abstract

Whilst following up large numbers of patients with irritable bowel syndrome we got the impression that wholemeal wheat and bran products made people with the condition worse rather than better. One hundred consecutive new referrals, all of whom had tried bran, were questioned to resolve this issue. 55% of patients were made worse by bran whereas only 10% had found it helpful. With the exception of fruit, other forms of dietary fibre were not as detrimental and proprietary supplements were found to be beneficial. All symptoms of irritable bowel syndrome were exacerbated by bran, with bowel disturbance most often adversely affected, followed by abdominal distension and pain. The results of this study suggest that the use of bran in irritable bowel syndrome should be reconsidered. The study also raises the possibility that excessive consumption of bran in the community may actually be creating patients with irritable bowel syndrome by exacerbating mild, non-complaining cases.

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Bran supplementation in the treatment of irritable bowel syndrome. - 1994 Oct 5

https://www.ncbi.nlm.nih.gov/pubmed/7865643

Abstract

BACKGROUND:

Irritable bowel syndrome remains the commonest reason for referral to a gastroenterology clinic. Patients with irritable bowel syndrome are frequently advised to increase their intake of bran fibre, despite inconclusive experimental evidence of benefit.

METHODS:

The effect of dietary supplementation with a bolus of bran fibre (12 g/day) was studied in a block-randomized, placebo-controlled, crossover study of 80 patients with irritable bowel syndrome referred to a District General Hospital outpatient clinic. Comparison of the benefits of bran and placebo was based upon personal assessment of individual and overall symptom profiles, determined from a simple daily symptom score and post-treatment interview.

RESULTS:

Overall symptomatic improvement was reported with bran by 52% and with placebo by 54% of patients. Bran supplementation was no more effective than placebo in improving individual symptoms of irritable bowel syndrome, and for wind-related symptoms it was significantly less effective (P < 0.001).

CONCLUSION:

Dietary supplementation with bran is of no value in the treatment of patients with irritable bowel syndrome referred to a hospital clinic.

Dr M Inoue, et al published in 1995 an investigation of cancers at several colorectal subsites: ascending, transverse, descending, sigmoid, andrectum, within a Japanese hospital environment. They concluded that loose or soft faeces are a significant risk factor for cancer at these sites.

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Abstract

To investigate the subsite-specific risk factors for colorectal cancer, we conducted a case-control study, using a common questionnaire which inquired about general lifestyles over the past five years (1988-92), at the Aichi Cancer Center Hospital, Nagoya, Japan. This study compared 432 patients with histopathologically diagnosed colorectal cancer (94 proximal colon [cecum, ascending colon, transverse colon]; 137 distal colon [descending colon, sigmoid colon]; 201 rectum [rectosigmoid, rectum]); and 31,782 first-visit outpatient controls who were free from cancer. In both genders, habitual smoking selectively increased the risk for rectum cancer. Soft or loose feces increased the risk for all subsites of colorectal cancer, particularly in female rectum cancer (odds ratio [OR] = 4.5). Among female dietary habits, Japanese-style foods decreased the risk for distal colon cancer, but increased the risk for proximal colon cancer. These results suggested that the risk factors for colorectal cancer differ by subsite among such a low-risk population as the Japanese. It is suggested also that 'irritable bowel' (soft or loose feces) might be associated with distal subsites of colorectal cancer, independently or combined with habitual smoking.

The following year Drs HS Wasan and RA Goodlad of the Imperial CancerResearch Fund showed that bran can increase the risk of colorectal cancers. (14) '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.' 

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Various. Fibre and colorectal cancer. Lancet 1996; 348: 956-9. 

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Fibre and colorectal cancer SIR—It is salutary to be reminded of the limitations of our knowledge of risk factors in health and disease. As Wasan and Goodlad maintain (Aug 3, p 319),1 assertions that up to two-thirds of the variation in incidence of colon cancer is attributable to differences in total fibre and fat consumptions are obviously erroneous. Account must be taken of the wide differences in rates found in Europe and of the enormous differences in incidence rates in adjacent districts, as in Scotland. In Japan, the mortality rate for colon cancer is falling, whereas, from knowledge of risk factors, it should be rising.2 In rural Africans in South Africa, appendicitis, diverticular disease, and colon cancer are near absent.3 Puzzlingly, these diseases are also rare in urban dwellers, despite considerable increases in the intakes of energy and fat and falls in dietary fibre. Equally puzzling, the self-same dietary changes have evoked huge increases in dental caries, obesity in women, hypertension, and diabetes. The authors urge, pragmatically, that for the prevention of colon cancer and other degenerative diseases, “we should continue to follow the general guidelines . . . to eat a diet with more fruit and vegetables and less fat”. Although these recommendations have been urged with evangelical fervour for 20 years, responses have been slight. In the USA energy from fat has fallen from 40% to about 35%, and in the UK the decrease has been even less. In both countries intakes of vegetables and fruit have not risen significantly and the proportion complying with full recommendations is small. The likelihood of increasing intakes of other plant foods (eg, bread or legumes) looks remote too. Since people cannot—or, rather, will not—change their diet, what about fibre supplements, fibre additions to foods, and antioxidant vitamins and minerals? Unfortunately, as Wasan and Goodlad note, benefits resulting from such additions have been mixed; moreover nutritional authorities stress that some of the benefits from plant foods consumption may arise from the fact that they contain additional, not-yet-identified health-promoting constituents. “Health is not a priority for most people in the course of their daily lives, and only surfaces when health problems emerge. Studies have found little evidence that changes in health related behaviour were a response to formal health messages.”4 Compliance with the requirements, dietary and non-dietary, for lessening the risk for colon cancer seems a forlorn hope, as with breast cancer also.5

 

A R P Walker, I Segal

 

*Human Biochemistry Research Unit, Department of Tropical Diseases,

School of Pathology of the University of the Witwatersrand, and the

South African Institute for Medical Research, Johannesburg 2000, South Africa; and Gastroenterology Unit, Baragwanath Hospital and University of the Witwatersrand