Digestion

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.

Odorless Doo-doo?

The John Harvey Kellogg character in the 1995 film Road to Wellville stated that his feces had no more odor than that of "freshly baked biscuits." One evening I offered a ride home from the university to an elderly colleague, an avid vegetarian. Upon entering my car, he declared: "When I drink carrot juice, my bowel movements have no odor."

Before I could respond, he said: "Rabbits eat lots of carrots, and their feces have no odor." The thought of someone running around sniffing little piles of rabbit doo-doo almost made me laugh, but I didn't want to be disrespectful. His idea that rabbits eat many carrots intrigued me. I had raised them in my boyhood and discovered that, despite the passion for carrots shown by Bugs Bunny, real bunnies are not particularly fond of carrots. Furthermore, wild rabbits seldom would have an opportunity to eat carrots. Luckily the ride was short.

The late Pulitzer Prize-winning anthropologist Ernest Becker argued that defecation is most closely associated with humankind's animality and mortality. 15 During a Bible class at an SDA school, I was taught that people did not defecate in the Garden of Eden but utilized the food they ingested in its entirety. Apparently, foul odors did not befit Paradise. (Perhaps the persistence of the miasmatic theory of disease the theory that diseases are due to foul-smelling emanations from the earth well into the nineteenth century, when SDA beliefs were developed, reinforced the idea of a poopless Paradise.) I was also taught that roughage became part of the human diet after the Fall. Allegedly, this broadening of the diet to include "the herb of the field" (Genesis 3:18, King James version) occurred because humans were now under the " death sentence" caused by original sin. Whether this reportedly was a voluntary dietary change or part of the curse of being ousted from Paradise is debatable. Some versions of the Bible imply that "the herb of the field" merely meant "wild foods" (New English Version), not a new source of food.

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.

Fibre has been accepted widely as an essential part of our diet. Most health promotion boards and doctors advocate its use, especially for constipation and in the prevention of colorectal cancer. It is hardly surprising that both a high-fibre diet and the prescription of fibre are common in the primary and secondary care management of constipation. Some doctors even believe that fibre lowers serum cholesterol and reduces excess serum fats. Both bran and oats have been widely promoted since the 1970s, but a critical review by the Human Nutrition Group concluded that dietary oats lower blood cholesterol only modestly, at best1. Fibre in the context of healthcare originally referred to the insoluble structural matrix fibres (cellulose, hemicelluloses and lignins) or roughage, but the term now includes those natural gel-forming fibres (pectins, gums and mucilages) that are soluble and it may be expanded to include any non-starch polysaccharide or even protein not degraded by bacteria in the hind-gut. Although it is said to increase stool bulk and reduce bowel transit time by stimulating peristalsis, the excessively long colons and the higher incidence of megacolon and volvulus commonly associated with highfibre intake seem to contradict this notion2. Indeed, the colons of severely constipated patients encountered by the authors are usually packed with partially or non-digested vegetable fibre. An understanding of the physical properties of fibre suggests that it does not make sense to add to the bulk of hard large stools in chronically constipated colons by increasing fibre intake. Even so, current recommendations continue to advocate this. In the authors’ experience, most patients with idiopathic constipation are helped by decreasing, not increasing, their intake of dietary fibre. A recent meta-analysis of 51 double-blind clinical trials examining the treatment of irritable bowel syndrome has confirmed that evidence is weak for the recommendation of bulking agents in the treatment of constipation in such patients3. Furthermore, a systematic review of 17 randomized controlled trials involving the treatment of irritable bowel syndrome with fibre showed that its benefits are only marginal in terms of symptom improvement and constipation; insoluble fibre may even increase abdominal pain and constipation4. In two well known randomized intervention trials increased fibre intake had no effect on the recurrence of colorectal adenoma5,6. These reports have raised considerable doubt about the wisdom of dietary advice promoting fibre consumption to prevent cancer. Although earlier epidemiological studies appeared to showed benefit, results from prospective studies have proved disappointing. The Nurses’ Health Study is the largest propective analysis to date. It employed semiquantitative questionnaires and standardized food tables, and detected no protective effect of dietary fibre against the development of colorectal cancer or adenomas in women after a follow-up of 16 years. In fact, greater consumption of vegetable fibre was associated with a 35 per cent increased risk of colonic cancer7. The Health Professionals Study involved over 47 000 men and also showed no protective effect from fibre8. A comprehensive review of all case–control, longitudinal and randomized controlled studies revealed that only 13 of 24 case–control studies and only three of 13 longitudinal studies demonstrated a protective effect of dietary fibre against colorectal neoplasia; none of five randomized controlled trials showed any significant protection. Although 15 of 19 experimental studies in animal models have demonstrated a protective effect of fibre against tumour induction compared with controls, evidence from more relevant human prospective trials does not support the use of fibre as means of reducing the risk of colorectal neoplasia9. On the other hand, two recent papers have shown a protective role for fibre on distal colonic adenomas and on colorectal cancer respectively10,11. However, it should be realized that trials on vegetable and fibre intake are inherently subject to recall bias, as patients who subsequently develop colorectal tumours often blame themselves for not taking enough of these materials although they may well have done so. On the basis of epidemiological, experimental and interventional data currently available, a strong case cannot be made for a protective effect of dietary fibre against constipation or colorectal cancer. Despite this uncertainty, current recommendations are still to promote an increase in fibre intake. The interactions of diet and the gut are complex and one must be wary of oversimplistic theories, even more so when such theories develop into widely popular fads. Recent studies have demonstrated that it is now time to adopt an open mind on fibre. Dietary fibre may have its merits but its efficacy in constipation, and on cancer prevention in colorectal adenoma, is equivocal at best. A preconceived assumption must not dominate either future research or clinical practice.