Colonic response to dietary fibre from carrot, cabbage, apple, bran

Dietary modification of intestinal bacterial enzyme activities--potential formation of toxic agents in the gut

The bacterial population colonising the large intestine is able to metabolise a variety of ingested or endogenously produced substances to products, some of which possess toxic, mutagenic or carcinogenic properties. Dietary components, resistant to digestion and absorption in the upper alimentary tract, may influence these reactions by altering the environment of the gut or through the provision of nutrients to the flora. Evidence for the involvement of bacterial enzymes in the formation of toxic products in vivo has come largely from animal studies, particularly where fermentable plant cell-wall components are present in the diet. The role of diet in the modification of toxicologically important bacterial biotransformation processes will be discussed. Preliminary data will also be presented from a study demonstrating changes in the enzymic activity of the human faecal flora induced by pectin and bran. The significance of these changes to the disposition of chemicals in the gut will be discussed.

The effect of age, sex and level of intake of dietary fibre from wheat on large-bowel function in thirty healthy subjects

1. To evaluate the effect of age, sex and level of intake on the colonic response to wheat fibre, thirty healthy volunteers aged 17-62 years (nineteen men, eleven women) recruited from a local industry, were divided into four groups and given a controlled diet for two 3-week periods. The diet contained white bread during one period or one of four different amounts of bran-enriched wholemeal bread during the other (30, 60, 110, 170 g/d). 2. Wide variation was observed between subjects in stool weight on the basal diet and in response to wheat fibre. Stepwise regression analysis showed that the variation in stool weight was significantly related to sex (t 4.0, P less than 0.001) but not to age, height, weight or energy:fibre intakes on the basal diet. Stool weight in men (162 (SE 11) g/d) was approximately double that in women (83 (SE 11) g/d). Transit time and stool weight were closely related and the effect of sex on stool weight could be explained entirely by differences in transit. 3. The increase in stool weight with fibre was significantly related to dose (t 4.18, P less than 0.001) with approximately 1 g non-starch polysaccharides (the main component of dietary fibre) increasing stool weight by 5 g/d. Smaller increases in stool weight were seen in females, persons with initially low stool weights and small people. 4. Faecal carbohydrate excretion increased with the addition of bran mainly due to increased amounts of cellulose and pentose (arabinose + xylose), whilst digestibility of dietary non-starch polysaccharide fell from 77.6 (SE 2.3)% on the white bread diet to 65.6 (SE 2.4)% with the added bran (t 7.4, P less than 0.01, n26). 5. Faecal pH was more acid in men than in women and was related to methane production. Methane producers had higher faecal pH than non-producers (7.06 (SE 0.11) v. 6.65 (SE 0.1], lower stool weight (g/d; 93 (SE 12) v. 156 (SE 13] and slower transit times (h; 84.6 (SE 11.7) v. 48.6 (SE 6.6]. 6. These studies show that, when on similar diets, women have much lower stool weights and slower transit times than men. Furthermore, within the range of amounts of wheat fibre used in this and other published work, stool weight increases in linear proportion to the dose of fibre added to the diet. Methane excretion in breath is associated in this group of subjects with slow transit time and high faecal pH.

Fermentation of dietary fibre in the intestinal tract: comparison between man and rat

1. The breakdown and faecal bulking capacity of dietary fibre preparations from wheat bran, apple, cabbage, carrot, and guar gum were compared in man and rat. 2. The degradation of the fibre showed good correlation between man and rat (r 0.99, regression coefficient 0.86). Wheat bran was the least well-digested, 66 and 59% of the neutral sugars being excreted in faeces of man and rat respectively. The breakdown of the fibre in apple, cabbage, carrot and guar gum was more complete and 4-29% of the neutral sugars were recovered in faeces. 3. The main dietary fibre constituents in each preparation were degraded to a similar extent in man and rat. The main dietary fibre constituents of apple, carrot, cabbage and guar gum were almost completely degraded. Of the xylose in wheat bran 45% (man) and 48% (rat) were recovered in faeces. However, the percentage excretion of glucose and arabinose from bran was higher in man. 4. A faecal glucan other than cellulose was identified in human faeces after guar gum, and has been provisionally identified as starch. No such glucan occurred in rat faeces. 5. A good correlation between the faecal bulking capacity in man and rat was seen (r 0.97, regression coefficient 0.56). Wheat bran had the best bulking capacity, while that of apple, cabbage, carrot and guar gum was less pronounced. Faecal bulking was inversely related to the amount of fibre which was water-soluble in each preparation. 6. It is concluded that this rat experimental model is useful for the prediction of fermentative breakdown and bulking capacity of dietary fibre in man. However, more comparative studies are needed to evaluate animal experiments regarding other physiological effects of dietary fibre.

The degradation of guar gum by a faecal incubation system

1. Homogenized and diluted faeces (50 g/l) from one human source were incubated with the complex plant polysaccharide, guar gum, to investigate the degradation of viscous polysaccharides by intestinal bacteria. 2. Incubation of the faecal homogenate with guar gum produced a rapid decrease in viscosity and in pH, accompanied by the release of hydrogen. 3. No changes in viscosity or pH were observed and there was no production of H2 gas when guar gum was incubated with autoclaved faecal homogenate (20 min, 1.03 x 10(5) Pa). 4. A bacteria-free filtrate of faeces was prepared by centrifuging the faecal homogenate (2400 g for 100 min) followed by filtration through a Seitz filter and then a millipore filter (size 0.45 micron). Incubating this with guar gum produced a slow decrease in viscosity, but no significant change in pH and no generation of H2. 5. Our results show that guar gum can be fermented by human colonic bacteria and suggest the possibility of predigestion by extracellular free enzymes.

An experimental design to study colonic fibre fermentation in the rat: the duration of feeding

1. The time-course of metabolic adaptation by rats to diets containing either wheat bran or gum arabic was studied during a 12-week period. 2. Stool weight was increased with wheat bran but not with gum arabic, and had stabilized after 4 weeks. 3. Bacterial mass as measured by diaminopimelic acid content had stabilized by week 4. Bacterial mass increased on feeding gum arabic but was unchanged with wheat bran. 4. There was increased caecal short-chain fatty acid, hydrogen and methane production with gum arabic but not with wheat bran. The change in caecal metabolic activity was slow to stabilize (8-12 weeks at least). 5. The faecal excretion of bile acids increased twofold with the wheat-bran-supplemented diet compared with the gum-arabic-supplemented and unsupplemented diets. Relatively greater amounts of muricholic acids were present in the caeca and faeces of gum-arabic-fed rats compared with the other groups.

Effects of laxative and nonlaxative hydrophilic polymers on canine small intestinal motor activity

Bulk-forming laxatives increase fecal volume and elicit aborally directed colonic motility patterns. Recently, it was demonstrated that test meals of the bulk-laxative fibers (cellulose and bran) elicited organized jejunal motor activity while nonlaxative fiber meals (guar) elicited unorganized jejunal motor activity. However, whether bulk-forming laxatives, as a class of compounds, differentially affect small intestinal motility has not been studied. Therefore, a study was made of the effects of the bulk laxatives psyllium and polycarbophil and the nonlaxative pectin on canine jejunal motor activity. Psyllium and pectin are examples of dietary fiber, while polycarbophil is a synthetic polymer. Pectin and psyllium test meals presented as viscous gels. In contrast, polycarbophil meals presented as a combination of discrete particles plus meal water. After each meal, measurements were made of the jejunal motility index, the time of reappearance of interdigestive burst activity, and overall motility patterns. Pectin and psyllium meals increased in viscosity as meal fiber content increased. As meal content and hence viscosity increased, both the laxative (psyllium) and nonlaxative (pectin) fiber meals elicited increasing jejunal motor activity and delays in the reappearance of the burst interval. For both fiber types, motor activity presented as randomly appearing contractions. In contrast, meals of the laxative polycarbophil elicited no more motor activity than the saline control meal. However, this control-level amount of activity presented as propagated clusters of contractions, ie, the "laxative-induced pattern." Polycarbophil did not delay the reappearance of burst activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of wheat bran on some reductive and hydrolytic activities of the rat cecal flora

For 30 days, male weanling rats were fed a semipurified, fiber-free diet or a diet that contained 5, 15, or 30% (wt/wt) wheat bran. The activities of four cecal microbial enzymes were determined. Wheat bran significantly increased the wet weight content of the cecum and total bacterial count per cecum at the intermediate- and high-treatment levels, but it had no effect on bacterial concentration per gram wet weight of cecal contents. Total beta-glucosidase and beta-glucuronidase activities per cecum were generally increased. Wheat bran decreased total nitrate reductase activity, but there was no change in total nitroreductase activity. Wheat bran significantly decreased enzyme activities for nitro-and nitrate reduction per gram of cecal contents but increased beta-glucosidase activity. The activities of the enzymes per 10(11) bacteria followed a similar pattern to that noted per gram of cecal contents. Such fiber-dependent changes in enzyme activity may alter the steady-state concentration of toxic and genotoxic chemicals in the lumen of the hindgut.

Effects of vegetable diets on nitrogen metabolism in cirrhotic subjects

This study compared the effect of a vegetable diet with an animal protein diet on various aspects of nitrogen metabolism to identify what components of the vegetable diet might be causing beneficial therapeutic effects in hepatic encephalopathy. Vegetable diets contained 4.5-fold greater amounts of fiber (56 +/- 3 g/day) and reduced amounts of methionine, tyrosine, and tryptophan. In 6 stable cirrhotic subjects without encephalopathy, vegetable diets caused a significant reduction in the urea production rate from 106 +/- 5 to 89 +/- 5 mg X kg-1 X 24 h-1 of urea nitrogen. This was mainly accounted for by a fall in urinary urea output. Vegetable diets also caused a fall in total urinary nitrogen, which was accounted for by the fall in urea nitrogen, and a comparable increase in fecal nitrogen from 12 +/- 2 to 28 +/- 5 mg X kg-1 X 24 h-1. The fecal bacterial fraction contained 63% of the increase in stool nitrogen. Most plasma amino acids, including methionine, tyrosine, phenylalanine, as well as total and free tryptophan, were unchanged. The effect of vegetable diets on nitrogen metabolism can be mainly accounted for by the increased intake of dietary fiber and increased incorporation and elimination of nitrogen in fecal bacteria.

The prevalence of appendiceal fecaliths in patients with and without appendicitis. A comparative study from Canada and South Africa

Appendicitis is more common in developed than in developing societies and appendiceal fecaliths are thought to have an etiologic role in the disease. The geographic distribution of appendiceal fecaliths was investigated by systematic, intraoperative palpation of the appendix in patients in Toronto, Canada and Johannesburg, South Africa. The incidences of fecaliths found on pathologic sectioning of the appendix in appendicitis patients in both societies were compared. In the Canadian population, the prevalence of fecaliths in patients whose appendices were palpated incidentally was 32% versus 52% for those with appendicitis (p less than 0.01). In the African population, the prevalence of fecaliths in patients whose appendices were palpated incidentally was four per cent versus 23% for those with appendicitis (p = 0.04). The difference in prevalence of incidental appendiceal fecaliths in the two populations was statistically significant (p less than 0.005). The prevalence of fecaliths is higher in developed countries, such as Canada, than in developing countries, such as Africa, and is also higher in patients with than in those without appendicitis. These data support the theory that the low-fiber diets consumed in developed countries lead to fecalith formation, which then predisposes to appendicitis.

Bowel function of healthy men consuming liquid diets with and without dietary fiber

The importance of the level of dietary fiber intake on bowel function was measured in 16 healthy young males consuming self-selected and liquid enteral diets. Subjects consumed liquid Ensure as their sole nutrient source plus 0 (diet a), 30 (diet c), and 60 (diet d) g/day soy fiber, a fiber source high in hemicellulose that was added to the Ensure. Further, to examine whether heat processing affects the physiologic action of fiber, subjects consumed Enrich, an enteral formula similar to Ensure, which contains 30 g of the same soy fiber (diet b). The four diets were consumed in randomized order each for 10 days. Daily wet stool weight averaged 144.6 g on the self-selected diet and decreased significantly to 67.3 g when Ensure was consumed alone. Average stool weights on diets (b), (c), and (d) were 114.6, 100.2, and 150.3 g/day, respectively. Average fecal dry weights for the four diets were 19.1, 28.7, 25.0, and 30.3 g/day for (a-d), respectively. Gastrointestinal transit time, as measured with radiopaque pellets, was longest on the Ensure diet, 72.4 hr, and approximately 2 days on the fiber-supplemented diets and the self-selected diet. Thus, soy fiber's physiologic effect on laxation was not changed by heat processing. Also, although stool weights were larger on higher fiber intakes, transit rates were similar on all the fiber-containing diets.

The digestion of fibre by pigs. 3. Effects of the amount and type of fibre on physical characteristics of segments of the gastrointestinal tract

The aim of the study was to determine the relative effects of feeding growing pigs with graded amounts of neutral-detergent fibre (NDF) from various sources on the empty wet weight of segments of the pig gastrointestinal tract, on the weight and moisture content of their digesta, and on the pattern of digesta movement in them. Increased NDF intakes were associated with significantly higher wet weights of all gastrointestinal segments and increased lengths of the caecum. The lengths of both the small and the large intestines were unaffected by the ingestion by the pigs of different amounts of NDF from various sources. However, the caecum responded to these increased intakes of NDF by significant increases in length. The source of NDF in the diet was a factor that markedly influenced both the length and the weight of the distal colon. The nature of these increases in weight and length morphologically and their biological significance have not been determined. Despite some significant differences, neither the type nor the level of dietary NDF had any appreciable effect on the dry weight and on the proportion of dry matter (DM) of the contents in the contents in the stomach. As the level of NDF intake was increased, more undigested dietary material was found in all segments of the digestive tract of the pigs. The proportion of DM in the residues decreased progressively from the caecal contents to the contents of the distal colon. In most cases the degree to which the level of NDF intake affected the weight of the contents and the proportion of DM in them was highly dependent on the source of NDF in the diet. The distribution of the feed consumed in the morning and in the evening, as measured with stained feed particles and polyethylene beads, was extremely variable. It is concluded that prolonged intakes by pigs of diets containing high levels of fibre may lead to a hypertrophy and hence increased weight of segments of the gastrointestinal tract.

The effect of coarse wheat bran in the irritable bowel syndrome. A double-blind cross-over study

Dietary supplementation with wheat bran has been widely advocated as a first-line treatment of patients with the irritable bowel syndrome (IBS). Few controlled trials have been reported, and the results are, furthermore, contradictory. The present study comprised 20 patients with IBS, of whom 18 (14 women, 4 men) completed the trial. The two treatment periods of 6 weeks each, with a daily intake of 30 g coarse wheat bran or 30 g placebo bran, respectively, were randomized in a double-blind cross-over design. Wheat bran significantly (P less than 0.05) increased the stool weight and shortened the intestinal transit time but was without significant effect on the colonic motility index was shown. We conclude that coarse wheat bran used as the only treatment in IBS does not provide a sufficient effect in a 6-week period. However, wheat bran seems to be justified in the treatment of constipation.

Fiber intake and childhood appendicitis

Parents of 135 children with appendicitis and of 212 comparison children were interviewed about their children's diet. Children in the upper two quartiles of fiber intake were estimated to have a 30 per cent lower risk of appendicitis than children in the lowest quartile. Estimated risk of appendicitis decreased as monthly intake of whole-grain foods increased. Children 7 to 18 years of age who had an intake of whole-grain foods in the upper fiftieth percentile were estimated to have a 50 per cent lower risk of appendicitis. This reduction in risk was not observed in the group of children less than 7 years of age.

The effect of dietary guar gum on the activities of some key enzymes of carbohydrate and lipid metabolism in mouse liver

The effects of a 100 g/kg substitution of guar gum on the body-weight gain, food consumption and faecal dry weight of mice fed on a high-sucrose diet and on the activities of hepatic glucose-6-phosphate dehydrogenase (EC 1.1.1.49), 6-phosphogluconate dehydrogenase (EC 1.1.1.44), malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+) (EC 1.1.1.40), ATP-citrate (pro-3S)-lyase (EC 4.1.3.8), 6-phosphofructokinase (EC 2.7.1.11), pyruvate kinase (EC 2.7.1.40) and fructose-1, 6-bisphosphatase (EC 3.1.3.11) were studied. Guar gum had no effect on body-weight gain or food consumption but increased faecal dry weight. Guar gum increased the activities of glucose-6-phosphate dehydrogenase, malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+) and 6-phosphofructokinase expressed on a wet-liver-weight basis. Guar gum increased the activities of glucose-6-phosphate dehydrogenase, malate dehydrogenase (oxaloacetate-decarboxylating)(NADP+), ATP-citrate (pro-3S)-lyase and 6-phosphofructokinase expressed on a liver-protein basis. Guar gum increased the activities of glucose-6-phosphate dehydrogenase and malate dehydrogenase (oxaloacetate-decarboxylating)(NADP+) expressed on a body-weight basis. These results suggest that guar gum increases the flux through some pathways of hepatic lipogenesis when mice are fed on high-sucrose diets.

Irritable bowel syndrome: current concepts and future trends

About five per cent of the adult population each year will see their doctor with complaints that are finally characterised as irritable bowel syndrome (IBS). The complaints are constipation (perhaps alternating with diarrhoea), abdominal pain (dull or colicky), abdominal distension, abdominal rumbling and flatulence. The diagnosis of IBS implies that a relevant examination has precluded any organic disease. The etiology is unknown and the syndrome probably does not represent a disease entity. It is therefore difficult, if not impossible, to produce a definite rationale of treatment. However, several aspects of the pathogenesis of the individual symptoms of IBS are well known: 1) chronic constipation is most likely due to fibre-depleted diet, psychological factors, local organic disorders (e.g., anal fissures, hemorrhoids, diverticulosis) and disturbance of the body fluid balance (e.g., high consumption of diuretic compounds such as coffee and tea); 2) pain is related to spasms and motility disturbances causing increased intraluminal pressure; 3) meteorism is not due to an increased amount of intestinal gas, but "air traps" and segmental accumulation of gas seem to occur. Furthermore, psychopathological factors and perhaps also food intolerance may play an etiological role. At present the rationale of treatment in IBS is: 1) management of constipation, 2) ease of spasms, 3) reduction of surface tension of intestinal contents, 4) ease of mental stress.

The effect of diet on the mammalian gut flora and its metabolic activities

The review will encompass the following points: A brief introduction to the role of the gut flora in the toxicology of ingested food components, contaminants, and additives, including known pathways of activation and detoxication of foreign compounds and the implication of the flora in enterohepatic circulation of xenobiotics. The advantages and disadvantages of the various methods of studying the gut flora (classical bacteriological techniques, metabolic and enzymological methods) will be critically discussed with special reference to their relevance to dietary, toxicological, and biochemical studies. Sources of nutrients available to the gut flora will be described including host products (mucus, sloughed mucosal cells, hormones, proteins) and exogenous nutrients derived from diet. An account of the problems involved in studies of dietary modification with special reference to the use of stock laboratory animal diets, purified diets, and human dietary studies. The influence of dietary modification on the flora will be assessed on the basis of changes in numbers and types of bacteria and their metabolic activity, drawing on data from human and animal studies. The effects of manipulation of the quantity and quality of protein, fat, and indigestible residues (fiber) of the diet will be described together with their possible implications for toxicity of ingested compounds.

Trends in bowel cancer in selected countries in relation to wartime changes in flour milling

Wartime changes in flour milling have been estimated to have more than doubled the intake of cereal fiber in England and Wales, Ireland, and Switzerland for periods of at least 6 years. These circumstances were used to test the hypothesis that cereal fiber inhibits colon carcinogenesis. Age-standardized rates for deaths attributed to bowel cancer were plotted from 1931 to the mid-1970s for England and Wales, Ireland, Switzerland, New Zealand, the US, and Australia. The ratio of the mortality rate observed 11 to 15 years after the change in extraction rates to that predicted from the prewar trend correlated with the increase in estimated cereal fiber consumption. The slope of the regression line suggested that any protective effect from cereal fiber was more modest than that inferred from other studies. The disparity between studies would be less if cereal fiber inhibited more than one stage of the process of carcinogenesis. Trends in six other countries with insufficient data for quantitative analysis were generally consistent (with the exception of those for Norway). The limitations of historical cause-of-death registrations as measures of cancer onset rates and the multiplicity of other changes during wartime require that our results be interpreted with caution.

Characterization of plant polysaccharide- and mucin-fermenting anaerobic bacteria from human feces

Organisms able to grow on arabinogalactan, pectin, xylan, wheat bran, guar, apple cell walls, and mucin were isolated by enrichment from human feces. The number of polysaccharide fermenters and the properties of the predominant bacteria varied between subjects. The ability to use one polysaccharide was not related to the ability to use others. Some organisms (e.g., Bacteroides spp.) isolated on other substrates also utilized mucin, but were not isolated in the mucin enrichment. The mucin fermenters isolated by enrichment had a very restricted ability to utilize complex polysaccharides and their constituent monosaccharides, suggesting that the presence of plant polysaccharides in the human colon is unlikely to prevent the use of colonic mucin as an energy source by bacteria. Characterization with a range of biochemical tests showed that many of the isolates, but especially the mucin fermenters, did not resemble organisms described previously.

Measurement of water-holding properties of fibre and their faecal bulking ability in man

Experiments to measure the effect of a fibre source in the diet on stool bulk are difficult and lack precision. In vitro methods which would identify fibre sources that are effective for clinical and epidemiologic use would be valuable. One important property of fibre which influences the ability of fibre to increase stool weight is its water-holding capacity (WHC). WHC was measured using centrifugation, filtration, suction pressure and water flow-rate techniques using fibre concentrates of potato, cereal bran and gum arabic. Dietary supplementation of three preparations of potato fibre (20 g/d) had no significant effect on stool weight but 16 g bran/d increased stool weight from 107 (SE 44) g/d to 174 (SE 51) g/d. The effects of these fibres on stool weight can be related to the nature of the water-holding properties of fibre rather than absolute WHC.

Metabolic effects of dietary fiber from dehulled soybeans in humans

The normal diet of six healthy volunteers was supplemented by 21 g of dietary fiber from two different soybean seed fiber preparations, either a nonpurified and never-dried soya pulp A (39% dietary fiber) or a purified soya fiber B (79%), for 3 wk each. Mean daily fecal wet weight was increased by 19 and 38% in the fiber periods A and B as compared to a 2-wk control period (p less than 0.05). Stool frequency and transit time remained unchanged. Fecal fiber increased by 52% only during period B. Fecal calcium, magnesium, and iron were increased (p less than 0.05), mainly after higher intakes during both fiber periods. Excretion of neutral steroids remained unchanged, but their concentration was lowered (p less than 0.05). A 21% increase of fecal bile acids by fiber A was specifically due to deoxycholic acid (+32%, p less than 0.01). Oral glucose tolerance was slightly improved after period B. Neither fiber changed serum triglycerides, but fiber B increased low-density lipoprotein-cholesterol by 19% (p less than 0.01) and low-density lipoprotein-phospholipids by 16% (p less than 0.05). The ratio high-density/low-density lipoprotein-cholesterol, however, did not change significantly. Thus, dietary fibers from soybean do not seem to contribute to the hypocholesterolemic effect of soya. The results of this study also demonstrate that two apparently similar dietary fibers, coming from a single source, can exert distinctly different metabolic effects.

Intestinal transit time in constipated and non-constipated geriatric patients

Intestinal transit was measured by following a radioisotope capsule through the gut. The transit in 16 elderly patients with chronic constipation was compared with that in 16 patients of the same age and with 10 healthy younger people without constipation. Although the constipated patients generally had a slower total transit time through the gut, some old and young people without constipation also showed a slow total transit. Constipated patients had a significantly slower transit only through the rectosigmoidal part of the colon. It is also suggested that old age per se does not imply an increased transit time.

Refined carbohydrates - a cause of suboptimal nutrient intake

During the refining of carbohydrate foods there is a sharp drop in the concentration of dietary fiber and of various vitamins and minerals. Estimates were made of the effect of refining on the total diet intake of fiber, selenium, folic acid, vitamins E and B6, choline, chromium, magnesium, zinc, manganese, copper, sodium and potassium. The health implications of this are discussed and it is concluded that the losses are likely to be detrimental.

Metabolic profile of caecal micro-organisms from rats fed indigestible plant cell-wall components

A fibre-free diet, or the same diet supplemented with 100 g cabbage or carrot cell-wall preparation/kg, was fed to rats for 28 days and the activities of a number of caecal microbial enzymes (azoreductase, aryl nitroreductase, beta-glucosidase, beta-glucuronidase, imidazole nitroreductase and nitrite reductase) were determined in vitro. The plant cell-wall preparations diluted the gut contents and decreased the number of bacteria per gram of caecal contents. Enzyme activities per gram of caecal contents were also decreased, with the exception of beta-glucosidase activity which was significantly increased. These plant cell-wall preparations also increased caecal size, and thereby significantly increased total activity per caecum of microbial azoreductase, aryl nitroreductase, beta-glucosidase and beta-glucuronidase. When bacterial metabolism was expressed per 10(9) bacteria, all enzyme activities were significantly increased in caecal samples from rats fed the plant cell-wall preparations. There was an overall concordance of 0.91 between all the enzymes when expressed per 10(9) bacteria, but of only 0.38 when enzyme activities were expressed per gram of caecal contents.

Intestinal helminths of man: the interpretation of egg counts

Of the 39 most common helminth parasites of man listed by Peters & Gilles (1977), 30 may be detected and often diagnosed by finding their eggs or larvae in the faeces of infected people. The preferred habitat of many of these helminths is the alimentary tract itself and the continual flow of material through the food tube provides a simple, passive and reliable means of transport and eventual exit from the host for the reproductive stages of a worm. Helminth eggs are generally less than 150 μm in diameter and although individually comprise a small material investment by the adult worm in the propagation of the species, the chances of infecting a host are so slim (though this may be a teleological inference) that adult worms are often highly fecund: a female Ascaris lumbricoides is estimated to release daily into the intestine approximately 200,000 eggs (WHO, 1967). Yet numbers should not always be equated with great substance or bulk – an equally important determinant of the chances of finding an egg in faeces: assuming a spherical diameter of 60 μm and a specific gravity of 1·2 (Sawitz, 1942) then a female Ascaris is estimated to produce only about 25 mg of eggs each day, which is 0·01% of a moderate daily output of 250 g of faeces.

Fermentation of dietary fibre components in the rat intestinal tract

1. The fermentative breakdown of dietary fibre from various sources in the intestinal tract was studied using rat balance experiments and gas-liquid chromatograhic analysis of dietary fibre monomers in feed and faces. 2. On a basal diet with 690 g maize starch/kg but no added fibre, small but detectable amounts of polymeric glucose, rhamnose, arabinose, xylose, galactose, mannose and uronic acids, i.e. sugars occurring in dietary fibre, were excreted in faeces. 3. Dietary fibre in wheat bran was rather resistant to fermentation; 63% was recovered in the faeces. Guar gum, on the other hand, was almost completely fermented, whereas 19 and 25% of the uronic acids in low and high methoxylated pectin respectively, were excreted in faeces. The various constituents of sugar-beet dietary fibre (approximately equal amounts of arabinose-based hemicellulose, pectin and non-starch glucan (cellulose)) showed quite variable availability for micro-organisms in that 6-12% of the arabinose, 17-25% of the uronic acids, and 52-58% of the cellulose were recovered in the faeces. 4. Faecal nitrogen excretion increased on addition of any one of the dietary fibre preparations studied, resulting in decreased true and apparent protein digestibility values. 5. The faecal dry weight increment was most pronounced when feeding bran and could then almost be accounted for by the remaining fibre and by protein. The less-prominent bulking effect of guar gum and pectins, that were much more extensively fermented, could be only partly explained by dietary fibre and protein.

Nonstarch polysaccharide consumption in four Scandinavian populations

Nonstarch polysaccharide (NSP) intake was measured in representative samples of 30 men aged 50-59 in 2 urban and 2 rural Scandinavian populations that exhibited a 3-4 fold difference in incidence of large bowel cancer. Intake was measured by chemical analysis of complete duplicate portions of all food eaten over one day by each individual. NSP intakes showed a rural-urban gradient, with 18.4 +/- 7.8 g/day in rural Finland and 18.0 +/- 6.4 g/day in rural Denmark versus 14.5 +/- 5.4 g/day in urban Finland and 13.2 +/- 4.8 g/day in urban Denmark. NSP intakes were also calculated (using food tables) from weighed food records kept over 4 days, one of which was the day on which the duplicate collection was made. Intakes were 2-2.5 g/day higher with this method than with direct chemical analysis, mainly because published tables of values have become outdated and inaccurate as a result of improved methods for measuring NSP in food. Individual variation from day to day in NSP intake was considerable. Average NSP intake and intake of some of its component sugars were inversely related to colon cancer incidence in this geographical comparison. To show a relationship at the individual level between diet and cancer risk in a prospective study would require detailed and accurate methods for the assessment of NSP consumption.

Colon cancer and large bowel function in Denmark and Finland

Stool weight and transit time through the gut were measured in 4 groups of 30 men, aged 50-59 years, randomly selected from populations in urban (Copenhagen) and rural (Them) Denmark and urban (Helsinki) and rural (Parikkala) Finland. These populations exhibited a 3-4 fold difference in risk for large bowel cancer. Mean transit time (37 +/- 1 hours, Copenhagen; 43 +/- 1 hours, Helsinki; 40 +/- 1 hours, Them; 37 +/- 1 hours, Parikkala) was not significantly different among populations, but average 24-hour stool weights (136 +/- 13 g, Copenhagen; 176 +/- 17 g, Helsinki; 169 +/- 16 g, Them; 196 +/- 15 g, Parikkala) were different and had a significant inverse relationship to total large bowel cancer incidence, with larger stool weights being found in the low-risk population. A high proportion of study subjects, especially in Finland, were found to be taking medication or to have a history of gastrointestinal illness, but neither of these variables related to bowel habit.