Dietary fibre, functions by modulating the entero-hepatic circulation.

Dietary Fibre (DF) is not an essential component of the diet but a modulator of the absorption and colonic metabolism of nutrients and xenobiotics along the small and large intestine. In the colon DF stimulates the bacterial flora, bacterial mass and metabolism, thereby influencing the entero-hepatic circulation (EHC) and faecal output. This modulation is dependent upon the amount and physical state of DF intake.

Acetylation polymorphism of sulfapyridine in patients with ulcerative colitis and Crohn's disease.

Sulfapyridine (SP) is one of the main metabolites of salicylazosulfapyridine (sulfasalazine) that is used extensively in the management of inflammatory bowel disease. One hundred and twenty-two patients with ulcerative colitis or Crohn's disease were studied, including 21 new, untreated patients and 101 previously treated patients. Patients were studied for at least one year during active disease and remission. It was shown that sulfapyridine shares the same acetylation polymorphism as sulfadimidine. The acetylation capability of each patient as determined in serum and urine was constant irrespective of dose (2 to 8 gm/day) and state of disease. A single study of serum can determine acetylator phenotype in patients on sulfasalazine therapy without using any other drug for this purpose and may help ascertain dosage and assess side effects.

Fiber in the gastrointestinal tract.

It has long been recognized that fruit, vegetables, and cereal fiber alter bowel function. The right colon can be regarded as a fermenter and an absorbing organ, and the left colon is for continence. A rationale for the use of fiber based on physical chemical properties is discussed. On this basis, the use of coarse wheat bran, apples, oranges, and carrots is recommended to treat diverticular disease, spastic colon, and constipation.

Physical properties of dietary fiber that influence physiological function: a model for polymers along the gastrointestinal tract.

The quantitative measurement of dietary fiber does not recognize its diverse actions on nutrient absorption, sterol metabolism, fermentation in the colon, and stool weight. These differences in action are more likely due to differences in physical characteristics along the gastrointestinal tract. This paper explores such physical characteristics and attempts to classify dietary fiber in a more physical manner. This approach recognizes the diverse and variant action of each dietary fiber, which may be modified as a result of processing and cooking without changing in any way the quantitative measurement of dietary fiber. The general principles developed in this paper could also be applied to other polymeric materials passing along the gastrointestinal tract.

An hypothesis for the action of dietary fiber along the gastrointestinal tract.

Dietary fiber consists of a sponge matrix with specific physicochemical properties. These properties are dependent on the structure and composition of the fiber components and determine the physiological effects of different food fibers in the upper and lower gastrointestinal tract.

Effect of Plantago ovata (psyllium) husk and seeds on sterol metabolism: studies in normal and ileostomy subjects.

The diet of six normal and five ileostomy subjects was supplemented with 10 g/d Plantago ovata psyllium husk for 3 wk while six normal and four ileostomy subjects received 10 g/d psyllium seed. Fecal and ileostomy output, sterol excretion, serum cholesterol, and triglycerides were measured before and after supplementation. The husk had no effect on cholesterol or triglyceride concentrations in either normal or ileostomy subjects. Total and high-density-lipoprotein-cholesterol concentrations were reduced on average by 6.4% and 9.3%, respectively, in the normal group after seed supplementation. No effect on fecal bile acid excretion in the normal subjects was found after both regimes. Ileostomy bile acids were increased (on average 25%) after seed supplementation, whereas no effect on cholesterol concentrations was found. These results suggest that psyllium seed might be more effective than the husk in reducing serum cholesterol, that this cholesterol-lowering effect is not mediated by increased fecal bile acid losses, and increased ileal losses of bile acids might be compensated for by enhanced reabsorption in the colon.

The effect of coarse and fine Canadian Red Spring Wheat and French Soft Wheat bran on colonic motility in patients with diverticular disease.

Bran from a Canadian Red Spring Wheat, of both a coarse and fine type, was compared with that from a French Soft Wheat, also with coarse and fine characteristics. The coarse type whether Canadian or French had the more significant effect on the stool weight, speeded the intestinal transit as measured by Hinton markers, and reduced intraluminal pressure in the colon more than did the fine types from the same sources in patients with diverticular disease. The texture of a bran may be important in relationship to its clinical efficacy.

Long-term effect of wholemeal bread on stool weight, transit time, fecal bile acids, fats, and neutral sterols.

Stool weight, fecal constituents, bile acids, fat, neutral sterols, and intestinal transit time were recorded in 28 subjects over 18 mo. During the first 12 mo the subjects ate white bread. They were studied for an initial period of 7 days, and after 6 mo (study period 1). For the first 6 mo they ate their usual intake of bread, they then increased their white bread intake by 62 g/day for 6 mo (study period 2). The subjects ate a self-selected diet throughout the 18 mo study. During the last 6 mo (study period 3) the subjects replaced white bread by the same amount of wholemeal bread as in study period 2. No increase in stool weight occurred until study period 3 when there was an increase of 20%. There developed a linear relationship between stool weight and intestinal transit time which was not found during the initial first and second study periods. A seasonal influence on serum cholesterol was not observed during the wholemeal bread period. Fecal bile acid excretion was unchanged throughout the experiment.

The effect of the polysaccharide composition and structure of dietary fibers on cecal fermentation and fecal excretion.

The fermentation of dietary fibers gives a clue to their mode of action. Wheat bran and gum tragacanth increase stool weight but have no effect on serum cholesterol or on hydrogen excretion. Gum arabic and pectin in the form of raw carrot have no effect on stool weight but decrease serum cholesterol and are associated with an increase in breath-hydrogen excretion. Other fiber sources like gum karaya have no effect on stool weight, serum cholesterol, or breath hydrogen. There are no correlations between the chemical composition and structure of the fibers studied and their physiological effects.

Dietary fiber: in vitro methods that anticipate nutrition and metabolic activity in humans.

Gravimetric measurement of dietary fiber (DF) gives no indication of the biological function of any particular fiber. This study describes simple methods based on dialysis and fermentation that enable a hierarchy of fibers to be described for each of the major actions of fiber along the gastro-intestinal tract: nutrient absorption, sterol metabolism, cecal fermentation, and fecal bulking. These results were compared with previous metabolic studies with the same fiber isolates in humans. DF that modifies nutrient absorption can be identified by using dialysis studies, whereas identifying DF that modifies sterol metabolism, cecal fermentation, and fecal weight requires formulas that incorporate dialysis and fermentation results. Results from dialysis and fermentation predicted the action of wheat bran, pectin, guar, gum arabic, carboxymethylcellulose, gellan, tragacanth, xanthan, and karaya in humans and generated anomalous results for karaya and tragacanth. These methods could form the basis of techniques that would enable a screening of novel and processed fibers before studies in animals, including humans.

A study of the effects of dietary gum arabic in humans.

Gum arabic administered to men for 3 wk has little effect on glucose tolerance and stool weight, but decreases the serum cholesterol. There was no significant increase in fecal bile acids and neutral sterols. Breath hydrogen increased only after chronic administration. Gum arabic could not be recovered from the stool which suggests metabolism of gum arabic in the colon.

Fecal characteristics contrasted in the irritable bowel syndrome and diverticular disease.

A comparison has been made of the fecal characteristics in controls and patients with the irritable bowel syndrome and diverticular disease. No detectable difference was found in the fecal wet weight, dry weight, or total bile acid excretion in the four groups. A significant increase in the percentage of the water content of the stool was seen in the idiopathic diarrhea group with irritable bowel syndrome. Significantly less magnesium, potassium, and calcium was found in the stools of patients with diverticular disease and a similar trend was noted in patients with the spastic colon. These changes did not relate to the age of the patients. This suggests a common etiology for these disorders. The presence of increased water and primary bile acids in the feces of patients with idiopathic diarrhea suggests that this is a separate entity.

A study of diet, serum lipids, and fecal constituents in spouses.

The diet, serum cholesterol, and fecal constituents of 23 healthy spouses have been compared. The pattern of food intake between couples was similar, but of dietary constituents, only dietary fat and fiber intake showed a significant correlation. Of fecal constituents, only fecal fat correlated significantly between couples.

The influence of pentose on breath methane.

In a population study the concentration of methane in the expired breath of methane-producing subjects was significantly related to the dietary intake of noncellulosic polysaccharide pentose (p less than 0.01) and to the intake of lignin (p less than 0.05). The single dose administration of complex polysaccharide sources rich in pentoses to fasting subjects did not result in an increase in methane production when measured over 5 h. The single dose administration of D(+) xylose and L(+) arabinose led to a significant increase in methane excretion in methane producers.

The effect of raw carrot on serum lipids and colon function.

Two hundred grams of raw carrot eaten at breakfast each day for 3 weeks significantly reduced serum cholesterol by 11%, increased fecal bile acid and fat excretion by 50%, and modestly increased stool weight by 25%. This suggests an associated change in bacterial flora or metabolism. The changes in serum cholesterol, fecal bile acids, and fat persisted 3 weeks after stopping treatment.

Fecal weight and composition, serum lipids, and diet among subjects aged 18 to 80 years not seeking health care.

Sixty-two subjects not seeking health care, aged 18 to 80 yr, recorded diet intake, collected feces for 7 days, and gave fasting blood lipids. There was a great variation in stool weight passed (19 to 278 g/24 h). Fecal constituents (bile acids, sterols, fat, electrolytes) correlated strongly with fecal mass. Fecal mass correlated inversely with transit time. There was no relationship between age and fecal weight or transit time. Multiple regression analysis showed that only dietary fiber contributed to stool weight. No single component of fiber appeared to be responsible for this relationship with stool mass. Multiple regression analysis of serum cholesterol showed a relationship only with age and fecal neutral sterols.

The effect of a natural high-fiber diet on serum lipids, fecal lipids, and colonic function.

In a cross-over experiment, 46 young healthy volunteers consumed in succession a high-fiber and a low-fiber diet for 3 weeks at two levels of dietary cholesterol. Half of the dietary fiber came from fruits and vegetables, and the rest from bread and other cereal products. On the high-fiber diet, concentrations of serum cholesterol decreased on average by 0.44 mmole/liter with high-cholesterol and 0.31 mmole/liter with low-cholesterol regimes; high density lipoprotein-cholesterole decreased by 0.1 mmole/liter; on average fecal weight increased by 115 g/day and mean transit time through the gut was decreased by 18 hr. Only part of the decrease in serum cholesterole may be due directly to the high intake of dietary fiber components. The remainder is due to differences in fat intake: during the high-fiber period subjects consumed less fat and cholesterol than had been planned.

The influence of peripheral vascular disease on methanogenesis in man.

Methane is produced by anaerobic bacterial metabolism in the colon and is excreted in the breath of only a proportion of healthy adults. Factors influencing methane excretion have still to be elucidated. The colonic vascular circulation may influence the intestinal environment facilitating growth of methanogens. The incidence of breath methane excretion has been investigated in patients with peripheral vascular disease and a control patient group. The proportions of subjects excreting methane in the control hospital group (43%) and in patients with predominantly femoro-popliteal disease (30%) were significantly less than in patients with predominantly aorto-iliac disease (83%) (P less than 0.005 and P less than 0.001, respectively). The presence of abdominal aortic arterial disease appears to be associated with a high incidence of methane excretion.

Enterohepatic circulation in man of a gamma-emitting bile-acid conjugate, 23-selena-25-homotaurocholic acid (SeHCAT).

A conjugated bile acid, 23-selena-25-homotaurocholic acid (SeHCAT), labeled with the gamma emitter Se-75, has been evaluated in man. Absorption and excretion were compared with that of simultaneously administered [23-14C]cholic acid. SeHCAT is absorbed quantitatively following oral administration, secreted into the bile at the same rate as cholic acid, reabsorbed from the small intestine, and resecreted. It is not absorbed when the terminal ileum has been excised or bypassed. SeHCAT is therefore the first of a new class of radiopharmaceuticals, namely, gamma-emitting tracers of the complete cycle of the enterohepatic circulation. Its use will simplify investigation of the functional state of the terminal ileum by eliminating the need to collect and process feces.