The fermentability of cellulose and dietary fibre in common clinical use (Inolaxol, Fiberform, Vi-Siblin, Lunelax, pectin) was measured as the in vitro production of short-chain fatty acids, lactate, and ammonia in 16.6% faecal homogenates from 18 healthy volunteers. The results were compared with the contents of soluble and insoluble non-starch polysaccharides as determined by the method of Englyst. The amounts of soluble non-starch polysaccharides in the fibre were closely associated with the mean productions of short-chain fatty acids after 6 h (R = 0.94, p < 0.002) and 24 h (R = 0.98, p < 0.0002) of incubation. The mean production of ammonia was inversely related to the soluble fraction of the fibre (after 6 h, R = -0.93, p < 0.003; after 24 h, R = -0.90, p < 0.006). These variables were not dependent on the insoluble fractions of the fibre. The in vitro fermentability differed considerably among the fibres: cellulose and Inolaxol (sterculia gum) were almost non-fermentable, Fiberform (wheat bran-based) was low-grade fermentable, Vi-Siblin and Lunelax (both ispaghula husk) were intermediately fermentable, and pectin was highly fermentable. These findings support that the water solubility determines the degree of fermentability of dietary fibre and thereby the corresponding bacterial assimilation of ammonia. In vitro measurements of short-chain fatty acid production in faecal homogenates may hence supplement commonly used methods to classify dietary fibre.

The present randomized study compared the influence of a gel-forming wheat bran with a nongel-forming bulk cathartic (an ispaghula formulation, Vi-Siblin S) on the steady state concentrations of digoxin in plasma in 30 geriatric in-patients treated with either combination (16 with wheat bran + digoxin, 14 with ispaghula + digoxin) for 4 weeks. After 2 but not after 4 weeks, wheat bran reduced the digoxin levels, although the levels were still within the therapeutic range. Ispaghula had no influence at any time. It is concluded that neither wheat bran nor the ispaghula formulation has any clinically relevant influence on therapeutic digoxin levels in geriatric patients.

The intestinal dietary fibre degradation and faecal bulking capacity of various bulk laxatives were investigated by means of balance experiments on rats. Nitrogen, fat, and mineral excretion in faeces was also studied. The dietary fibre content of the various bulk laxatives was quite different (in g/kg dry matter): ACO fibre tablets (barley and citrus pulp), 451; Fiberform (wheat bran-based), 817; Inolaxol (sterkulia gum), 696; and Vi-Siblin (ispaghula husk), 533. The increase in faecal dry matter per 1 g dietary fibre was similar with ACO fibre tablets, Fiberform, and Vi-Siblin. Inolaxol gave a significantly (p less than 0.001) higher faecal dry-weight increment, mainly due to an increased mineral excretion. Of the dry-weight increment, 59-82% constituted undegraded dietary fibre. Thus, 68-97% of the fibre passed through the gastrointestinal tract without being degraded. All the bulk laxatives caused a similar increase in the faecal N content, whereas the increase in faecal lipids was most pronounced with Vi-Siblin. The water-holding capacity of faeces was more pronounced with Inolaxol and Vi-Siblin than with ACO fibre tablets and Fiberform.

A fibre made of psyllium husk was given to 12 elderly patients for 4 months in order to investigate their faecal output and selected serum parameters. The fibre significantly improved bowel function and faecal output confirming its value as a non-irritant, harmless bulk-forming laxative. Serum cholesterol was decreased by 20% while triglycerides remained unchanged. There was a significant reduction in serum calcium after withdrawal of the fibre supplement. There were no significant changes in serum iron, total iron binding capacity, fibrinogen, or in the haematological parameters (ESR, haemoglobin, leucocyte count) attributable to the fibre. The high phytate content of the fibre does not appear to have any clinically significant effect on mineral absorption. It is suggested that dietary fibre (at least psyllium-based fibre preparations) may have significant cholesterol lowering capacity due to the binding of bile-acids in the intestine.

The effects of activated charcoal and fibre on absorption and stationary plasma levels of digoxin and digitoxin have been studied. The effect of fibre alone is small but an interactive effect on absorption may occur if fibre and digoxin are ingested simultaneously. Charcoal effectively decreases glycoside absorption even when administered after the glycosides. During maintenance therapy with digoxin or digitoxin, charcoal administration decreased the glycoside plasma levels by 31.2% and 18.3% respectively. It is suggested that even digoxin may have a significant biliary excretion and enterohepatic circulation or that this glycoside has a significant intestinal secretion. The therapeutic implication of this study is that charcoal may be of value, not only in the management of acute glycoside poisoning, but also in some cases of more chronic intoxication.

Nine patients complaining of constipation and with diverticuli of the colon on barium-enema were examined with regard to transit-time, bowel movements and subjective symptoms. They were treated with placebo and Vi-SiblinR, using a doubleblind cross-over technique. The transit-time remained normal during the Vi-SiblinR treatment. The feces became softer and increased in weight and the subjective symptoms were significantly reduced (p less than 0,05).

Transit time, as estimated from the passage through the gut of an isotope (131I)-containing capsule, was studied in 10 constipated, geriatric in-patients on a bulk laxative regimen and during treatment with wheat bran. The patients received a conventional bulk laxative (Vi-Siblin, 6 g twice daily) during a period of 8 weeks. The bulk laxative was then replaced by bran (10 g twice daily) during the following 8-week period. Measurements of transit time were taken after 4 and 6 weeks on each regimen. The mean transit time was 126 h for the bulk laxative regimen and 89 h for the bran treatment, the difference being statistically significant. The decrease in transit time for the bran treatment was essentially due to a faster passage through the rectosigmoid part of the bowel. Less additional laxative therapy was needed during bran treatment than during the bulk laxative treatment. The favourable properties of bran may tentatively be explained by the effects remaining in the distal part of the colon. A slight but significant lowering of the serum calcium level and a significant increase of the total iron-binding capacity of the serum were found after 7 weeks of bran administration, whereas no change was observed after 42 weeks. No significant change was demonstrated in serum iron during bran treatment.

A new method for the determination of the gastrointestinal transit time (TT) is described. The normal range of the TT was 40--95 h in 58 normal subjects. No age or sex variation of the TT was disclosed. In 25 out-patients with the irritable bowel syndrome the TT was determined before and after 3 weeks' treatment with Vi-Siblin. Of these patients, 20% initially showed a prolonged TT; this decreased during treatment with Vi-Siblin. In the patients with normal TT, this remained unchanged during the treatment. Our study suggests that patients with long TT, long intervals between bowel movements, and frequent attacks of colicky abdominal pain may derive benefit from a plant fibre supplement to their diet. The method for the determination of the TT described is well suited to out-patient studies--also in large populations--since it is relatively easy to perform, stool collection is unnecessary, and the method shows good reproducibility.

Bulk laxatives have been said to have a good effect in normalizing both hard and loose stools in geriatric patients as concluded from some open studies. In a double-blind study Vi-Siblin, Lunelax and placebo were compared in the six weeks treatment of 29 patients (8 patients on Vi-Siblin, 8 patients on Lunelax, 13 patients on placebo). Two weeks prior to the study and the two last weeks of the study defecation frequency, consistency of stools and the use of additional laxatives were registered by the personnel. Results showed no significant differences between groups or between substances. From this controlled double-blind study it is not possible to draw any definite conclusions regarding the efficacy of bulk laxatives on geriatric patients.