Constipation during pregnancy: dietary fibre intake and the effect of fibre supplementation. Randomised-controlled trial of a fibre supplement on the symptoms of irritable bowel syndrome.
Forty women who complained of constipation during the third trimester of pregnancy completed 14-day weighed diet records and bowel function charts over a 4-week period. After 2 weeks of baseline observation the women were randomly allocated into three groups which were asked to take 10 g dietary fibre supplements per day in the form of either a corn-based biscuit (Group A), or as wheat bran (Gp B), or to continue without intervention (Gp C). Mean (+/- s.e.m.) daily dietary fibre intake in the first 2 weeks was similar to that in the general population, at 20.4 +/- 1.2 g, for the whole group, and 21.1 +/- 1.6 g for the 26 women who said they had already increased their dietary fibre intakes in attempts to relieve their symptoms. In the final 2 weeks changes in fibre intakes were: Gp A, mean increase 7.2 +/- 1.0 g per day (P less than 0.001); Gp B, mean increase 9.1 +/- 1.6 g per day (P less than 0.001); Gp C mean decrease 3.50 +/- 1.6 g per day (P less than 0.005). These changes were accompanied by an increase in the number of bowel movements and a change to a softer stool consistency in Gps A and B, with no changes in number of bowel movements or stool consistency in Gp C. The aim of this study was to assess the effect of coarse wheat bran on specific bowel function parameters and symptoms in patients with irritable bowel syndrome (IBS). A longitudinal, prospective, randomised, placebo-controlled trial was undertaken. The duration of treatment was eight to 12 weeks and this consisted of 10-20 g/day of coarse wheat bran or a low fibre placebo taken in addition to the normal diet. Twenty-eight outpatients fulfilling the Rome criteria for constipation-predominant IBS were recruited to the trial (14 in the treatment group; 14 in the placebo group). Twelve people completed the trial in the treatment group and ten in the placebo group. The main outcome measures included changes in symptoms recorded in a diary, changes in objective measurements of bowel function and subjective overall feelings of improvement. The bran group significantly increased their non-starch polysaccharide (NSP) intake over that of the placebo group (p < 0.05). Mean stool wet weight increased significantly more in the bran group than in the placebo group (p < 0.05), but other bowel function measurements and all recorded symptoms were not different. Many patients reported changes in bowel habit that were not reflected in the objective measurements. The addition of coarse wheat bran to the diet increased NSP ingestion and stool wet weight in this group of IBS patients, but no evidence was obtained that such treatment was of benefit to these patients, other than a placebo effect on symptoms.
Dietary supplements of fibre in the form of bran or wheat fibre are likely to help women experiencing constipation in pregnancy. If the problem fails to resolve, stimulant laxatives are likely to prove more effective.