Bowel Function and Non-Starch Polysaccharide Intake During the Menstrual Cycle

Previous studies have indicated that there might be an association between aspects of bowel function, food intake and the menstrual cycle. The aims of the work reported in this thesis were to assess women's perception of changes in bowel function during the course of the menstrual cycle, and then to determine in a prospective, subject blind trial whether there is an actual association between indices of bowel function and non-starch polysaccharide (NSP) intake with defined times during the menstrual cycle. Perceptions of bowel function were assessed from 279 replies to an anonymous postal questionnaire sent to a random sample of 1000 female students. The reported incidence of five symptoms of diarrhoea was significantly greater at the bleed than premenstrually or midcycle e.g. 33% of respondents reported increased defecation frequency during menses compared with 8% during the premenstrual phase and 2% at midcycle. There was no consistent pattern for the symptoms of constipation; however, decreased defecation frequency and difficult defecation were reported by significantly more women (maximum 16%) during the premenses and bleed than at midcycle. Four indices of bowel function (faecal wet weight and form, whole gut transit time and defecation frequency) and dietary intake were recorded for 45 consecutive days in 36 apparently healthy volunteers. The study started at any time during the menstrual cycle. Volunteers collected daily samples of early morning urine for the subsequent analysis of oestradiol, luteinizing hormone (LH) and progesterone metabolites and recorded the start of menses. Data from 22 women (61%) with good compliance and an apparently normal menstrual cycle were available for analysis. There was no evidence of bowel hypo- or hypermotility, or changes in energy or NSP intake during the 5 day peak oestrogenic, peak progestogenic, premenses or menses phases. There was, however, a significant increase (P< 0.05) in whole gut transit time at the onset of menses (days 1 and 2) compared with the premenses phase. These findings show that perceived changes indicative of diarrhoea do occur during menses, but they are of minimal intensity and short duration.