VARIABILITY OF GASTROINTESTINAL TRANSIT IN HEALTHY WOMEN AND MEN

Background and Aims-Measurements of gastrointestinal transit are made in clinical and research gastroenterology, yet their intrinsic variabi lity is not well characterised. In particular, an influence of hormone s on transit has been proposed as the basis for gastrointestinal sympt oms that vary with the menstrual cycle. Our aims were to quantify indi vidual differences in transit during the menstrual cycle in healthy wo men and to compare these with the intrinsic variability in healthy men . Methods-On two occasions, whole gut transit was assessed scintigraph ically and colonic transit quantified by radioopaque markers. Thirty t wo healthy volunteers (12 women, 20 men) were studied, women during th e follicular and luteal phases, men twice within a similar four week p eriod. Diets and exercise were standardised prior to and during both s tudies. Results-Colonic transit was significantly faster in men, and p ostlag gastric emptying was also more rapid; other indices of regional transit were not different between the sexes. Total colonic transit t ime was equally well reflected by the scintigraphic and radio-opaque m arker methods. Important intraindividual differences were noted in bot h sexes. The variances in our samples predicted an 80% chance of detec ting (with 95% confidence) a mean effect of menstrual hormones on tran sit that was in the same range as the intrinsic variation in men. Conc lusions-Colonic transit was faster in men than in women. Although grou p means in the two studies were almost identical, single assessments o f transit in subjects sometimes exhibited considerable variability, im plying broad biological variations. Given this intrinsic variability, the influence of menstrual hormones on gastrointestinal transit must b e small and of doubtful clinical significance.