The menstrual cycle has no effect on gastrointestinal transit time. Evaluation by means of the lactulose H2 breath test.

Gastrointestinal transit time was studied by means of the H2 breath test (after administration of 20 g of lactulose) in 20 healthy women with regular menstrual cycles. The mean transit time measured in the follicular phase of the cycle (M +/- SE = 71.25 +/- 6.69 min) did not differ statistically from that measured in the luteal phase (66.75 +/- 5.49 min). Data were statistically analyzed using Student's t test for paired data and the Wilcoxon Test for non-parametric data. Our results show that, in physiological conditions, female sex hormones do not affect mouth-to-caecum transit time. The H2 breath test is easy to perform and well tolerated; it thus proves particularly suitable for use in women of child-bearing age.