Intestinal absorption of oestrogen: the effect of altering transit-time

The mechanism by which a high fibre diet may reduce serum oestrogens is unknown. We hypothesized that time is a rate-limiting factor in oestrogen absorption from the colon so that changes in colonic transit-rate affect the proportion of oestrogen that is deconjugated and/or absorbed.

To determine if alteration of intestinal transit rate would influence the absorption of an oral dose of oestradiol glucuronide.

Twenty healthy postmenopausal women recruited by advertisement.

Department of Medicine, Bristol Royal Infirmary.

Volunteers consumed, in turn, wheat bran, senna, loperamide and bran shaped plastic flakes, each for 10 days with a minimum 2 week washout period between study periods, dietary intake being unchanged. Before and in the last 4 days of each intervention whole-gut transit-time, defecation frequency, stool form, stool beta-glucuronidase activity, stool pH and the absorption of a 1.5 mg dose of oestradiol glucuronide were measured.

Wheat bran, senna and plastic flakes led to the intended reduction in whole-gut transit-time, increase in defecatory frequency and increase in stool form score. Loperamide caused the opposite effect. The length of time the absorbed oestrogen was detectable in the serum fell with wheat bran and senna, although this was only significant for oestradiol. Oestrone, but not oestradiol, was detectable for a longer time with loperamide. Plastic flakes had no effect on either oestrogen. Areas under the curve did not change significantly but tended to fall with the three transit-accelerating agents and to rise with loperamide.

Our data indicate there is likely to be an effect of intestinal transit on the absorption of oestrogens but more refined techniques are needed to characterize this properly.