Yogurt consumption and estrogen metabolism in healthy premenopausal women

Dietary modification of intestinal microflora by yogurt or Lactobacilli supplementation has been shown to decrease fecal beta-glucuronidase activity, thereby possibly affecting estrogen metabolism and lowering breast cancer risk. To determine if yogurt consumption modifies fecal beta-glucuronidase activity and plasma and urine estrogen concentrations, 16 women (24.8 +/- 1.0 y; mean +/- SEM) were assigned randomly to two groups, control (CON;n=7) or yogurt treatment (YOG;n=9). Control subjects refrained from yogurt consumption for three months, whereas the YOG group consumed two cups (454 g/d) of commercially produced yogurt made with a culture (1:1 ratio) of Lactobacillus delbrueckii ssp bulgaricus and Lactococcus salivarius ssp thermophilus (>10(7) colony forming units/g yogurt) for three consecutive months. Prior yogurt consumption did not exceed 4-6 cups/month and subjects consumed their usual diets during the study. Three-day diet records, fasting mid-luteal blood, and 24 h urine collections were obtained during three consecutive days of subjects' first-, second-, and fourth-menstrual cycles. Fecal samples were collected once during each menstrual cycle. Dietary nutrient intakes were not significantly different within or between groups throughout the study. The YOG group was consuming a low-fat diet (19-22% of total calories). Fecal beta-glucuronidase activity and plasma and urinary estrone and estradiol-17 beta concentrations were assessed following baseline and months one and three for CON and YOG consumers. No significant differences were observed within or between groups for any of the aforementioned biochemical variables. In conclusion, three months of yogurt consumption did not alter fecal beta-glucuronidase activity or plasma and urine estrogen concentrations. (C) 1999 Elsevier Science Inc.