Fecal, urinary, and plasma estrogens and plasma androgens were studied in healthy pre- and postmenopausal vegetarian and omnivorous women. Dietary histories of the subjects revealed that omnivores consumed a higher percentage of total protein and fat from animal sources. The total 72-hr fecal excretion as measured by dry weight was higher for vegetarlans. Preliminary results indicate that vegetarian women excrete 2 to 3 times more estrogens in feces than do omnivores and that omnivores have about 50% higher mean plasma level of unconjugated estrone and estradial than vegetarians. Estriol-3-glucuronide, a compound that is formed upon reabsorption of free estriol from the intestine, is found in lower concentrations in the urine of vegetarians. These data suggest that in vegetarians a greater amount of the biliary estrogens escape reabsorption and are excreted with the feces. The differences in estrogen metabolism may explain the lower incidence of breast cancer in vegetarian women.


Presented at the Workshop on Fat and Cancer, December 10 to 12, 1979, Bethesda, Md. These studies were supported by Contract CB-74104 from the National Breast Cancer Task Force, National Cancer Institute.