EFFECT OF DIET ON LIGNANS AND ISOFLAVONOID PHYTOESTROGENS IN CHIMPANZEES

Diphenolic compounds belonging to the classes of lignans and isoflavon oids have been identified in urine of man and animals, including the c himpanzee. Some of these compounds, formed by intestinal bacteria from plant lignans and phytoestrogens, have been shown in animal studies t o exhibit biological activities that suggest they could function as ca ncer-protective compounds. The effect of diet on urinary excretion of these compounds in the adult male chimpanzee has been studied. It was found that the chimpanzees consuming their regular food excreted large amounts of the isoflavonoid phytoestrogens, equol (mean +/- SE) (127. 5 +/- 34.0 nmol/mg cr.) and daidzein (20.7 +/- 9.0 nmol/mg cr.) and th e lignan, enterolactone (14.1 + 3.5 nmol/mg cr.). Small amounts of the lignan, enterodiol, (0.4 +/- 0.2 nmol/mg cr.) were also excreted. On all other four test diets (high protein, high carbohydrate, high veget able, and high fat), the excretion was less, particularly on a high fa t diet where the excretion of all diphenolic compounds was reduced by more than 90% to a level observed in omnivorous human subjects or wome n with boast cancer. These results suggest that diet profoundly influe nces the excretion of both animal lignans and phytoestrogens in urine. Because non-human primates are particularly resistant to mammary and genital carcinoma on estrogen treatment, the present data suggest that the very high levels of phytoestrogens and lignans as found during ex posure to the regular diet may partially account for why these primate s are so resistant to hormonal manipulations to induce cancer.