HORMONAL RESPONSE TO DIETS HIGH IN SOY OR ANIMAL PROTEIN WITHOUT AND WITH ISOFLAVONES IN MODERATELY HYPERCHOLESTEROLEMIC SUBJECTS

Authors: GOLDIN, BARRY - TUFTS UNIVERSITY; BRAUNER, EDGAR - TUFTS UNIVERSITY; ADLERCREUTZ, HERMAN - UNIV OF HELSINKI FINLAND; AUSMAN, LYNNE - TUFTS/HNRCA; LICHTENSTEIN, ALICE - TUFTS/HNRCA

Submitted to: Nutrition and Cancer
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2004
Publication Date: 1/1/2005
Citation: Goldin, B.R., Brauner, E., Adlercreutz, H., Ausman, L.M., Lichtenstein, A.H. 2005. Hormonal response to diets high in soy or animal protein without and with isoflavones in moderately hypercholesterolemic subjects. Nutrition and Cancer. 51(1):1-6.

Interpretive Summary: Soy protein has been associated with altered risk of developing endocrine regulated cancers. This study was designed to assess the effect of soy protein compared to common sources of animal protein and compounds normally found in soybeans, termed isoflavones, on the level of estrogen and androgen in blood. Both postmenopausal women and older men were included in the study. Forty-two subjects (>50 years) with LDL cholesterol 130 mg/dL were fed each of four diets in randomized order for 6 weeks each. All food and drink were provided. Diets contained 25 g soy protein or common sources of animal protein per 1000 calories and trace or 50 mg isoflavones per 1000 calories. At the end of each diet phase concentrations of the most prevalent estrogens and androgens were measured. In postmenopausal women, concentrations of estrone were higher and the compound it is made from, dehydroepiandrosterone, lower after the subjects ate the diets containing soy protein. There was no effect of isoflavones on any of the hormones measured. In older men, dehydroepiandrosterone sulfate concentrations were lower after they ate the diets containing isoflavone and higher after they ate the diets containing animal protein diet. These data suggest that relatively large amounts of soy protein or soy derived isoflavones had modest and limited gender specific effects on circulating hormone levels.

Technical Abstract: Consumption of soy protein has been associated with altered risk of developing endocrine regulated cancers. This study was designed to assess the independent effect of soy relative to animal protein and soy derived isoflavones on circulating estrogen and androgen concentrations in postmenopausal women and older men. Forty-two subjects (>50 years) with LDL cholesterol >3.36 mmol/L were fed each of four diets in randomized order for 6 weeks/phase. All food and drink were provided. Diets contained 25 g soy or common sources of animal protein/4.2 MJ containing trace or 50 mg isoflavones/4.2 MJ. At the end of each diet phase concentrations of estrone sulfate, estrone, estradiol, testosterone, androstendione, dihydrotestosterone, dehydroepiandrosterone and dehydroepiandrosterone sulfate were measured. In postmenopausal women, concentrations of estrone were higher and its precursor, dehydroepiandrosterone, lower after consuming the soy compared to animal protein diets (P=0.0396 and 0.0374, respectively). There was no significant effect of isoflavones on any of the hormones measured. In older men, dehydroepiandrosterone sulfate concentrations were lower after consuming the isoflavone (P=0.0106) and higher after consuming the animal protein diets (P=0.0118). These data suggest that relatively large amounts of soy protein or soy derived isoflavones had modest and limited gender specific effects on circulating hormone levels.