title: Effects of replacing meat with soyabean in the diet on sex hormone concentrations in healthy adult males.
abstract: A randomised crossover dietary intervention study was performed to evaluate the effects of replacing meat protein in the diet with a soyabean product, tofu, on blood concentrations of testosterone, dihydrotestosterone, androstanediol glucuronide, oestradiol, sex hormone-binding globulin (SHBG), and the free androgen index (total testosterone concentration/SHBG concentration x 100; FAI). Forty-two healthy adult males aged 35-62 years were studied. Diets were isoenergetic, with either 150 g lean meat or 290 g tofu daily providing an equivalent amount of macronutrients, with only the source of protein differing between the two diets. Each diet lasted for 4 weeks, with a 2-week interval between interventions. Fasting blood samples were taken between 07.00 and 09.30 hours. Urinary excretion of genistein and daidzein was significantly higher after the tofu diet (P < 0.001). Blood concentrations of sex hormones did not differ after the two diets, but the mean testosterone:oestradiol value was 10% higher (P = 0.06) after the meat diet. SHBG was 3% higher (P = 0.07), whereas the FAI was 7% lower (P = 0.06), after the tofu diet compared with the meat diet. There was a significant correlation between the difference in SHBG and testosterone:oestradiol and weight change. Adjusting for weight change revealed SHBG to be 8.8% higher on the tofu diet (mean difference 3 (95% CI 0.7, 5.2) nmol/l; P = 0.01) and testosterone:oestradiol to be significantly lower, P = 0.049). Thus, replacement of meat protein with soyabean protein, as tofu, may have a minor effect on biologically-active sex hormones, which could influence prostate cancer risk. However, other factors or mechanisms may also be responsible for the different incidence rates in men on different diets.
authors: School of Biological and Chemical Sciences, Deakin University, Melbourne, Australia.
authors: R C
authors: RC
authors: Habito
authors: J
authors: J
authors: Montalto
authors: E
authors: E
authors: Leslie
authors: M J
authors: MJ
authors: Ball
mesh_terms: D000328:Adult; D015113:Androstane-3,17-diol / Q000031:analogs & derivatives / Q000097:blood; D018592:Cross-Over Studies; D004044:Dietary Proteins / Q000008:administration & dosage*; D013196:Dihydrotestosterone / Q000097:blood; D004958:Estradiol / Q000097:blood; D012739:Gonadal Steroid Hormones / Q000097:blood*; D006801:Humans; D008297:Male; D008460:Meat; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000517:prevention & control; D012738:Sex Hormone-Binding Globulin / Q000032:analysis; D013025:Glycine max; D013739:Testosterone / Q000097:blood
chemical_list: D004044:Dietary Proteins; D012739:Gonadal Steroid Hormones; D012738:Sex Hormone-Binding Globulin; D013196:Dihydrotestosterone; D015113:Androstane-3,17-diol; C028895:androstane-3,17-diol glucuronide; D013739:Testosterone; D004958:Estradiol