Damn, already found some that use humans for testing instead of animals. Now we have a conspiracy.
http://meeting.jco.org/cgi/content/a.../14_suppl/4611
Clinical and biologic activity of soy protein powder (SPP) in healthy male volunteers: effect on testosterone and luteinizing hormone (LH)
S. Goodin, F. Shen, W. Shih, N. Dave', M. Kane, G. Lambert, M. Gallo and R. Dipaola
Cancer Institute of New Jersey, New Brunswick, NJ; UMDNJ/Robert Wood Johnson Medical School, Piscataway, NJ
4611
Background: Epidemiologic studies and a recent prospective trial have revealed a reduced risk of prostate cancer associated with consumption of soy foods, possibly due to the estrogenic properties of soy. To determine if a commonly used SPP can have estrogenic activity in men, we specifically evaluated supplementation with SPP in healthy male volunteers and the effect on testosterone and LH. Methods:
Healthy volunteers recruited to this study were men 18 years of age or older that were in good health with no known allergy to soy or phenylalanine. Treatment consisted of consuming two scoops (56g) of pure SPP (Puritan's Pride, Oakdale, New York) daily for 28 days. Serum testosterone and LH levels were collected prior to initiation of supplementation with soy protein powder, throughout the 28 days, and 14 days after the completion of therapy. Patients maintained a food diary throughout the 28-day period. Results: Twelve healthy volunteers were enrolled with a mean age of 32 years (range 25 to 47). Serum testosterone concentrations decreased during the 4-week use of SPP and increased within two weeks after SPP was discontinued, with a statistically significant percent change in testosterone over the four-week period (P=0.021). At no time did the mean serum testosterone fall below the normal reference range. Serum LH concentrations decreased during the 4 week use of soy protein powder then increased within two weeks after soy protein powder was discontinued but the changes did not reach statistical significance (P =0.20). There were no side effects reported by any participants. Using a yeast based assay transfected with the alpha and beta estrogen receptor (ER), we found that the soy protein selectively activated ER-beta. Conclusions: Soy protein powder decreases testosterone levels in healthy patients, which is reversible upon removal of SPP from the diet. These data support further study of these hormonal effects as a mechanism in prostate cancer prevention.
No significant financial relationships to disclose.