Re: Soy as contraceptive

Clinical and biological activity of soy protein powder supplementation
in healthy male volunteers.

Goodin S, Shen F, Shih WJ, Dave N, Kane MP, Medina P, Lambert GH,
Aisner J, Gallo M, DiPaola RS.
Department of Medicine, University of Medicine and Dentistry of New
Jersey/Robert Wood Johnson Medical School, New Brunswick, NJ
08903-2681, USA.

PURPOSE: To determine if a commonly used soy protein supplement
exhibits biological activity in vivo and in vitro, we evaluated an
over-the-counter soy protein powder supplement using blood from
healthy male volunteers and in an estrogen receptor in vitro assay.
SUBJECTS AND METHODS: We recruited healthy male volunteers 18 years of
age or older that were in good health. Treatment consisted of
consuming two scoops (56 g) of pure soy protein powder (Puritan's
Pride, Oakdale, NY) daily for 28 days. Serum testosterone and
luteinizing hormone (LH) levels were collected on days -7, 0, 14, and
28 of therapy, and day 42. A reporter estrogen receptor (ER) assay was
used to determine the effect on ER-beta and ER-alpha in vitro.
RESULTS: Twelve subjects were enrolled with a mean age of 32.25 years
(range 25 to 47). Serum testosterone decreased 19%(+/-22%) during the
4-week use of soy protein powder (P = 0.021) and increased within 2
weeks after we discontinued soy protein powder. Serum LH
concentrations decreased during the 4-week use of soy protein powder
then increased within 2 weeks after we stopped the soy protein powder,
but the changes did not reach statistical significance (P = 0.20). Soy
protein powder was found to induce agonist activity to ER-beta using a
reporter estrogen receptor assay in yeast. CONCLUSION: Soy protein
powder decreases serum testosterone levels in healthy men and acts as
an ER-beta agonist; the significance of this biological effect with
respect to cancer prevention needs further study.
PMID: 17416779
.

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