ZKaudio, Soy and soy isoflavone consumption reduces estrogen levels in both men and women. It has no significant impact on testosterone levels or fertility in men (this is in contrast to the plethora of rat studies that the anti-soy club like to bandy around). Soy protein is as good as any other protein for building or maintaining muscle. All in all, I would think the reduction in estrogen levels alone would make soy protein a highly prized bodybuilding supplement, but the propaganda machinery is a strong force. Suits me just fine. While all those other women that compete against me wonder what my secret weapon is to get extra lean, I'll just be quietly sitting and sipping my soy shake!
Here is just a small sampling of the research IN HUMANS that shows the potential benefits of regular soy consumption.
Effect of soymilk consumption on serum estrogen and androgen concentrations in Japanese men.
Nagata C, Takatsuka N, Shimizu H, Hayashi H, Akamatsu T, Murase K.
Department of Public Health, Gifu University School of Medicine, Japan.
Soy consumption has been associated with a reduced risk of prostate cancer. The mechanism for this association may involve the
effect of soy on the endocrine system. We conducted a randomized dietary intervention study to determine the effects of soy
consumption on serum levels of steroid hormones in men. Thirty-five men were randomly assigned to either a soymilk-supplemented
group or a control group. The men in the soy-supplemented group were asked to consume 400 ml of soymilk daily for 8 weeks. The
men in the control group maintained their usual diet. Blood samples were obtained just before the initiation of the dietary period and
thereafter every two weeks for 12 weeks. Changes in hormone concentrations were analyzed and compared between the two groups
using the mixed linear regression model against weeks from the start of the dietary period. The mean (SD) soymilk intake estimated
from dietary records during the dietary study period was 342.9 ml in the soymilk-supplemented group. There was a
significant difference between the two groups in terms of changes in serum estrone concentrations, which tended to decrease in the
soy-supplemented group and increase in the control group over time. None of the other hormones measured (total and
free-testosterone, or sex hormone-binding globulin) showed any statistical difference between the two groups in terms of patterns of
change. The results of the study indicate that soymilk consumption may modify circulating estrone concentrations in men.
The specific role of isoflavones on estrogen metabolism in premenopausal women.
Kumar NB, Cantor A, Allen K, Riccardi D, Cox CE.
Department of Nutrition, H. Lee Moffitt Cancer Center and Research Institute, University of South Florida, Tampa, Florida 33612,
USA.
[email protected]
BACKGROUND: There is increasing evidence that dietary factors may play a role in the production, metabolism, and bioavailability
of sex hormones and their impact on target tissues. The specific objective of this study was to evaluate the effectiveness of
supplementing a group of premenopausal women who were free of breast carcinoma with a dietary supplement of isoflavones (40 mg
per day) in producing a change in steroid hormones and menstrual cycle length. METHODS: Sixty-eight consecutively recruited,
premenopausal, omnivorous women of all races and ethnicities between the ages of 25 years and 55 years were admitted to the study
and randomized to an experimental group supplemented with soy (40 mg genistein per day) or to a control group that consumed a
placebo for a 12-week period. Changes in their anthropometric, nutritional, and hormonal biomarkers from early follicular phase were
analyzed at baseline and post-intervention. RESULTS: Serum-free estradiol and estrone levels decreased moderately in the
experimental group. Serum hormone-binding globulin levels increased in 41.4% of women in the experimental group compared with
37.5% of women in the placebo group. Free estradiol decreased in 53.85% of women in the experimental group compared with
37.5% of women in the placebo group. Estrone decreased in 55.56% of women in the experimental group compared with 42.86% in
the placebo group. Those women in the experimental group who were consuming soy had their mean menstrual cycle length increased
by 3.52 days compared with a mean decrease of 0.06 days for women in the placebo group from baseline to the third
menstrual cycle. In addition, women who were taking soy had their mean follicular phase increase by 1.46 days compared with a mean
increase of 0.14 days for women who were taking the placebo (P = 0.08). CONCLUSIONS: These data suggest that increased
isoflavone intake affects estrogen metabolism by altering the steroid hormone concentrations and menstrual cycle length, thereby
demonstrating a potential to reduce the risk for breast carcinoma
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