Effect of protein source and resistance training on body composition and sex hormones

A lot has been said about the alleged lowering of testosterone, raising of oestrogen & lessening of muscular growth when comparing soya protein powder to whey. Well here's a head to head comparison. It's only one study, so it's not proof, but in this one we find similar muscular growth, similar testosterone & oestrogen changes. The study is for 12 weeks. Here's some highlights of the study:

Quote :

No significant differences were observed between groups for total and free testosterone, SHBG, percentage body fat, BMI or body weight. The Testosterone/Estradiol ratio increased across all groups (+13.4, p = 0.005) and estradiol decreased (p = 0.002).

Quote :

This investigation shows that 12 week supplementation with soy protein does not decrease serum testosterone or inhibit lean body mass changes in subjects engaged in a resistance exercise program.

You can read the full study here, but the basics in this study are they are similar.

I still think adding just a little L-Leucine to a soya protein will enhance the effectiveness of the product - I could be wrong though, but as I can't see it hurting & L-Leucine is the main anabolic amino acid adding a little more can't hurt & may help IF you are training & eating 100% & need that extra 1 or 2 % more just to push you beyond what you'd achieve otherwise.