There is a myth that if a man takes vast amounts of soy protein it will lead to the production of estrogen. But any rational human would like to do it for a long period of time.
If a bodybuilder starts taking soy he won’t notice any changes comparing to the person that has never consumed soy.
 The results of a long-term investigation of the metabolic balance in young men which determined the nutritional quality of an isolated soy protein and beef proteins held by V.R. Young, A. Wayler, C. Garza, F.H. Steinke, E. Murray, W.M. Rand, and N.S. Scrimshaw were published in 1984 in the American Journal of Clinical Nutrition (Am. J. Clinical Nutrition, Jan 1984; 39: 8 – 15).
After the 84- day study of two groups where one group consumed totally isolated soy protein and the other used beef proteins they have managed to arrive at the conclusion and found out the dependence between soy protein and bodybuilding.
The measurement of the mass of the body cells didn’t show any deterioration in the protein nutritional status. They have managed to prove the predication, derived from the short-term investigations of the nitrogen balance, that isolated soy protein has high nutritional quality and this protein can be used as the source of essential amino acids and nitrogen in order to preserve the proteins in adults.
In conclusion it should be said that soy is not the best source for achieving huge anabolic muscle growth. In the post workout period it will be useful to consume high quality whey protein then the soy protein. But soy is not harmful for bodybuilding in case if you don’t take the most of your protein source consuming only soy products, which is not optimal. It should be necessary to ingest quite a bit during the day in order to reveal any negative effects of soy. It especially concerns male individuals.
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