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Bodybuilding FAQ - Is Soy Bad for Your Bodybuilding Endeavors?

By November 19, 2008

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Soy has been shown to exhibit positive health benefits for both men and women. Studies have shown it may reduce the risk of hormone-dependent cancers (breast, prostate, etc), and other cancers as well. Soy's primary health benefits include reducing high cholesterol and easing the symptoms of menopause in women. Soy has also been shown to help with osteoporosis by building up bone mass. Because of this, I like to recommend 1 serving of soy protein per day for women.

However, in the muscle building department, I don't feel that soy is very useful when used on its own since it is an incomplete protein lacking in the sulfur containing amino acid methionine (which is very important for protein synthesis and immunity) and its Biological Value (a value that measures how well the body can absorb and utilize a protein based on nitrogen retention) is a distant 74 (as opposed to the BV of whole eggs which is 100 and of whey which is 104). Soy is high in branched chain amino acids (BCAAs), however. Therefore, if combined in small quantities with a complete and more bioavailable protein like egg, whey or chicken one can benefit from its high BCAA content.

So is soy bad to achieving your bodybuilding endeavors? Not at all but if you are looking to build muscle, make sure that this is not your main source of protein and be sure to combine it with complete proteins when you ingest it.


January 5, 2009 at 6:35 am
(1) Vanessa says:

It’s a shame how ill-imformed this posting is. Soy IS actually a COMPLETE protein with a BV of 79! Please, research sources before making such claims.

January 5, 2009 at 1:51 pm
(2) bodybuilding says:

Hello Vanessa. Thank you so much for pointing out the typo. Yes, you are correct; soy has a higher BV value than the one I had originally posted. I am surprised that no one else caught this sooner. Per my sources, the BV value of soybean protein isolate is 74.

In regards to whether soy is complete or not, perhaps I can offer some clarification on this matter.

While soy technically does contain all amino acids, it is extremely lacking in the amino acid methionine. As a result, this makes it an unbalanced source of protein, and thus incomplete on its own for the purposes of muscle building and fat loss.

Again, I am not saying that soy is bad at all. I am simply saying that on its own it is not the best muscle building protein and therefore it should be used in conjunction with a more balanced and complete source.

Thanks again for the comment.


June 19, 2009 at 1:18 am
(3) Alexandra says:

How does the rating work exactly? I remember reading that egg protein absorb sat only about 3 grams per hour, as opposed to 11 grams per hour for whey.

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