Question:
I always hear about the benefits of soy protein but you are totally against it. What is so bad about soy protein?
Answer:
Soy protein is just not a very good protein for building muscle. Its biological value is low and it contains large amounts of naturally occurring toxins that many food scientists refer to as antinutrients. Among these antinutrients are enzyme inhibitors that block the action of trypsin and other critical enzymes involved in protein digestion. These inhibitors can cause gastric distress, reduced protein digestion and chronic deficiencies in amino acid uptake. Studies have also shown that diets high in trypsin inhibitors can be carcinogenic.
Soy contains haemagglutinin, a clot-promoting chemical that causes red blood cells to clump together. And soy also contains phytic acid that can block the uptake of essential minerals - calcium, magnesium, copper, iron, and zinc - in the intestinal track. These chemicals are called "growth inhibitors".
An equally nasty component of soy protein is its high isoflavone content. Isoflavones are estrogen-like compounds also called natural estrogens. In fact just 100 grams of soy protein has the estrogenic equivalent of a typical birth control pill. Studies have also shown isoflavones inhibit the synthesis of certain steroid hormones and inhibit beta-hydroxysteroid dehydrogenase - the key enzyme that converts pro-hormone compounds into testosterone.
It amazes me that some supplement companies ignorantly continue to market isoflavones such as chrysin as a way to promote testosterone production and inhibit estrogen when, in fact, it does just the opposite. It increases estrogen and decreases testosterone. Ever wonder why those andro supplements that contained chrysin never worked? Now you know.
These are a few major reasons why soy protein and its isoflavone content are not only poor nutritional sources for building muscle, but there is mounting evidence that they can actually stunt growth and may be harmful to your health.
I know this is probably exactly opposite of what you've been told by the "spin-doctors" that are promoting their supplements, but if you take a good look at the research you'll discover there are many things they say that doesn't mesh with the science.
Answered By Paul Delia
AST Sports Science
Originally posted: 7/31/2000
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