Soy Protein

A huge debate in the Bodybuilding Industry has been to determine which is better at building muscle - soy or whey protein. Many bodybuilders are decidedly anti-soy, and many rumors circulate about the different “non-anabolic” effects of soy, as well as it's low BV index. On the flip side of the coin, some people swear by soy protein. The debate isn't restricted to bodybuilding though; an article on the website fortitech.com states: “Soy and whey build muscle equally- in rats at least”. Lets take a look at the positive and negatives for each.

Soy Protein Advantages

-Soybeans contain all of the amino acids necessary for good nutrition

-Clinical studies consistently show that soy protein can lower cholesterol levels (Henkel, 2000)

-May reduce the risk of various illnesses including osteoporosis, prostate cancer, and colon cancer (Henkel, 2000)

-Suitable for vegetarian diets

-Like whey protein, increases levels of gluathione in the body

Soy Protein Disadvantages

- Soy protein has a lower biological value (BV) than whey protein. This scale rates how efficiently your body can use a protein source. Basically, the higher the BV, the more nitrogen your body can absorb and retain. Soy protein has a BV of 74 and whey protein has a BV of about 100. So, in terms of bodybuilding, whey protein will help you to add muscle more quickly than soy. However, some studies on rats have shown that the BV of soy protein isolates may be equal to that of animal proteins, especially when enriched with the amino acid methionine (Wikipedia, 2007).

- The isoflavones daidzein and genistein are available in supplement form and are a component of soy protein. Isoflavones are phytoestrogens, a weak form of estrogen. Some studies have suggested that high isoflavone levels in the body might increase cancer risk. However, the results are inconclusive, and not all studies have found similar effects (Henkel, 2000). Note that this is a concern with isolated substances from soy protein, not the intact soy protein.

- Some scientific data using rats suggest that the component of soy protein, genistein, may prompt undesirable effects such as the growth of breast tissue in males (Henkel, 2000)