Whey or Soy Protein - which is best?

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)

Whey Protein Advantages

-Whey protein contains high levels of both essential and non-essential amino acids

-In its purest form, as whey protein isolate, it contains very little fat and lactose

-Whey protein is an excellent source of the essential amino acid, leucine, which helps to promote muscle growth. Whey protein isolate has approximately 50% more leucine than soy protein isolate

- Increases glutathione levels in the body. Gluathione is an anti-oxidant that boosts the immune system (Whey Protein Institute, 2007)

-Bioactive components may help to reduce cholesterol

Whey Protein Disadvantages

-Possible concerns about using whey protein from cows that have been immunized against certain diseases. However, many studies, including one published in Regulatory toxicology and pharmacology have concluded that there is no danger in using milk from hyperimmunized cows (Gingerich and McPhillips, 2005)

-Possibility of milk being contaminated by foodborne pathogens (Oliver et al., 2005).

-Some people are allergic to whey protein

-Not suitable for vegetarian diets

Overall, whey and soy protein both have many advantages. However, some soy protein components have shown negative effects in scientific studies. A variety of factors need to be taken into consideration when deciding whether to take whey or soy protein as a Bodybuilding Supplement. Although apparently if you’re a rat, both will build muscle equally…

References

Fortitech (2006). Soy and Whey Build Muscle Equally-in rats at least. Schenectady (NY) (online). Available from http://www.fortitech.com/default.aspx?CurrenttabID=49&ArticleID=16204&TabID=49

[Cited Feb.28, 2007].

Gingerich and McPhillips (2005). Analytical approach to determination of safety of milk ingredients from hyperimmunized cows. Regulatory toxicology and pharmacology; (41)(2):102-112. Epub 2004 Dec.9. Abstract available online from http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&
cmd=Retrieve&dopt=AbstractPlus&list_uids=15698533&query_hl=7&itool=pubmed_docsum [Cited Feb.28, 2007].

Henkel (2000). Soy: Health Claims for Soy Protein, Questions About Other Components. U.S. Food and Drug Administration (online). Available from http://www.fda.gov/Fdac/features/2000/300_soy.html [Cited Feb.28, 2007].

Oliver et al. (2005). Foodborne pathogens in milk and the dairy farm environment: food safety and public health implications. Foodborne Pathogens and Disease; 2(2)115-29. Abstract available online from http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?itool=abstractplus&db=pubmed&
cmd=Retrieve&dopt=abstractplus&list_uids=15992306 [Cited Feb.28, 2007].

Whey Protein Institute (2001). Available online from http://www.wheyoflife.org/ [Cited Feb.28, 2007].

Wikipedia.org (2007). Soy protein. Available online from http://en.wikipedia.org/wiki/Soy_protein [Cited feb.28, 2007].