Soy Protein: How does soy compare to whey protein for weightlifters?

Dear Tom,

How do soy and whey protein differ in benefits for weightlifters? I was reading on the site “Tim’s Nutrition & Weighlifting Page”, that protein isn’t measured by B.V. anymore but by PDCAAS (Protein Digestibility Corrected Amino Acid Score) and that whey and soy both have the highest scores. The author seems biased towards soy, and I’ve been conditioned that whey is the best, so I am hoping that you can offer additional input on soy vs. whey protein. Thanks in advance.

For weightlifters and bodybuilders, I am very partial to whey as a protein suppplement. I am even more partial to lean whole food proteins as your primary protein sources. For more information on the difference between whole protein foods and protein supplements (whey powders, etc.), please refer to my article: Protein Supplements vs. protein foods

I really don’t want to get into the “soy and your health” debate in this article, but from a bodybuilding perspective, to say that soy is better than whey is utterly ridiculous. Soy is a poor quality protein compared to whey, milk or egg protein, because soy is lacking in the amino acid methionine.

One way the soy manufacturers promote their product in the bodybuilding industry is to simply select the protein ranking method that ranks their brand of protein the highest.There are many methods of measuring protein quality including Net Protein Utilization (NPU), Biological Value (BV), Protein Efficiency ratio (PER) and protein digestibility corrected amino acid score (PDCAA).

Not surprisingly, soy ranks higher on the PDCAA scale than on other scales of protein quality. That’s why every time you read an article on the benefits of soy protein, you’ll see PDCAA quoted and other measures of protein quality “flamed” or called inferior.

Biological Value makes the most sense for measuring the quality of protein because BV measures the amount of nitrogen retained for growth as expressed as a percentage of nitrogen absorbed.

BV = (N retained/N absorbed) X 100

Based on this formula, BV must be expressed as a percentage; therefore, its obvious that BV cannot exceed 100 and that inflated claims like “Brand XYZ protein has a biological value of 150″ are not possible. Whey protein has a high BV, but it cannot exceed 100. On that note, the author of the article you quoted is correct.

I have never used soy protein and I don’t know any other successful competitive bodybuilders who use it either. Personally, for bodybulding purposes, I use 80-90% whole protein foods, including egg whites, lean red meat, chicken, fish, and turkey and 10-20% whey protein. This has worked extremely well for me and will probably work well for you too if bodybuilding or body composition improvement is your goal.