There are two major groups of studies in the literature. Most of these studies look at both muscle size and strength measures as outcomes. They include:

1. Protein vs placebo.

2. Protein source comparisons. (Whey vs Soy)

There have been many different studies looking at the effects of different protein supplements on strength and muscle mass gains, and there is a different outcome for almost every study. Unfortunately the vast majority of these studies are plagued by poor research design. The most common problems are:

• Small sample size

• Absent or inappropriate blinding of subjects/researchers

• Ineffective outcome measures

• Lack of randomization

Due to the poor design of these studies it is no surprise that the outcomes are as varied as they are. The following chart summarizes the outcomes of the major recent studies.

It should be noted that in the above chart one of the studies included in the no effect column was a meta-analysis study that included 4 different studies prior to 2001, which showed a net outcome of no effect. However, this was only included as one study. Also, several of the studies in the strength and muscle mass columns are newer studies from the past few years.

The studies looking at protein source comparisons had the following outcomes:

• Whey protein is more effective than casein

• Milk proteins (whey/casein) are superior to soy

• Soy proteins are equal to whey in efficacy

As you can see, there is a discrepancy between these studies just as the studies above, and the irony of the situation is that these studies are looking at the differences between the efficacies of individual protein sources while there is insufficient evidence that protein supplementation even works at all.