Study Favors Whey Protein over Soy for Muscle

Why Whey Weighs in Better than Soy for MPS

Protein supplementation is one of the largest money makers for the fitness industry. We enjoy the convenience of having it readily available after a workout. Specialty stores are lined from floor to ceiling with an overwhelming amount of differing protein brands, varieties and blends to give any consumer a case of confusion.

Finding the best protein powder to supplement a healthy nutrition plan takes some research. Trial and error sorting the best taste, texture, and even stomach upset are essential. The option to use protein powder is always a personal choice and the stuff does not come cheap.

When science takes the time to research and prepare feedback on the effectiveness of protein powder, it removes at least some of the guess work. It helps us feel better about our choices. Let’s take a look at the recent study published by the American Society of Nutrition and comparing whey to soy protein.

Study Purpose and Requirements

Whey Protein Found More Effective
Whey Protein Found More Effective than Soy for Muscle. Jorge Gonzalez E+/Getty Images

The Journal of Nutrition released a printable pdf version of the whey vs. soy protein study. The purpose of the research was to determine how different sources of protein (whey or soy) would affect muscle protein synthesis (muscle growth) and lipolysis (fat breakdown).

The short-term controlled study was for a period of 14 days. The trial included 19 male and 21 female participants in good health and age ranges between 35 to 65 years. All subjects entered the clinical trial with a body mass index (BMI) of 28-50 which means overweight to obese.

They consumed a hypoenergetic (low calorie) diet during the study.  Participants were randomly assigned, double-blind, to receive either isolated whey protein (27g), soy protein (26g) or carbohydrate (25 g) supplement twice daily.

The total protein intake was 1.3g per kg of bodyweight daily instead of the recommended dietary allowance (RDA) of .8g per kg of bodyweight.

Now that the study purpose and clinical requirements have been explained let’s take a look at the findings.

The Findings Show Whey More Effective

Whey Protein
Whey Protein Preserves MPS Better than Soy. MR.BIG-PHOTOGRAPHY E+/Getty Images

Whole body lipolysis (fat breakdown) showed no significant difference in either group. However, results indicated that participants consuming whey protein twice daily sustained muscle protein synthesis (MPS) for a longer period compared to the soy and carb supplemented groups.

“This is an important discovery because it indicates that proteins such as whey may be more effective at preserving MPS and potentially LBM in longer-term weight loss interventions.” Once the 14-day study was complete, the MPS decreased in all groups as consistent with other studies.

Other similar research reported those who consumed whey protein were able to sustain muscle protein synthesis (MPS) the longest. “The difference between whey and soy protein supplementation could be the result of the greater leucine content in whey” and is speculated as the reason for greater stimulus of MPS.

Leucine is an amino acid supporting muscle growth and according to Wikipedia “is the only dietary amino acid that has the capacity to directly stimulate muscle protein synthesis.”

Closing Thoughts

Whey Protein
Whey Protein Found to Sustain MPS Longer than Soy. Milos Markovic E+/Getty Images

Researchers do acknowledge most of the data was obtained from short-term trials. Further research is needed to obtain even more information on muscle protein synthesis (MPS) and muscle protein breakdown (MPB).

All participants did lose fat and muscle but showed no body composition change due to the limited time of the study. A limitation of the study was the use of DXA scan instead of a more accurate method of body fat measure.

Taking into consideration the focus of the study was on muscle protein synthesis and not body fat composition, the study was sufficient to prove their objective.

“These results demonstrate the impact of protein quality on MPS during energy restriction, and may be of importance in the development of nutritional strategies to promote higher-quality weight loss, which involves the loss of a high ratio of fat to LBM.”


American Society of Nutrition, Journal of Nutrition, Whey Protein Supplementation Preserves Postprandial Myofibrillar Protein Synthesis during Short-Term Energy Restriction in Overweight and Obese Adults, Amy J Hector et al., 2015

U.S. National Institutes of Health, Clinical Trials, Impact of Whey and Soy Protein Ingestion in Conjunction With Energy Restriction in Overweight/Obese Individuals, NCT01530646, 6/15

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