Overweight and obese adults consuming a low calorie diet supplemented with whey protein displayed a greater increase in muscle protein synthesis, compared with soy protein supplements, report scientists from McMaster University in Canada and the University of Birmingham in the UK.
“[O]ur data demonstrated that whey protein supplementation during energy restriction provided greater stimulation of MPS [myofibrillar protein synthesis] and maintenance of postprandial MPS rates,” they wrote in The Journal of Nutrition.
“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 [lean body mass].”
The researchers recruited 40 obese and overweight men and women to participate in their randomized, double-blind, 14 day study. The participants were all assigned to hypoenergetic diets supplemented with whey (Agropur Isochill 8000 Whey Protein Concentrate) or soy (SoyPro950M, International Trade Company) protein two times per day (about 27 grams per supplement) or carbohydrate (25 g maltodextrin/supplement).
The low calorie diet was preceded by three days of supplementation which showed that the whey supplement stimulated myofibrillar protein synthesis more than the soy and carb supplements.
After two weeks of intervention, MPS following a meal (post-prandial) was found to be reduced by 9%, companies with 28% and 31% in the soy and carb groups, respectively.
“The novel finding from this study was that twice-daily consumption of whey protein resulted in an attenuation of the postprandial decline in MPS during a short-term dietary hypoenergetic diet vs. twice-daily supplementation with soy protein or carbohydrate,” wrote the researchers.
“This is an important discovery because it indicates that proteins such as whey may be more effective at preserving MPS and potentially [lean body mass] in longer-term weight loss interventions.”
“The difference between whey and soy protein supplementation could be the result of the greater leucine content in whey, which results in greater postprandial hyperleucinemia and stimulus for MPS,” they added.
“Indeed, our data showed a greater peak and net (AUC) exposure to leucine and essential amino acids with whey than with soy and carbohydrate. There is evidence that whey protein, as opposed to soy protein, results in amino acids being directed more toward peripheral (i.e., muscular) rather than splanchnic tissues.”
‘Leucine is the trigger’
It has been reported that leucine is the trigger for muscle protein synthesis. The same researchers from McMaster reported earlier this year that suboptimal protein intake can be compensated by supplemental leucine. The results of that study, published in the American Journal of Clinical Nutrition, supported leucine’s role as a powerful nutritional activator of muscle protein synthesis.
Source: The Journal of Nutrition
Published online ahead of print, doi:10.3945/jn.114.20083
“Whey Protein Supplementation Preserves Postprandial Myofibrillar Protein Synthesis during Short-Term Energy Restriction in Overweight and Obese Adults”
Authors: A.J. Hector, G.R. Marcotte, T.A. Churchward-Venne, et al.