Researchers at the University of Texas Medical Branch partnered with ingredient company DuPont to complete the study, and published their findings in the Journal of Nutrition.
“Sarcopenia is estimated to affect 30% of individuals over 60 years of age and more than 50% of people over 80 years. It has significant quality of life consequences for aging individuals, and contributes substantially to direct healthcare costs,” said Jean Heggie, strategic marketing lead, DuPont Nutrition & Health.
“Resistance training and dietary intervention, with a focus on high-quality protein, is certain to be part of the solution. Lean, high-quality proteins, like soy, will have an important role in nutritional solutions targeting this condition,” she added.
The double-blind, randomized controlled trial builds science “for the use of targeted nutritional interventions to overcome a critical condition of aging, anabolic resistance, to counteract sarcopenia,” said Blake Rasmussen, PhD, chair, department of Nutrition & Metabolism at the University of Texas Medical Branch and lead researcher of the study.
Study design and supplements
Twenty healthy men aged 55-75 were recruited. Requirements included a recreationally active lifestyle (no high-intensity regimen), nonsmoking, and not currently using any protein supplements. They were then divided into two groups, one supplemented with 30g of a protein blend, and the other a single-source protein in the same amount as a control.
The blend consisted of soy and dairy proteins (25% isolated Danisco SUPRO soy protein by DuPont, 50% caseinate, 25% whey protein isolate) while the single protein source was whey protein isolate.
Dietary supplements were provided in beverage form, consumed one hour after basic set of leg extension exercises. Blood and muscle amino acid concentrations and basal and post exercise muscle protein turnover were measured by using a biopsy, done at the very beginning (baseline) and up to five hours after resistance exercise.
Results
The soy-dairy protein blend induced amino acid delivery to muscle tissue, muscle protein synthesis and activated a recognized pathway that initiates muscle protein turnover after exercise. These results were similar in both groups.
“In this study, the two groups were not matched for leucine content but both groups received enough leucine to exceed the minimum threshold to shift protein turnover into an anabolic state,” said Rasmussen.
The researchers noted several of the study’s limitations. “First, we included only men. Although sex differences are not apparent in younger populations for mTORC1 signaling and muscle protein synthesis after [resistance exercise], we cannot make any inferences on the potential sex differences in older populations when combining exercise with a protein blend,” they wrote.
“Second, our randomization procedure resulted in subjects in the protein blend group being slightly younger. This may have contributed to the tendency for baseline fractional synthesis rate values to be higher in this group,” they added.
But the study is only the first to “investigate muscle protein metabolism in aging individuals in response to consumption of a blend of proteins,” DuPont said in a press release, “which is more representative of how people consume protein.”
Source: Journal of Nutrition
First published October 26, 2016, doi: 10.3945/jn.116.231159
Authors: Blake B. Rasmussen, et al.