But the volunteers were permitted a 30-minute, moderate-intensity treadmill walk during each inpatient stay to avoid any artificial issue with 36 hours of complete bedrest for the metabolic study. To ensure that any changes were due to the diet alone and not muscle repair after exercise, the participants were instructed to avoid strenuous physical activity for the three days preceding each metabolic study. The researchers did this metabolic study on the first day and then again after the volunteers spent seven days on the diet. Muscle protein synthesis was measured by injecting the participants with a specially-tagged version of the amino acid, phenylalanine, waiting 24 hours, then taking samples of one of their thigh muscles. These diets were a mix of foods with high-quality protein and not any sort of protein supplement. The skewed diet consisted of 10 grams at breakfast, 15 grams at lunch, and 65 grams at dinner. One was, as I said earlier, a roughly even 30 grams of protein at each meal.
Each subject received both diets for seven days with a 30-day washout period between the two. While the sample size is quite small as compared with drug trials, these sorts of nutritional studies require intense participant commitment in adhering to strict diets, having multiple blood draws in two 36-hour inpatient hospital stays, and multiple muscle biopsies – a total of 12, across the two phases of the study.īut these smaller studies allow conditions to be very tightly controlled, and it's worth taking a moment to examine how the researchers minimizing any confounding variables. Making sure any findings were due to diet alone This is the first study testing that hypothesis in young and middle-aged adults. Paddon-Jones and colleague, Blake Rasmussen, Ph.D., originally proposed in 2009 that the even ingestion of protein at each meal could reduce aging-related sarcopenia, the progressive 3-8% loss of muscle that we inevitably face with each decade after age 30.
Mamerow, Ph.D., a postdoctoral research fellow at UTMB-Galveston. Layman, Ph.D., at the University of Illinois at Urbana-Champaign, and the paper's primary author was Madonna M. The research team was led by Douglas Paddon-Jones, Ph.D., at the University of Texas Medical Branch in Galveston and Donald K. The subjects were physically active, but not athletically trained, averaging 32% body fat and with an average body mass index in the normal range. The study was conducted with a group of five men and three women between ages 25 and 55. In a new paper published in the Journal of Nutrition, researchers asked a simple question, assuming that a total of 90 grams per day would be best: Would human subjects make more muscle protein if their optimal intake was evenly split across the three meals when compared with typical protein intake patterns skewed toward a protein-heavy dinner? A mix of high-quality proteins for breakfast might very well be good for your muscles.
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