American researchers conducted randomized controlled trials and found that ground beef stimulates protein synthesis in muscles and the body as a whole significantly more than soy-based meat alternatives. The study was published in the American Journal of Clinical Nutrition.
Elevated blood amino acid levels after protein consumption act as a powerful stimulator of muscle protein synthesis, which is necessary for the replacement of old, low-functioning muscle fibers in skeletal muscle. Essential amino acids play a key role in this process. Their blood levels are the primary predictor of anabolism and depend on the composition and bioavailability of dietary protein. In recent years, plant-based meat alternatives, most often containing soy, have become increasingly popular. Their protein and amino acid composition differs slightly from that of meat, which could potentially impact muscle protein synthesis.
To test this hypothesis, David Church of the University of Arkansas for Medical Sciences and colleagues recruited 24 healthy volunteers (14 women) aged 18–40 years (average 31.8 years). Their body mass index ranged from 20 (normal) to 32 (mildly obese) kilograms per square meter. Participants were randomly divided into three groups: one was offered a beef patty (80/20 protein to fat ratio) weighing approximately 110 grams, the second received a patty made from a soy-based beef substitute of the same weight, and the third received two such soy-based patties.
To assess fractional muscle protein synthesis, the amino acids phenylalanine and tyrosine labeled with stable isotopes (deuterium, carbon-13, and nitrogen-15) were used. Infusions began four hours before and continued for six hours after meals. Blood samples were taken every half hour before and three hours after the infusion for analysis of isotopes, essential amino acids, and insulin. Skeletal muscle biopsies were performed before and at 240 and 600 minutes. Protein synthesis in the muscle was measured directly by isotope accumulation, and overall protein kinetics in the body (synthesis, breakdown, and net protein balance) was calculated using the isotope bioavailability method.
It was found that after consuming a beef patty, fractional muscle protein synthesis significantly increased from 0.035 ± 0.008 to 0.055 ± 0.010 percent (p = 0.008). Two soy patties had a similar effect: from 0.037 ± 0.008 to 0.050 ± 0.010 percent (p = 0.003). One soy patty did not significantly stimulate muscle protein synthesis: from 0.041 ± 0.009 to 0.044 ± 0.011 percent (p = 0.435). The contribution of muscle proteins to total protein synthesis in the body was greatest after consuming beef, slightly lower after two soy patties, and significantly lower after one. Moreover, the change in fractional protein synthesis in muscles from basal to postprandial significantly correlated with the maximum concentration of essential amino acids in the blood (p = 0.046; r = 0.411) and with the corresponding change in total protein synthesis in the body (p = 0.046; r = 0.412).
Thus, consuming a 110-gram beef patty, like two soy patties of the same weight, stimulates muscle protein synthesis. However, the total calorie content of such a serving of beef is significantly lower than that of double the soy portion—279 kilocalories versus 462 kilocalories, the study's authors noted.
Previously, another American scientific group performed a metabolomic analysis of 18 samples of animal and plant meat of the same weight and also questioned their interchangeability: 90 percent of the 191 metabolites analyzed differed significantly in concentration in the animal and plant samples.
