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 alternatives to meat. A report on the work was published in the American Journal of Clinical Nutrition.
Increased amino acid levels in the blood after consuming protein act as a powerful stimulator of muscle protein synthesis, which is necessary to replace old, low-functioning muscle fibers in skeletal muscles. Essential amino acids play a major role in this process. Their levels in the blood are the main predictor of anabolism and depend on the composition and bioavailability of dietary protein. In recent years, plant-based meat alternatives, which most often contain soy, have become increasingly popular. Its protein and amino acid composition differs somewhat from that of meat, which can potentially affect the level of muscle protein synthesis.
To test this hypothesis, David Church of the University of Arkansas for Medical Sciences and colleagues recruited 24 healthy volunteers (14 of them 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 of which was then offered a beef patty (80/20 protein to fat ratio) weighing about 110 grams, the second - a patty made of soy substitute beef of the same weight, and the third - two such soy patties.
To assess fractional protein synthesis in muscles, we used the amino acids phenylalanine and tyrosine labeled with stable isotopes (deuterium, carbon-13, and nitrogen-15). Their infusion was started four hours before a meal and continued for six hours after it. Before the infusion and three hours after its start, blood samples were taken every half hour for analysis of isotopes, essential amino acids, and insulin; before the infusion and at 240 and 600 minutes, a biopsy of skeletal muscles was performed. Protein synthesis in them was measured directly by the accumulation of isotopes, the overall protein kinetics in the body (synthesis, decay, final balance) was calculated by the isotope bioavailability method.
It was found that after eating a beef patty, fractional muscle protein synthesis increased significantly 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 eating 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, eating a 110-gram beef patty, like two soy patties of the same weight, stimulates muscle protein synthesis. At the same time, the total caloric content of such a portion of beef is significantly less than that of a double portion of soy - 279 versus 462 kilocalories, the authors of the study 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 animal and plant samples.