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According to researchers at Purdue University, protein from two-ounce equivalents (oz-eq) of animal-based meals has better bioavailability of essential amino acids (EAAs) than the same quantity of protein from plant-based sources.
The protein quality of that food or meal determines how effectively the body can use amino acids to create muscle and protein in general.
The Dietary Guidelines for Americans (DGAs) emphasize consuming protein-rich foods in amounts that are of equivalent size and have comparable nutritional value. One ounce of meat, one entire egg, 0.25 cup of beans, or 0.5 ounces of nuts are all considered to be one oz-eq.
Dr. Wayne Campbell, the lead researcher on this study and a professor in the Department of Nutrition Science at Purdue University, questions the DGA's assertion that these protein foods are "equivalent" and have "similar nutritional content". Considering protein quantity and quality, protein foods vary in their calorie and nutrient content. Furthermore, little is known about how consuming oz-eq portions of protein foods from various sources as part of a mixed meal affects the body's capacity to digest and utilize protein.
Researchers wanted to see how eating two oz-eq servings of plant-based versus animal-based protein sources as part of a meal composed of a variety of whole foods might affect the bioavailability of EAAs for protein synthesis.
According to Dr. Gavin Connolly, clinical trials project manager and research associate in the Department of Nutrition Science at Purdue University, "In line with our hypothesis before starting this study, consuming meals with two oz-eq of animal-based protein led to more EAAs in the bloodstream compared to meals with two oz-eq of plant-based protein foods in both young and older adults, separately and combined." He notes that there were no differences in EAA bioavailability between young and elderly individuals.
This indicates that animal-based proteins, like scrambled eggs and unprocessed lean pork loin, provide EAAs more efficiently. "This is an important consideration for muscle and whole-body health and physical function across the life course," he advises.
Lean pork had a higher bioavailability of EAAs than eggs, whether consumed separately or together, according to additional research findings. No differences were observed in the bioavailability of EAAs between almonds and black beans. No differences in the bioavailability of EAAs were found between young and older individuals.
The current study has certain limitations.
"Portion sizes of the protein foods in the study might not accurately reflect the amounts consumed on a meal-to-meal or weekly basis by young or older adults," says Dr. Connolly. Furthermore, the effects of the meals comprising the various protein sources on changes in muscle protein synthesis or whole-body protein balance were not directly measured, according to him.
More research is required to better understand the potential effects of animal versus plant-based protein diets on muscle and overall health over the lifespan.