The 2015-2020 Dietary Guidelines for Americans (DGA) recommends how much “Protein Foods” should be consumed per day and per week as part of a Healthy U.S.-Style Eating Pattern. The predominant protein sources include lean meats, poultry, and eggs, along with nuts, seeds, and soy products. “Ounce-equivalents” (oz-eq) are used as a standard unit of measure to compare animal to non-animal protein sources. One oz-eq of lean meat (1 oz) is equal to 0.5 oz of nuts (1 oz-eq), 0.25 cups (1 oz-eq) of beans, and one whole egg (1 oz-eq). One limitation of this unit of measure is that the protein quantity and quality of the foods are not considered. For example regarding protein quantity, 1 oz-eq of pork loin contains ~7 g of dietary protein whereas 1 oz-eq of almonds contains ~3 g of protein. Protein quality is based on the essential amino acid (EAA) composition of a protein as it relates to human needs and the ability of the protein to be digested, absorbed, and retained by the body1. Of the 20 amino acids in body protein, 9 are considered essential as they cannot be made within the human body and must be provided from the diet, whereas the other 11 amino acids are considered non-essential as they can be made within the human body. Animal-derived protein foods contain all of the EAAs required by humans, whereas plant-based protein foods, other than soy, are lacking in one or more of the EAAs2. This is an important distinction as the EAA content of a protein-containing food or a meal is the primary determining factor in the anabolic response (building new proteins in the body) to feeding3,4. This has important implications for muscle and whole-body health. Consequently, consuming one oz-eq portion of protein foods from different sources could have different effects on the anabolic response to feeding. The purpose of this study was to assess the effect of consuming ounce-equivalent portions of fresh lean pork versus nuts, beans, and eggs on how much essential amino acids get into the bloodstream and are available for building proteins in young adults. In this investigator-blinded, randomized crossover study, 30 participants (15 male, 15 female; age: 26 ± 4.9 y; BMI: 26.4 ± 4.5 kg/m2; mean ± SE) completed four testing sessions where they consumed a standardized test salad on each day with 2 oz-eq of lean pork, whole eggs, canned black beans, or sliced raw almonds. Blood samples were taken at baseline (prior to beginning meal consumption) and at 30, 60, 120, 180, 240, and 300 minutes after consuming the salad. Plasma from the blood samples was analyzed for amino acid concentrations. The results showed that consuming a meal with 2 oz-eq of lean pork or whole egg resulted in a greater essential amino acid availability over the 5-hour period following the meal compared to a meal with 2 oz-eq of black beans or almonds. In addition, pork resulted in greater essential amino acid availability over a 5-hour period compared to eggs. In conclusion, based on the oz-eq concept used for the DGA, the protein sources included in this study, namely lean pork, whole egg, black beans, and almonds, are not equivalent regarding plasma essential amino acids availability for protein anabolism in young adults, in response to being consumed as part of a meal. More specifically on an oz-eq basis, lean pork provides a greater response than whole egg, followed by black beans and almonds, in terms of its ability to provide plasma essential amino acids as a substrate for protein anabolism. This research serves as an important resource for future Dietary Guidelines Advisory Committees to reevaluate the appropriateness of equating Protein Foods based on protein ounce-equivalents. Animal-derived protein-rich foods, including fresh lean pork and whole eggs, are excellent sources of amino acids needed to build new proteins in a person’s body.

For additional information contact Wayne W. Campbell, Ph.D., Professor, Department of Nutrition Science, Purdue University, 765-494-8236, campbeww@purdue.edu.