The consumption of equivalent ounce-equivalent portions of animal-based and plant-based protein foods, as outlined in the Dietary Guidelines for Americans (DGAs), yields varying levels of essential amino acid bioavailability in both young and older adults, according to recent research by Purdue University scientists. The quality of protein derived from two-ounce-equivalent (oz-eq) portions of animal-based and plant-based sources significantly affects the body’s ability to utilize amino acids for muscle and overall protein synthesis.

While DGAs emphasize diverse protein intake based on ounce-equivalent portions with similar nutritional content, the basis for deeming these protein foods “equivalent” remains unclear. Dr. Wayne Campbell, the study’s primary investigator and a professor in the Department of Nutrition Science at Purdue University, highlights the disparities in energy, nutrient content, and protein quality among protein foods. The study sought to examine how consuming two oz-eq portions of animal-based and plant-based protein foods as part of a mixed meal impacts essential amino acid (EAA) bioavailability for protein building.

The researchers conducted two randomized controlled trials involving 30 young adults and 25 older adults. Participants completed four separate 300-minute trials, consuming standardized meals with two oz-eq of animal-based protein foods (such as lean pork loin and scrambled eggs) or plant-based protein foods (black beans and raw almonds). Blood samples were collected at various intervals to measure EAA bioavailability, blood sugar, and insulin levels.

Key Findings: In line with the study’s hypothesis, meals containing animal-based protein foods led to higher EAA levels in the bloodstream compared to meals with plant-based protein foods in both young and older adults. This indicates that animal-based proteins are more effective at providing essential amino acids, which are crucial for muscle and whole-body health.

Additional Insights:

  • Lean pork demonstrated greater EAA bioavailability than eggs in both young and older adults.
  • No differences in EAA bioavailability were observed between black beans and almonds.
  • There were no age-related differences in EAA bioavailability.

Limitations and Future Implications: The study acknowledges limitations in portion sizes and the absence of direct measures of changes in muscle protein synthesis or whole-body protein balance. Further research is needed to comprehensively understand how animal-based and plant-based proteins influence muscle and overall health across different life stages.

Public Health Nutrition Implications: The study’s findings suggest potential implications for public health nutrition guidance, urging reevaluation of equating diverse protein sources on an ounce-equivalent basis. While promoting plant-based foods has its benefits, recognizing the importance of nutrient-dense animal-based protein sources remains crucial for dietary recommendations and healthy aging.

By Impact Lab