Animal protein foods contain more essential amino acids

According to scientists, protein from two ounce-equivalents (oz-eq) of animal-based protein foods provides greater essential amino acids (EAA) bioavailability than an equal two oz-eq of plant-based protein foods.

The protein quality of a food or meal (i.e., its EAA content) is an important factor in determining how the body can use amino acids for muscle and whole-body protein building.4ial amino acids compared to plant protein.

The Dietary Guidelines for Americans (DGAs) emphasise consuming a variety of protein foods with similar nutritional content in ounce-equivalent portions.

One ounce-equivalent equals one ounce of meat, one whole egg, 0.25 cup beans, or 0.5 ounces nuts.

“The basis for the DGAs stating that these protein foods are ‘equivalent’ and have ‘similar nutritional content’ is unclear,” suggests Dr. Wayne Campbell, primary investigator on this study and professor in the Department of Nutrition Science at Purdue University.

Protein foods differ in their energy and nutrient content, including protein quantity and quality he added.

Additionally, there is limited information on how eating oz-eq amounts of protein foods from different sources as part of a mixed meal impacts the body’s ability to digest and use protein.

From Connolly et al. (2023).1; The protein from the test meal is included in the protein quantity for each trial: lean pork (20 g), whole eggs (18.5 g), black beans (13.5 g), and almonds (12 g). The EAA from the test meal is included in the total amount of EAA for each trial: lean pork loin (9.45 g), whole eggs (7.47 g), black beans (5.11 g), and almonds (3.94 g). EAA stands for essential amino acids.

This includes populations like younger adults who may be vulnerable to a lack of variety in their protein choices, as well as older adults who may be under-consuming high-quality sources of nutrient-dense protein despite higher nutrient needs.

As a result, researchers wanted to see if eating two oz-eq portions of animal-based versus plant-based protein foods as part of a mixed whole foods meal affected EAA bioavailability for protein building differently in these populations.

Two cross-over randomised controlled trials on 30 otherwise healthy young adults and 25 older adults were conducted. Each participant in the study completed four separate 300-minute trials, each separated by at least three days.

The order in which the participants completed their protein food assignments was kept a secret from the study investigators until all participants completed their testing and the results were analysed.

During the trial period, study participants were required to eat a standardised meal containing two oz-eq of either animal-based protein foods (e.g., unprocessed lean pork loin, scrambled whole eggs) or plant-based protein foods (black beans, raw sliced almonds).

To determine EAA bioavailability as well as blood sugar and insulin levels, blood samples were taken at baseline and 30, 60, 120, 180, 240, and 300 minutes after eating.

“In line with our hypothesis before starting this study, consuming meals with two oz-eq of animal-based protein foods resulted in 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,” explains Dr. Gavin Connolly, clinical trials project manager and research associate in the Department of Nutrition Science at Purdue University.

Also, there were no differences in EAA bioavailability between young and older adults, he added

“In line with our hypothesis before starting this study, consuming meals with two oz-eq of animal-based protein foods resulted in 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,” explained Dr Gavin Connolly, clinical trials project manager and research associate in the Department of Nutrition Science at Purdue University.

Also, there were no differences in EAA bioavailability between young and older adults, he added

“Portion sizes of the protein foods in the study likely do not truly reflect the amounts consumed on a meal-to-meal or weekly basis by young or older adults,” according to Dr Connolly.

Additionally, there were no direct measures of changes in muscle protein synthesis or whole-body protein balance in response to the meals containing the different protein foods, he explained.