Animal-based protein provide greater essential amino acids (EAA) bioavailability than the same quantity of plant-based protein.
A study by Purdue University researchers found that protein from animal-based sources, such as meat, eggs, and dairy, provides more bioavailable essential amino acids (EAAs) than the same amount of protein from plant-based sources, such as beans, nuts, and seeds.
The quality of protein in a food or meal, as measured by its EAA content, is an important factor in how well the body can use amino acids to build muscle and repair tissues.
The Dietary Guidelines for Americans (DGAs) recommend consuming a variety of protein foods from different sources to ensure that one gets all the essential amino acids they need. One ounce of meat, one egg, one-quarter cup of dried beans, or one-half ounce of nuts or seeds each count as one ounce-equivalent of protein.
However, some experts question the basis for the DGAs’ recommendation that these protein sources are equivalent in terms of their nutritional content. They point out that protein foods vary in their energy and nutrient content, including protein quantity and quality. Additionally, there is limited research on how eating different types of protein together in a mixed meal affects the body’s ability to absorb and use the protein.
This study suggests that people who want to maximize their intake of bioavailable EAAs may want to consider including more animal-based protein sources in their diet. However, it is important to note that plant-based protein sources can still be a valuable part of a healthy diet, especially for people who are following a vegetarian or vegan diet.
| Energy (kcal) | Fat (g) | Carbohydrate (g) | Protein (g) | EAA (g) | |
| Test meal | 218 | 11.5 | 25.8 | 6 | 2.09 |
| Lean pork loin (2 oz-eq) | 73 | 1 | 0 | 14 | 7.36 |
| Whole eggs (2 oz-eq) | 145 | 10 | 0 | 12.5 | 5.38 |
| Black beans (2 oz-eq) | 113 | 0.5 | 20 | 7.5 | 3.02 |
| Almonds (2 oz-eq) | 161 | 14 | 6 | 6 | 1.85 |
Animal-Based Proteins Offer More Usable EAAs
The study utilized a cross-over design, where participants consumed controlled meals containing either two ounces of animal-based protein (lean pork loin, scrambled eggs) or plant-based protein (black beans, almonds). Blood samples were collected throughout the trial to measure EAA bioavailability, alongside blood sugar and insulin levels.
Results indicate that meals with animal-based protein delivered more usable EAAs into the bloodstream compared to plant-based options, regardless of age group. This aligns with the concept of protein quality, where the EAA composition of a food determines its effectiveness in supporting protein synthesis.
Implications for Muscle and Whole-Body Health
Dr. Gavin Connolly, lead researcher on the project, highlights the significance of these findings. Animal-based proteins provide a more efficient source of EAAs, crucial for building and maintaining muscle mass, which is vital for physical function and overall well-being across all ages.
Further Research Needed
While this study provides valuable insights, Dr. Connolly emphasizes the need for further research to explore the long-term impact of protein source and EAA absorption on various populations. This will help optimize dietary recommendations for individuals with specific needs and ensure optimal protein utilization for muscle and whole-body health.
The Purdue University research revealed additional nuances in how protein source affects essential amino acid (EAA) absorption:
- Lean Pork Outperformed Eggs
For both young and older adults, lean pork demonstrated superior EAA bioavailability compared to eggs. - Black Beans vs. Almonds
No significant differences in EAA absorption were observed between black beans and almonds. - Age Didn’t Influence EAA Absorption
Interestingly, age did not play a role in EAA bioavailability across both groups.
Study Limitations Acknowledged
The researchers recognize limitations in their study.
- Portion Sizes Not Representative
The chosen protein portions might not accurately reflect real-life consumption patterns for young or older adults. - Muscle Protein Synthesis Not Measured
Direct measurements of muscle protein synthesis or whole-body protein balance in response to different protein sources were not assessed.
Implications for Future Research
Further investigation is needed to clarify how animal and plant-based protein sources impact muscle and whole-body health throughout life, particularly for promoting healthy aging.
Public Health Nutrition Considerations
The study authors believe their findings could have implications for public health nutrition guidance and future Dietary Guidelines for Americans (DGAs). They suggest reevaluating the appropriateness of equating different protein sources solely based on ounce-equivalents across all age groups.
“While embracing plant-based options is important, incorporating guidance on the value of nutrient-dense animal-based protein sources, which offer high-quality protein, is crucial for comprehensive dietary recommendations.”
Dr. Campbell
The research was funded by the National Pork Board and the American Egg Board—Egg Nutrition Center. 😀
Abstract
Background: The Dietary Guidelines for Americans (DGA) recommends consuming a variety of “Protein Foods” based on “ounce-equivalent” (oz-eq) portions. No study has assessed the same oz-eq portions of animal- vs. plant-based protein foods on essential amino acid (EAA) bioavailability for protein anabolism in young and older adults. Objectives: We assessed the effects of consuming two oz-eq portions of pork, eggs, black beans, and almonds on postprandial EAA bioavailability in young and older adults. Methods: We conducted two investigator-blinded, randomized crossover trials in young (n = 30; mean age ± SD: 26.0 ± 4.9 y) and older adults (n = 25; mean age ± SD: 64.2 ± 6.6 y). Participants completed four testing sessions where they consumed a standardized meal with two oz-eq of either unprocessed lean pork, whole eggs, black beans, or sliced almonds. Blood samples were taken at baseline and 30, 60, 120, 180, 240, and 300 min postprandially. Plasma EAA bioavailability was based on postprandial integrated positive areas under the curve. Results: Participant age did not affect EAA bioavailability among the four protein foods tested. Two oz-eq portions of pork (7.36 g EAA) and eggs (5.38 g EAA) resulted in greater EAA bioavailability than black beans (3.02 g EAA) and almonds (1.85 g EAA) in young and older adults, separately or combined (p < 0.0001 for all). Pork resulted in greater EAA bioavailability than eggs in young adults (p < 0.0001), older adults (p = 0.0007), and combined (p < 0.0001). There were no differences in EAA bioavailability between black beans and almonds. Conclusions: The same “oz-eq” portions of animal- and plant-based protein foods do not provide equivalent EAA content and postprandial bioavailability for protein anabolism in young and older adults.