Plant- and animal-based proteins are not the same
Effects of Consuming Ounce-Equivalent Portions of Animal- vs. Plant-Based Protein Foods (2023) Connolly et al
Context
In August 2023 I came across a blog post by Joy Kiddie, one of the registered dietitians I follow online entitled “Is Animal-based and Plant-based Protein equivalent?” [1]. I eat a range of animal- and plant-based macronutrients and am constantly on the lookout for ways to fine-tune my approach.
Joy drew attention to a recent publication [2] that I read and want to describe here.
Incidentally, Joy has written about the role diet has played in her own health. She has put her type 2 diabetes and high blood pressure into remission, lost “substantial weight”, and reduced other symptoms due to the anti-inflammatory effect of an improved diet.
She perfectly captures a foundational principle that I share when she states:
“I believe that there is no one-size-fits-all approach, but that Nutrition is BetterByDesign©.”
Objective and results of the study
The authors investigated two main objectives. Is there a difference in blood essential amino acid (EAA) content after eating protein from animal-based (unprocessed pork, whole eggs) or plant-based (black beans, sliced almonds) ingredients as part of a mixed whole foods meal? Secondly, is there a difference between younger and older people?
Regarding the first main objective, blood concentrations of EAA were greater for pork and eggs than for black beans and sliced almonds. Pork had a greater effect than eggs and there was no difference between the plant-based foods (Figure 1).
There was no difference between younger and older adults.
It should also be noted that the authors also measured total amino acids, branched chain amino acids, and leucine. Each of those measures showed the same results as EAA (Figure 1). Each was highest in pork and lowest in plant-based ingredients, with eggs being between the two.
Figure 1: Total blood plasma EAA concentration (micrograms per mL) measured over 300 minutes after eating
Why are the results of the study interesting?
Two aspects of this study strike me as powerful, namely its design and the nature of the results.
This study design was about as strong as they come (see below).
The nature of the results is also very important. The concentrations of EAA measured in blood post-meal are a measure of bioavailable protein building blocks. This is very important because it means that irrespective of the EAA starting content of the pork, eggs, black beans, and almonds, this study measured the amount that made it into human blood and was available for human metabolism.
The difference between bioavailable and total nutrients in food is important to understand. It doesn’t matter how much nutrition (protein, fat, carbohydrate, micronutrient) any food ingredient contains, if it isn’t bioavailable to us, we can’t use it. When we consider bioavailability, we can see that 4-oz plant-based vs meat-based patties, and vegan protein powder vs whey protein powder are not the same. The meat and whey products offer more amino acids for our body to use [1].
How do the results of the study help me to understand health and longevity?
As we age, we gradually lose muscle mass and strength, beginning around age 30 and accelerating (just trust me on this) with the years. This age-related loss is called sarcopenia and if left to its own devices, it can lead to disabilities and general reduction in quality of life. There are things we can do to slow the process, however, such as eating enough bioavailable protein and exercising properly.
Leucine and other essential amino acids (EAA) are referred to as such because we need them to survive and can only get them from the foods we eat [1] (we can’t make them ourselves). Leucine has a unique role in that when we get enough, it signals to the body that muscle can be built. Thereafter, the other EAAs provide the building blocks to retain or build muscle when we exercise properly [1].
Getting enough bioavailable EAAs is essential minimize the health impact of sarcopenia as we age.
“Getting enough bioavailable EAAs is essential minimize the health impact of sarcopenia as we age”
Study outline
The study was conducted in humans, was investigator-blinded and of a cross-over design. In other words, it was a real study (not a summary of past results) in people (not mice or rats) in which the investigators were least likely to inadvertently bias the results (they didn’t know during the study who received which foodstuffs), and in which other potentially complicating factors were minimized (the same people received the same meals, just at different times).
References
Is Animal-based and Plant-based Protein Equivalent? https://www.bbdnutrition.com/2023/08/20/is-animal-based-and-plant-based-protein-equivalent/
Connolly G, et al (2023) Effects of Consuming Ounce-Equivalent Portions of Animal- vs. Plant-Based Protein Foods, as Defined by the Dietary Guidelines for Americans on Essential Amino Acids Bioavailability in Young and Older Adults: Two Cross-Over Randomized Controlled Trials. Nutrients. 15(13):2870. doi: 10.3390/nu15132870. PMID: 37447197; PMCID: PMC10343739
Additional reading
Is Animal-based and Plant-based Protein Equivalent? https://www.bbdnutrition.com/2023/08/20/is-animal-based-and-plant-based-protein-equivalent/