Animal vs Plant Proteins: Which Better Supports Muscle Growth?

# Muscle Growth: New October 2026 Study Gives Animal Proteins the Edge Over Plant Proteins

**by Laurent Glatz – for Athletic Carnivore**

You might consume 30 grams of animal protein or 30 grams of plant protein. On paper, the outcome seems identical. But once digested, does your body truly receive the same amount of essential amino acids needed to build and repair muscle?

An American study published in the October 2026 issue of the *American Journal of Clinical Nutrition* provides a particularly insightful answer: **animal proteins cause a significantly greater increase in blood concentrations of essential amino acids and BCAAs compared to plant proteins.**

These amino acids are precisely what the body requires to synthesize its own proteins, especially muscle proteins.

This finding raises a fundamental question for bodybuilders, athletes, and anyone aiming to preserve muscle mass with age: do all dietary proteins really offer the same potential to nourish muscle?

An American Study Published in October 2026

This research was conducted by Alan Fappi, Vasavi Shabrish, Hunter Hollomon, Tanhaul Islam, Xiangyu Zhang, Babak Razani, Samuel Klein, and Bettina Mittendorfer.

The team includes researchers from the University of Missouri, University of Pittsburgh, and Washington University School of Medicine in St. Louis.

The study was first published online on August 10, 2026, then included in the October 2026 issue of the *American Journal of Clinical Nutrition*, a scientific journal specializing in human nutrition.

Initially, the scientists aimed primarily to understand the relationships between protein intake, blood amino acids, and blood sugar regulation.

However, their observations also provide valuable insights into the quality of dietary proteins.

The researchers used a randomized crossover protocol involving overweight or obese participants.

Two experimental comparisons, each with 21 participants, were conducted.

They compared a standard meal providing about 18 grams of protein to higher-protein meals containing approximately 28 grams, mainly from animal or plant sources.

For three hours after the meals, scientists measured blood concentrations of amino acids, glucose, and several metabolic hormones.

The goal was straightforward: to observe what actually happens in the body after ingesting proteins from different origins.

Results: A Clear Advantage for Animal Proteins in Essential Amino Acids

Here the study becomes particularly compelling.

Compared to the standard meal, blood concentrations of essential amino acids rose by 28% after the animal protein-enriched meal, versus 19% after the plant protein-enriched meal.

This difference was statistically significant.

The researchers also focused on a particularly important category for muscle metabolism: the branched-chain amino acids (BCAAs).

These include leucine, isoleucine, and valine.

They play a crucial role in muscle energy and protein metabolism.

The results are revealing.

After the animal protein meal, blood BCAA levels increased by 36% compared to the standard meal.

After the plant protein meal, the increase was only 24%.

In other words, **animal proteins triggered a noticeably greater elevation of circulating BCAAs.**

The difference was not just about total protein quantity consumed but the biological response observed after ingestion.

It’s important to clarify that these percentages reflect increases relative to the standard meal, not a 36% or 24% increase in muscle mass.

They measure blood amino acid availability over a three-hour period.

This distinction leads us to the most interesting biological mechanism.

More BCAAs Available: Greater Potential for Muscle Building?

To build muscle, the body must have the necessary amino acids to synthesize muscle proteins.

Resistance training is a major stimulus for this synthesis, but nutrition must supply the essential building blocks for tissue repair and renewal.

Among essential amino acids, leucine holds a special role.

It activates the mTORC1 signaling pathway, a mechanism involved in regulating muscle protein synthesis.

Simply put, leucine signals muscle cells that the resources needed to build proteins are available.

But a signal alone isn’t enough: other essential amino acids must also be present.

This is where the difference observed in this study deserves close attention.

**If a protein source provides greater availability of essential amino acids and BCAAs, it is biologically plausible that it could, under certain conditions, promote a stronger muscle protein synthesis response.**

This hypothesis aligns with current knowledge of muscle metabolism.

However, higher blood availability does not automatically guarantee greater muscle hypertrophy.

The body can use amino acids for various processes: protein turnover, synthesis of other molecules, energy metabolism, or oxidation.

A higher blood concentration does not necessarily mean the muscle absorbs and incorporates proportionally more amino acids.

To directly prove superiority in muscle gain, one would need to measure muscle protein synthesis or track muscle mass changes during a prolonged training program.

That was not the aim of this experiment.

Nonetheless, the measured biological difference remains significant.

Not All Proteins Are Created Equal

For a long time, protein source comparisons focused mainly on total quantity.

Yet, 30 grams of protein from an animal food and 30 grams from a plant food do not necessarily have the same amino acid profile or digestibility.

Meat, eggs, fish, and dairy generally provide all nine essential amino acids in proportions well-suited to human needs.

Some plant proteins, especially soy, also have favorable profiles, but their composition and digestibility vary depending on source and processing.

This difference becomes especially relevant when muscle demands are high.

For someone regularly training with weights, the goal is not just to consume enough protein.

It’s also about supplying the essential amino acids needed for recovery and muscle adaptation.

With aging, this issue becomes even more critical.

Aging muscle may show a reduced anabolic response to certain nutritional stimuli, a phenomenon called anabolic resistance.

In this context, protein quality and its ability to provide sufficient essential amino acids become particularly important parameters.

The study’s results do not prove that plant proteins prevent muscle growth.

They do show, however, that at comparable protein intake, some animal sources can produce higher blood availability of essential amino acids.

This observation deserves consideration in any serious discussion about sports nutrition.

An Interesting Finding Regarding Blood Sugar

The researchers also noted another difference—or rather, a lack of difference.

Despite a higher essential amino acid response with animal proteins, both high-protein meals induced generally comparable glycemic and hormonal responses.

Compared to the standard meal, blood sugar response decreased by 4.3% with animal proteins and 5.2% with plant proteins.

The difference between the two high-protein meals was not statistically significant.

Responses of glucagon, GLP-1, and insulin relative to glucose also showed no significant difference between the two sources.

This is interesting because it shows that a higher circulating BCAA concentration does not necessarily cause immediate disruption of blood sugar control.

The researchers do not conclude that animal proteins are better for diabetes prevention or muscle growth.

Their conclusion focuses on how protein quantity and source influence circulating amino acids and the absence of significant short-term glycemic differences.

What This Means for Athletic Carnivore

This study adds a biological argument supporting the value of animal proteins in diets aimed at maintaining muscle mass.

It confirms that protein origin influences metabolic response after ingestion.

Animal proteins led to higher availability of essential amino acids and BCAAs, two categories directly involved in protein metabolism.

For someone training or wanting to preserve muscle, this availability is a relevant factor.

But it’s crucial not to confuse biological potential with guaranteed results.

Muscle gain also depends on mechanical training stimulus, recovery, energy intake, age, and individual response.

This is an important distinction: consuming more protein alone does not necessarily produce more muscle.

Two people can have the same daily protein intake but achieve different results depending on their needs and physiological context.

An experienced bodybuilder, a sedentary 60-year-old, and an athlete in an energy deficit face very different metabolic demands.

Their nutritional strategies cannot rely solely on a daily protein number.

The Real Challenge: Providing Muscle with What It Can Actually Use

These research results should encourage us to move beyond simplistic comparisons between grams of animal and plant protein.

The question is not just how much protein a food contains.

It also concerns the amino acids it provides, their availability after digestion, and the body’s actual needs.

The October 2026 *American Journal of Clinical Nutrition* study shows animal proteins produce a higher blood response of essential amino acids and BCAAs.

This is a measured, statistically significant, and biologically relevant result.

**The hypothesis that this greater availability could promote muscle building aligns with muscle physiology, but this study did not directly demonstrate it.**

For Athletic Carnivore, the issue is not to treat animal protein as a magic formula but to understand why its composition and amino acid availability can offer advantages in certain nutritional strategies.

And above all, to determine if these advantages match individual needs.

Because when someone trains regularly, already consumes plenty of protein, and plateaus, increasing quantity further is not necessarily the right answer.

Analyzing their diet, needs, recovery, and metabolic context can be far more informative than generic new advice.

**Understand Your Nutritional Terrain — [Athletic Carnivore](https://athleticcarnivore.fr/en)**

**What if your difficulty in building or preserving muscle mass isn’t just about how much protein you consume, but also about its quality and how your body uses it?**

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Scientific Reference

Fappi A., Shabrish V., Hollomon H., Islam T., Zhang X., Razani B., Klein S., Mittendorfer B.

*High-animal protein and high-plant protein meals differentially alter postprandial plasma amino acid concentrations but not glucose homeostasis in people with overweight/obesity in a randomized, crossover, single-meal study.*

**The American Journal of Clinical Nutrition**, volume 124, issue 4, October 2026, article 101468.

First published online: August 10, 2026.

DOI: https://doi.org/10.1016/j.ajcnut.2026.101468

PubMed: https://pubmed.ncbi.nlm.nih.gov/42575285/

#AthleticCarnivore #AnimalProteins #PlantProteins #MuscleGrowth #Bodybuilding #BCAA #Leucine #MuscleHypertrophy #SportsNutrition #ProteinSynthesis #CarnivoreDiet #ScientificNutrition