Does Your Body Absorb Animal Protein Better Than Plant Protein?

November 3, 2025 •

5 min read

According to nutrition experts, animal proteins are typically absorbed 10 to 20 percent more efficiently than plant proteins due to differences in their cellular structure. This raises the question: Does your body absorb animal protein better than plant protein?

Quick Summary

Animal protein is generally more easily absorbed than plant protein due to matrix differences and antinutrients, but the distinction is minor for most people meeting daily protein needs.

Key Points

Bioavailability Difference: Animal protein is generally more bioavailable, meaning more of it is absorbed and utilized by the body, compared to plant protein.
Antinutrient Effects: Compounds in plants like phytates, tannins, and protease inhibitors can interfere with protein digestion and absorption.
DIAAS Metric: The Digestible Indispensable Amino Acid Score (DIAAS) is a modern measure that confirms animal proteins often score higher than many plant proteins.
Preparation is Key: Simple methods like soaking, sprouting, and cooking legumes and grains can significantly enhance the digestibility of plant proteins.
Complete Protein Intake: While most plant foods are not 'complete' in all essential amino acids individually, eating a variety of plant sources throughout the day ensures all amino acids are consumed.
Overall Diet Matters Most: For most healthy adults consuming enough total protein, the slight difference in absorption rate between animal and plant sources is not a significant nutritional concern.
Beyond Protein: Plant proteins come with added benefits like fiber and phytonutrients, while animal proteins offer high levels of specific micronutrients like Vitamin B12 and heme-iron.

For decades, the debate over protein sources has centered on animal versus plant-based options. A common assertion is that animal protein is inherently superior because it is more readily absorbed by the body. While there is a scientific basis for this claim, the full picture is far more nuanced and depends heavily on individual needs, dietary variety, and food preparation methods. Understanding the mechanisms behind protein digestion and absorption is crucial for making informed nutritional choices, regardless of your dietary preference.

Understanding Protein Bioavailability and Quality

Bioavailability refers to the proportion of a nutrient that is absorbed and utilized by the body. For protein, this means how efficiently the amino acids—the building blocks of protein—are released and enter the bloodstream to be used for various bodily functions, such as building and repairing tissue.

Two key metrics are used to assess protein quality and absorption:

Protein Digestibility Corrected Amino Acid Score (PDCAAS): An older method that assesses protein quality based on a human's amino acid requirements and the protein's overall fecal digestibility. However, it is now considered less accurate because it doesn't account for amino acids lost to gut bacteria.
Digestible Indispensable Amino Acid Score (DIAAS): The newer, more accurate standard proposed by the Food and Agriculture Organization (FAO). It measures digestibility at the end of the small intestine (ileal digestibility), providing a truer reflection of the amino acids the body actually absorbs. DIAAS scores can also exceed 100%, indicating a protein's excellent amino acid profile and high digestibility.

Proteins are also categorized by their amino acid profile. Animal proteins are considered 'complete' because they contain all nine essential amino acids (EAAs) in amounts sufficient for human needs. Plant proteins, on the other hand, are often 'limiting' in one or more EAAs, such as lysine in cereals or methionine in legumes. However, this does not mean plant-based diets are inadequate. A varied diet that includes a range of plant foods ensures a complete EAA profile over the course of a day.

The Factors Influencing Plant Protein Absorption

Several characteristics of plant-based foods explain their generally lower protein absorption rates compared to animal sources. These can largely be attributed to the food matrix itself and the presence of natural compounds known as antinutrients.

Antinutrients and Fiber

Antinutrients are compounds in plants that can interfere with the absorption of other nutrients, including protein.

Protease Inhibitors: Found in legumes and cereals, these compounds can block the activity of digestive enzymes like trypsin and chymotrypsin, hindering protein breakdown.
Phytates: Phytic acid, present in seeds, legumes, and grains, can bind to minerals and proteins, making them less available for absorption.
Tannins: These polyphenolic compounds can bind to proteins and digestive enzymes, reducing digestibility.

The Impact of Plant Cell Walls

Unlike animal cells, which have permeable membranes, plant protein is often encapsulated within fibrous cell walls. These indigestible fibers physically hinder digestive enzymes from accessing the protein, thereby slowing down or reducing its release and absorption in the small intestine.

Comparing Animal and Plant Proteins: A Digestibility Deep Dive

When assessing protein sources, comparing DIAAS scores offers a more complete picture of protein quality and absorption. The following table provides examples based on data from the FAO and other research.


Protein Source	DIAAS for 0.5-3 yo (approx.)	Typical Limiting Amino Acid	Key Factors Affecting Digestibility
Animal
Milk Protein Concentrate	~1.18	None (high quality)	Easily digested; high bioavailability.
Beef	~1.12	None (high quality)	High digestibility and complete amino acid profile.
Chicken Breast	~1.08	Tryptophan	Highly digestible, but specific EAAs can be limiting.
Egg	~1.01-1.13	Histidine (in one study)	Considered a gold standard for protein quality.
Plant
Soy Protein Isolate	~0.90-1.05	Methionine + Cysteine	Isolated form removes many antinutrients, boosting quality.
Chickpeas (Cooked)	~0.83	Methionine + Cysteine	Soaking and cooking improve digestibility by reducing antinutrients.
Pea Protein Concentrate	~0.82	Methionine + Cysteine	Processing into concentrate improves digestibility.
Wheat	~0.40-0.48	Lysine	Low digestibility partly due to antinutrients; often combined with other proteins.
Almonds	~0.40	Lysine	Raw state contains inhibitors; processing and preparation can improve score.

Strategies to Boost Plant Protein Absorption

While animal proteins offer a slight bioavailability advantage, it is a myth that a plant-based diet cannot provide sufficient protein for health and muscle building. With mindful preparation, you can significantly enhance the absorption and nutritional value of plant proteins.

Here are some effective strategies:

Soaking and Sprouting: Soaking grains, nuts, and legumes before cooking helps break down enzyme inhibitors and phytic acid, improving mineral and protein bioavailability. Sprouting takes this a step further, causing an increase in certain amino acids.
Cooking and Fermenting: Heat treatment, like cooking or roasting, can deactivate antinutrients and improve protein digestibility. Fermentation, used to make foods like tempeh or miso, utilizes microorganisms to break down complex molecules, enhancing nutrient availability.
Pairing and Combining: As our bodies maintain a pool of amino acids, it's not necessary to perfectly combine proteins at every meal. However, intentionally combining complementary proteins—like beans (high in lysine) and rice (high in methionine)—can optimize the amino acid profile of a meal.
Hydration and Chewing: Staying well-hydrated is crucial for all digestive processes. Chewing food thoroughly helps break down tough plant cell walls, making proteins more accessible to enzymes.

Does the Absorption Difference Really Matter for Most People?

For the average person consuming a varied diet that meets their daily protein needs, the marginal difference in absorption rate between animal and plant protein is largely inconsequential. A healthy individual consuming 15% of their daily calories from a variety of protein sources is unlikely to experience any deficit due to differences in bioavailability alone.

However, for certain individuals with higher protein requirements, such as the elderly or athletes, maximizing protein absorption can be more relevant. As we age, the efficiency of protein digestion can decrease. In these cases, prioritizing higher-quality proteins (which can include highly processed plant protein isolates) or strategically using supplements can be beneficial. For athletes, maximizing muscle protein synthesis is often a goal, and the amino acid profile and absorption rate can influence this process.

The Holistic View: Beyond Absorption

Focusing solely on absorption overlooks the broader health and nutritional implications of each food source. A key advantage of plant-based proteins is their association with other beneficial nutrients.

Additional Benefits of Plant Protein

Fiber: Plant proteins are often packaged with dietary fiber, which is essential for gut health, blood sugar management, and a reduced risk of chronic diseases.
Micronutrients: Many plant foods contain a wealth of vitamins, minerals, and phytonutrients that support overall well-being.
Lower Saturated Fat: Plant-based options typically have lower saturated fat and cholesterol content than animal sources.

The Takeaway on Protein Choices

Ultimately, the choice between animal and plant protein is not a simple matter of one being 'better' than the other across all metrics. The superiority of animal protein in bioavailability and amino acid profile is a fact, but it doesn't nullify the nutritional value or potential health benefits of a well-planned plant-based diet. A varied, balanced diet is the most reliable way to ensure you receive all the necessary amino acids, regardless of your protein source preference.

Learn more about building a healthy diet on the World Health Organization website.

Frequently Asked Questions

Protein bioavailability is a measure of how efficiently your body can break down, absorb, and utilize the amino acids from a food source. Higher bioavailability means more of the protein is available for the body's use.

No, this is a myth. While many plant foods are limiting in one or more essential amino acids, all plant foods contain all nine essential amino acids. By consuming a variety of plant-based protein sources throughout the day, you can easily obtain a complete amino acid profile.

Antinutrients are compounds naturally found in plants, such as phytates, tannins, and protease inhibitors, that can interfere with protein digestion and the absorption of other minerals. Processing methods like soaking and cooking can significantly reduce their presence.

Yes, it is entirely possible to build muscle with plant protein. Research shows that well-planned plant-based diets can support muscle growth comparable to animal-based diets. The key is ensuring adequate total protein intake from a variety of sources to provide all necessary amino acids.

You can improve plant protein absorption by using preparation methods like soaking and sprouting legumes and grains, which reduces antinutrients. Combining different plant protein sources in your diet also ensures a more complete amino acid profile.

Yes, soy protein isolate is an exception among plant proteins, showing high digestibility and a complete amino acid profile comparable to animal sources. This is because the isolation process removes most of the antinutrients present in the whole soybean.

The DIAAS (Digestible Indispensable Amino Acid Score) is the most accurate metric for evaluating protein quality. It measures the digestibility of individual amino acids at the end of the small intestine, providing a more precise assessment of the protein's true nutritional value to the human body.