Plant Protein vs. Animal Protein

Plant-based diets have been on the rise for the past decade with a focus on plant protein as a primary area of both interest and concern. While plant protein has generally been considered inferior to animal protein, claims continue to be made that plant protein is just as nutritious, if not more, than animal protein, but what does the research say? Here’s everything you need to know about plant protein vs. animal protein and the nutrition difference between the two.

Plant Protein vs. Animal Protein: What’s the Difference?

Protein is one of three essential macronutrients, along with carbohydrates and fat, that are present in food. Proteins are made up of smaller molecules called amino acids, of which there are 20 in total, which are considered the building blocks of life and are found in every cell in the body. Amino acids are joined together by chemical bonds to form chains, which play various roles in the human body including the production of enzymes, hormones, and neurotransmitters; cellular structure, growth, and repair; support to the immune system, and transportation of nutrients. (1)

The primary difference between plant protein and animal protein is the composition of amino acids. Amino acids can be classified into three different groups; essential, nonessential, and conditionally essential amino acids. (2)

• Essential amino acids cannot be made by the body and, therefore, must be consumed through food. These include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
• Nonessential amino acids can be made by the body from essential amino acids or in the normal breakdown of proteins. These include alanine, arginine, asparagine, aspartic acid, glutamic acid, glutamine, glycine, proline, serine, and tyrosine.
• Conditionally essential amino acids are not essential, except in times of illness and stress. These include arginine, cysteine, glutamine, tyrosine, glycine, ornithine, proline, and serine.

Generally speaking, animal protein contains all essential amino acids but plant proteins do not. It is for this reason that animal proteins are typically considered complete proteins and plant proteins are typically considered incomplete proteins.

What is animal protein?

All animal meats and animal by-products, such as eggs or dairy, are considered animal proteins. Animal proteins are known as complete protein sources as they contain all nine essential amino acids. Sources of animal protein include:

• Red meat and game meat
• Fish and seafood
• Poultry
• Eggs
• Dairy products, such as milk, yogurt, and cheese

What is plant protein?

Plant proteins are plants that contain a meaningful amount of protein. While many plants contain protein, certain plants contain protein at higher levels or in more concentrated amounts. In most cases, plant proteins contain more carbohydrate or fat, gram per gram, than protein but compared to other plants are relatively high in protein and are, therefore, considered plant proteins. Plant proteins, also referred to as vegan proteins or vegetarian proteins, are typically considered incomplete proteins, as they do not contain all nine essential amino acids. Sources of plant protein include:

• Soy products, such as tofu, tempeh, and edamame
• Beans
• Lentils
• Whole grains
• Nuts
• Seeds

Certain plant proteins, such as soybeans, tofu, and quinoa, do contain all essential amino acids and are, therefore, considered complete protein sources, however, the ratio of their amino acid profile is not considered optimal. While these plant proteins do contain all essential amino acids they tend to contain lower levels of certain amino acids, namely leucine. (3) It is for this reason that combining complementary plant proteins is often recommended in plant-based diets. While it was once considered best practice to combine complementary plant proteins at every meal to balance amino acid ratios, it is now generally agreed that it is best to consider amino acid intake in the overall diet throughout the entire day.

Nutrition of Plant Protein vs. Animal Protein

While plant and animal sources of protein both contain protein, they contain different macronutrient ratios and, therefore, vary widely in protein content. Here is a comparison of a 100-gram serving of cooked chicken breast, extra-firm tofu, cooked black beans, and raw almonds. (4)(5)(6)(7)

Per 100 Grams	CHICKEN	TOFU	BEANS	ALMONDS
Calories	158 calories	83 calories	132 calories	579 calories
Protein	32 grams	10 grams	9 grams	21 grams
Fat	3 grams	5 grams	0 grams	50 grams
Carbohydrate	0 grams	1 gram	24 grams	22 grams

Calories: Calorie content varies widely in plant and animal proteins depending on the source. While chicken, tofu, and black beans contain a similar calorie content per 100-gram serving, almonds contain 3.5 or more times more calories per serving given their high-fat content.

Protein: Compared gram per gram, animal proteins typically contain more protein than plant proteins. Per 100-gram serving, chicken contains 220% more protein than tofu, 256% more protein than black beans, and 52% more protein than almonds.

Fat: The fat content of plant and animal proteins varies widely based on the source. While soy products, beans, and lentils are generally low in fat, animal protein sources can contain both high and low levels of fat depending on the type of meat and cut of meat, while nuts and seeds are primarily composed of fat and, therefore, always high in fat content.

Carbohydrate: Animal proteins are low in carbohydrate content while plant proteins vary depending on the source. Beans and lentils typically contain two to three times more carbohydrates than protein per serving, nuts and seeds typically contain similar amounts of carbohydrates and protein, and soy products contain the least.

Pros and Cons of Plant and Animal Protein

There are important pros and cons to consider in both plant and animal protein sources.

Benefits of Animal Protein

Provides All Amino Acids: Animal proteins are considered complete proteins as they contain all essential amino acids and are, therefore, often considered superior protein sources compared to plant sources.

Better Digestibility and Bioavailability: According to both the protein digestibility corrected amino acid score (PDCAAS) and digestible indispensable amino acid score (DIAAS) used to assess the ability of a dietary protein to meet the body’s amino acid requirements; animal protein sources have higher digestibility and bioavailability than plant protein sources. (8)(9) The amino acids found in animal foods survive digestion better than those in plant foods providing a higher bioavailability.

Higher Concentration of Protein: Gram per gram and calorie per calorie, animal protein sources contain higher levels of protein. This means, on average, one will need to consume fewer calories to reach similar or higher levels of protein intake compared to plants.

Contain Essential Nutrients: In addition to containing all essential amino acids, overall, animal proteins are better sources of essential vitamins and minerals, specifically vitamin B12, vitamin D, DHA, iron and zinc. (10)

Cons of Animal Protein

More Expensive: Compared to plant proteins, animal protein does have a higher price point per serving; however, per gram of protein provided they may actually be more expensive.

Format Matters: Processed forms of animal protein, specifically processed forms of red meat such as hot dogs and corned beef, have been linked to adverse health effects including heart disease and cancer. (11)(12) However, the direct causation remains disputed within the scientific community and, while unprocessed red meat has shown lesser correlations, there have been no links to leaner animal protein sources such as poultry or seafood. (13)(14)

Benefits of Plant Protein

Plant Foods Linked to Health Benefits: A diet high in plant foods has been linked to numerous health benefits including lower cholesterol levels, lower risk of heart disease, and improved heart health. (15)(16) While you can consume animal proteins and still consume a diet rich in plant foods, generally speaking adding more plants to your diet is beneficial to overall health.

Less Expensive: Compared to animal proteins, plant proteins are typically cheaper. However, while 100 grams of beans, lentils or tofu generally has a lower price point than 100 grams of chicken or beef, it does contain less protein overall.

Highly Versatile: While one could argue on both sides, plant protein sources are generally considered more versatile ingredients as they can be used in both savory and sweet dishes, from veggie scrambled to curries to dips and sauce, for breakfast, lunch, dinner, and snacks.

Cons of Plant Protein

Missing Amino Acids: Most plant proteins do not contain all essential amino acids and those that do contain them don’t contain them in optimal ratios, however, by consuming a wide range of plant proteins an individual can likely consume all essential amino acids.

Lower Concentrations of Protein: Gram per gram, plant proteins are less concentrated in protein than animal sources, therefore, one will need to consume more calories to reach the same protein intake as animal sources.

Contain Antinutrients: Plants contain antinutrients that impair the digestion and absorption of protein, vitamins, and minerals. This natural defense mechanism helps to protect the plant from infections or consumption by animals and insects and includes phytates, lectins, oxalates, tannins, glucosinolates, and saponins. For example, when phytic acid binds zinc, an essential mineral, it forms an unabsorbable complex that your body cannot use. (17)  While, in most cases, these antinutrients can be destroyed or denatured through proper preparation, these are things that animal proteins do not contain.

Missing Essential Nutrients: Certain essential micronutrients are simply not found in the plant kingdom. There are no reliable plant protein sources of vitamin B12, Vitamin D3, vitamin K, creatine, or DHA. In fact, the only source of K2 from plants is from fermented vegetables, such as natto, while it’s widely found in animal foods and highest in liver and dairy products. (18) Moreover, taurine is a sulfur compound that’s only found in animal-based foods. (19)

Plant vs. Animal Protein for Muscle Building

While protein has many important functions, one of the best known and popular is its requirement for and ability to build muscle. A systematic review and meta-analysis found that animal protein tends to have a more favorable effect on lean mass compared to plant protein, and the benefit appears more pronounced in younger adults. (20) While it is possible to consume exclusively plant proteins and experience similar muscle-building results, on a gram-per-gram basis, animal proteins are generally more anabolic. This anabolic advantage is due to higher concentrations of essential amino acids, particularly leucine, and also due to constituents such as taurine, carnosine, creatine, collagen and even cholesterol, none of which are present in plant foods. (21) The lower anabolic effect in plant proteins is partly due to their lower digestibility and lower amino acid content than animal protein sources.

Animal Protein vs. Plant Protein Powder

Protein powder is a commonly used supplement and is now available in both plant and animal forms. The most common source of animal protein powder is whey, while egg and beef protein powders also exist, and the most common sources of plant protein powder include soy, peas, hemp, rice, or a blend.

Much like whole foods, animal protein powders contain all essential amino acids, which is especially important as leucine is a key amino acid required for building muscle; one of the primary reasons for using protein powder supplements. While many plant-based protein powders will add incremental leucine to their blend, one study demonstrated that when amino acid and leucine levels are controlled for, whey protein still provides a significantly greater response in blood levels of amino acids once consumed. (23)

Regardless of the source chosen, while protein powder can be a valuable addition to a healthy diet, and there are many ways to use it, it’s best to read labels carefully as they are technically still a form of processed food.

The Bottom Line

The primary difference between plant proteins and animal proteins is their composition of amino acids; animal protein sources are considered complete proteins as they contain all essential amino acids, while plant protein sources are considered incomplete proteins as they are lacking in different amino acids. While animal proteins have a slight advantage as they contain essential nutrients not found in plant foods and provide a slight anabolic advantage for muscle growth compared to plant proteins, both plant and animal proteins have benefits and drawbacks. Overall, all whole food protein sources are nutrient-dense options, so instead of picking one or the other, focus on incorporating both plant and animal proteins into a healthy and well-balanced diet.