Animal Proteins vs. Plant Proteins: How Do They Compare?

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Last Updated on August 5, 2019 by Michael Joseph

In recent times, we can hear the words “plant protein” much easier than we could in the past.

With the promotion of legumes such as lentils, beans, and the wide range of vegan “meat” products, there are many different plant proteins out there.

However, how do they compare with traditional animal proteins?

This article takes a balanced look at what the data shows about the respective protein quality of animal and plant foods.

Various Animal and Plant Proteins Next To Each Other.What Is Animal Protein?

Animal protein refers to the dietary protein we can get from animal-based foods.

Some of the most popular sources of animal protein include;

  • Dairy foods such as cheese, milk, yogurt, and whey
  • Eggs
  • Fish, shellfish, and other types of seafood
  • Poultry from chicken, duck, and turkey
  • Red meat such as beef, lamb, and pork

What Is Plant Protein?

Plant protein is simply a dietary protein from non-animal sources.

These plant proteins typically come from beans, legumes, nuts, and soy.

For instance, here are some of the most popular types of plant protein;

  • Black beans
  • Edamame
  • Isolated proteins from wheat, pea, rice, etc
  • Kidney beans
  • Pea protein
  • Soybeans
  • Tempeh
  • Tofu
  • Various vegetarian/vegan burger products
Key Point: Animal proteins are proteins that we can consume from meat, dairy, eggs, and seafood. In contrast, plant proteins refer to dietary proteins from plant foods.

How Can We Assess the Quality of Protein?

Firstly, the quality of protein can vary from food to food. In short, this means we can absorb and digest some proteins better than others.

For this reason, twenty grams of protein from some foods can be a better source than twenty grams of protein from another.

But how can we assess the quality?

There are two primary ways;

  • The amino acid profile of the food
  • Protein bioavailability ratings
Key Point: We can judge the quality of a protein by its amino acid profile and bioavailability.

Amino Acid Profiles of Animal and Plant Proteins

In this next section, we will analyze how much of each essential amino acid popular animal and plant proteins contain.

However, before we do this, let’s first look at the essential amino acid requirements.

According to the National Academies of Sciences, Engineering, and Medicine, we should strive to get the following daily amount of essential amino acids (1);

Essential Amino Acid Requirements For Adults
Amino acid Daily Requirement per Kg of Body Weight
Histidine 14 mg
Isoleucine 19 mg
Leucine 42 mg
Lysine 38 mg
Methionine & Cysteine 19 mg
Phenylalanine & Tyrosine 33 mg
Threonine 20 mg
Tryptophan 5 mg
Valine 24 mg

Amino Acid Profiles: Animal Proteins vs. Plant Proteins

In this next table, you can see the amino acid profile of four of the most popular animal proteins compared to popular plant proteins.

For this comparison, the animal foods are;

  • Beef
  • Chicken
  • Eggs
  • Salmon

You can see how these foods compare with four of the most popular plant-based proteins;

  • Lentils
  • Red kidney beans
  • Tempeh
  • Tofu

For each source, you can see the essential amino acids they contain based on a 100-gram (cooked) serving, as well as their overall protein content (2, 3, 4, 5, 6, 7, 8, 9);

Essential Amino Acid Profile of Animal and Plant Proteins (Per 100 Grams)
Essential Amino Acid Beef Chicken Breast Eggs Salmon Lentils Kidney Beans Tempeh Tofu
Histidine (mg) 848 963 308 749 254 238 466 499
Isoleucine (mg) 1154 1638 669 1172 390 383 880 852
Leucine (mg) 2035 2328 1082 2067 654 693 1430 1306
Lysine (mg) 2161 2635 909 2336 630 595 908 1131
Methionine & Cysteine (mg) 940 1256 649 1026 195 224 368 458
Phenylalanine & Tyrosine (mg) 1821 2278 1174 1852 686 713 1557 1412
Threonine (mg) 1010 1310 553 1115 323 365 796 701
Tryptophan (mg) 133 0362 166 285 81 103 194 268
Valine (mg) 1282 1539 855 1310 448 454 920 867
Total Protein (g) 26.1 31.0 12.5 25.4 9.0 8.67 18.5 18.8

As shown in the above table, meat and fish tends to provide the highest amounts of protein per gram.

Following meat, the soybean-based foods, tempeh and tofu, offer the next highest concentrations of protein.

After this, eggs are next, followed by kidney beans and lentils.

However, the total amount of protein and amino acids in food doesn’t tell the whole story.

As previously mentioned, the bioavailability of these amino acids is crucial, and the amount we can digest differs depending on the food.

Key Point: Fish and meat offer the highest amounts of protein overall. Among plant foods, soy-based foods are the most concentrated of these protein sources.

Protein and Amino Acid Bioavailability From Animal and Plant Foods

It is important to be aware of how the protein bioavailability of foods may affect total protein intake.

For instance, choosing only low-quality protein sources could potentially result in a protein deficiency.

There have been many different systems that try to ascertain the quality of protein over the years.

Some of these have included the biological value (BV) and nitrogen balance.

However, the two protein quality scoring systems that hold the most value today are PDCAAS and DIAAS.

PDCAAS

Since 1993, the preferred way of determining protein quality has been the protein digestibility-corrected amino acid score (PDCAAS).

This system measures the quality of protein sources by looking at the amino acids they contain and how capable the human body is of digesting the total amount of protein (10).

DIAAS

In recent years, there have been proposals by the Food and Agriculture Organization (FAO) to replace the PDCAAS system with a new method of measuring protein quality.

The new proposed system is called the digestible indispensable amino acid score (DIAAS) (11).

One of the primary difference between PDCAAS and DIAAS systems is that the latter takes anti-nutrients into account. Anti-nutrients are compounds in plant foods that can limit the absorption of amino acids (and minerals such as zinc and iron) (12, 13).

Additionally, unlike PDCAAS, which assumes we digest all protein equally, the DIAAS score measures individual amino acid digestibility by analyzing fecal matter at the end of the small intestine (14).

PDCAAS Ratings For Protein Foods

First of all, we will look at the quality scores of animal and plant proteins based on the existing PDCAAS system.

These scores analyze the eight proteins we profiled earlier alongside some additional proteins (15, 16, 17).

(Note: the highest possible PDCAAS protein quality score is 1.0).

PDCAAS Protein Quality Ratings of Animal and Plant Proteins
Animal Protein PDCAAS Protein Quality Score
Beef 0.92
Chicken 0.92
Eggs 1.0
Milk 1.0
Salmon 0.99
Whey protein 1.00
Plant Protein PDCAAS Protein Quality Score
Black beans 0.75
Chickpeas 0.52
Lentils (red) 0.54
Lentils (yellow) 0.64
Peanuts 0.52
Pea protein isolate 0.53
Red kidney beans 0.55
Soy protein 1.0

According to the PDCAAS ratings, which is the current standard for measuring protein quality, the most bioavailable proteins are;

  • Dairy products like milk and whey
  • Eggs
  • Soy foods

Generally speaking, according to PDCAAS, all animal foods have a high protein quality rating.

For plant foods, there is a gap between soy-based products and the rest.

In particular, peanuts, red lentils, and kidney beans are quite a lot lower in protein quality.

Key Point: Dairy, eggs, and soy have the highest PDCAAS scores. Apart from this, animal proteins generally score better than plant proteins.

DIAAS Ratings For Protein Foods

As discussed earlier, there is a new (and more accurate) proposed way of measuring protein quality known as DIAAS.

The DIAAS scoring system grades quality by the following classifications (18);

  • DIAAS >100: high-quality protein
  • DIAAS >75 and <100: good quality protein
  • DIAAS <75: low-quality protein

Since DIAAS scores are relatively new, they can be difficult to find. However, the table below shows the available DIAAS protein quality scores for animal and plant proteins (19, 20, 21, 22).

DIAAS Protein Quality Ratings of Animal and Plant Proteins
Animal Protein DIAAS Protein Quality Score
Beef 111 (high quality)
Chicken 108 (high quality)
Eggs 113 (high quality)
Milk 114 (high quality)
Milk protein concentrate 118 (high quality)
Whey protein isolate 109 (high quality)
Plant Protein DIAAS Protein Quality Score
Almonds 40 (low quality)
Chickpeas 83 (medium quality)
Lentils (red) 50 (low quality)
Lentils (yellow) 73 (low quality)
Pinto beans 70 (low quality)
Pea protein concentrate 82 (medium quality)
Red kidney beans 58 (low quality)
Soybean 99.6 (medium quality)
Soy protein 91.5 (medium quality)
Tofu 52 (low quality)

Comparing animal and plant proteins via the DIAAS system shows a greater contrast than PDCAAS.

As shown, the amino acids in animal foods survive digestion better than those in plant foods, giving them a higher bioavailability.

According to DIAAS, all animal proteins are of high quality.

On the other hand, most plant proteins are low-medium quality.

However, it is worth noting that soy-based proteins are only slightly under the ‘high quality’ threshold.

For an in-depth guide to the highest-quality protein supplements, see here.

Key Point: The individual amino acids in animal proteins appear to be more bioavailable than in plant proteins. Animal proteins are thus higher quality.

Animal Proteins vs. Plant Proteins: Which Are Better?

As shown in this article, if we look purely at the quality of protein, then animal proteins are the best choice;

  • Animal proteins mostly have a higher total amount of protein and better amino acid profiles.
  • The proteins in animal foods are more bioavailable than plant sources.

For these reasons, foods like dairy, eggs, fish, and meat are the most effective ways to get protein.

Considerations For Vegetarians/Vegans

For any vegetarian or vegans reading this, it is more challenging to get a sufficient amount of essential amino acids from a diet free of animal proteins.

However, that does not mean it isn’t possible.

By eating a higher amount of these plant foods, it is still possible to meet essential amino acid requirements.

As shown in the amino acid profiles and protein quality ratings, the best plant proteins tend to be soy-based.

Some different soy-based foods from around the world include;

  • Cheonggukjang
  • Edamame
  • Miso
  • Natto
  • Tofu
  • Tempeh
Key Point: Animal foods offer the most bioavailable sources of protein, but we can still meet our requirements through plant foods.

Final Thoughts

There are often many disagreements between animal and plant-protein proponents.

However, there doesn’t need to be; both sources of protein can provide our daily requirements for the nutrient.

That said, gram-for-gram, animal sources of protein tend to be the most effective way to meet these requirements.

For more on protein, see this guide to the macronutrient’s benefits.

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Dr. Sylvia Karpagam
1 year ago

You forgot to say that soya is highly allergenic, contains anti-nutrient, and is difficult to digest.

sammy pepys
1 year ago
Reply to  Michael Joseph

You make a good point. Too many nutrition articles mix up their facts and sources to adjust the outcome and suit their pov. Your refreshing approach takes topics one by one without bias.

Algy
Algy
1 year ago
Reply to  Michael Joseph

Great article again – thank you MIchael Re the comments around Soy – your strategy to stay on topic is probably the best – thank you for giving balanced reports on nutrition in general – always appreciated! As for Soy – I quickly did a search on your website and couldn’t find anything on soy specifically. It might be worth doing something, since it’s a staple for many vegetarians & vegans alike. I haven’t read much about the allergenic properties of it and we used to consume some slightly steamed organic edamame, but we haven’t done that in years now.… Read more »