ANIMAL VS PLANT PROTEIN
In the past few years eating plant-based has become somewhat of a trend and it looks like it’s here to stay.
For some reason people want to make the food they eat their whole personality which has sparked fierce debate over what lifestyle choice is better – eating meat or plants.
One affront chosen by the carnivores is that vegans and vegetarians (seen as the same) cannot get enough protein in their diet. But is this true?
More to the point, how does animal and plant-based protein stack up?
Here’s what the research says.
First of All, What is Protein?
Protein is a molecule necessary for pretty much every process which occurs in the body but is most closely associated with its necessity for cell renewal and growth (gains).
It is made up of 20 amino acids, 9 of which are essential because they cannot be produced by the body and must be obtained through your diet.
The main amino acids of concern are leucine, lysine, and methionine as they are all heavily involved in protein synthesis (the process of muscle growth and repair).
You can see where team animal protein is going with this – if you don’t get enough essential amino acids, you might as well kiss your hard-earned gym gains goodbye.
But is this the case?
Digestibility
Plant-based proteins, especially legumes, are harder to digest than animal proteins due to their molecular structure and the presence of anti-nutritional factors. [11]
Anti-nutritional factors such as trypsin and protease inhibitors prevent the breakdown of proteins and phytic acid reduces the body’s ability to absorb minerals. [2] [4]
As such, one study found animal proteins to have higher absorption rates (~85-95%) compared to plant proteins (~50-75%), due to these antinutritional factors. [9]
However, this same study also found that isolated or concentrated plant proteins (powdered form) improve absorbability, making them comparable to animal proteins in terms of digestion and absorption. [9]
A comparison which can be drawn between plant-based and animal protein is their DIAAS (Digestible Indispensable Amino Acid Score).
One study found that animal proteins such as pork, casein (milk), egg, and whey protein ranked the highest in terms of DIAAS, with values exceeding 100, classifying them as “excellent” quality proteins. [3]
The same study found that potato ranked the highest among plant proteins, scoring over 100 and being of “excellent” quality. Soy protein also ranked highly being in the 75-99 range whereas many other plant proteins such as wheat, corn, and hemp fell below a DIAAS of 75, indicating lower quality. [3] [11]
Pseudocereals such as quinoa, amaranth and buckwheat are also highlighted for their high protein digestibility compared to other plant proteins. [4] [11]
Put simply?
Plant proteins are more difficult to digest which can limit their anabolic potential compared to animal proteins.
Amino Acid Composition
Animal proteins are considered complete proteins as they contain all 9 essential amino acids in sufficient quantities to meet our nutritional needs. [8]
Comparably, plant proteins often have deficiencies in one or more essential amino acids, particularly lysine (in grains) and methionine (in legumes). Quinoa and soy are notable plant exceptions with better amino acid profiles. [2] [4] [9]
One particular essential amino acid plant proteins lack is leucine which is important for activating the mTOR pathway. The mTOR pathway stimulates muscle protein synthesis and having lower leucine levels therefore affects anabolic capacity. [6] [9]
However, some plant proteins such as soy, pea and potato do have comparable essential amino acid contents to casein (milk) and egg proteins. [9]
Common protein sources ranked by colour according to the amount of essential amino acids in them compared to the other sources (dark green is highest and white is lowest), n.d. = not determined. [2]
One study compared the amino acid content of various plant proteins to the World Health Organisation standards which is summarised as follows:
Legumes (soybeans, chickpeas, peas, and lentils) contain higher amounts of lysine.
Cereals (rice, wheat, and corn) tend to lack lysine but are rich in methionine.
Pseudocereals (quinoa, amaranth, and buckwheat) have a complete essential amino acid profile, making them superior to many other plant protein sources. [10]
So, what does all this mean?
Essentially, animal proteins are nutritionally superior compared to plant proteins in terms of their amino acid profile, but the deficiencies in plant protein are not drastic, and can be enhanced in a few ways.
Is It Possible to Improve Plant-Based Proteins?
Increase Protein Quantity
Plain and simple. Consuming greater amounts of plant protein can compensate for its amino acid deficiencies. [9]
Keep in mind their protein content varies, with legumes and nuts having higher protein levels compared to cereals. [11]
Blend Proteins
Combining plant proteins with complementary amino acid profiles (such as pea and rice protein) can improve their overall anabolic potential by creating a balance amino acid profile and enhancing muscle protein synthesis [9] [10]
Fortification
Essentially, the idea is to add the missing essential amino acids to plant-based protein. By adding free essential amino acids, especially leucine, plant protein’s anabolic response will increase. [9]
One such study found no statistically significant difference in muscle protein synthesis between plant-based protein with added leucine and whey protein, which were both better than the plant-based protein by itself. [6]
Macronutrient and amino acid composition of the supplements. [6]
Why Even Bother With Protein?
Aside from the fact protein is necessary for pretty much all bodily functions and to realise your hard work in the gym (most importantly) there are some other benefits that may be of interest too.
One systematic review and dose-response meta-analysis examined the associations between the intake of animal and plant and mortality outcomes. Overall, a higher intake of total protein was associated with a lower risk of all-cause mortality by around 6%. [3]
Plant-based proteins specifically had a stronger correlation with reduced all-cause and cardiovascular disease mortality risks. [8] [4] [5]
Plant proteins have also been associated with improved blood glucose regulation, renoprotective benefits (benefits the kidneys), reducing inflammation, supporting immune function and assisting appetite regulation. [4]
Award a point to team plant-based!
Key Differences
Plant protein stimulates a lower anabolic response than animal protein due to differences in digestion, absorption and amino acid composition - particularly deficiencies in essential amino acids such as leucine, lysine, and methionine. [9]
However, although animal proteins are more effective in promoting lean mass gains, the difference is slight, and there is practically no difference in terms of muscular strength changes. [7]
It is worth noting that the difference is more pronounced in older adults – mainly due to the age-related decline in muscle responsiveness to dietary protein. [6]
What Do I Take Away From All This?
Apart from the fact I have far too much spare time to have written this I know you probably want a definitive answer, so here it is - animal protein beats out plant protein in terms of anabolic potential (giving you the gift of gains).
That being said it is best to consume a combination of the two as part of a varied, nutrient-dense diet and that way you can’t go wrong – I’m not trying to sound like your mother but seriously, eat your greens.
References
[1] Berrazaga, I., Micard, V., Gueugneau, M., & Walrand, S. (2019). The role of the anabolic properties of plant-versus animal-based protein sources in supporting muscle mass maintenance: a critical review. Nutrients, 11(8), 1825.
[2] Day, L., Cakebread, J. A., & Loveday, S. M. (2022). Food proteins from animals and plants: Differences in the nutritional and functional properties. Trends in Food Science & Technology, 119, 428-442.
[3] Herreman, L., Nommensen, P., Pennings, B., & Laus, M. C. (2020). Comprehensive overview of the quality of plant‐And animal‐sourced proteins based on the digestible indispensable amino acid score. Food science & nutrition, 8(10), 5379-5391.
[4] Hertzler, S. R., Lieblein-Boff, J. C., Weiler, M., & Allgeier, C. (2020). Plant proteins: assessing their nutritional quality and effects on health and physical function. Nutrients, 12(12), 3704.
[5] Langyan, S., Yadava, P., Khan, F. N., Dar, Z. A., Singh, R., & Kumar, A. (2022). Sustaining protein nutrition through plant-based foods. Frontiers in nutrition, 8, 772573.
[6] Lim, C., Janssen, T. A., Currier, B. S., Paramanantharajah, N., McKendry, J., Abou Sawan, S., & Phillips, S. M. (2024). Muscle Protein Synthesis in Response to Plant-Based Protein Isolates With and Without Added Leucine Versus Whey Protein in Young Men and Women. Current Developments in Nutrition, 8(6), 103769.
[7] Lim, M. T., Pan, B. J., Toh, D. W. K., Sutanto, C. N., & Kim, J. E. (2021). Animal protein versus plant protein in supporting lean mass and muscle strength: a systematic review and meta-analysis of randomized controlled trials. Nutrients, 13(2), 661.
[8] Naghshi, S., Sadeghi, O., Willett, W. C., & Esmaillzadeh, A. (2020). Dietary intake of total, animal, and plant proteins and risk of all cause, cardiovascular, and cancer mortality: systematic review and dose-response meta-analysis of prospective cohort studies. Bmj, 370.
[9] Pinckaers, P. J., Trommelen, J., Snijders, T., & van Loon, L. J. (2021). The anabolic response to plant-based protein ingestion. Sports Medicine, 51(Suppl 1), 59-74.
[10] Sá, A. G. A., Moreno, Y. M. F., & Carciofi, B. A. M. (2020). Plant proteins as high-quality nutritional source for human diet. Trends in Food Science & Technology, 97, 170-184.
[11] Thakur, S., Pandey, A. K., Verma, K., Shrivastava, A., & Singh, N. (2024). Plant‐based protein as an alternative to animal proteins: A review of sources, extraction methods and applications. International Journal of Food Science & Technology, 59(1), 488-497.