Animal vs Plant Protein: What’s Better?
Whether protein from animal sources or plant source is superior for health & performance is a long-standing debate.
The truth, it seems to me, is that the answer is both. Based on the available research, choosing one or the other is the wrong choice; no matter which you pick. Furthermore, this is a choice almost nobody is actually faced with.
In this article, I hope to outline why the answer is both, as well as some strategies to incorporate both animal and plant protein into your diet.
What is protein?
Before diving in, it’s worth covering what protein actually is so that you have a better understanding of the actual differences.
Proteins are long chains of smaller compounds called amino acids, similar to a chain of beads. In this analogy, the chain is the protein and the beads are the amino acids.
There are 20 amino acids that form the proteins in food and within our bodies. 9 of which are considered the Essential Amino Acids (EAAs) because we cannot produce them within our bodies; therefore, it is essential we get them from diet. [1]
One of these amino acids, leucine, has been shown to be the “trigger” for muscle protein synthesis. That is, it acts as the on-switch for the process of building muscle. [2]
A protein is often considered high-quality if:
It has all of the essential amino acids
It has a sufficient amount of leucine
It is highly bioavailable
The case for animal proteins
Protein that is derived from animal foods such as meat, eggs, and dairy tends to be of a higher quality than plant proteins.
Animal proteins tend to be much more bioavailable, are almost always complete proteins, and usually have high compositions of leucine within the protein chains. [3]
As a result of this, protein intakes from animal sources tend to lead to greater muscular adaptations long-term compared to plant-only diets. [4]
On a plant-only diet, two considerations need to be made to get the same results from an animal-protein including diet:
More protein overall may need to be eaten in a day to compensate for the lower bioavailability [5]
Protein pairings may need to be planned-out
Since many plant proteins are incomplete (they lack one or more of the essential amino acids), they may need to be paired. In other words, one plant protein may contain the amino acid the other is missing and vice versa.
From a physical performance perspective, animal protein is the clear winner. It more greatly stimulates muscle protein synthesis and consistently leads to more muscle built; although results on strength are mixed. [4]
Furthermore, building muscle is a health benefit in its own right. Doing so significantly improves glucose metabolism, reduces prevalence of metabolic syndrome, reduces risk of cardiovascular disease, and reduces all-cause mortality (increases lifespan). [6,7,8]
The case for the inclusion of plant proteins
As previously mentioned, the primary benefit of animal protein is that protein derived from animal sources is guaranteed to be complete and usually contains a high amount of leucine. Most sources of plant protein are incomplete or less bioavailable. [5]
However, it is not true that having the entirety of protein intake come from animal foods is better than if ~50% of your protein came from animals and the other half came from plants; assuming sufficient total protein intake. In fact, even if a decent amount of a complete protein is taken in (plant or animal), the musculoskeletal adaptations will be the same if enough total protein is eaten. [9,10]
There are plant proteins that are complete and highly bioavailable. Soy is the best example, particularly given that soy products such as protein powder, tempeh, tofu, etc. have a high amount of protein per calorie. The same can’t be said about many other complete plant proteins.
It would be impractical, though, to eat soy as your only real source of protein in the diet. In light of this, the real advantage that animal protein foods provide is a wide variety of complete protein options that are within good protein to calorie ratio.
With that said, there’s lots of research examining what happens when you substitute animal protein for plant protein. As long as total protein intakes are sufficient and calorie intake is the same, substituting plant protein for animal protein significantly improves health and reduces risk of various chronic disease such as heart disease and diabetes. [11,12]
The reason for this is not because of anything different about the individual protein molecules, but rather because of what you are consuming alongside the protein.
Animal foods, such as meat, usually also have a high amount of saturated fat accompanying them, the intake of which has been clearly demonstrated to increase risk of cardiovascular disease and diabetes. [13,14] It is for this reason that leaner cuts of meat (ones lower in saturated fat), such as chicken, are often considered ‘healthier’ than fattier cuts of meat, such as a rib eye.
Conversely, plant foods typically contain nutrients such as polyphenols and isoflavones, which improve health outcomes. [15]
More nuance on animal proteins
It’s worth mentioning that not all animal foods should be grouped into the same bracket. There is great variance in what constitutes an “animal food” including meat, poultry, dairy, fish, eggs, etc.
What these foods have in common is that they all provide high-quality, highly bioavailable protein and that they come with a variety of vitamins & minerals; as most whole foods do. Where they differ is what sort of fat comes along with that protein.
Meat, poultry, and pork tend to be the most commonly consumed given their affordability. These foods also are the animal foods that provide saturated fat; which is known to harm health as previously mentioned.
Eggs contain saturated fat, but most of the fat within an egg yolk is a monounsaturated fat: oleic acid, the same that is found in olive oil. Oleic acid and other monounsaturated fats have been shown to improve health. [16]
Fatty fish, such as salmon, contain omega-3 polyunsaturated fats: eicosapentaenoic acid (EPA) & docosahexaenoic acid (DHA). These are very well-known to improve various health outcomes, arguably more so than any other dietary fat. [17,18]
To be clear: this isn’t to say that meat is inherently bad for you or that you should only eat eggs and salmon. What is true, though, is that a high saturated fat intake can be harmful to your health and a high intake of meat products may contribute to this. It’s commonly recommended to keep saturated fat intake to below 10% of total calorie intake. So, if you eat 2000 calories in a day, then you’d want to eat 22 grams or less of saturated fat (because fat provides 9 calories per gram).
The overall take-home
All-in-all, the message I want to drive home is this: your best bet is to have a high degree of diversity in the foods you derive protein from. Almost always: the more nutritional diversity you have, the better. This is one more example of this.
At the beginning of this article I mentioned that the answer is both, not one or the other. Hopefully, I’ve done a decent enough job explaining why that is.
