Plant Protein v Animal Protein

Our main feature on vegan protein looks in general terms at the subject of protein. There we explain what protein is, why we need it and how much protein we need to be healthy. We also explain that there are lots of excellent vegan sources of protein, be they things like Quorn or seitan, or less processed foods, such as lentils, pulses, nuts or seeds.

In this more specific feature, we compare animal protein and plant protein and see whether such terms are helpful, correct and valid. We will also look at what, if any, the differences between protein that comes from plants and protein that comes from animals are.

What Is Protein?

In order to better understand the difference between so-called animal protein and plant protein, it would be helpful to look once again at what protein is. As with many words and seemingly everyday items and substances, many people know what it is on one level without really knowing what it is or what makes a protein a protein, rather than a fat, carbohydrate or anything else.

Whilst we speak of “protein” as if it is a singular entity, there are actually many, many different proteins. And, we really do mean many. The exact number is still a mystery to science but it is thought there are potentially billions of different proteins in the human body alone.

What makes these different molecules proteins is that they are chains of amino acids. It is beyond the scope of this article to go into too much more chemical detail but there are more than 200 amino acids. According to fascinatingly titled book, The History of the Discovery of the Amino Acids (Vickery HB, Schmidt CL, 1931), the first of these were discovered in the early 1800s.

Whilst there are over 200 amino acids, the term is quite commonly used to refer to the 22 proteinogenic ones. The word itself (proteinogenic) means “protein creating” and it is these substances that matter when it comes to the make-up of the proteins we consume. There is some debate over exactly how many amino acids humans use and need but we will go with the information from the British Nutrition Foundation, which states that there are about 20 different amino acids commonly found in plant and animal proteins.

Essential Amino Acids

There is even some debate as to whether there are eight or nine that are classed as essential amino acids, essential because they must be obtained through diet and cannot be made by the body. Once again, we will go with the BNF who list the following as the eight essential amino acids (sometimes referred to as indispensable):

• Isoleucine
• Leucine
• Lysine
• Methionine
• Phenylalanine
• Threonine
• Tryptophan
• Valine

Other Key Amino Acids

Among the other key amino acids are the following:

• Histidine (some consider to be essential and it is for children)
• Alanine
• Arginine
• Asparagine
• Aspartic acid
• Cysteine
• Glutamic acid
• Glutamine
• Glycine
• Proline
• Tyrosine

These amino acids come together in different quantities and structures in different foods to create the billions of different proteins that exist. The eight (or possibly nine if we include histidine) essential amino acids are the most important from a dietary perspective.

Some of the other amino acids are classed as being conditionally essential and this means that we do sometimes need them when we are ill. In addition, children may well need some of these, for example, arginine and proline.

Is Plant Protein the Same as Animal Protein?

All living things contain at least some protein and that means that all plants and all animals offer protein to the diet. We would actually argue it is not overly helpful to speak of “animal protein” or “plant protein” as, beyond the self-explanatory fact that they appear in plant or animal product, these terms do not really tell us anything. What matters is that the human body gets enough protein overall and also gets all the essential amino acids it needs. Looked at in this way, the vegan diet is perfectly satisfactory from a protein perspective.

Vegans can certainly get enough protein and you only need to look at vegan bodybuilders to see that. Moreover, by eating a wide and varied range of plants, vegans can easily get all of the essential amino acids too. We know this as a matter of scientific and nutritional fact and it is also anecdotally exemplified by the supreme performances of many vegan athletes. Clearly, if their diets had been inadequate they would not be able to achieve what they have and the likes of Novak Djokovic and Serena Williams both registered some of their best results whilst eating a plant-based diet.

A lot of the misinformation about plant protein was based on the belief that plants were somehow “incomplete”. It was long thought that there were no plants that offered all of the essential amino acids but we now know that quinoa is a complete protein, as are certain other plant foods, such as chia seeds. According to the BNF, “in the past, this difference has lead (sic) to a concept of first-class and second-class proteins, for animal and plant foods respectively.”

Some people felt that because no single plant source could offer all the essential amino acids, and because generally speaking, animal protein has a wider range of them, that animal protein was somehow higher quality or better. However, as said, we now know that there are plants that offer complete proteins. The more important issue, though, is that we do not tend to eat single foods in isolation.

Combining Proteins

Whilst just about all animal sources of proteins provide high levels of all of the essential amino acids, many plant sources, be they legumes, nuts, seeds or even fruit and veg, do not. Given this, if we were simply to eat chicken all day and nothing else, we would get all the amino acids we need. In contrast, if we ate almonds alone, we would not. However, anyone eating in either of those ways would not last long anyway and incomplete protein would probably be the least of their worries.

The fact is that even someone with a relatively limited diet still eats a range of plants. We now know that eating in this way is more than capable of fulfilling our amino acid requirements. For a long time, the idea of “complementary” proteins was popular. This meant that a vegetarian or vegan would eat different plants in the same meal that would combine to offer all eight (or nine!) essential amino acids. One classic example was beans on toast, with the beans delivering the amino acids that the wheat in the bread did not (and vice versa).

However, we now know that it is not necessary to consume all essential amino acids at the same time. You do not need to have all of them in the same meal, or even in the same day. This means that as long as a vegan eats a reasonably varied diet they will definitely obtain the right mix and blend of proteins (and, more importantly, amino acids) that they need for optimum health.

A good mix of popular vegan foods is, in other words, as good as meat in terms of the quality of the protein it provides. When we talk about the “quality” of protein, nutritionists are usually talking about its ability to provide essential amino acids. Viewed in this way only the very few plant-based foods that deliver all of the essential amino acids are of the same quality as animal-derived protein. However, now we know that it is not necessary to consume all of the acids simultaneously, this concept of quality is outdated.

Vegan Sources of Essential Amino Acids

For the purpose of this feature we will include histidine in our discussion of essential amino acids. The table below shows you just some of the plant-based foods that offer each of them. As you can see, these are very “normal” foods and so there is no need for a vegan to take any special steps in order to consume them all.

Amino Acid	Food source
Histidine	Nuts, seeds, tofu, whole grains, beans, such as soy or kidney, lentils, whole wheat pasta
Isoleucine	Nuts and seeds, tofu, beans and lentils, whole grains, many veg, such as spinach, chard, peas or sweet potatoes
Leucine	Tofu and soy products, beans, nuts (pistachios, peanuts and almonds are best), lentils
Lysine	Tofu, beans (especially black beans and edamame), lentils, peas, quinoa, pumpkin seeds, cashew nuts
Methionine	Tofu, nuts, beans, quinoa and other whole grains, such as teff, seeds
Phenylalanine	Pasta, whole grains, many veg, nuts and seeds, beans, tofu (and other soy products)
Threonine	Nuts and seeds, and beans and lentils (including all soy products)
Tryptophan	Soy products, many beans and lentils, nuts and seeds, whole grains, veg such as sweet potatoes or peas
Valine	Tofu, beans, peas, seeds, nuts, many whole grains

How to Obtain the indispensable Amino Acids You Need

In terms of the recommended intake of these nutrients, the exact amounts vary according to a person’s weight. There are no specific targets and no Reference Nutrient Intake (RNI) for any of the amino acids in the UK. The following stats are based on some more broad and approximate figures taken from a United Nations University Report entitled Protein and amino acid requirements in human nutrition. The information is based on a person weighing 70KG (around 11 stone).

This following list gives you a quick and easy guide as to how much of each of the acids above can be delivered by a certain vegan food.

• Histidine – Vegans can get 72% of their required amount from a cup of lentils
• Isoleucine – Soy products provide great amounts of most but mix things up with some seeds: a 50g serving gives you more than 50%
• Leucine – Tofu is again the best option, with 200g of firm tofu giving you your daily requirement and more
• Lysine – A cup of edamame beans delivers more than 90% of daily requirement
• Methionine – 25g of Brazil nuts gives you 44% of your needs (and also more than your RDI of selenium
• Phenylalanine – One cup of many beans offers more than 100% of your suggested intake (pinto, haricot, adzuki, white, kidney or lentils all deliver the goods)
• Threonine – Get more than 100% of your recommended intake with a cup of wheat germ
• Tryptophan – Mix things up with some sweet potato: a big serving delivers around 60% of your needs
• Valine – A 200g serving of tofu would deliver 96% of your daily needs

From the list and table above, a few things should become apparent. First, as we said in our dedicated piece about soy, it really is a wonder food. A 100g serving of edamame, for example, would deliver at least 18% and up to 56% of 11 amino acids. That includes all nine of the indispensable ones we have discussed, soy being another brilliant, complete vegan protein.

The second is that soy is not alone in delivering multiple amino acids. In fact, all plant foods contain all 20 amino acids, including the 9 indispensable amino acids. That feature in the US National Library of Medicine goes on to explain, “Importantly, rather than ‘missing’ indispensable amino acids, a more accurate statement would be that the amino acid distribution profile is less optimal in plant foods than in animal foods.”

So, whilst some vegan foods might not have huge amounts of all the required amino acids, they all have at least some and many have good quantities. This makes getting all the different types of protein very easily on a vegan diet. You don’t need to go to much effort in order to consume the vital amino acids as typically just a couple of the classic high protein vegan foods will usually deliver them all.

Secondly, the foods that feature regularly as the best sources of the various amino acids are all foods that most vegans eat. They are certainly items that people who have gone vegan for health reasons are likely to eat as they are among the healthiest foods around. Taken together, all this means that for the vast majority of vegans, the fact they are eating “plant” protein rather than animal protein really should not matter at all.

Are Any Amino Acids Difficult for Vegans to Get?

Whilst some popular and incredibly healthy vegan staples, such as quinoa, chia seeds and soy, are usually considered to be complete proteins by themselves, almost all protein that comes from plants is lacking in one or more indispensable amino acid.

You will sometimes see different sites and sources disagreeing about whether a particular food is a complete protein or not. This is mainly because there is no fixed definition of what is meant by the term. Whilst some foods do contain all of the essential amino acids, they may not contain them in sufficient amounts.

Take Quinoa for Example

Quinoa is an example of this, with Harvard Health Online explaining that quinoa “contains more lysine than wheat or rice does” but that “by some standards, quinoa falls just short of the lysine needed to be classified as a complete provider of all eight essential amino acids”.

It is important not to be too worried about the concept of complete proteins though for the reasons already stated, chiefly that you do not need to consume all of the essential amino acids at the same time in order to be healthy. What is far more important is that overall your diet is delivering the nutrients that you need. With this in mind, are there any amino acids that vegans might struggle to consume in sufficient amounts?

The Simple Answer Is “Not Really”

As explained in a journal article entitled Plant Foods Have a Complete Amino Acid Composition (catchy hey?), views about plant protein continue to be shaped by very old ideas (dating from the 1950s). These are incorrect, misleading and potentially damaging.

The journal explained that a “diet based on any single one or combination of these unprocessed starches (e.g. rice, corn, potatoes, beans), with the addition of vegetables and fruits, supplies all the protein, amino acids, essential fats, minerals, and vitamins (with the exception of vitamin B12) necessary for excellent health”. Vitamin B12 is a nutrient that can be difficult for vegans to obtain, though great vegan supplements exist.

The article goes on to explain that “To wrongly suggest that people need to eat animal protein for nutrients will encourage them to add foods that are known to contribute to heart disease, diabetes, obesity, and many forms of cancer, to name just a few common problems.” We will look at this issue more closely in the next section but let us return to the key consideration of this one first.

A Less Well Structured Vegan Diet

Whilst it is safe to say that all vegans eating a healthy, varied diet will obtain all the essential amino acids in good quantities with no special effort, might some vegans eating a less well-structured diet struggle? Well, again, the answer is that it is unlikely.

It would take a particularly bad and limited diet to miss out on any of the indispensable acids. That said, lysine is generally considered to be one of the hardest, relatively, for vegans to obtain. It is largely available in low amounts in cereals, pseudo-cereal quinoa aside, but it would take an incredibly grain-focussed diet for someone to eat enough.

An article linked to previously in this piece, Dietary Protein and Amino Acids in Vegetarian Diets—A Review, concluded that “even when eating a plant-based diet of limited variety, significant amounts of total protein can be achieved from a high intake of low-protein foods such as vegetables and fruits”. They also quoted information from a huge study into diet, the famous EPIC-Oxford Study, stating that in the “vegans assessed, based on an average bodyweight of 65 kg, we calculated that lysine intakes were … 43mg/kg … largely higher than the 30 mg/kg estimated average requirement”.

That is because although cereals may not be a great source, reasonable amounts of lysine are found in many other vegan foods. As per the table above (and with extra sources of lysine), these include tofu, soy beans, edamame, soy milk, haricot, pinto, black, white and kidney beans, peas, sweet potatoes, spinach, asparagus, broccoli, kale, cauliflower, potatoes, mushrooms and many more vegetables.

Another Way to View the Quality of Protein?

If the traditional view has long been that “animal” protein is higher quality than “plant” protein, it is certainly fair to say that many now view things rather differently. Rather than considering the amino acid profile of a given protein source as the key indicator of quality, many now consider the wider micro- and macro-nutrient picture instead.

Given what we know about the outdated concept of complete proteins and the relative ease with which even those who do not eat animal products can obtain all the essential amino acids, this makes sense. If consuming sufficient amounts of the amino acids is not a concern, then looking beyond the protein at the wider nutritional picture gives us a better idea of what really is “good” protein.

Red Meat Strongly Linked to Health Issues

Few dietary or nutrition experts would disagree that plant-derived protein is in general healthier, better and of greater quality viewed from this point of view. Meat, in particular red and processed meat, has been widely and strongly linked to a huge number of health issues.

Whilst it is true that meat is generally a better source of some nutrients, such as iron or vitamin B12, on the whole, plants provide so much more nutritionally. We look at this in more detail in our feature about vegan health but to summarise, we can say that plant sources of protein:

1. Tend to contain much lower levels of fat, especially saturated fat and also cholesterol
2. Always contain a lot more fibre (animal products do not contain fibre)
3. Generally have more vitamins and minerals
4. Generally have a much stronger anti-oxidative affect
5. Usually contain fewer calories (related to their lower fat content)

We must stress that we are talking in general terms here. So, for example, with regards to point one, a chicken breast contains less fat than nuts or seeds but on the whole, the argument remains valid. Equally, as we have already said, there are some nutrients that are more readily available in animal sources of protein but that does not invalidate our third point.

Plant v Animal Protein Conclusion

If you’ve made it this far, well done. We’ll keep our conclusions brief!

• The terms “animal” and “plant” protein are not very helpful
• They are generally used when discussing the amino acid profile of a given food’s protein
• Animal sources of protein are better at delivering all eight (or nine) essential amino acids from a single food; However, this doesn’t matter as long as vegans consume them all over the course of a day
• Even a restricted, non-varied and poorly constructed vegan diet is highly likely to provide enough of each of the indispensable amino acids
• Given the point above, there is a strong argument that protein from plants is “better” as it typically provides more vitamins and minerals, less fat, more fibre and fewer calories