The biologist Jordi Casamitjana gives the ultimate vegan answer to “Where do you get your protein from,” an annoying question vegans have to constantly face.

“Where do you get your oxygen from?”

This is how the question “Where do you get your protein from?” sounds to us, vegans. It sounds surreal, it sounds insincere, it sounds, frankly, kind of stupid. They don’t ask us where we get our sunshine from. They don’t ask us where we get our water from. They don’t ask us where we get our carbs or our fats from. They already know where we get all this from, but, somehow, they don’t seem to know where we get our proteins from. 

Why is that? Do they think that we are no longer humans? Do they think we are no longer animals? Do they think we are from another planet where proteins come from some very mysterious source? Whether those who ask this question are vegan-ignorant, vegan-deniers, or veganphobes, the question itself has often little to do with proteins and lots to do with ignorance, prejudice, and propaganda.

We, vegans, have answered this question in many ways because the question is odd in itself and we wonder what is behind it. Sometimes we sense it does not come from sincere interest but from negative prejudgement. Sometimes we feel is not a genuine enquiry about the origin of a macronutrient, but rather a passive-aggressive reaction against the diet choices associated with the philosophy we follow. 

In any event, after having answered this question hundreds of times during the more than 20 years I have been vegan, I decided I would give it a go and craft what I consider the ultimate answer to this annoying question. One all vegans can use in any situation because it covers all the basis and possible interpretations. One that would spare you from wasting your time any more so you can share it when ask, and move on. 

I will give the short version of this ultimate answer to what I call the “classical annoying question” at the end of this article, but for now, let’s unpack the question.

What Are Proteins?

Educational chart with all the common amino acids By Cristian Victor Rete via Shutterstock (386426320)

The first thought that crosses my mind when someone asks me the classical annoying question is, “Do you even know what a protein is?” The very few occasions I have verbalised this thought out loud confirmed what I suspected: most people have very little idea of what proteins are, yet they use this term as if they know it.

As the first three years of my five-year zoology degree were a shorter degree in biology, I do have some knowledge of biochemistry, so I know what proteins are. Under the risk of sounding patronising — or even worse, daring to mansplain — I will try to give a brief explanation about what they are that is both detailed and digestible — punt intended.

You could say proteins are the molecules of life. If DNA and RNA are the molecules where the information of life is encoded, proteins are different molecules that are created after reading such information, which then will end up being different structures to form the tissues and organs of the organism — their building blocks — as well as the pieces that would operate the organism metabolism — the “cooking pots” and “utensils” to make the organism alive —  and express its genes —  the “reading glasses” that read and express the genetic code in an orderly fashion. Proteins are molecular machines and architectural pieces that allow living organisms to function. In other words, without proteins, there cannot be life as we know it, as all live organisms alive today, from bacteria to trees, or from algae to whales, are made of proteins — and a few more things, but mainly proteins. 

So, if someone asks where proteins come from, one answer is “from life”. Anything or anybody alive, be it a bacterium, an alga, a plant, a fungus, or an animal, is mostly made of proteins, so while strict meat eaters may get their proteins mostly from animals, we vegans get them from all the other living beings, which happen to be far more abundant than animals — and they are easier to grab and eat.

Although each living cell has proteins (otherwise it would not be living), some parts of animals and plants have more proteins than others. In the case of mammals, the muscles have more proteins than bones or most organs (in terms of mass, not variety). In the case of plants, seeds, nuts, and fruits have more protein than leaves, roots, and stems (per gram), so those human foods that derive from seeds and nuts (such as grains and legumes) will be very rich in proteins. In the case of fungi, their reproductive organs, the mushrooms, are also higher in protein.   

But which sort of molecules proteins are? Well, buckle up, because here comes a complete biochemical definition: Proteins are large biomolecules that comprise one or more long chains of amino acid residues. Amino acids are organic compounds (which means they have carbon molecules) that contain both amino (with a basic nitrogen atom with a lone pair of valence electrons that are not shared with another atom) and carboxylic acid (that contains a carboxyl group, which is two functional groups attached to a single carbon atom, namely, hydroxyl and carbonyl) functional groups

The interesting thing about amino acids is that they can easily join in chains (called peptides). Each link in the chain has an amino group (Nitrogen with hydrogen and spare electrons) and a Carboxylic acid group (hence “acid”), as well as a sidechain. The amino group of one molecule can join the carboxyl group of the next in a strong bond (called a peptide bond).

I know, all this sounds complicated, but just remember for now that proteins are made of different amino acids joined in chains, which are molecules that have carbon and nitrogen combined in different ways. Although there are over 500 amino acids in nature, by far the most important are the α-amino acids, from which proteins are composed. However, only 22 α-amino acids appear encoded in the genetic code of all life, which means that different proteins are just chains of these 22 amino acids in a different order, of a different length, and folded in different ways. 

The amino acid chains fold up into the right shapes to do their jobs in a complicated process of molecular origami. The complete structure of a protein can be described at four different levels of complexity (primary, secondary, tertiary, and quaternary structure) where a protein chain is expressed into its native three-dimensional structure, which is the one that has the function each protein evolved to have. Each protein exists first as an unfolded polypeptide (or random coil) after being translated from a sequence of mRNA (with a cellular organ called ribosome) into a linear chain of amino acids, but then it needs to be folded in its three-dimensional structure by the amino acids lightly bonding with each other sideways, sometimes with their hydrogen atoms (Ian McDonald is a vegan biochemists friend of mine who did his doctoral thesis on this issue, in particular about studying when hydrogen bonding in globular proteins is formed and the role it plays in protein structure). 

Methanogenic archaea are a group of primitive bacterium-like microorganisms which are the only ones that can synthesize proteins containing two rare amino acids, selenocysteine or pyrrolysine. The remaining 20 amino acids of life are found in the proteins of all the other organisms, but not all organisms have these 20 amino acids. All these amino acids critical to life have names, and if you want to know them, here they are: alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine.

Nine of these amino acids (histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine) cannot be synthesized by mammals despite they still need them, so they are dietarily essential or indispensable nutrients which they need to consume with their food. These are commonly called the “essential amino acids”, and as we are mammals, these are the ones we need to consume to be able to grow, repair our tissues, and get our cells and organs functioning properly. 

So, if someone asks you “were do you get your proteins from?”, they are basically asking you where you get your essential amino acids from (even if they don’t know it) because, with these, and the other 11 that our bodies can synthesise, we can make all the proteins we need. 

By the way, it’s not that we, vegans, have to build proteins from amino acids while meat-eaters don’t, as if they could pick up intact animal proteins and incorporate them into their bodies. They cannot do that. All proteins are broken down through digestion, so meat-eaters who need to build the protein haemoglobin for their blood red cells and eat bloody cow stakes with loads of it, will still break down the cow’s haemoglobin into amino acids during digestion and then build their own haemoglobin with them. In adults, essentially all protein ingested is absorbed as tripeptides, dipeptides, or amino acids and this process occurs in the small intestine. 

Where Do Essential Amino Acids Come From?

Light shining on a green sprout plant By Greg Brave via Shutterstock (287326268)

If the “classical annoying question” can be broken down into the nine essential amino acids, then the new question is where these come from, and whether humans get them from different sources than the rest of animals, and vegans from different sources than the rest of humans.

The answer is that all the nine essential amino acids come from algae and plants (which can synthesise all amino acids themselves). In other words, from living organisms with the capacity to synthesise organic compounds from light via photosynthesis. Remember that, when I described what amino acids are, I mentioned carbon several times. Well, living organisms that can do photosynthesis can grab the carbon from CO2 in the air and use light to create carbon hydrates (glucose), then create new organic molecules from them, and finally add nitrogen they got from the water or the soil (and this is why we use fertilisers in crops, as they are sources of nitrogen) to create all biological amino acids, which then can combine to produce proteins. 

When other organisms that cannot do photosynthesis need to use essential amino acids, they will do that by either consuming algae and plants that made them, or consuming other organisms that got them by consuming algae or plants that made them. Then, during digestion, they will break down the proteins of those organisms they consumed into their individual amino acids and build their own proteins with them. So, although animals that eat other animals get their proteins by breaking down the proteins of these animals they have eaten into their amino acids and then using those, those amino acids ultimately originated from algae and plants which created them from air, sunlight, and Nitrogen from the substrate where they live. 

Therefore, another answer to the “classical annoying questions” is that we got our proteins from algae and plants, like any other human. The only difference between us vegans and strict meat-eating humans is that we obtain them directly from the original source, while they through an intermediate source that got them directly from the plants or algae (in the case they eat a herbivorous animal such as a cow or a sheep) or got them from an intermediate source that got them from another intermediate source that got them directly from the plants or algae (in the case they eat, for instance, carnivore fishes, octopuses or, cats — some cultures do). 

Gorillas (who I very much doubt non-vegans would suspect are deficient in any nutrients), got their proteins from eating mostly leaves, as they are the folivore apes. Bulls (often regarded as the epitome of strong animals), got them from eating grass (the leaves and the grain), as they are classical herbivores. The biggest mammals on land today, the elephants, also got all their protein from the plants they eat. In fact, most megafauna, the biggest animals on earth, got all the proteins they need to build their enormous bodies directly from plants, the sources of all biological amino acids. The land animal with the maximum amount of protein in their bodies that ever lived was likely the largest dinosaur discovered, Argentinosaurus, who measured from 37 to 40 meters (about 121 to 131 feet). You know what I am going to say about them, right? They were plant-eating dinosaurs who fed leaves growing in the upper branches of tall trees, and that is where the 100 tons of proteins in their bodies, with all their amino acids, came from. 

What About “Complete Proteins” Then? 

Asian vegan bowl with rice, broccoli and fried tofu By Kattecat via Shutterstock (1891573444)

If all proteins in life are made of up to 22 amino acids, and all mammals need to ingest foods that contain proteins with nine of them, can they eat any plant or algae to get them? Not quite. Not all organisms have the same amino-acid profile. Some lack particular amino acids in all their proteins, so if an animal only eats those organisms, and the missing amino acids are one of the essential nine amino acids, that animal may not be able to build all proteins needed as some of their building blogs would be missing. 

The concept of “complete protein” means a protein that contains all essential amino acids. Most proteins of the flesh of animals people normally consume are complete proteins but not all plant proteins used for food are. Ah, is this the root of the classical annoying question? Do those who ask it mean “Where do you get your complete proteins from?” Perhaps this is where the question originated, but it is built under a false premise that vegans only eat one type of plant, which is obviously not true.

Like many animal proteins, some plant proteins are also “complete proteins” that contain all the essential amino acids, so eating only those would provide all the protein requirements for people. For instance, Quinoa, Soy, Buckwheat, Hemp, Chia seeds, Spirulina, and Amaranth are all plant-based ingredients that contain complete proteins, and in great quantities. And, of course, any foods made from them, such as tofu, tempeh, or soya milk, all derived from soy, also do (100 grams of tofu has about 8 grams of complete proteins). 

But what about the other plant-based ingredients? Well, not all lack the same amino acids, so you need different plant sources to get them all. In fact, most plant-based dishes already have the right combination of plants so the entire dish contains proteins with all the amino acids needed. For instance, grains and legumes are called complementary proteins because when you combine them, you get all of the essential amino acids. Nuts and seeds are also complementary to legumes. Rice and beans are a classic combination of plant-based foods that together provide all amino acids needed (both brown and white rice are low in lysine but high in methionine, but beans are high in lysine but low in methionine). Even the humble hummus and pita bread, or the wholegrain peanut butter sandwich, have the right combination of proteins (and many fake meats vegan chefs have been creating also have complete plant-based proteins, especially if made of soy). 

In terms of the quantity of protein in the diet, many vegan foods outperform animal foods. For instance, hemp seeds have 31.6 grams of protein per 100 grams while the flesh from a chicken breast has only 29.8. Peanuts have 25.8 while “Ground beef” has 25.6. Dried seaweed has 57.4 while pig flesh has 21.9. Regarding processed food, several plant-based foods have more protein than most meat. Seitan (made of wheat gluten) contains 25 grams of protein per 100g. Quorn, which is made of fungi, has 21g (more or less the same amount as ham). A vegan burrito may contain 19 g of protein. There are even websites that list more than 100 recipes of vegan dishes that provide more than 20g of protein per serving (including the Bangin’ Buffalo Cauliflower Pizza from One Green Planet with 57g protein per serving or the Curried Tofu Wraps from BBC Good Food with 54 g protein per serving).

An adult weighing 60kg needs 45g per day, and a person weighing 74kg would need 55g per day, so you can see how easy would it be to reach these amounts with plant-based food. In fact, it’s easy to surpass them. In 2013, the Journal of the Academy of Nutrition and Dietetics published the largest study to date comparing the nutrient intake of more than 71,000 non-vegetarians, vegetarians, and vegans, and found that, on average, vegetarians and vegans got 70% more protein than they needed every day. 

Therefore, all the standard plant-based food vegans eat already have a sufficient amount of proteins, and the right combination of plants to cover all the essential amino acids needed, which explains something that those who ask the “classical annoying question” seem to have missed: if we did not consume all the amino acids we need we would be malnourished and suffer diseases associated with protein deficiency, which are unheard in the immense majority of vegans, most of whom live long and healthy lives. The only exception might be some extreme raw vegans/fruitarians who may only eat one or two types of fruit and not take any supplements, who are as rare as meat-eaters that only eat mussels, or who only eat rabbits (there have been cases of people dying from only eating rabbits, not because of lack of protein, but because of excess of it — known as protein poising — due to the fact rabbit flesh is very lean).

What About Bioavailability?

Microbiome of digestive system model in hands By FOTOGRIN via Shutterstock (2271088929)

There is another factor to consider. Perhaps the right combination of plants may contain all the essential amino acids in the right quantities, but they are not floating free in the leaves and fruits but are part of proteins that, as you will remember, are folded in complex structures. If we cannot untangle such structures, we may not be able to remove the amino acids from the chain, and the protein may pass through our digestive system intact. In other words, we need to get foods that contain amino acids that will be bioavailable to us. 

Animals have several ways to break down proteins into their constituents. First, using teeth to destroy the walls of the cells that protect the proteins, then acid in the stomachs that begin to break the light bonds that keep the proteins folded, then enzymes that break the now less tangled protein filaments into smaller and smaller chunks, and finally using friendly bacteria living in their guts that finalised the digestion. In the last two million years or so, we, humans, were able to go further and, by cooking, help the disentangling process before we eat the proteins. Heat can break down proteins, and acids we may add during the processing of food (such as vinegar or lemon juice) also can. Sometimes, we recruit other creatures, such as bacteria or fungi, to help us to break down our food through a process known as fermentation (and this is how we make cheese, beer, injera bread, yoghurt, kimchi, wine, or sauerkraut). 

In any event, through food processing, cooking, and digestion, we can dismantle most proteins we eat and then use the resulting amino acids to build our proteins. We cannot do it with all, though. Some proteins are so tightly folded that nothing seems to untangle them. For instance, keratin is a protein found in nails and hair, but it is not digestible by humans, as well as by many other animals.

This brings me to the last possible justification of the “classical annoying question”. Do those who ask it assume that all the processing and digestion of plant-based food by vegans is insufficient because humans cannot break down plant-based proteins, while other animals who are herbivores, such as cows or sheeps, can? Perhaps that’s what they think, but they would be wrong. Ruminants have indeed specialised digestive systems that allow them to break down some plant-based food that carnivores would not be able to digest, but remember that we are not carnivores. We, humans, are apes, and no apes are carnivores (although they may eat meat occasionally). Apes are folivores who mostly eat leaves (like gorillas), or frugivores who mostly eat fruit (like chimps and orangutans), but not carnivores. 

When about four million years ago early hominids moved from the trees to the savannahs in Africa, we widen our frugivore biology to be able to digest grains and roots better, especially when we started migrating to cooler places where plants store energy with starch. Therefore, we started to move a bit toward being omnivores, and this is why we were able to eat meat as well — when we found it, as our bodies were not adapted to hunt. But that was not that long ago, evolutionary speaking, and our digestive system did not change much, and it is still very much adapted to eating fruits. Therefore, although we cannot digest grass well, we can digest perfectly well fruits, nuts, seeds, and soft leaves, and as far as the grains, pulses, and roots are concerned, with a little processing (such as making flour or cooking) we can digest them well too. 

Some animal proteins may indeed be easier to access because animal cells do not have walls of cellulose, which is a hard carbon hydrate most vertebrates cannot digest, and some animal proteins may be more easily absorbable than equivalent plant-based proteins when tested in a lab with human cells. However, this is not necessarily a good thing, because, to have a complete breakdown from the protein intact to all its amino acids, you need some time, especially to allow the intestinal bacterial flora to do their job with those big proteins that have not completely broken down in the small intestine. The fibre in plant-based food not only gives that time to slow down the digestion process but also gives surfaces for the good bacteria to grow, making digestion more efficient — and this is why doctors recommend both a diet with lots of fibre but also fermented foods with friendly bacteria.

Besides, once we break those cellular walls down by cooking or choosing the plant species that have the thinner ones (and this is why vegans do not just eat any plant, but plants which people, through millennia, have either already identified as edible to us, or they have been modified by artificial selection to made them more digestible), then there is no problem for us to get to the proteins from plants and break them down into amino acids.

The Diet Suitable for People of All Ages

vegan runner completes the Swansea Half Marathon By Matt_David via Shutterstock (1921033823)

The last piece of evidence to support this is that, in general, vegans and people who eat a well-balanced plant-based diet not only do not suffer from malnutrition but are generally healthier than meat-eaters, not just less obese and fitter (there are top bodybuilders and champion powerlifters that built their strong bodies without eating animal products) but with lower risk of cardiovascular diseases, type two diabetes, and many cancers — so, our biology welcomes the vegan diet. And this is why most official dietary bodies have stated that a well-balanced vegan diet is suitable for people of all ages. 

Therefore, another answer to the “classical annoying question” we can give is that we get our proteins from plant and fungus-based food, selected by humans from many cultures and geographies for millennia as food suitable for human consumption. The same sources from which we get our carbs, fats, minerals, and vitamins. The same sources that allow us to carry on living as vegans for the rest of our lives. The same sources that allow us to win athletic competitions and outperform non-vegans in many sports

It is so obvious if you think about it, right? That’s why we often feel the classical question is annoying, and we know it is the result of carnist propaganda that has overrated the role of protein in food  (leading to obesity and making cancers worse when people eat too much protein) and has misled people into believing that proteins mostly come from animal flesh. We know that, on most occasions, when a non-vegan asks us this question, they are not really interested in our diet, but they are questioning it, and perhaps they are suggesting that we are not being honest and we may eat some animals when nobody is looking. This is why the question is so annoying to us, as it often feels like a kind of passive-aggressive disguised insult.   

In summary, the ultimate vegan answer to the question “Where do you get your protein from?” is, we get our protein from plant and fungus-based food, made from a combination of different edible non-animal sources, mostly plants, which together with algae are the only organisms on Earth that can create the building blogs from which all the proteins we need are made — we get our proteins from the natural source of proteins. 

We get our oxygen from the air; we get our sunlight from the sun; we get our water from rivers and springs.

We get our proteins from real food.

“Originally from Catalonia, but resident in the UK for several decades, Jordi is a vegan zoologist and author, who has been involved in different aspects of animal protection for many years. In addition to scientific research, he has worked mostly as an undercover investigator, animal welfare consultant, and animal protection campaigner. He has been an ethical vegan since 2002, and in 2020 he secured the legal protection of all ethical vegans in Great Britain from discrimination in a landmark employment tribunal case that was discussed all over the world. He is also the author of the book, ‘Ethical Vegan: a personal and political journey to change the world’.