Home / G. Health and nutrition / Part IND

"We need animal protein."

Before answering: an indirect argument

This argument is about health and nutrition, not whether animals deserve respect. Many activists question this kind of argument in defending animals, because it sidesteps what matters: no one defends the rights of people who face discrimination by saying that treating them fairly is good for the environment.

Why it is not good to use it, or why always to pair it with an ethical argument: If veganism were defended on health grounds, anyone who manages to be healthy eating animals, and many people do, would have no reason to change. And if an animal product turned out to be demonstrably healthier, the same argument would start defending exploitation. The eater's health says nothing about whether what is done to the animal is just.

When used to justify exploitation, arguments like this one usually fail twice. They get the facts wrong, which often arrive distorted. And they get the morality wrong, because they leap from what is to what ought to be: even a real benefit would not show it is just to make someone suffer and die to obtain it.

So show the facts and correct what is wrong, but always come back to what matters: respect for animals and justice toward them. Learn why

The answer in one sentence

we need protein, not animal protein. Legumes such as beans, lentils, chickpeas and soy, along with grains, nuts and seeds, provide all the protein and all the essential amino acids an adult needs, as long as the diet is varied and supplies enough energy. Nutrition bodies in several countries, such as the US Academy of Nutrition and Dietetics and Brazil's Federal Council of Nutritionists, recognize that well-planned vegan diets can be adequate at all stages of life; others, such as the German Nutrition Society, don't yet take a position for pregnant women, children and older people, and call for professional supervision.

Short answer

We need protein, not animal protein. Beans, lentils, chickpeas, soy, tofu, nuts and grains provide all the protein and all the amino acids we need, as long as we eat a varied diet over the day and in sufficient quantity. There's no need to combine foods in the same meal. The US Academy of Nutrition and Dietetics and Brazil's Federal Council of Nutritionists recognize that well-planned vegan diets can be adequate at all stages of life. Rice and beans, a staple from Brazil to Mexico to the Caribbean, is already an excellent source of protein.

For children

Protein helps the body grow and get strong. And it isn't only in meat! Beans, lentils, chickpeas, peanuts and soy have lots of protein. Rice and beans, for example, is a great combination. And lots of people, even athletes, don't eat meat and get all the protein they need.

Ask a question back

"If beans, lentils and soy provide all the protein we need, is the need for protein or for meat?"

Como pode aparecer

"Where do you get your protein?"

Everyday conversation

"Without meat you'll be weak."

Everyday conversation

"You need quality protein."

Everyday conversation

"Vegans can't build muscle."

Social media

"Animal proteins have higher biological value."

Technical version

"Athletes need meat." (which is G9)

Disguised version

The strongest version

How it is said

"Where do you get your protein? Without meat you'll be weak. You need quality protein."

Strongest version (steelman):

P1Human beings need protein, with all the essential amino acids.
P2Animal foods are concentrated, complete sources of protein.
P3It's hard to get enough complete protein from plants alone.
CSo we need to eat animal products.

P1 and P2 are true. The problem lies in P3: the evidence shows that varied plant diets provide enough complete protein for adults.

The argument is valid. Its soundness fails at P3.

Full answer

Reconstruction and diagnosis

The argument confuses the nutrient with the source:

What the body needs	Where it can come from
Protein	Meat, eggs, milk, but also beans, lentils, chickpeas, soy, tofu, nuts, grains
Essential amino acids	Plant foods contain all nine essential amino acids, but in different proportions: cereals are low in lysine, which legumes make up for. Variety over the day solves it

b
Where the argument breaks
1. Plant protein is enough.
A 2019 review concluded that protein-rich foods such as legumes, nuts and seeds are enough to ensure protein adequacy for adults on vegetarian and vegan diets.
2. The amino acids are in plants.
The idea that foods must be combined in the same meal is an old myth. Eating a varied diet over the day provides all the essential amino acids (G2).
3. Nutrition bodies recognize adequacy.
The US Academy of Nutrition and Dietetics states that well-planned vegan diets are healthy, nutritionally adequate and appropriate for all stages of life, including pregnancy, childhood and for athletes. In Brazil, the Federal Council of Nutritionists says the same in a 2022 technical opinion. It isn't unanimous: the German Nutrition Society considers a vegan diet adequate for healthy adults but, for lack of data, neither recommends nor advises against it for pregnant women, children and older people, and calls for professional supervision. None of these bodies says animal protein is necessary.
4. Traditional plates are already rich in protein.
Rice and beans, dal and rice, hummus and bread: traditional combinations around the world provide good-quality protein.
5. Animal protein comes from plants.
Chickens and pigs get their protein from soy and corn feed; cattle, from pasture and grain, with the help of rumen microorganisms that the human digestive system lacks. So it doesn't work to say "if the ox gets strong eating grass, so would we": the digestion is different. The point is another: eating the animal means getting, by a longer route and with more losses, nutrients that came from plants, and humans get enough protein by eating legumes, grains and seeds directly.

Data and sources

Source	What it says	Note
Mariotti and Gardner, 2019, Nutrients	Legumes, nuts and seeds are enough for protein adequacy in adults on vegetarian and vegan diets	Scientific review
Academy of Nutrition and Dietetics, 2016	Well-planned vegan diets are appropriate at all stages of life	Official position of the largest US body of dietitians
Brazil's Federal Council of Nutritionists, technical opinion, 2022 (in Portuguese)	Nutritional needs can be met with a strict vegetarian diet at all life stages and for athletes, if well planned	A Brazilian position
German Nutrition Society (DGE), 2024 position (in German)	A vegan diet is adequate for healthy adults; no recommendation for or against for pregnant women, children and older people, for lack of data	Requires B12 supplements, planning and supervision

d
The strongest counter-reply: some groups need more attention
The most serious version grants that healthy adults get enough protein from plants, but points out that older people, children and athletes have greater needs, and that some vegans eat less protein than they should, especially those who eat little overall. Mariotti and Gardner's review acknowledges these risks and adds that the digestibility of plant protein is only a few percentage points lower.
e
Why the counter-reply doesn't reach the conclusion
Needing attention isn't needing meat.
Groups with greater needs can meet them with more legumes, soy and planning.
Every diet requires attention.
Many people who eat meat also have inadequate diets.
The solution is planning, not exploitation.
Guidance from a dietitian solves most cases.
f
Back to the moral question
This is an indirect argument: it doesn't say animals don't matter, but that we need them. Since the need doesn't hold for those with access to a varied diet, the question returns to its starting point: if we don't need it, what justifies making animals suffer and die?

Reasoning errors

Logical

Is the form valid?

Confusing nutrient and source

"We need protein" becomes "we need meat"

Epistemological

Does the evidence support it?

Nutrition myth

Assumes plant protein is insufficient

Not knowing the official positions

Ignores the consensus of nutrition bodies

Moral

Is the criterion coherent?

Invented necessity

Uses a need that doesn't exist to justify the harm

Biases

Rationalization through the 4Ns

"Necessary" is one of the most used justifications

Piazza et al., 2015

Confirmation bias

Remembers cases of vegans with deficiencies and forgets the others

General literature on confirmation bias

Illusory truth effect

After hearing so often that only meat has protein, the phrase seems like fact

Questão de Ética, vol. X, ch. 4

Extrapolations

The principle being tested is: "if a food contains a nutrient, we need that food".

If it applied to…Vitamin CTap to see

We'd need oranges, not any fruit with vitamin C

No one thinks this way

If it applied to…CalciumTap to see

We'd need milk, not other sources

This is the argument of G5

If it applied to…ProteinTap to see

We'd need meat, not beans

The error is the same

Contradictions

Eats beans.

And knows they contain protein.

Doesn't ask where people who eat badly get their protein.

The concern only comes up with vegans.

The animals they eat get protein from plants.

Chickens and pigs eat soy and corn feed.

What the argument gets right

What is true

Concern about nutrition is legitimate. Protein is essential, and any diet, vegan or not, needs to be planned to provide enough. Some groups, such as older people and children, deserve special attention.

But

But the need is for protein, not for animals. With beans, lentils, soy and variety, protein is covered, and the moral question becomes the main one again: if we don't need it, why carry on?

Connections

Usually comes before

C1 It's natural to eat meat.When the natural doesn't convince, people appeal to the necessary

C2 Lions eat other animals.If nature doesn't convince, people appeal to necessity

C3 We have canine teeth; we are omnivores.From anatomy to necessity

D9 My grandparents ate meat and lived to 90.Concludes that meat is necessary

G1this argument

Usually comes after

G2 Plant protein is incomplete.From the quantity of protein to its quality

G9 Athletes need meat.Moves to the case of athletes

G16 Vegans are weak, pale and depressed.The necessity becomes a stereotype

Go deeper in Questão de Ética

Chapters from the open-access collection A Journey Through Animal Ethics that discuss this argument in more detail:

"We need animal protein."

Short answer

For children

Como pode aparecer

The strongest version

Full answer

Reconstruction and diagnosis

Where the argument breaks

Data and sources

The strongest counter-reply: some groups need more attention

Why the counter-reply doesn't reach the conclusion

Back to the moral question

Reasoning errors

Logical

Epistemological

Moral

Biases

Rationalization through the 4Ns

Confirmation bias

Illusory truth effect

Extrapolations

Contradictions

What the argument gets right

Connections

Go deeper in Questão de Ética

References

Nutrition

Psychology