Here is the ultimate guide to plant-based proteins. Long victims of prejudice, they are now recognized by science as perfectly capable of supporting muscle growth and overall health, provided their mechanisms are properly understood.

The complete guide to plant-based proteins: from biochemistry to your plate

In the collective imagination, protein is often associated with muscle and meat. Yet the plant kingdom is the primary source of all amino acids on the planet (animals simply recycle the proteins from the plants they consume).

For vegetarians and vegans, protein is not a problem but an opportunity to diversify nutrients. This guide breaks down for you the science of amino acids, digestibility indexes, and the best strategies to optimize your metabolism.

Biochemistry: what is a protein?

Imagine a protein as a necklace of pearls. Each pearl is an amino acid. To build your own tissues (muscles, hormones, antibodies), your body dismantles the plant “necklaces” you eat to retrieve the pearls and create its own chains.

Essential amino acids (EAAs)

There are 20 amino acids, but 9 are considered “essential”: your body cannot produce them. They must absolutely come from your diet.

Leucine, Isoleucine, Valine (the famous BCAAs for muscle).
Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Histidine.

Scientific fact: Contrary to a persistent misconception, all plants contain the 9 essential amino acids. The difference simply lies in their proportion. Some plants are slightly lower in a specific amino acid (called a “limiting amino acid”).

The concept of absorption and quality: PDCAAS and DIAAS

To measure the “quality” of a protein, science uses scores that compare amino acid composition and how easily we digest them.

The PDCAAS score (Protein Digestibility Corrected Amino Acid Score)

This is the current reference. It ranges from 0 to 1.

Soy isolate: 1.0 (equivalent to egg white or milk).
Chickpeas: 0.78.
Whole wheat: 0.40 to 0.50 (limited by lysine).

The DIAAS (Digestible Indispensable Amino Acid Score)

DIAAS is a more recent method recommended by the FAO for assessing protein quality. Unlike PDCAAS, it does not cap scores at 1.0 and analyzes each essential amino acid individually, taking into account its actual digestibility in the small intestine. This allows for a more precise assessment, particularly for plant-based proteins.

In practice, DIAAS better highlights the differences between sources: soy remains very highly rated, while cereals (such as wheat) appear more limited in lysine, and some legumes in sulfur-containing amino acids.

Key takeaways:
👉 PDCAAS provides a good initial estimate
👉 DIAAS is now considered more scientifically reliable

However, in practice, these scores remain theoretical tools. A varied diet, combining different plant sources, naturally provides a good amino acid profile, without the need to calculate these indices daily.

Why are plant protein scores often lower than animal proteins?

This is due to anti-nutrients (fiber, phytates) that protect the plant and slightly slow down the action of our digestive enzymes. There are solutions to counter them, such as soaking legumes before cooking or sprouting them. Cooking also significantly increases the digestibility of plant proteins.

Do you need to combine different protein sources at every meal?

This is the concept of protein complementarity.

Cereals are rich in methionine but low in lysine.
Legumes are rich in lysine but low in methionine.

Modern science (American Dietetic Association) is clear: it is absolutely not necessary to combine cereals and legumes within the same meal. Your body has an amino acid “pool” in reserve. As long as you consume both families during the same day, your body will assemble them itself.

Examples of winning combinations throughout the day:

Semolina (cereal/methionine) + Chickpeas (legume/lysine).
Rice (cereal) + Black beans (legume).
Rice (cereal) + Tofu/Soy (legume).
Whole bread (cereal) + Hummus or lentil spread (legume).

Top 10 best 100% plant-based protein sources

Food	Protein content (per 100g)	Specific advantage
1. Seitan (Wheat gluten)	25 g to 75 g	Closest to meat in texture.
2. Soybeans (dry)	36 g	Complete protein (PDCAAS of 1).
3. Lentils (cooked)	9 g	Rich in iron and fiber.
4. Pumpkin seeds	30 g	Champions of magnesium and zinc.
5. Firm tofu	12 g to 15 g	Very digestible and versatile.
6. Peanut butter	25 g	Calorie-dense and rich in vitamin B3.
7. Tempeh (fermented soy)	19 g	Probiotics and excellent digestibility.
8. Chickpeas (cooked)	8 g	Very low glycemic index.
9. Quinoa (cooked)	4.5 g	Perfect balance of amino acids.
10. Nutritional yeast	45 g	Perfect for sprinkling on your dishes.

Protein requirements: plant vs animal

Official recommendations are 0.8 g per kilogram of body weight, but protein needs are not fixed. They adjust according to your energy expenditure, the mechanical stress applied to your muscle fibers, and your body composition goals.

In plant-based nutrition, a +10% to +20% correction factor is generally applied compared to standard omnivorous recommendations to compensate for slightly lower digestibility (due to fiber and phytates).

For someone following a vegan diet, here are the protein needs depending on activity level:

1. Sedentary level (low activity)

This profile corresponds to people with desk jobs, taking fewer than 5,000 steps per day and not practicing regular sports.

Omnivore recommendation: 0.8 g / kg
Plant-based target (vegan): 0.9 g to 1.0 g / kg
Goal: Basic cellular renewal and maintenance of lean mass.
Example (70 kg): about 63 g to 70 g of protein per day.

2. Moderate level (average activity)

For people practicing physical activity 2 to 3 times per week (light fitness, brisk walking, recreational swimming) or with physically active jobs.

Omnivore recommendation: 1.1 g to 1.2 g / kg
Plant-based target (vegan): 1.2 g to 1.4 g / kg
Goal: Tissue repair after effort and support for increased metabolic demand.
Example (70 kg): about 84 g to 98 g per day.

3. High level (high activity)

This level concerns people training 3 to 5 times per week.

Omnivore recommendation: 1.5 g to 1.7 g / kg
Plant-based target (vegan): 1.6 g to 1.9 g / kg
Goal: Muscle hypertrophy or compensation for amino acid oxidation during endurance exercise.
Example (70 kg): about 112 g to 133 g per day.

4. Very high level (intense activity)

This level concerns competitors, people with very physical jobs, or those in a caloric deficit.

Omnivore recommendation: 1.8 g to 2.2 g / kg
Plant-based target (vegan): 2.0 g to 2.4 g / kg
Goal: Maximum protection of muscle mass against catabolism.
Example (70 kg): about 140 g to 168 g per day.

Scientific references

WHO/FAO: Reports on protein and amino acid requirements.
Journal of the International Society of Sports Nutrition: Comparison of plant and animal proteins on muscle hypertrophy.
The American Journal of Clinical Nutrition: Protein digestibility and DIAAS scores.
EPIC-Oxford Study: Nutritional intake and long-term health outcomes in plant-based populations.