The discussion about protein often revolves around quantity. But there's an even more important question: how much of the protein you consume does your body actually use?

Ultimately, it's not enough to simply ingest protein . It needs to be properly digested, absorbed, and provide the essential amino acids in the proportions necessary for the body.

It is precisely to answer this question that science has developed methods to evaluate the protein quality of foods . Among them, the most modern and currently considered most accurate is the Digestible Indispensable Amino Acid Score (DIAAS ).

For those following a vegan diet, understanding the DIAAS helps in making smarter, more balanced, and evidence-based choices, without falling for myths or oversimplifications.

What is DIAAS?

The DIAAS - Digestible Indispensable Amino Acid Score is a method proposed by the Food and Agriculture Organization (FAO) to assess protein quality.

Unlike previous methods, DIAAS considers:

✔ The essential amino acid profile of the food

✔ The actual digestibility of each amino acid

✔ Absorption that occurs in the small intestine

✔ The ability of protein to meet human needs

In summary : the DIAAS doesn't just measure how much protein a food contains, but how much of that protein can actually be used by the body . That's the difference between quantity and quality of protein.

What are essential amino acids?

Amino acids function as the "building blocks" of proteins.. When they connect through peptide bonds, They give rise to vital structures. for the organism, participating in Formation and maintenance of muscles, tissues, hormones, enzymes, and the immune system.There are 20 main amino acids, but 9 are considered indispensable (essential)Because the body is unable to produce them adequately. These are:

🔸Histidine
🔸Isoleucine
🔸Leucine
🔸Lysine
🔸Methionine
🔸Phenylalanine
🔸Threonine
🔸Tryptophan
🔸Valina

A protein is considered high quality when it provides all of these amino acids in adequate amounts.

Amino Acid Profile

The amino acid profile represents the quantity and proportion of essential amino acids present in a food.

Eg

✦ Soybeans have an excellent content of lysine and leucine..
✦ Beans are rich in lysine, but contain less methionine..
✦ Rice has more methionine, but less lysine..
✦ Oats have a more balanced nutritional profile than most cereals..
✦ Quinoa contains all the essential amino acids in good proportions..
✦ Pea protein is rich in lysine and BCAAs, but has less methionine..

Generally speaking, legumes are richer in lysine, while cereals tend to provide more methionine. It is precisely this complementarity that explains why traditional combinations like rice and beans work so well nutritionally.

Digestibility

Not all ingested protein is completely absorbed . Digestibility represents the percentage of protein that is effectively digested and absorbed.

Simplified example :

✧ 100 g of protein consumed → 95 g absorbed

✧ Digestibility = 95%

Factors that influence :

🔹Presence of fiber
🔹Phytates
🔹Tannins
🔹Preparation method
🔹Fermentation
🔹Germination
🔹Processing

Bioavailability

Bioavailability goes beyond digestion.. It represents the amount effectively available for use by the body after digestion, absorption, and metabolism.A protein can be highly digestible and still have reduced absorption if there is a deficiency in any essential amino acid.

How to Interpret the DIAAS?

Broadly speaking:

DIAAS Interpretation

≥100 Excellent quality
75-99 Good quality
50-74 Moderate quality
<50 Lower quality

→ Values ​​above 100 indicate that the protein provides essential amino acids in amounts exceeding the reference requirements (this does not mean that the food is healthier, but only that its protein has a greater potential for utilization).

Foods with the Highest Values ​​of DIAAS

DIAAS values ​​can vary depending on the cultivar, processing, analytical method, and reference population evaluated. For this reason, the scientific literature usually presents ranges of values ​​rather than absolute numbers . The table below presents the estimates frequently cited.

Is DIAAS Everything?

No, the DIAAS is an extremely useful tool, but it should not be interpreted in isolation . A healthy diet also depends on:

✔ Total amount of protein
✔ Distribution throughout the day
✔ Adequate energy intake
✔ Dietary variety
✔ Presence of micronutrients
✔ Digestibility of the diet as a whole

Furthermore, humans rarely consume food in isolation . We consume meals... Therefore, food combinations often have a higher protein quality than foods analyzed individually.

What does this mean for vegans?

Current scientific evidence shows that well-planned vegan diets can fully meet the protein needs of most people.

The most effective strategies include:

✅ Consume legumes daily

✅ Vary your protein sources throughout the day.

✅ Include soy-based foods regularly.

✅ Use tofu, tempeh, edamame, and soy milk. 

✅ Combine grains and legumes

✅ Ensure adequate calorie intake

✅ Consider isolated plant-based proteins when there is a higher demand for sports performance.

The DIAAS represents an important advance in the evaluation of protein quality because it considers not only the amount of protein present in the food, but also the profile of essential amino acids and their actual digestibility . Although foods of animal origin have on average the highest scores, several plant sources, especially soy and its derivatives, demonstrate excellent protein quality and can compose nutritionally adequate, fully vegan diets.

In practice, the most important factor is not finding a single "perfect" food, but building a varied diet rich in legumes, whole grains, nuts, and soy products . When we look at the diet as a whole and not isolated foods, it becomes clear that different plant sources can complement each other extremely efficiently , providing all the essential amino acids necessary for health, physical performance, and longevity.

Sources:

Access : https://pubmed.ncbi.nlm.nih.gov/33409931/

Access : https://pubmed.ncbi.nlm.nih.gov/27452871/