Biological value is an old measure from nitrogen balance experiments, with whole egg as the reference. DIAAS compares the digestible amino acids directly with human requirements and has been recommended by the FAO since 2013. For your own meals, only DIAAS can be calculated cleanly.
The three scores compared
| Biological value | PDCAAS | DIAAS | |
|---|---|---|---|
| Introduced | 1909 (Thomas), later Kofrányi | 1991 (FAO/WHO) | 2013 (FAO) |
| Measures | Share of absorbed nitrogen that stays in the body | Amino acid score × overall digestibility | Digestible amount of each essential amino acid compared with requirements |
| Digestibility | Included indirectly | One value for the whole protein, measured in feces | Per amino acid, measured at the end of the small intestine |
| Reference | Whole egg = 100 | Requirement pattern | Requirement pattern by age group |
| Upper limit | None, combinations above 100 | Capped at 1.0 | Not capped |
| Calculable | No, can only be measured in experiments | Yes | Yes, from table values |
| Status today | Outdated, still common in German-speaking countries | Still required for labeling in the US and Canada | Standard recommended by the FAO |
Biological value
Biological value tells you how many grams of body protein are formed from 100 grams of dietary protein. It is measured via nitrogen balance: how much nitrogen does a person take in, and how much do they excrete again? Whole egg serves as the reference with a value of 100.
The experiments run at a low protein intake close to the minimum requirement. Under these conditions, a missing amino acid carries particularly heavy weight. At the protein intakes athletes eat, the value therefore says little.
Why egg with potato reaches 136
The best-known value in the table comes from Kofrányi's experiments in the 1960s. With a mix of about 36 % egg protein and 64 % potato protein, more nitrogen was retained than with egg alone. The two proteins fill each other's gaps in their amino acid profiles.
The same principle applies to DIAAS: combinations can score better than their individual parts. But the number 136 can't be translated into DIAAS, because the two methods measure different things.
DIAAS
DIAAS stands for Digestible Indispensable Amino Acid Score. For each of the nine essential amino acids, it calculates how much of it is digestible in the protein and how that compares with requirements. The scarcest amino acid sets the score. A DIAAS of 100 means: even the scarcest amino acid covers exactly the requirement.
Because DIAAS is derived from amino acid contents and digestibility values, it can be calculated for any combination of foods. That is exactly what the calculator does. You'll find the formula on the Method page.
Values for common foods
| Food | Biol. value | DIAAS | Limited by |
|---|
Many DIAAS tables online use the reference pattern for young children, which assumes higher requirements. Their values are therefore often lower than the ones shown here. You'll find a longer list with all amino acids in the food table.
What does this mean for you?
- Mixed diet with enough protein: Quality pretty much takes care of itself. Focus mainly on the total amount and about 2.5 g of leucine per meal.
- Vegan or vegetarian: Combine legumes with grains, nuts or seeds. Legumes usually lack methionine, grains lack lysine.
- One main source per meal: Here it pays to check the DIAAS, especially with bread, pasta or rice as the only protein source.
Frequently asked questions
Is a DIAAS above 100 better?
Not for the protein on its own. From 100 it is fully usable, and the body can't use more than 100 %. The surplus of essential amino acids can, however, upgrade a weaker protein in the same meal, for example milk with oatmeal.
Can I simply average DIAAS values?
No. You have to add up the amino acids of all ingredients and then look for the scarcest one again. Rice (about 71) and lentils (about 88) together reach about 98, because they have different gaps.
Do I need to pay attention to biological value when building muscle?
Hardly, with a mixed diet and 1.6 to 2 g of protein per kg of body weight. It becomes relevant on a vegan diet or when a meal consists almost entirely of a single plant source.
Which vegan combination is best?
The classics are legumes with grains, such as lentils with rice, beans with corn or hummus with bread. Soy and pea protein are already fairly good on their own.
How does your meal score?
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