# Digestible Indispensable Amino Acid Score

Digestible Indispensable Amino Acid Score (DIAAS) is a protein quality method proposed in March 2013 by the Food and Agriculture Organization to replace the current protein ranking standard, the Protein Digestibility Corrected Amino Acid Score (PDCAAS).
The DIAAS accounts for amino acid digestibility at the end of the small intestine, providing a more accurate measure of the amounts of amino acids absorbed by the body and the protein's contribution to human amino acid and nitrogen requirements. This is in contrast to the PDCAAS, which is based on an estimate of digestibility over the total digestive tract. Values stated using this method generally overestimate the amount of amino acids absorbed.

## Reference pattern

Amino acid requirements were determined in two parts. The amino acid distribution of breast milk was used for the 0 to 6 month age range, and existing amino acid data was used for older ages after adjustment for digestibility. The reference amino acid requirements are presented below.$^{:29}$
| | Requirements by age (mg/g protein) | Requirements by age (mg/g protein) | Requirements by age (mg/g protein) |
| Amino acid | 0 to 6 months | 6 months to 3 years | Over 3 years |
| Histidine | 21 | 20 | 16 |
| Isoleucine | 55 | 32 | 30 |
| Leucine | 96 | 66 | 61 |
| Lysine | 69 | 57 | 48 |
| Methionine + Cysteine (SAA) | 33 | 27 | 23 |
| Phenylalanine + Tyrosine (AAA) | 94 | 52 | 41 |
| Threonine | 44 | 31 | 25 |
| Tryptophan | 17 | 8.5 | 6.6 |
| Valine | 55 | 43 | 40 |

## Example values

The table shows the ratings of selected foods comparing PDCAAS to DIAAS. The quality of various sources of protein depends on how it is processed, refined, stored, or cooked. (preparation is unspecified for some values in the table, but does not necessarily differ in preparation from the foods where preparation is specified). A major difference between DIAAS and PDCAAS, is that PDCAAS is truncated at 100%, while DIAAS is not. Multiple protein sources can also be combined to increase DIAAS, which can be effective at raising the max DIAAS of plant-based diets.
| Food | PDCAAS | DIAAS for 0.5-3 yo | Limiting AA |
| Milk Protein Concentrate | 1.00 | 1.18 | Met + Cys |
| Whey Protein Isolate | 1.00 | 1.09 | Val |
| Soy Protein Isolate | 0.98 | 0.898 | Met + Cys |
| Pea Protein Concentrate | 0.893 | 0.822 | Met + Cys |
| Rice Protein Concentrate | 0.419 | 0.371 | Lys |
| Whole milk powder | 1.000 | 1.159 | |
| Tilapia | | 1.00 | |
| Tuna (canned in oil) | 1.00 | | |
| Chicken breast | 1.00 | 1.08 | Trp |
| Pork | | 1.17 | |
| Beef | 1.000 | 1.116 | |
| Whole milk | 1.00 | 1.14 | Met + Cys |
| Egg (hard boiled) | 1.00 | 1.13 | His |
| Egg | | 1.01 | |
| Chickpeas | 0.74 | 0.83 | Met + Cys |
| Tofu | 0.70 | 0.97 | Met + Cys |
| Peas | 0.782 | 0.647 | |
| Cooked peas | 0.597 | 0.579 | Met + Cys |
| Soybean | 1.000 | 0.996 | |
| Soy | | 0.91 | Met + Cys |
| Soya Flour | 1.00 | 1.05 | |
| Fava Bean | | 0.55 | Met + Cys |
| Cooked kidney beans | 0.648 | 0.588 | |
| Roasted peanuts | 0.509 | 0.434 | |
| Almonds | 0.39 | 0.40 | Lys |
| Wheat | 0.463 | 0.40-0.48 | |
| Wheat flour | 0.40 | | |
| Wheat bran | 0.53-0.60 | 0.41-0.49 | |
| Barley | 0.591 | 0.472 | |
| Rye | 0.553 | 0.476 | |
| Triticale | 0.553 | 0.498 | |
| Corn | 0.37 | 0.36 | Met + Cys |
| Corn Grain | 0.473 | 0.424 | |
| Corn-based cereal | 0.078 | 0.012 | Lys |
| Rice | | 0.47 | Lys |
| Cooked rice | 0.616 | 0.595 | Lys |
| Oats | | 0.57 | Lys |
| Cooked rolled oats | 0.670 | 0.542 | |
| Potato | 0.99 | 1.00 | |
| Quinoa | 0.677 | | |
| Quinoa flour | 0.79 | | |
| Gelatin | | 0.02 | Trp |
| Wheat/potato (30/70) | | 1.00 | |
| Vegetables | 0.73-0.89 | | |
| Tubercles | 0.74-0.89 | | |
| Fresh Fruits | 0.64-0.76 | | |
| Dried Fruits | 0.48-0.66 | | |
| Legumes | 0.70-0.89 | | |

## Comparing DIAAS to PDCAAS

* The PDCAAS uses the faecal digestibility while the DIAAS considers the ileal digestibility.
* The PDCAAS is truncated at 100% while DIAAS is not
* The PDCAAS experimentation protocol that determines the digestibility involves rats while the DIAAS advises to use pigs preferably as the pig digestive system is closer to the human's system.
* The PDCAAS considers the global digestibility of the product's protein (a single figure) while the DIAAS accounts for a specific digestibility percentage for each indispensable amino acid
* The reference values for the PDCAAS are based on a unique age group, the 2 to 5-year-old child which is deemed to be the more demanding. The DIAAS provides values for three different age groups, with more up to date data about human needs.