Amino acids and protein quality
What it is and what it does
- Of the 20 amino acids the body needs for all its functions, nine are 'essential'. (ICMR-NIN. Dietary Guidelines for Indians 2024)
- Essential amino acids cannot be made by the body, so they must come from food. (MedlinePlus Medical Encyclopedia (US National Library of Medicine): Amino acids (review date 1/21/2025))
- Non-essential amino acids are ones the body can make, even if food does not supply them. (MedlinePlus Medical Encyclopedia (US National Library of Medicine): Amino acids (review date 1/21/2025))
- Conditionally essential amino acids are usually not essential, except in times of illness and stress. (MedlinePlus Medical Encyclopedia (US National Library of Medicine): Amino acids (review date 1/21/2025))
- WHO/FAO/UNU give cysteine, tyrosine, taurine, glycine, arginine, glutamine and proline as examples of amino acids that can become indispensable in certain conditions. (WHO/FAO/UNU (2007). Protein and amino acid requirements in human nutrition: report of a joint FAO/WHO/UNU expert consultation. WHO Technical Report Series 935)
- The limiting amino acid score compares the first-limiting amino acid in a gram of a food's protein with the amount in a reference protein (or requirement pattern). (FAO (2013). Dietary protein quality evaluation in human nutrition: report of an FAO Expert Consultation. FAO Food and Nutrition Paper 92)
- DIAAS (digestible indispensable amino acid score) is the lowest of these digestible amino acid ratios, expressed as a percentage. (FAO (2013). Dietary protein quality evaluation in human nutrition: report of an FAO Expert Consultation. FAO Food and Nutrition Paper 92)
- The body uses amino acids to make proteins that help it break down food, grow and repair body tissue. (MedlinePlus Medical Encyclopedia (US National Library of Medicine): Amino acids (review date 1/21/2025))
- Amino acids are also needed to make many non-protein substances, such as creatine, taurine, glutathione, catecholamines, thyroxine, serotonin, dopamine and nitric oxide. (WHO/FAO/UNU (2007). Protein and amino acid requirements in human nutrition: report of a joint FAO/WHO/UNU expert consultation. WHO Technical Report Series 935)
- In the older PDCAAS method, the limiting amino acid score is multiplied by protein digestibility. (FAO (2013). Dietary protein quality evaluation in human nutrition: report of an FAO Expert Consultation. FAO Food and Nutrition Paper 92)
- The main difference between DIAAS and PDCAAS is that DIAAS uses the true ileal digestibility (measured at the end of the small intestine) of each essential amino acid. (FAO (2013). Dietary protein quality evaluation in human nutrition: report of an FAO Expert Consultation. FAO Food and Nutrition Paper 92)
- FAO's 2011 expert consultation recommended DIAAS to replace PDCAAS. (FAO (2013). Dietary protein quality evaluation in human nutrition: report of an FAO Expert Consultation. FAO Food and Nutrition Paper 92)
- ICMR-NIN 2020 introduced DIAAS, based on the true ileal digestibility of individual amino acids, as a newer protein quality index. (ICMR-NIN Expert Group. Short Report of Nutrient Requirements for Indians: Recommended Dietary Allowances and Estimated Average Requirements - 2020)
Why it matters
- ICMR-NIN says that the quality of protein - meeting the requirement for every essential amino acid - is the primary challenge. (ICMR-NIN. Dietary Guidelines for Indians 2024)
- Some diets, mainly those that are mostly cereal-based, may not provide all the essential amino acids. (ICMR-NIN. Dietary Guidelines for Indians 2024)
- When essential amino acid intake is inadequate, symptoms may include depression, anxiety, poor sleep, fatigue, weakness and stunted growth in the young. (Lopez MJ, Mohiuddin SS. Biochemistry, Essential Amino Acids. StatPearls [Internet], StatPearls Publishing (NCBI Bookshelf NBK557845; last update April 30, 2024))
- Kwashiorkor and marasmus are severe disorders caused by malnutrition, including inadequate intake of essential amino acids. (Lopez MJ, Mohiuddin SS. Biochemistry, Essential Amino Acids. StatPearls [Internet], StatPearls Publishing (NCBI Bookshelf NBK557845; last update April 30, 2024))
- Faults in amino acid metabolism are linked to inherited diseases such as phenylketonuria, tyrosinaemia, homocystinuria, non-ketotic hyperglycinaemia and maple syrup urine disease. (Lopez MJ, Mohiuddin SS. Biochemistry, Essential Amino Acids. StatPearls [Internet], StatPearls Publishing (NCBI Bookshelf NBK557845; last update April 30, 2024))
- ICMR-NIN explains that bone mineral loss can occur from the acid produced when the body breaks down excess amino acids. (ICMR-NIN. Dietary Guidelines for Indians 2024)
- Excessive intake of a single amino acid can reduce the availability of other amino acids and affect the whole body's metabolism. (Holecek M. Lysine: Sources, Metabolism, Physiological Importance, and Use as a Supplement. Int J Mol Sci 2025;26(18):8791. doi:10.3390/ijms26188791 (open access, CC BY))
General information, not medical advice — for your own needs, ask a doctor or dietitian.
How much is needed
| Who | Amount | What the figure is | Whose figure |
|---|---|---|---|
| Healthy adults | 0.83 g protein/kg body weight/day | RDA for protein (context; no per-amino-acid table in the Short Report) | ICMR-NIN 2020 |
| People eating a cereal-based diet with low-quality protein (context) | 1.0 g protein/kg body weight/day | Protein requirement (footnote to Table 2a) | ICMR-NIN 2020 |
| Basis of the protein RDA (context) | PDCAAS correction removed; DIAAS introduced | Method note | ICMR-NIN 2020 |
| India, all groups | FAO/WHO/UNU 2007 indispensable amino acid requirements | Basis adopted by ICMR-NIN 2020 | ICMR-NIN 2020 |
| People eating a cereal-based diet with low-quality protein | 1.0 g protein/kg body weight/day | Protein requirement (footnote to Table 2a) | ICMR-NIN 2020 |
| Adults (mean requirement) | 184 mg/kg body weight/day (277 mg per g protein) | Total indispensable amino acids | FAO/WHO/UNU 2007 (not an Indian value) |
| Adults | average requirement + 24% | Safe level of intake of each indispensable amino acid | FAO/WHO/UNU 2007 (not an Indian value) |
India’s own figure (ICMR-NIN 2020) comes first. Figures from other bodies are shown only where they help, and say whose they are.
Sources: ICMR-NIN. A Brief Note on Nutrient Requirements for Indians, the Recommended Dietary Allowances (RDA) and the Estimated Average Requirements (EAR), ICMR-NIN 2020; ICMR-NIN Expert Group. Short Report of Nutrient Requirements for Indians: Recommended Dietary Allowances and Estimated Average Requirements - 2020; WHO/FAO/UNU (2007). Protein and amino acid requirements in human nutrition: report of a joint FAO/WHO/UNU expert consultation. WHO Technical Report Series 935
In every millet and pseudo-cereal, per 100 g raw
| Grain | Amount | Source |
|---|---|---|
| Alanine | ||
| Kodo millet | 11 g per 100 g protein | IFCT A017 |
| Jowar (sorghum) | 9.19 g per 100 g protein | IFCT A005 |
| Little millet | 8.6 g per 100 g protein | IFCT A016 |
| Bajra (pearl millet) | 7.68 g per 100 g protein | IFCT A003 |
| Ragi (finger millet) | 6.71 g per 100 g protein | IFCT A010 |
| Quinoa | 4.35 g per 100 g protein | IFCT A009 |
| Rajgira (amaranth) | 3.83 g per 100 g protein | IFCT A002 |
| Proso millet | 0.986 g | USDA FDC 169702 |
| Kuttu (buckwheat) | 0.748 g | USDA FDC 170286 |
| Teff | 0.747 g | USDA FDC 169747 |
| Arginine | ||
| Quinoa | 7.85 g per 100 g protein | IFCT A009 |
| Rajgira (amaranth) | 7.21 g per 100 g protein | IFCT A002 |
| Little millet | 5.96 g per 100 g protein | IFCT A016 |
| Bajra (pearl millet) | 4.54 g per 100 g protein | IFCT A003 |
| Ragi (finger millet) | 4.33 g per 100 g protein | IFCT A010 |
| Jowar (sorghum) | 3.96 g per 100 g protein | IFCT A005 |
| Kodo millet | 3.18 g per 100 g protein | IFCT A017 |
| Kuttu (buckwheat) | 0.982 g | USDA FDC 170286 |
| Teff | 0.517 g | USDA FDC 169747 |
| Proso millet | 0.382 g | USDA FDC 169702 |
| Aspartic acid | ||
| Rajgira (amaranth) | 12.7 g per 100 g protein | IFCT A002 |
| Quinoa | 8.4 g per 100 g protein | IFCT A009 |
| Bajra (pearl millet) | 7.77 g per 100 g protein | IFCT A003 |
| Jowar (sorghum) | 7.09 g per 100 g protein | IFCT A005 |
| Ragi (finger millet) | 6.4 g per 100 g protein | IFCT A010 |
| Kodo millet | 5.61 g per 100 g protein | IFCT A017 |
| Little millet | 5.51 g per 100 g protein | IFCT A016 |
| Kuttu (buckwheat) | 1.133 g | USDA FDC 170286 |
| Teff | 0.82 g | USDA FDC 169747 |
| Proso millet | 0.726 g | USDA FDC 169702 |
| Glutamic acid | ||
| Jowar (sorghum) | 21.54 g per 100 g protein | IFCT A005 |
| Ragi (finger millet) | 20.22 g per 100 g protein | IFCT A010 |
| Little millet | 20.22 g per 100 g protein | IFCT A016 |
| Kodo millet | 18.25 g per 100 g protein | IFCT A017 |
| Bajra (pearl millet) | 17.42 g per 100 g protein | IFCT A003 |
| Rajgira (amaranth) | 17.39 g per 100 g protein | IFCT A002 |
| Quinoa | 13.75 g per 100 g protein | IFCT A009 |
| Teff | 3.349 g | USDA FDC 169747 |
| Proso millet | 2.396 g | USDA FDC 169702 |
| Kuttu (buckwheat) | 2.046 g | USDA FDC 170286 |
| Glycine | ||
| Rajgira (amaranth) | 8.28 g per 100 g protein | IFCT A002 |
| Quinoa | 4.8 g per 100 g protein | IFCT A009 |
| Ragi (finger millet) | 3.59 g per 100 g protein | IFCT A010 |
| Bajra (pearl millet) | 3.52 g per 100 g protein | IFCT A003 |
| Little millet | 3.43 g per 100 g protein | IFCT A016 |
| Kodo millet | 3.12 g per 100 g protein | IFCT A017 |
| Jowar (sorghum) | 3.08 g per 100 g protein | IFCT A005 |
| Kuttu (buckwheat) | 1.031 g | USDA FDC 170286 |
| Teff | 0.477 g | USDA FDC 169747 |
| Proso millet | 0.287 g | USDA FDC 169702 |
| Proline | ||
| Kodo millet | 7.33 g per 100 g protein | IFCT A017 |
| Jowar (sorghum) | 6.99 g per 100 g protein | IFCT A005 |
| Little millet | 6.04 g per 100 g protein | IFCT A016 |
| Quinoa | 5.67 g per 100 g protein | IFCT A009 |
| Ragi (finger millet) | 5.42 g per 100 g protein | IFCT A010 |
| Bajra (pearl millet) | 5.3 g per 100 g protein | IFCT A003 |
| Rajgira (amaranth) | 3.83 g per 100 g protein | IFCT A002 |
| Proso millet | 0.877 g | USDA FDC 169702 |
| Teff | 0.664 g | USDA FDC 169747 |
| Kuttu (buckwheat) | 0.507 g | USDA FDC 170286 |
| Serine | ||
| Rajgira (amaranth) | 7.27 g per 100 g protein | IFCT A002 |
| Little millet | 5.6 g per 100 g protein | IFCT A016 |
| Kodo millet | 5.5 g per 100 g protein | IFCT A017 |
| Ragi (finger millet) | 4.81 g per 100 g protein | IFCT A010 |
| Quinoa | 4.56 g per 100 g protein | IFCT A009 |
| Bajra (pearl millet) | 4.44 g per 100 g protein | IFCT A003 |
| Jowar (sorghum) | 4.02 g per 100 g protein | IFCT A005 |
| Kuttu (buckwheat) | 0.685 g | USDA FDC 170286 |
| Proso millet | 0.644 g | USDA FDC 169702 |
| Teff | 0.622 g | USDA FDC 169747 |
Each grain has ONE source, named on its page: IFCT = Indian Food Composition Tables 2017 (ICMR-NIN) with its food code; USDA FDC; FAO WAFCT 2019; NIN 2007 via ICAR-IIMR. Values exactly as printed, not converted — tables differ in method, so compare within a source. Published values for the grain, not a laboratory test of our packs.
Absorption and food
- Digestibility is the proportion of food protein that is absorbed. (WHO/FAO/UNU (2007). Protein and amino acid requirements in human nutrition: report of a joint FAO/WHO/UNU expert consultation. WHO Technical Report Series 935)
- ICMR-NIN: most vegetarian foods have a protein digestibility of 70-85%. (ICMR-NIN. Dietary Guidelines for Indians 2024)
- ICMR-NIN's balanced diet for a moderately active man supplies 88 g total protein, of which 71 g is digestible; its PDCAAS is 84%. (ICMR-NIN Expert Group. Short Report of Nutrient Requirements for Indians: Recommended Dietary Allowances and Estimated Average Requirements - 2020)
- For foods that processing can damage, FAO recommends using 'reactive' lysine rather than total lysine when judging protein quality. (FAO (2013). Dietary protein quality evaluation in human nutrition: report of an FAO Expert Consultation. FAO Food and Nutrition Paper 92)
- In raw, unwashed quinoa flour the amino acids are not fully available, because it contains substances (saponin glycosides) that interfere with use of nutrients. (FAO (2011). Quinoa: An ancient crop to contribute to world food security (aq287e))
- In practice, food proteins are usually limited only by lysine (most cereal proteins), the sulphur amino acids (pulse/legume proteins), tryptophan (some cereals such as maize) or threonine (some cereals). (WHO/FAO/UNU (2007). Protein and amino acid requirements in human nutrition: report of a joint FAO/WHO/UNU expert consultation. WHO Technical Report Series 935)
- ICMR-NIN lists the limiting amino acids in plant foods: lysine, threonine and tryptophan in grains (cereals, millets); methionine in pulses; lysine in nuts and seeds. (ICMR-NIN. Dietary Guidelines for Indians 2024)
- WHO/FAO/UNU found lysine in cereal proteins at 57-86% of the requirement level. (WHO/FAO/UNU (2007). Protein and amino acid requirements in human nutrition: report of a joint FAO/WHO/UNU expert consultation. WHO Technical Report Series 935)
- A meal with both pulses and grains supplies all the amino acids and is of higher quality than pulses alone or grains alone. (ICMR-NIN. Dietary Guidelines for Indians 2024)
- Combining cereals with pulses in a 3:1 ratio (raw weight) can meet the requirements of all essential amino acids. (ICMR-NIN. Dietary Guidelines for Indians 2024)
- Adding 250 ml milk to the daily diet further increases essential amino acid intake. (ICMR-NIN. Dietary Guidelines for Indians 2024)
- In FAO's worked example, wheat protein had 28 mg lysine and 38 mg sulphur amino acids per g protein, while pea protein had 71 mg lysine and 25 mg sulphur amino acids. (FAO (2013). Dietary protein quality evaluation in human nutrition: report of an FAO Expert Consultation. FAO Food and Nutrition Paper 92)
- The same worked example (wheat, peas and whole milk powder) scored a DIAAS of 68 for young children and 82 for older children, adolescents and adults, with lysine limiting. (FAO (2013). Dietary protein quality evaluation in human nutrition: report of an FAO Expert Consultation. FAO Food and Nutrition Paper 92)