Tryptophan
What it is and what it does
- Tryptophan is one of the nine essential amino acids, along with the others listed by MedlinePlus. (MedlinePlus Medical Encyclopedia (US National Library of Medicine): Amino acids (review date 1/21/2025))
- Tryptophan occurs in proteins in smaller amounts than many other amino acids, but it is nutritionally important. (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 body's need for tryptophan is the lowest of all the essential amino acids. (Holecek M. Serotonin, Kynurenine, and Indole Pathways of Tryptophan Metabolism in Humans in Health and Disease. Nutrients 2026;18(3):507. doi:10.3390/nu18030507 (open access, CC BY))
- Tryptophan is used to make serotonin and nicotinamide; through nicotinamide it can stand in for dietary niacin (vitamin B3). (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)
- About 5% of dietary tryptophan goes to make serotonin and melatonin, in the brain and in special (enterochromaffin) cells of the gut. (Holecek M. Serotonin, Kynurenine, and Indole Pathways of Tryptophan Metabolism in Humans in Health and Disease. Nutrients 2026;18(3):507. doi:10.3390/nu18030507 (open access, CC BY))
- ICMR-NIN's food composition tables count niacin equivalents as niacin (mg) plus tryptophan (mg) divided by 60. (ICMR-NIN. Indian Food Composition Tables 2017 (Longvah T et al.))
Why it matters
- Niacin deficiency can develop if the diet does not supply enough niacin or tryptophan. (NIH Office of Dietary Supplements. Niacin Fact Sheet for Consumers (updated 2021-03-22))
- Severe niacin deficiency leads to a disease called pellagra. (NIH Office of Dietary Supplements. Niacin Fact Sheet for Consumers (updated 2021-03-22))
- People who do not get enough riboflavin (vitamin B2), vitamin B6 or iron convert less tryptophan to niacin. (NIH Office of Dietary Supplements. Niacin Fact Sheet for Health Professionals (updated 2022-11-18))
- Taking tryptophan at the same time as serotonin reuptake inhibitors or MAO inhibitors (medicines) can lead to a dangerous reaction. (Holecek M. Serotonin, Kynurenine, and Indole Pathways of Tryptophan Metabolism in Humans in Health and Disease. Nutrients 2026;18(3):507. doi:10.3390/nu18030507 (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 |
|---|---|---|---|
| Adults | 6 mg per g protein | Recommended amino acid pattern (ICMR-NIN 2020) | ICMR-NIN 2020 (as printed in DGI 2024 Table 8.2) |
| Adults (mean requirement) | 4 mg/kg body weight/day | Average requirement | FAO/WHO/UNU 2007 (not an Indian value) |
| Older children, adolescents and adults | 6.6 mg per g protein | Scoring pattern for protein quality | FAO 2013 (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. Dietary Guidelines for Indians 2024; 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; FAO (2013). Dietary protein quality evaluation in human nutrition: report of an FAO Expert Consultation. FAO Food and Nutrition Paper 92
In every millet and pseudo-cereal, per 100 g raw
| Grain | Amount | Source |
|---|---|---|
| Rajgira (amaranth) | 1.69 g per 100 g protein | IFCT A002 |
| Little millet | 1.35 g per 100 g protein | IFCT A016 |
| Bajra (pearl millet) | 1.33 g per 100 g protein | IFCT A003 |
| Kodo millet | 1.32 g per 100 g protein | IFCT A017 |
| Quinoa | 1.25 g per 100 g protein | IFCT A009 |
| Jowar (sorghum) | 1.03 g per 100 g protein | IFCT A005 |
| Ragi (finger millet) | 0.91 g per 100 g protein | IFCT A010 |
| Kuttu (buckwheat) | 0.192 g | USDA FDC 170286 |
| Teff | 0.139 g | USDA FDC 169747 |
| Proso millet | 0.119 g | USDA FDC 169702 |
| Fonio | 104 mg | FAO WAFCT 2019 |
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
- Tryptophan content is low in cereals, especially maize. (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)
- Among plant foods, potatoes and legumes (pulses) are named as suitable providers of tryptophan. (Holecek M. Serotonin, Kynurenine, and Indole Pathways of Tryptophan Metabolism in Humans in Health and Disease. Nutrients 2026;18(3):507. doi:10.3390/nu18030507 (open access, CC BY))
- ICMR-NIN's model vegetarian diet ('My Plate for the Day') provides 10.8 mg tryptophan per g of protein, more than the 6 mg/g recommendation. (ICMR-NIN. Dietary Guidelines for Indians 2024)