Tryptophan: Requirement, Indian Sources, Niacin and Sleep

Tryptophan is one of the nine essential amino acids, and the one needed in the smallest amount. Your body uses it to build protein and also turns part of it into serotonin, melatonin and the B vitamin niacin. An adult needs about 4 mg per kg of body weight a day, and ICMR-NIN's 2020 recommendation is 6 mg of tryptophan in every gram of dietary protein. Rice, wheat, dals and milk all clear that pattern; maize, at 5.7 mg, does not. You are reading one entry in the handbook's proteins and amino acids section.

What is tryptophan and what does it do?

Tryptophan is an amino acid that has to come from food and that the body puts to several uses. A 2009 review in the International Journal of Tryptophan Research notes that it is found in the lowest concentration of all the amino acids in the body. Its first job is protein synthesis. Of the tryptophan that is broken down, about 90 per cent passes along the kynurenine pathway, the route that also produces niacin. Serotonin is made from part of what remains.

The same review calls tryptophan the sole precursor of serotonin, a chemical messenger made in nerve cells, and describes melatonin as a hormone made further along the serotonin pathway. Melatonin is released by the pineal gland in darkness and sets the daily rhythm of sleep; the handbook's entry on melatonin covers it as a supplement. This chain from an amino acid to a sleep hormone is the root of every claim about milk, bananas and sleep.

How much tryptophan do you need?

An adult needs about 4 mg of tryptophan per kg of body weight a day, by the WHO/FAO/UNU 2007 requirement as printed in the FAO's 2013 report. That is about 260 mg for a 65 kg man and 220 mg for a 55 kg woman. Written as a pattern it is 6 mg per gram of protein, and ICMR-NIN's 2024 guidelines print 6 mg as the ICMR-NIN 2020 recommendation. Infants and small children need more for their size.

These amounts are small beside a day's protein. A diet that supplies the adult protein requirement and meets the pattern automatically meets the tryptophan need, which is why nobody is asked to count it. No separate tryptophan figure for pregnancy or lactation was found in the documents opened for this entry, so none is quoted. To find your own protein target, use the protein calculator.

Tryptophan in Indian foods

Soya bean, milk, paneer, bajra and rice have the most tryptophan per gram of protein in the Indian Food Composition Tables 2017, and maize the least. The tables give 1.68 g per 100 g of protein for white soya bean, 1.46 for cow's milk, 1.42 for paneer, 1.33 for bajra and 1.27 for raw milled rice. Toor dal, at 0.71, and masoor dal, at 0.81, are lower than most people expect, though both still pass the adult pattern of 0.6. The amino acid table covers plant foods and milk products and gives no profile for egg, meat or fish.

Household descriptions are approximate and the figures are for raw food. The banana is in the table to show scale: its protein is ordinary in quality but there is very little of it. NNWA's table of protein in Indian foods ranks the whole database by protein, and the milk page compares cow's and buffalo milk.

How does tryptophan become niacin?

Your body converts part of its tryptophan into niacin, at an average rate of 60 mg of tryptophan for 1 mg of niacin. The joint FAO and WHO consultation on vitamin requirements uses that factor and cautions that individuals differ substantially. It adds that the conversion depends on riboflavin and vitamin B6, so a shortage of either can reduce the yield. IFCT 2017 prints the same rule: niacin equivalents are the niacin in a food plus its tryptophan in mg divided by 60.

This is why the niacin column of a food table understates what a protein-rich food supplies: IFCT's niacin values count only the preformed vitamin, and the tryptophan in milk, dal or soya adds to them. The handbook's entry on niacin has the requirement and the full arithmetic, and the table of niacin in Indian foods lists the preformed vitamin.

Maize, jowar and pellagra: the Indian history

Pellagra is the disease of too little niacin and tryptophan together. WHO describes it as classically associated with a diet based on maize that has not been treated with alkali, and has recorded outbreaks since 1988 among refugees and displaced people. Maize is doubly poor: IFCT 2017 puts its tryptophan at 5.7 mg per gram of protein, below the adult pattern of 6 and well below the 8.5 mg the FAO sets for children from 6 months to 3 years. The maize page has the grain's other figures.

In India the grain involved was jowar. C. Gopalan, writing in the Indian Journal of Medical Research in 2013, recalled that pellagra was endemic up to the 1950s among people who ate jowar almost exclusively. Research at the time blamed the millet's high leucine content. Jowar's tryptophan, 10.3 mg per gram of protein in IFCT 2017, is not low, so the Indian story was never a simple tryptophan shortage. People were advised to vary their cereals, and the disease faded after cheaper rice and wheat reached ration shops in the late 1960s.

Too little tryptophan: who is at risk?

People living on one cereal with almost nothing beside it, above all maize, and people whose illness blocks the amino acid's absorption or use. The FAO and WHO consultation lists Hartnup disease, in which tryptophan is poorly absorbed, carcinoid syndrome, chronic alcoholism and Crohn's disease among the medical causes of pellagra-like illness. This entry found no Indian survey of tryptophan intake or status, so no prevalence figure is given.

For most Indian plates the risk is low. ICMR-NIN's 2024 guidelines name tryptophan, with lysine and threonine, as a limiting amino acid of cereals and millets, and point to pulses, chickpea and beans to supply what grains lack. Their vegetarian My Plate for the Day delivers 10.8 mg of tryptophan per gram of protein and the non-vegetarian plate 11.3 mg, against the recommended 6. Lysine is the tighter constraint in cereal diets, as the entry on lysine explains.

Does tryptophan help you sleep?

As a supplement of a gram or more, it shortened the time people spent awake during the night in a small set of trials; in food amounts there is no such evidence. A 2022 systematic review in Nutrition Reviews collected 18 articles, of which four could be pooled. Doses of 1 g or more were linked with 28.91 minutes awake after sleep onset against 56.55 minutes on less than 1 g. No other measure of sleep changed.

Set that beside the food table. A 250 g glass of cow's milk holds about 119 mg of tryptophan, so 1 g would take more than eight glasses, and a banana holds about 12 mg. The 2009 review adds a second obstacle: tryptophan competes with other amino acids to enter the brain, and a protein meal raises the competitors more than it raises tryptophan. The article on drinking milk at night looks at the habit itself.

A worked example: counting tryptophan in a vegetarian day

This is an illustration, not a real person. Take a 45-year-old vegetarian shopkeeper in Indore who weighs 65 kg and so needs about 260 mg of tryptophan a day. His day holds rotis from 200 g of atta, 100 g of rice, two katoris of dal from 60 g of toor dal and one glass of milk.

He gets about 521 mg, twice his need, at 10.4 mg per gram of protein. By the IFCT formula that tryptophan is also worth about 8.7 mg of niacin equivalents, on top of the niacin already in the food. Now picture a day of 400 g of dry maize and nothing else: 35.2 g of protein but only about 201 mg of tryptophan, short of 260 mg. The sums ignore digestibility and are a comparison of two plates, not a measured intake.

Common mistakes and myths about tryptophan

The commonest mistake is to credit a single food with a drug-like effect. The second is to read only the niacin column of a food table and forget that the tryptophan in the same food adds to it. The third is to think of maize or jowar as harmful, when the old disease belonged to diets of one grain and little else.

A fourth mistake runs the other way: assuming vegetarians run short. On IFCT figures every common dal, cereal other than maize, and dairy food meets the adult pattern, and ICMR-NIN's vegetarian plate supplies almost twice the recommended amount per gram of protein.

Tryptophan supplements: side effects, medicines and when to see a doctor

The main caution is the combination with medicines that act on serotonin. A 2012 review in the Journal of Nutrition reports occasional tremor, nausea and dizziness at high intakes, and rare cases of serotonin syndrome when tryptophan is taken with serotonin drugs such as antidepressants; its signs include delirium, muscle jerks, high body temperature and coma. If you take an antidepressant or any other medicine that acts on serotonin, do not add a tryptophan supplement without asking the prescribing doctor.

The same review recounts the 1989 outbreak of eosinophilia myalgia syndrome, a disabling illness of muscle pain linked to tryptophan supplements and later traced to a contaminant in certain production batches. A 2013 trial gave 17 healthy young women up to 5 g a day for 21 days without adverse effects, which is reassuring but small. FSSAI's health supplement regulations list L-tryptophan as a permitted amino acid; the pack must say HEALTH SUPPLEMENT and NOT FOR MEDICINAL USE and may not claim to treat a disease. This entry recommends no dose.

See a doctor if poor sleep has lasted more than a few weeks, if low mood is affecting your work or relationships, or if you have a dark, scaly rash on sun-exposed skin with diarrhoea. Never stop a prescribed medicine in order to try a supplement.

Studying amino acids with NNWA

The essential amino acids and the vitamins made from them are part of what NNWA teaches. It is a private skill academy in Kolkata with online classes in English and Hindi. The Certification in Nutrition and the Diploma in Nutrition prepare people to guide healthy clients on food and to send medical questions to a doctor; neither is a degree or a dietitian qualification.