In 30 seconds
- Tryptophan is one of the 8 essential amino acids: your body cannot make it, and it uses it to produce proteins, serotonin, melatonin and niacin.
- An adult needs around 3.5-6 mg per kg of body weight a day, between 250 and 425 mg, and a normal diet usually provides 900-1,000 mg.
- It is found in foods with protein: meat, poultry, fish, eggs, dairy, soya, nuts and seeds such as pumpkin seeds.
- In a meta-analysis, supplemental tryptophan reduced time spent awake during the night, more so with 1 g or more a day.
Tryptophan is an essential amino acid: you have to get it from food, and your body uses it to make proteins, serotonin, melatonin and niacin. It is found in almost every food that contains protein, and a normal diet provides more than enough. As a supplement, a meta-analysis found that it shortens the time you spend awake at night.
What tryptophan is
It is one of the 8 essential amino acids, the ones your body cannot make 1. It has to come from your diet, and it does as soon as you eat protein.
The form your body uses is the L form, the one found in food. It is the one that forms part of proteins and the one that can enter the brain 1.
From your plate to melatonin
How tryptophan becomes melatonin
What it does
- Proteins. This is its main use: tryptophan is one more building block of your body's proteins 1.
- Serotonin and melatonin. Around 3% of dietary tryptophan is used to make serotonin, and only 1% in the brain 1. Melatonin, the sleep hormone, is made from serotonin 5.
- Niacin. Your body can convert it into this B vitamin, although not very efficiently: it takes around 60 mg to obtain 1 mg of niacin 1.
The rest, around 90% of the tryptophan that is broken down, follows another route, the kynurenine pathway 1.
Tryptophan a day
What you need compared with what you already get
How much you need
The estimated requirement for an adult is 3.5 to 6 mg per kg of body weight a day, between 250 and 425 mg 1:
| Your weight | Estimated requirement (3.5-6 mg per kg) |
|---|---|
| 60 kg | 210-360 mg |
| 70 kg | 245-420 mg |
| 80 kg | 280-480 mg |
| 90 kg | 315-540 mg |
Source: Richard et al., 2009. A normal diet provides around 900-1,000 mg a day.
A normal diet provides around 900-1,000 mg a day 1. In other words, more than twice what you need. If you eat protein at every meal, you are not short of it.
Which foods contain it
Almost all foods that contain protein 1 5:
| Group | Foods |
|---|---|
| Meat and poultry | Chicken, turkey, red meat |
| Fish | Tuna and fish in general |
| Eggs and dairy | Eggs, milk, cheese |
| Nuts and seeds | Almonds, peanuts, pumpkin and sesame seeds |
| Other | Soya, oats, bread, bananas, prunes, chocolate |
Sources: Richard et al., 2009, and Oklahoma State University.
To give you an idea of the amounts: 1 g of this amino acid is equivalent to around 300 g of turkey or around 200 g of pumpkin seeds 3.
The turkey myth
In the United States it is a classic: Thanksgiving turkey makes you sleepy because of its tryptophan. It is a myth. Turkey does not have much more tryptophan than other poultry, and drowsiness is linked more to a large meal rich in carbohydrates 5.
The explanation lies in how tryptophan reaches the brain. To get in, it competes with other large amino acids, such as leucine or valine 1:
- Carbohydrates do not raise blood tryptophan, but, through insulin, they lower its competitors. That way more of it enters the brain 1.
- A protein-rich meal does the opposite: it provides tryptophan, but many more competitors. Just 4% protein in a carbohydrate meal is enough to cancel out the advantage 1.
Even so, the authors of the review believe that normal dietary changes are unlikely to have a noticeable effect on the behaviour of a healthy person 1.
Supplement meta-analysis
Time awake at night, by dose
Tryptophan and sleep: what the studies say
Studies with supplements provide the most data.
- Less time awake at night. A meta-analysis found that tryptophan shortened the time spent awake after falling asleep, while the rest of sleep stayed the same 2.
- Better with 1 g or more. With 1 g or more a day, that time awake was around 29 minutes, compared with around 57 with less than 1 g 2.
- Falling asleep sooner. A review on sleep in athletes notes that doses from 1 g may improve the time it takes to fall asleep and perceived sleep quality 3.
At the table too: a cereal enriched with tryptophan, with 60 mg per 30 g, eaten at breakfast and dinner, improved the sleep efficiency and sleep time of middle-aged and older adults, compared with a control week with a cereal containing 22.5 mg per 30 g 4. In a study of 29,687 US adults, a higher dietary tryptophan intake was associated with sleeping for more hours 4.
If you wake up in the early hours, this is the finding that interests you most. We look at it in why you wake up at night, and you have the summary of the studies in L-theanine and tryptophan: what the studies say.
Is it safe?
In 1988-1989 there was an outbreak of a condition called eosinophilia-myalgia syndrome, which was attributed to synthetic tryptophan from a single manufacturer, after a change in its production process. The United States withdrew it from general sale and allowed it again in 2001, and since then it has been used in research without incident 1.
For tryptophan added to the diet, a no-observed-adverse-effect level of 4.5 g a day has been proposed for young adults 4. If you are pregnant, take medication or have a medical condition, check with your doctor.
Frequently asked questions
What is tryptophan good for?
Your body uses it to make proteins, serotonin, melatonin and niacin, a B vitamin. It is an essential amino acid, so you have to get it from food.
Which foods are highest in tryptophan?
Protein-rich foods: meat, poultry, fish, eggs, dairy, soya, nuts and seeds such as pumpkin and sesame seeds. Oats, bananas and chocolate also provide some.
Does turkey make you sleepy because of tryptophan?
It is a myth: turkey does not have much more tryptophan than other poultry. Drowsiness after a large meal is linked more to the amount of food and carbohydrates.
Does tryptophan help you sleep?
A meta-analysis found that supplemental tryptophan shortened time spent awake during the night, especially with 1 g or more a day. Other aspects of sleep stayed the same.
Sources
- Richard DM, Dawes MA, Mathias CW, Acheson A, Hill-Kapturczak N, Dougherty DM. L-tryptophan: basic metabolic functions, behavioral research and therapeutic indications. Int J Tryptophan Res. 2009. View publication
- Sutanto CN, Loh WW, Kim JE. The impact of tryptophan supplementation on sleep quality: a systematic review, meta-analysis, and meta-regression. Nutr Rev. 2022;80(2):306-316. View publication
- Halson SL. Sleep in elite athletes and nutritional interventions to enhance sleep. Sports Med. 2014;44(Suppl 1):S13-S23. View publication
- Friedman M. Analysis, nutrition, and health benefits of tryptophan. Int J Tryptophan Res. 2018;11. View publication
- Oklahoma State University, Robert M. Kerr Food and Agricultural Products Center. News item on turkey, tryptophan and sleepiness. OSU News, 2020. View publication
Information based on published studies. It does not replace the advice of a doctor or registered dietitian. The results describe what was measured in each study, not the properties of any specific product. A varied and balanced diet and a healthy lifestyle are important.
