Tryptophan
Also known as L-tryptophan, Trp
Tryptophan is an essential amino acid that the body cannot make, so it must come from food. It builds proteins and is the precursor to serotonin and melatonin, the messengers that regulate mood and sleep, and it also helps make niacin (vitamin B3).
Why it matters
What it does in your body
- Protein building block
- Precursor to serotonin for mood regulation
- Precursor to melatonin for sleep
- Contributes to niacin (vitamin B3) production
Intake guidance
How much you need
The IOM sets the requirement at 5 mg/kg/day, about 0.35 g/day for a 70 kg adult. Any diet with enough total protein provides plenty.
What affects it
What affects your intake
Total protein intake
Tryptophan is the least abundant essential amino acid in food, but a protein-adequate diet still meets the small requirement easily.
Competition with other amino acids
Tryptophan competes with other large amino acids to enter the brain, which is why carbohydrate-containing meals can raise its uptake.
Niacin status
The body can convert tryptophan to niacin, so intake also supports vitamin B3 needs.
In practice
Good to know
Deficiency is unlikely on a normal diet despite tryptophan being the scarcest essential amino acid. Because it feeds serotonin and melatonin, it is marketed for sleep and mood, and its metabolite 5-HTP is a related sleep supplement. The famous idea that turkey makes you sleepy is overstated, since turkey is no higher in tryptophan than other meats. Most people do not need to supplement it.
Where to get it
Best food sources
The bottom line
A protein-adequate diet covers tryptophan even though it is the rarest essential amino acid. Sleep and mood supplements exist, but food normally suffices.
Track tryptophan automatically
Tryptophan is one of the 92 nutrients Vora reads from a photo of your meal, so you can see where you stand without weighing or logging by hand.
Sources and method
The classification, roles, and guidance on this page come from the references below, drawing on the Institute of Medicine (now the National Academies) Dietary Reference Intakes and reputable nutrition science.
- Institute of Medicine (2005), Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids
This page is for general education, not medical advice. Reference intakes are population averages for healthy people and do not replace guidance from your doctor or a registered dietitian, especially if you are pregnant, managing a health condition, or considering supplements.