Nutrient glossary
What is tryptophan?
Tryptophan is the scarcest essential amino acid and the raw material for serotonin, melatonin and niacin.
Reviewed 20 July 2026. General information, not medical advice.
The short version
Tryptophan is needed in the smallest amounts but does outsized work: it becomes serotonin, then melatonin, and the body can also convert it to niacin. It is the least abundant essential amino acid in food, which is why it gets the attention.
Pumpkin seeds, soy, cheese, poultry, oats and eggs are the practical sources. Carbohydrate in a meal helps tryptophan cross into the brain, which is the kernel of truth in carbs-and-sleep folklore.
Daily reference
300 mg a day
The adult requirement is about 4 mg per kg of body weight a day, the smallest of the nine.
This is the fixed adult reference used across these pages. In the app, your amount adjusts to your body and way of eating.
Best food sources of tryptophan
| Food | Per serving | Per 100g |
|---|---|---|
| Chicken Breast | 580 mg | 341 mg |
| Duck Breast | 532 mg | 380 mg |
| Ribeye Steak | 485 mg | 323 mg |
| Roast Chicken | 473 mg | 338 mg |
| Tuna Steak | 407 mg | 313 mg |
| Halibut | 396 mg | 283 mg |
| Turkey Breast | 396 mg | 330 mg |
| Whey Protein | 395 mg | 1.28 g |
Common questions
- Does turkey make you sleepy?
- Turkey has no more tryptophan than chicken. Holiday drowsiness is the meal size and the wine, not the bird.
- Can tryptophan help sleep?
- A tryptophan-containing evening snack with some carbohydrate can nudge melatonin production; the effect is modest and gentler than supplements claim.