Tryptophan
Macronutrients
The precursor of serotonin — most of which is made in the gut, not in the brain.
It competes with the other amino acids to get into the brain: that is why a carbohydrate-rich meal gets it through better than a protein-rich one.
Effects and benefits
The rarest amino acid in our proteins is the precursor of serotonin, then of the sleep hormone melatonin, and of part of vitamin B3. And most of the body's serotonin is made in the gut, not the brain.
About 90% of the body's serotonin is produced by cells in the gut wall, where it regulates the movements of the digestive tract; it does not cross into the brain, which makes its own from the tryptophan in the blood (Yano et al., 2015).
At night, a small gland in the brain, the pineal gland, turns this serotonin into melatonin, the hormone that announces darkness to the rest of the body.
About 60 mg of tryptophan give 1 mg of vitamin B3. Adult needs are estimated at 4 mg per kilo per day (WHO, 2007).
Colon bacteria draw indoles from it, including indole-3-propionate, which strengthens the gut barrier. It is one of the few amino acids whose microbial fate is well described.
Sources: Yano et al., Cell, 2015 · WHO, FAO, UNU, 2007
Where to find it (16)
- Almond
- Black chickpea
- Black soybean
- Cashew
- Chickpeas
- Cocoa
- Fermented tofu
- Green / brown lentil
- Hemp seeds
- Oats
- Pumpkin seeds
- Quinoa
- Sesame seeds
- Soybeans / edamame
- Sunflower seeds
- Tempeh