Tryptophan
Tryptophan is an essential amino acid and the direct precursor to serotonin, melatonin, and niacin. It plays an outsized role in mood, sleep quality, and appetite regulation despite being needed in relatively small amounts.
Why It Matters
Tryptophan crosses the blood-brain barrier and gets converted into serotonin, the calming neurotransmitter, which in turn becomes melatonin at night. Adequate tryptophan intake is one reason whole-protein meals (or a casein shake before bed) can improve sleep onset compared to going to bed underfed.
Tryptophan needs are small (about 280mg per day for a 70kg adult), and any reasonable protein intake covers it. The bigger lever is what you eat tryptophan with. Pairing it with some carbohydrate raises insulin, which clears competing amino acids and lets tryptophan reach the brain more efficiently.
How to Spot It on a Label
Tryptophan is the smallest entry on a typical amino panel. Whey isolate lists about 0.4g per 25g serving. Casein and turkey are the classic high-tryptophan foods. Collagen contains zero tryptophan, which is why it cannot be your only protein source.
Examples from real products
Related Terms
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