L-tryptophan is a proven natural antidepressant
MisleadingThe Claim
Because it is converted into serotonin, L-tryptophan is often presented as a natural substitute for antidepressant medication.
Origin
The serotonin hypothesis of depression and decades-old small trials led to its promotion as a 'natural antidepressant'.
What Science Says
A Cochrane review found 108 trials but only 2 (64 patients in total) of sufficient quality; these suggested benefit over placebo, but the evidence was judged insufficient to be conclusive and its clinical usefulness limited given proven alternatives. A 2025 network meta-analysis found a signal for tryptophan mainly as an add-on to antidepressants (SMD 1.24, wide 95% CI 0.32–2.16), not as a proven stand-alone treatment.
Verdict
Misleading