Comparison
L-Tryptophan vs. 5-HTP
L-tryptophan or 5-HTP – what really works for sleep and mood?
The short answer
Both supply raw material for serotonin, and for both the biochemistry has been measured in humans. Clinically, L-tryptophan stands on firmer ground: in Germany it is approved as an over-the-counter pharmacy medicine to promote sleep readiness, a meta-analysis of 4 studies found shorter wake time after sleep onset, and in premenstrual dysphoric disorder symptoms fell by 34.5 versus 10.4 percent. 5-HTP measurably raises serotonin in the blood, but the largest modern placebo-controlled RCT with 166 patients showed no clinical difference, and there has been no approved medicine in Germany since 1992. In depression, both share the same thin Cochrane finding: 2 usable studies with 64 patients. No study compares the two directly. Combined with antidepressants or with each other, both count as a risky combination.
The numbers side by side
| Axis | L-Tryptophan | 5-HTP | Difference |
|---|---|---|---|
| Human evidenceHow much and how good the data in humans are | 5 | 5 | even |
| MechanismHow well the chain of action is understood | 6 | 6 | even |
| Safety dataHow well safety has been studied – not how safe it is | 6 | 4 | L-Tryptophan better studied |
| Hype gap10 means: the advertising stays level with the data | 5 | 3 | L-Tryptophan closer to the data |
| Track record of useHow much documented use in humans exists – does not measure whether it works | 7 | 6 | L-Tryptophan in use longer |
| Rating | Thin human evidence · Thin human evidence | ||
“Track record of use” measures how long and how widely something has been used in humans – not whether it works. The BK-Score is a subjective assessment by Biohacking Kompakt based on published scoring rules (German). It is not a scientific rating, not the consensus of a professional society and not a medical recommendation.
Why these numbers
L-Tryptophan
Evidence 5, because the sleep data come mostly from small studies from 1979 to 1987 that partly contradict each other (Hartmann 1979 with 15 people positive, Adam and Oswald 1979 negative, Demisch 1987 with 39 people only depending on the order), and the meta-analysis of 4 studies finds an effect only on wake time after sleep onset (SMD -1.08; Sutanto 2022). Added to this are a positive RCT in premenstrual dysphoria (34.5 versus 10.4 percent; Steinberg 1999), mixed mood data in healthy people (4 of 11 RCTs; Kikuchi 2021) and, for depression, only 2 usable studies with 64 patients (Cochrane 2002). Mechanism 6, because it has been shown in humans that tryptophan uptake into the brain and serotonin synthesis depend on the supply in the blood (Fernstrom 2013), but the chain to mood is indirect: tryptophan depletion does not lower mood in healthy people (Ruhé 2007, 45 studies). Safety 6, because a controlled dose study of up to 5 g per day over 21 days found no side effects (Hiratsuka 2013) and the interactions are known from the drug approval, but long-term data are lacking and the EMS epidemic with 27 deaths shows the importance of purity. Hype 5, because tryptophan is marketed as a natural sleep and happiness aid, although only individual sleep parameters and individual mood studies are positive. Use 7, because tryptophan is approved in Germany as a pharmacy-only medicine and regulated as a dietary supplement with a BVL upper limit of 500 mg per day. Direction mixed: positive signals for sleep and premenstrual dysphoria, contradictory or absent effects on other endpoints.
5-HTP
The biochemistry has been shown in humans: 5-HTP crosses the blood-brain barrier (PET, 8 healthy people, 6 patients, Acta Psychiatr Scand 1991) and markedly raises serum 5-HTP and serum serotonin in randomized studies (Gastroenterology 2022; Clin Nutr 2024). Clinically, the picture is mixed. For depression, the Cochrane review finds only 2 of 108 studies, with 64 patients, of sufficient quality (Peto OR 4.10; 95 % CI 1.28–13.15); a meta-analysis (Nutr Rev 2020) arrives at Hedges g 1.11 across 7 studies, with I² 76 % and few placebo groups. Newer studies are small: 30 older adults, 12 weeks, single-blind, better sleep score only in poor sleepers. The largest modern placebo-controlled RCT (166 patients, 2 × 8 weeks) missed its primary endpoint fatigue (35.6 vs. 37.6 percent) despite rising serotonin levels; an acute RCT with 112 participants found no effect on distractibility. An umbrella review of 17 papers does not support the serotonin-deficiency theory of depression (Mol Psychiatry 2023). On the safety side there are only short-term data; according to Cochrane, the EMS question after the 1989 L-tryptophan outbreak is unresolved; documented are a family case with a contaminated product and the risk of serotonergic combinations.
Frequently asked questions
What is the difference between L-tryptophan and 5-HTP?
5-HTP is the next step on the way to serotonin and skips the slowest conversion step. Tryptophan, by contrast, is also used for protein and, via the kynurenine pathway, for niacin among other things, and it competes with other large amino acids at the blood-brain barrier. The legal difference is clear: tryptophan is approved as a medicine in Germany and regulated as a dietary supplement, while 5-HTP is not an approved medicine; the former product Levothym was withdrawn in 1992.
Is 5-HTP stronger than L-tryptophan?
Biochemically, 5-HTP acts more directly on serotonin levels, but clinically this has not been shown to be an advantage. There is no head-to-head study. In the largest modern placebo-controlled study with 166 patients, serum 5-HTP and serotonin rose markedly on 5-HTP, but the primary endpoint fatigue was missed at 35.6 versus 37.6 percent. An umbrella review of 17 papers also does not support the idea that serotonin deficiency causes depression. More serotonin in the blood does not automatically mean feeling better.
Can you combine L-tryptophan and 5-HTP?
The sources advise against it. Both drive serotonin production, and the tryptophan topic page states explicitly that it should not be combined with 5-HTP. Both carry the same risk with antidepressants: together with MAO inhibitors or serotonin reuptake inhibitors, serotonin syndrome can occur, with confusion, tremor, fever and rising blood pressure. Anyone taking medication should clarify every combination with a doctor beforehand.
Which is safer, L-tryptophan or 5-HTP?
The safety data are better for tryptophan; the BK-Score gives 6 versus 4 points. For tryptophan there is a controlled dose study over 21 days per phase without side effects, and interactions are known from the drug approval; after the 1989 EMS epidemic with 27 deaths caused by contaminated product, the BVL requires pharmacopoeia-grade purity. For 5-HTP there are only short-term data, and Cochrane considers the EMS question unresolved. Long-term data are lacking for both.
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Information only, not medical advice and not a usage or dosage recommendation. Prescription-only and unapproved substances belong in a doctor's hands.