5-HTP is serotonin, one step upstream. Your brain builds serotonin from tryptophan, but the first enzyme in that chain is a bottleneck. 5-HTP is the intermediate that sits just past it, so a small oral dose raises serotonin where whole tryptophan barely moves the needle 1. After dark the brain turns some of that serotonin into melatonin, which is why an evening dose reads as a sleep aid.
The sleep effect is the solid one. Fifty years of small trials land in the same place: a bedtime dose trims sleep-onset latency by roughly ten to twenty minutes, biggest for poor sleepers, near-invisible for good ones, and the night that follows looks normal rather than sedated 2 3. The appetite effect is real but smaller: obese women on 900 mg a day ate less and lost about three kilograms more than placebo over twelve weeks 4. Depression is where the claim collapses — the Cochrane review found only two adequate trials, sixty-four people between them 5.
Check your medication list before anything else. If you take any serotonergic prescription, stop here. Otherwise, start low and take it at night.
The three effects arrive on different clocks. Sleep onset lands the first night: the gap between lights-out and asleep is just shorter 2. Appetite loosens over the first week — the afternoon snack reach feels less automatic 4. Mood, if it shows at all, takes a month, closer to an antidepressant's timeline than a sleeping pill's. Past that, most people find the effect fades on a continuous run and prefer a few weeks on, a week off.
The fine print — when to skip it, and what people get wrong
Never combine it with a serotonergic drug. SSRIs, SNRIs, MAOIs, tricyclics, tramadol, migraine triptans, or St John's wort stacked with this can trigger serotonin syndrome 6. Pregnancy, breastfeeding, valve disease, or a carcinoid history: avoid. If a doctor adds any new drug, tell them you take this.
"Natural" is not "safe." A 1989 outbreak of eosinophilia-myalgia syndrome, dozens dead, traced to contaminated tryptophan from one manufacturer, not the molecule itself 7. And turkey isn't special: the post-dinner drowsiness comes from the carbohydrate side dishes rather than the meat 8.
Nausea day one is the usual snag — most of the dose hits gut serotonin receptors first. Lower it, take it with food, wait a few days. Non-response is the other: if you already sleep fine, there's no latency to shorten.
- 1Birdsall TC (1998). 5-Hydroxytryptophan: a clinically-effective serotonin precursor. Alternative Medicine Review. link
- 2Hartmann E (1982). Effects of L-tryptophan on sleepiness and on sleep. Journal of Psychiatric Research. link
- 3Silber BY, Schmitt JAJ (2010). Effects of tryptophan loading on human cognition, mood, and sleep. Neuroscience and Biobehavioral Reviews. link
- 4Cangiano C, Ceci F, Cascino A, et al. (1992). Eating behavior and adherence to dietary prescriptions in obese adult subjects treated with 5-hydroxytryptophan. American Journal of Clinical Nutrition. link
- 5Shaw K, Turner J, Del Mar C (2002). Tryptophan and 5-Hydroxytryptophan for depression. Cochrane Database of Systematic Reviews. link
- 6Boyer EW, Shannon M (2005). The serotonin syndrome. New England Journal of Medicine. link
- 7Slutsker L, Hoesly FC, Miller L, et al. (1990). Eosinophilia-myalgia syndrome associated with exposure to tryptophan from a single manufacturer. JAMA. link
- 8Fernstrom JD, Wurtman RJ (1972). Brain serotonin content: physiological regulation by plasma neutral amino acids. Science. link
5-HTP and Tryptophan
Standard 100 mg 5-HTP from a reputable brand runs $10–20/month, well under $250/year. Cheap unbranded product is cheaper but carries contamination concern; the reasonable-quality version still sits in the trivial-cost band.
One capsule at bedtime; the protocol is a sub-minute daily action with no lifestyle reorganization. Lowest non-zero effort tier.
Modest, replicated effects across three small consequence-domains: ~10–20 min shorter sleep onset latency at bedtime (Hartmann 1982), reduced caloric intake and earlier satiety at 900 mg/day 5-HTP (Cangiano 1992), and modest fibromyalgia pain reduction (Caruso 1990). Effect sizes below an SSRI or hypnotic but real and additive for the responder population.
Sleep-onset latency reduction of roughly 10–20 minutes at 1–4 g L-tryptophan or 100–300 mg 5-HTP before bed, replicated from Wyatt et al. (Lancet 1970) through Hartmann (1982) and synthesised by Silber and Schmitt (2010). Larger effect in self-reported poor sleepers; minimal in good sleepers; architecture not distorted.
Acute tryptophan depletion reliably lowers mood in vulnerable subjects (Young 2013), establishing the system as causally upstream. Loading is less reliable: the Cochrane review found only 2 of 108 candidate trials methodologically adequate (Shaw 2002), pooled direction-correct, total n = 64. Real but modest mood effect; far below SSRIs.
Sparse and methodologically uneven for depression (Cochrane: 2 of 108 trials adequate; Shaw 2002). Better for sleep onset (multiple replications; Silber and Schmitt 2010 review). Modest single-group support for appetite (Cangiano 1992) and fibromyalgia (Caruso 1990). Mechanism is fully worked out. No large modern RCT has refreshed the depression evidence base.
No direct vitality effect in the literature. Downstream-from-sleep energy lift is plausible for poor sleepers whose latency shortens, but the supplement is not a stimulant or fatigue intervention in its own right.