5-HTP (5-Hydroxytryptophan)
A naturally occurring amino acid that the body uses to produce serotonin — the brain chemical involved in mood, sleep, and appetite. Found in small amounts in food (especially turkey, eggs, and seeds) and extracted commercially from Griffonia simplicifolia seeds. Several small clinical trials show meaningful appetite reduction and weight loss, particularly for reducing carbohydrate cravings.
Quick read · 3 min
- •Evidence: Weak — limited or inconsistent trial data
- •Several small randomised controlled trials (primarily from Cangiano et al.
- •GI side effects (nausea, diarrhoea, heartburn, vomiting) are common, especially at higher doses (900 mg/day), and are the main reason people stop taking it.
- •Prescription weight loss drugs produce 7–21% weight loss in trials. Most supplements in this category produce less than 2 kg.
Based on clinical trials · No rankings · Every claim linked to source
Last reviewed: March 2026
How it works
5-HTP is the direct precursor to serotonin. When taken as a supplement, it crosses the blood-brain barrier and increases serotonin production. Higher serotonin levels in the brain's appetite centres are associated with reduced hunger, earlier feelings of fullness, and — specifically — reduced cravings for carbohydrates. Unlike tryptophan (which must compete with other amino acids to enter the brain), 5-HTP has more direct access and a more reliable serotonin-raising effect.
What the evidence shows
Several small randomised controlled trials (primarily from Cangiano et al., 1991–1998) showed meaningful weight loss with 750–900 mg/day: in a 12-week trial, participants lost an average of 5 kg (11 lbs) vs. 1.1 kg on placebo, largely by spontaneously reducing calorie intake — especially carbohydrates. A lower-dose study (100 mg/day in physically fit adults) found approximately 0.8 kg fat mass reduction vs. a small gain in placebo. The trial evidence is promising but largely from small, older studies. Larger, more recent independent trials are lacking. The effect on carbohydrate cravings is one of the more distinct findings.
Safety
GI side effects (nausea, diarrhoea, heartburn, vomiting) are common, especially at higher doses (900 mg/day), and are the main reason people stop taking it. Starting at 50 mg and increasing gradually helps. Important interactions: 5-HTP should not be combined with antidepressants (SSRIs, SNRIs, MAOIs) due to the risk of serotonin syndrome — a potentially serious condition caused by too much serotonin activity. Also avoid with tramadol, triptans (migraine medications), or St John's Wort. Not recommended in pregnancy. Eosinophilia-myalgia syndrome was associated with contaminated tryptophan supplements in the 1980s — quality-controlled 5-HTP has not been linked to this, but buying from reputable manufacturers matters.
Community insights
These are personal experiences shared in public online communities — not medical advice.
“The nausea is real at higher doses. Start with 50 mg once daily before bed and increase slowly over 2–3 weeks. Many people find the sweet spot is 100–200 mg/day rather than the 900 mg used in some trials.”
“Do not take this with antidepressants — serotonin syndrome is a real risk. If you're on any psychiatric medication, check with your doctor first.”
“Many people take it before bed — it also helps with sleep quality for some, since serotonin is a precursor to melatonin. Two potential benefits from one supplement.”
Common questions
After reading this page, most people compare this with other supplements, look at prescription options, or check what they can do today without a prescription.