5-HTP is an intermediate in the biosynthesis of serotonin – a neurotransmitter that is crucial for many cognitive processes. Serotonin acts on many parts of the brain, and is thought to participate in a wide variety of different neural functions. 5-HTP is readily converted to serotonin, and also effectively crosses the blood-brain barrier.
Serotonin Biosynthesis Pathway. The initial conversion of L-Tryptophan to 5-hydroxy-L-tryptophan is the rate-limiting step in serotonin biosynthesis. Thus, 5-HTP supplementation skips this step, resulting in a direct route to serotonin biosynthesis.
5-HTP and appetite
Some of the strongest effects of 5-HTP supplementation appear to be in promoting satiety, or a reduction in hunger. In a study of obese female subjects, 5-HTP administration reduced food intake and increased weight loss. Furthermore, no adverse effects on mood were observed with 5HTP supplementation. In a double-blind, placebo-controlled trial, it was found that 900 mg or 5-HTP/day, reduced carbohydrate intake, and increased satiety. In a follow-up study with diabetic patients, it was observed that 750 mg/day of 5-HTP successfully resulted in a reduction of carbohydrate intake, lipid intake, energy intake, and weight loss (average of 1.1 kilograms lost).
These results demonstrate that 5HTP can reduce feelings of hunger, and these gains can translate to reduced energy intake (mediated by less consumption of carbohydrates and lipids), and this results in increased weight loss.
Editorial Opinion: The effects of 5-HTP on satiety are well-established: 5-HTP supplementation reduces macronutrient in-take and can lead to weight loss. The effect of 5-HTP in modulating stress and anxiety is equivocal, and no conclusions can be drawn from currently available data.