Serotonin, an important brain neurotransmitter, is key in the regulation of appetite, mood, and melatonin
production. The presence of serotonin in the brain is associated with a balanced emotional state. This is
achieved in part by decreasing the activity of certain excitatory hormones, including dopamine and
noradrenaline. Serotonin also acts as a satiety signal in the brain, thereby naturally regulating food intake.
Additionally, as a precursor of melatonin, serotonin is involved in regulating sleep patterns. Serotonin is unable
to cross the blood-brain barrier and is therefore synthesized in the brain. Tryptophan, an essential amino acid,
is a precursor for the synthesis of serotonin. Tryptophan crosses the blood-brain barrier and is converted to L-
5-hydroxytryptophan, which in turn is converted into serotonin. Unfortunately, tryptophan faces many obstacles
during its journey into brain tissue. First, dietary intake directly affects body levels of tryptophan, as the body
can not endogenously produce it. High protein diets often provide greater amounts of tryptophan, yet higher
carbohydrate diets appear to enhance tryptophan uptake into the brain. Secondly, tryptophan must compete
with other amino acids for entry into the brain. Finally, tryptophan may be taken up by other tissues for protein
or niacin synthesis, and thus is not exclusively for use by the brain. As a metabolic intermediate in the
conversion of tryptophan into serotonin, 5-HTP can also serve as a precursor of serotonin. 5-HTP offers a
number of advantages over tryptophan. 5-HTP is derived naturally from the seeds of the Griffonia plant, unlike
tryptophan which is produced synthetically or through bacterial fermentation. 5-HTP crosses into the brain
more readily than tryptophan as it is able to cross the blood-brain barrier without competition for uptake.
5-HTP is significantly more effective than tryptophan; one 50 mg capsule of 5-HTP is roughly equivalent to
500 mg of tryptophan. Finally, research studies have shown 5-HTP to be safe at levels as high as 900 mg.
As a result, 5-HTP is a safe and effective means of increasing brain serotonin levels.
Agren H, Reibring L, Hartvig P, Tedroff J, Bjurling P, Hornfeldt K, Andersson Y, Lundqvist H, Langstrom B.
Low brain uptake of L-[11C]5-hydroxytryptophan in major depression: a positron emission tomography study
on patients and healthy volunteers. Acta Psychiatr Scand 1991;83:449-55.
Alvarado R, Contreras S, Segovia-Riquelme N, Mardones J. Effects of serotonin uptake blockers and of
5-hydroxytryptophan on the voluntary consumption of ethanol, water and solid food by UChA and UChB rats.
Angel I, Taranger MA, Claustre Y, Scatton B, Langer SZ. Anorectic activities of serotonin uptake inhibitors:
correlation with their potencies at inhibiting serotonin uptake in vivo and 3H-mazindol binding in vitro. Life Sci
Birdsall TC. 5-Hydroxytryptophan: a clinically-effective serotonin precursor. Altern Med Rev 1998;3:271-80.
Blundell JE. Serotonin and appetite. Neuropharmacology 1984;23:1537-51.
Blundell JE, Leshem MB. The effect of 5-hydroxytryptophan on food intake and on the anorexic action of
amphetamine and fenfluramine. J Pharm Pharmacol 1975;27:31-7.
Cangiano C, Ceci F, Cairella M, Cascino A, Del Ben M, Laviano A, Muscaritoli M, Rossi-Fanelli F. Effects of
5-hydroxytryptophan on eating behavior and adherence to dietary prescriptions in obese adult subjects. Adv
Exp Med Biol 1991;294:591-3.
Cangiano C, Ceci F, Cascino A, Del Ben M, Laviano A, Muscaritoli M, Antonucci F, Rossi-Fanelli F. Eating
behavior and adherence to dietary prescriptions in obese adult subjects treated with 5-hydroxytryptophan. Am
J Clin Nutr 1992;56:863-7.
Ceci F, Cangiano C, Cairella M, Cascino A, Del Ben M, Muscaritoli M, Sibilia L, Rossi Fanelli F. The effects of
oral 5-hydroxytryptophan administration on feeding behavior in obese adult female subjects. J Neural Transm
Ernouf D, Daoust M, Poulain D, Narcisse G. Triptosine, an L-5-hydroxytryptophan derivative, reduces alcohol
consumption in alcohol-preferring rats. Alcohol Alcohol 1992;27:273-6.
Ferstrom JD. Modification of brain serotonin by the diet. Annu Rev Med 1974;25:1-8.
Fletcher PJ, Burton MJ. Dissociation of the anorectic actions of 5-HTP and fenfluramine. Psychopharmacology
Martinelli I, Mainini E, Mazzi C. [Effect of 5-hydroxytryptophan on the secretion of PRL, GH, TSH and cortisol
in obesity]. Minerva Endocrinol 1992;17:121-6.
Turner P, Bichi LA, Slusarczyk H, Franklin CS. The peripheral actions of antiobesity drugs. Int J Obes