5-HTP is a natural extract from the Griffonia Simplicifolia seed and a pre-cursor to Serotonin (5-HT) [1, 2]. Once ingested it crosses the blood-brain barrier without the need for a transporter molecule. It subsequently interacts with the dopa-decarboxylase enzyme which strips off a piece of the molecule resulting in serotonin.
What is serotonin?
Serotonin is one of our most important neurotransmitters which is responsible for regulation of a person’s concentration span and mood [3, 4]. If there is an inadequate amount of serotonin there is often a decrease in a person’s performance and emotional state which is why serotonin deficit is implicated in many cases of severe depression .
Unlike many anti-depressants such as Prozac, Paxil, Citalopram & Fluoxamine which block the reuptake of serotonin, 5-htp acts to increase the amount of serotonin being produced and released at the presynaptic neuron.
What does it do?
Studies have shown that 5-HTP is beneficial for alleviating the effects of depression, anxiety, suppressing appetite and sleep  because of the role serotonin has on our physiology. It's most widely studied application is on depression including tests on the effects of 5-HTP on patients who were unresponsive to other treatment available for depression  and on people exhibiting depressive symptoms in which 5-htp has shown to alleviate symptoms 
5-HTP had been shown to act as an appetite suppressant. This was demonstrated in 1992 by Cangiano et al. They studied the effects of 5-HTP in 20 obese patients and found that during 5-HTP administration, the participants lost significant amount of a weight .
5-HTP has also been shown to improve sleep and fibromyalgia. This was demonstrated when 50 fibromyalgia patients were given 100mg of 5-HTP, three times per day for 30 days . Patients reported improvements in sleep, as well as a number of other symptoms including muscle soreness, anxiety and stiffness. So, 5-HTP may provide a useful treatment for insomnia and fibromyalgia .
- Berumen, L.C., et al., Serotonin Receptors in Hippocampus. The Scientific World Journal, 2012. 2012: p. 15.
- Birdsall, T.C., 5-Hydroxytryptophan: A Clinically-Effective Serotonin Precursor. Alternative Medicine Review, 1998. 3(4): p. 271-280.
- Lira, A., et al., Altered depression-related behaviors and functional changes in the dorsal raphe nucleus of serotonin transporter-deficient mice. Biological Psychiatry, 2003. 54(10): p. 960-971.
- Prasad, C., Food, mood and health: a neurobiologic outlook. Brazilian Journal of Medical and Biological Research, 1998. 31: p. 1517-1527.
- Martini, Nath, and Bartholomew, Fundamentals of Anatomy and Physiology. 9th ed, ed. L. Berriman. 2012, San Francisco: Pearson
- van Praag, H.M., et al., A pilot study of the predictive value of the probenecid test in application of 5-hydroxytryptophan as antidepressant. Psychopharmacologia, 1972. 25(1): p. 14-21.
- von Sano, T., L-5-Hydroxytryptophan-(L-5-HTP) Therapie*. Psychiatry and Clinical Neurosciences, 1972. 26(1): p. 7-17.
- Cangiano, C., et al., Eating behavior and adherence to dietary prescriptions in obese adult subjects treated with 5-hydroxytryptophan. Am J Clin Nutr, 1992. 56(5): p. 863-7.