5 HTP Clinical Evidence

Journal of Neural Transmission Ceci F, et al.

The effects of oral l 5-hydroxytrptophan administration on feeding behavior in obese adult female subjects. 1989;76(2):109-17.  Topic: Can 5-HTP help obese women lose weight? Background: 5-hydroxytrypophan, or 5-HTP, is the raw material the body uses to manufacture serotonin, a brain chemical. Low levels of serotonin are associated with food cravings and weight gain. Study Type: Human clinical intervention trial Study Design: Double-blind crossover. Subjects took either 5-HTP or placebo for five weeks and kept a food diary. Mood was measured using several scales: Beck Depression Inventory, Symptom Intensity Scale, State-Trait Anxiety Inventory and State-Trait Anxiety Inventory State Subjects: 19 obese women with a body mass index between 30 and 40. (A BMI of 30 or higher is considered obese.) Dosage: 8 mg/kg/day (approximately 656 mg/day for a 180-lb woman) for 5 weeks Results: Administration of 5-HTP did not affect the subjects’ mood, but did result in decreased appetite, reduced food intake and significant weight loss.

International Clinical Psychopharmacology.

Kahn RS, et al. Effects of a serotonin precursor and uptake inhibitor in anxiety disorders: a double-blind comparison of 5-hydroxytryptophan, clomipramine and placebo. 1987 Jan;2(1):33-45.  Topic: How well does 5-HTP treat anxiety disorders compared to the drug clomipramine, and what is the role of serotonin in these disorders? Background: Clomipramine is a tricyclic antidepressant developed in the 1960s and used to treat Obsessive Compulsive Disorder. It has numerous side effects. 5-hydroxytryptophan is the raw material the body uses to build serotonin, a brain chemical associated with mood. Could it be a good alternative to clomipramine? Study Type: Human clinical intervention trial Study Design: Double-blind, placebo-controlled Subjects: 45 patients with anxiety Results: Subjects taking clomipramine improved on all rating scales compared to placebo. Subjects taking 5-HTP showed moderate improvement of symptoms on the 90-item symptoms checklist (SCL-90) and the State Scale of the Spielberger State-Trait Anxiety Inventory, but their depressive symptoms did not improve. This particular study indicates that 5-HTP is helpful for people suffering from anxious mood, but not depression. However, other studies have found 5-HTP effective for depression. Conclusion: “The results support the hypothesis that brain serotoninergic pathways are involved in the pathogenesis of anxiety disorders, particularly in agoraphobia and panic disorders.”

Alternative Medicine Review.

Birdsall, TC. 5-Hydoxytryptophan: a clinically-effective serotonin precursor. 1998 Aug;3(4):271-80. Topic: What does the evidence on 5-HTP show to date? Background: Serotonin levels regulate sleep, mood disorders such as depression and anxiety, aggression, appetite, body temperature, sexual behavior and the perception of pain. 5-Hydroxytryptophan is an intermediate product formed in the process of converting the amino acid L-tryptophan into the brain chemical serotonin. Study Type: Review paper Dosage: Varied by study Results: The author finds that:
  • 5-HTP is well absorbed from an oral dose; 70% makes it to the bloodstream.
  • 5-HTP crosses the blood-brain barrier and increases production of serotonin by the
  • central nervous system.
  • 5-HTP has been shown effective in human clinical trials in treating numerous health conditions.
Conclusion: “Therapeutic administration of 5-HTP has been shown to be effective in treating a wide variety of conditions, including depression, fibromylagia, binge eating associated with obesity, chronic headache, and insomnia.”

Pharmacology and Therapeutics.

Turner E, Loftis J, Blackwell A. Seratonin a la carte: supplementation with the serotonin precursor 5-hydroxytryptophan. 2006;109:325-338. Topic: What is the evidence for supplementation with 5-HTP to treat depression? Background: 5-HTP has been used clinically to treat depression and other ailments for several decades, but most studies were conducted over 25 years ago. When SSRI drugs were approved in the United States in 1987, interest in research on 5-HTP dwindled. Is it time to reconsider the use of 5-HTP as a viable treatment for depression? Study Type: Review paper Dosage: Varied by study Results: The author finds that:
  • Scientific support for the use of 5-HTP to treat depression is not definitive, because
  • of insufficient numbers of large-scale, double-blind, placebo-controlled studies. Also,
  • many studies tested 5-HTP in combination with other ingredients.
  • However, seven out of eleven small, double-blind, placebo-controlled studies found
  • 5-HTP to outperform placebo, indicating some efficacy in the treatment of depression.
  • While very high levels of serotonin can cause anxiety and seizures, no cases of
  • serotonin syndrome associated with 5-HTP have been reported.
  • More studies of efficacy and safety are needed.
Conclusion: “[W]e believe that 5-HTP supplementation deserves to be reconsidered as a possible significant addition to the antidepressant armamentarium.”

5-HTP Mechanism of Action

Research has shown that when levels of 5-HTP are increased, levels of serotonin — a brain chemical necessary for a positive mood — are also increased. That’s because 5-HTP is the direct precursor to serotonin. Tryptophan, another ingredient used to boost serotonin, is the direct precursor to 5-HTP. Therefore, 5-HTP provides a more direct route for increasing serotonin production.