5-Hydroxytryptophan (5-HTP) is a biochemical compound synthesized in the conversion pathway from the amino acid, tryptophan, to serotonin. Tryptophan undergoes a chemical reaction known as hydroxylation, whereby a hydroxyl group is added, resulting in the product, 5-hydroxytryptophan (5-HTP). This reaction is catalyzed by the enzyme hydroxylase. Hydroxylase is also coupled in the conversion of tetrahydrobiopterin to dihydrobiopterin, aiding in the release of one molecule of water.
5-HTP undergoes its conversion to serotonin via the chemical reaction, decarboxylation. It is catalyzed by a decarboxylase enzyme, thereby releasing one molecule of carbon dioxide.  Conversion of 5-HTP to serotonin is greater than that of Tryptophan to serotonin. Actually, over 70% of 5-HTP is converted to serotonin, while only 3% of tryptophan results in serotonin production.  However, tryptophan remains important, serving as a precursor to other significant biochemical compounds.
Interest in 5-HTP is primarily linked to its effect on serotonin production. Serotonin is also called 5-hydroxytryptamine and is widely recognized as one of the most critical neurotransmitters in human physiology. Neurotransmitters are chemicals that transmit impulses from one neuron (nerve cell) to another. The largest amount of serotonin is actually found in the cells of the intestinal mucosa. Other sites where serotonin exists are the platelets and other areas of the central nervous system. Serotonin is important for regulation of blood pressure, respiration, and mental/emotional function.
Contrary to popular belief, tryptophan and 5-HTP are not interchangeable when taken as a dietary supplement. Unlike tryptophan, 5-HTP is not a precursor to niacin (vitamin B3) and picolinic acid. Furthermore, 5-HTP does not cross the blood brain barrier very readily because it cannot be converted to kynurenine, like tryptophan. Kynurenine is a biochemical compound that is formed when tryptophan is acted on by the enzyme, tryptophan oxygenase.
It is worthy to mention a controversy regarding L-tryptophan which occurred in 1989. Some people may confuse this with 5-HTP because of their chemical similarity, however it had nothing to do with 5-HTP. A contaminated batch of L-tryptophan supplements entered the marketplace from a manufacturing facility in Japan.  A number of consumers became ill and 38 people died from a disorder called eosinophilia-myalgia syndrome (EMS). The causative agent was not L-tryptophan itself, but from a particular strain of bacteria that was used to synthesize L-tryptophan. Following this unfortunate incident, L-tryptophan-containing supplements were banned in the United States. It was not until 1996 that the ban was partially lifted, allowing only physicians prescribe the synthetic supplement.
The contamination problem that were associated with L-tryptophan did not apply to 5-HTP-containing products.
There are no food sources of 5-HTP. 5-HTP is plant based and extracted from the seed of the African plant, Griffonia simplicifolia. However, tryptophan is found in highest amounts in brown rice, cottage cheese, meat, peanuts and soy proteins.  Because only small amounts of tryptophan are actually converted to serotonin, dietary sources of tryptophan are considered ineffective in achieving the therapeutic effects of 5-HTP supplements.
Most research involving the use of 5-HTP has focused on cognitive disorders, namely, the treatment of depression. A number of double-blind controlled studies have demonstrated the effectiveness of 5-HTP in the treatment this condition, as compared to the commonly prescribed drug classes of tricyclic antidepressants and selective serotonin reuptake inhibitors (SSRIs). [5-8] In these studies, 5-HTP was observed to be comparable in effect to drugs such as Luvox, Prozac and Paxi with fewer and less severe side effects. Additionally, 5-HTP therapy is much less expensive. In another study, the effect on sleep was examined. Patients receiving 5-HTP actually showed improvements in their quality of sleep, whereas patients taking prescription antidepressant medication experienced disturbed sleep patterns.
5-HTP has also been studied in the prevention of headaches (prophylaxis) in both adults and children. [9-12] Again, patients receiving 5-HTP therapy exhibited far fewer side effects. Its action was also comparable in efficacy to prescription medications like Sansert (methysergride). Patients receiving 5-HTP therapy for migraine prophylaxis also experienced improved mood.
Fibromyalgia is another condition that is backed by clinical evidence, supporting the use of 5-HTP as a legitimate treatment option. [13, 14] Because serotonin deficiencies have been linked to fibromyalgia patients, 5-HTP may be effective in treating this disorder.  Patients taking a dose of 100mg three times per day for thirty days experienced significant improvements in symptoms such as; a reduction in the number of painful areas, regulated sleep patterns, and a reduction in both anxiety and fatigue. 
Other conditions for which 5-HTP has been found useful include insomnia, bipolar disorder, and obesity. [16-20] Patients with bipolar disorder should only take 5-HTP under the supervision of their physician.
There is no established Recommended Dietary Allowance (RDA) for 5-HTP. It is not an essential nutrient, meaning it can be made in the body. Doses of 5-HTP that have been reported for studies involving depression and migraine, exist in the range of 200 -600 milligrams (mg) per day. Caution must be taken when taking 5-HTP, as L-tryptophan at a dosage of 8 grams daily has been shown to be teratogenic to animals. Therefore, as a Category C drug, 5-HTP should be used with caution in pregnant women.
Administration with small amounts of simple carbohydrates, such as fruit or fruit juice, is likely to facilitate 5-HTP absorption.
Deficiency of 5-HTP has not been documented, as it is a compound that is biosynthesized in the body from tryptophan. It is unlikely that 5-HTP supplementation would correct any problems associated with tryptophan deficiency, such as the reduced synthesis of the nutrients; protein, picolinic acid, and niacin.
A toxic syndrome from contaminated L-tryptophan resulted in a condition called eosinophilia-myalgia syndrome (EMS), which lead to the death of 38 people. (See Introduction) Symptoms of this disorder include muscular pain, rash, edema, respiratory ailments, fatigue, and elevated white blood cell count. There have been a few cases of EMS associated with 5-HTP ingestion, but a cause-effect relationship has not been established.
Interactions with selective serotonin reuptake inhibitors (SSRIs) such as Prozac, Zoloft and Paxil; monoamine oxidase inhibitors and some other antidepressants have been documented for L-tryptophan and are likely to occur with 5-HTP as well. When patients are taking these medications along with 5-HTP or L-tryptophan, they should be monitored closely by a physician for serotonin syndrome, which can be potentially dangerous.
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