Serotonin is one of the most important of the neurotransmitters, regulating processes in the body as diverse as digestion and temperature control. It is best known, however, for its role in regulating mood. It also is the direct precursor to melatonin, a hormone produced in the pineal gland that plays an important role in regulating sleep cycles. Deficiencies in serotonin have long been known to cause depression and sleep disturbance, leading to the investigation of serotonin precursors l-tryptophan and 5-hydroxytryptophan, or 5-HTP, as possible treatments. Although both of these supplements have been used to treat these conditions for more than 20 years, more research is needed to confirm their efficacy.
L-Tryptophan
L-tryptophan is one of eight essential amino acids and is found naturally in a wide variety of foods. Attempts to increase serum tryptophan levels by modifying the diet, however, have been found to be largely ineffective. This is likely due to the fact that the amino acid is rarely found alone in nature but alongside other amino acids that compete with it for absorption. According to the University of Maryland Medical Center, when an isolated form of L-tryptophan is taken, as in the drug Aminomine, it has been shown to increase synaptic serotonin levels. In the mid 90s, the FDA banned the sale of L-tryptophan after a batch contaminated with the poison Peak X poisoned thousands; it has only recently been re-released on the market, as of the time of publication.
5-Hydroxytryptophan
The ban on the sale of L-tryptophan spurred the search for alternatives, resulting in the release of the products containing 5-HTP. While L-tryptophan can be metabolized into a variety of different chemicals within the body, 5-HTP can only be used for the production of serotonin. Consequently, 5-HTP is faster acting than L-tryptophan, potentially making it more suitable for the treatment of insomnia. Its effects, however, are shorter lasting than L-tryptophan, perhaps making it less suitable for the treatment of depression.
Free Serotonin
Since 5-HTP is the direct precursor to serotonin and cannot be made into anything else, virtually 100 percent of 5-HTP absorbed in the gut is converted to serotonin. L-tryptophan, by contrast, can be converted into niacin and other enzymes used by the body. It is important, however, to note that 5-HTP is converted into serotonin wherever it encounters L-aromatic amino decarboxylase, a compound found throughout the body. This serotonin has no effects on mood or sleep as it is unable to cross the blood-brain barrier. There has been no research into whether the free serotonin produced by 5-HTP supplementation may have unintended effects throughout the rest of the body before it is destroyed by monoamine oxidase.
Side Effects
According to the National Institutes of Health, these supplements may cause nausea, bloating or loss of appetite. It is important to consult with your doctor before taking these supplements as they may interact with a number of medications. According to the University of Maryland Medical Center, combining either of these supplements with antidepressant medications, cough syrups containing dextromethorphan, triptan migraine medications, carbidopa, Demerol, tramadol, or pentazocine may cause the potentially fatal serotonin syndrome.
References
- "Neurology"; Normalization of Brain Serotonin by L-Tryptophan in Levodopa-Treated Rats; S. Fahn, et al; September 1975
- University of Maryland Medical Center; Insomnia; December 2009
- National Center for Complementary and Alternative Medicine; Sleep Disorders and CAM At a Glance; September 2010
- MayoClinic.com; Tryptophan (Oral Route); May 2011
- University of Maryland Medical Center; 5-Hydroxytryptophan; December 2009
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