Serotonin is a neurotransmitter, or chemical messenger, used by your body for a wide variety of physiologic processes. Serotonin is not found in foods, so it must be manufactured in your cells from precursors acquired from your diet. Several neurotransmitters, including serotonin, are synthesized from amino acids, which are nitrogen-containing molecules commonly used to build proteins, enzymes and other useful compounds. According to "The Merck Manual of Diagnosis and Therapy," serotonin is generated from L-tryptophan, an essential amino acid. Your physician can help you decide if more L-tryptophan could be beneficial for you.
Synthesis
L-tryptophan is classified as an essential amino acid because it cannot be manufactured from other substances in your body and must be obtained from your diet. In a two-stage process, L-tryptophan is converted to serotonin in your brain and in specialized cells in the wall of your gastrointestinal tract. In the first step, an enzyme called L-tryptophan hydroxylase converts L-tryptophan to 5-hydroxytryptophan, or 5-HTP. Serotonin is then generated from 5-HTP by another enzyme, aromatic amino acid decarboxylase. Some of the serotonin produced by your intestine is released into your bloodstream, where it is captured and stored by platelets.
Actions
At least 15 different types of serotonin receptors have been identified in humans. The specific actions of many of these receptors have not been defined, but serotonin is known to affect intestinal motility and digestion, blood vessel diameter, bone metabolism, blood clotting, wound healing, reproductive behavior, sleep cycles, mood, appetite, aggression, perception and memory. With such wide-ranging effects, it is no wonder that many drugs used to treat anxiety, depression, fibromyalgia, obesity and other disorders are designed to target serotonin receptors. Adding serotonin precursors to your diet may help to increase serotonin levels in your tissues.
Sources
In his book "Staying Healthy with Nutrition," Dr. Elson Haas states that the dietary intake of L-tryptophan of most people is lower than that of other amino acids because this nutrient is not particularly prevalent in many foods. However, it is found in reasonable amounts in animal foods, such as poultry, fish, eggs and dairy products, and it can be found in many nuts, seeds and legumes. Both L-tryptophan and 5-HTP, the precursors of serotonin, are available as supplements.
Considerations and Recommendations
L-tryptophan, an essential amino acid, is required for serotonin synthesis. The many actions in your body that use serotonin attest to its importance, and drugs that stimulate or block serotonin receptors or enhance serotonin concentrations in your tissues are commonly used to treat depression, anxiety, obesity, fibromyalgia and other disorders. Supplemental L-tryptophan, in doses of 500 to 2,000 mg daily, or 5-HTP, in doses of 50 to 100 mg daily, may help to increase your levels of serotonin. Check with your doctor to see if you need more serotonin.
References
- "The Merck Manual of Diagnosis and Therapy, 18th Edition"; Major Neurotransmitters and Receptors; Mark H. Beers, M.D., ed.; 2006
- University of Arizona; The Biology Project: The Chemistry of Amino Acids; September 2003
- "Staying Healthy with Nutrition"; Tryptophan; Elson M. Haas, M.D.; 2006
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