L-tryptophan, also known simply as tryptophan, is an essential amino acid, so-called because your body cannot make it and must obtain it through food. Tryptophan occurs naturally in a variety of protein-rich foods and, like all other amino acids, plays a key role in your body’s synthesis of protein, which is needed to develop and repair cells. Tryptophan also has some unique properties that affect mood control, niacin synthesis and psychomotor function.
Tryptophan is one of 20 or so amino acids that collectively provide your body with the building blocks it needs to produce protein, essential for cell growth and maintenance. Tryptophan is one of the 10 essential amino acids, all of which work in collaboration with a similar number of nonessential amino acids -- produced in your body -- in the synthesis of protein. Failure to get enough dietary tryptophan or any one of the other essential amino acids can result in a breakdown of your body’s existing protein structures, including muscle. Your body is unable to store excess amino acids, and you must get a fresh supply of tryptophan and all other essential amino acids every day.
Although the jury is still out on the question of whether tryptophan supplementation can ease mood disorders, most notably depression, it’s clear that your body needs the amino acid to produce serotonin, a brain chemical closely linked to mood stability. However, studies on the effects of tryptophan supplements to treat mood disorders have produced inconsistent findings. In a review of existing studies, two Australian researchers found that while many depressed patients appear to have significantly lower tryptophan levels, it’s unclear whether that phenomenon represents a cause or a consequence of mood disorder. Writing in the December 2011 issue of “Acta Psychiatrica Scandinavica,” the researchers say further studies are needed to definitively determine whether tryptophan supplementation is an effective therapy for mood disorders.
Your body can convert tryptophan into niacin, a member of the B-complex family of vitamins that collectively facilitate the conversion of the food you eat into the energy your body needs to function normally. Niacin, also known as vitamin B3 and nicotinic acid, also promotes healthy nervous system function and helps in the production of sex and stress-related hormones. If your diet is low in niacin-rich foods but contains plenty of foods high in tryptophan, your body can convert tryptophan into nicotinic acid, one of two active forms of niacin, according to “Oxford Handbook of Nutrition and Dietetics.” Roughly half of your body’s niacin is synthesized from tryptophan.
Psychomotor Function and Memory
Tryptophan may help older people to maintain better psychomotor function and working memory, according to the findings of an international research team. Psychomotor function refers to movements directly related to cognitive function. Researchers found that acute tryptophan depletion was associated with impaired psychomotor function and memory among elderly test subjects, although younger test subjects displayed no such impairments when they were tryptophan-deprived. Researchers published their findings in a 2011 issue of “Journal of Psychopharmacology.”
- MedlinePlus: Tryptophan
- University of Maryland Medical Center: Tryptophan -- Overview
- The Biology Project: The Chemistry of Amino Acids
- Acta Psychiatrica Scandinavica: Mood Effects of the Amino Acids Tryptophan and Tyrosine
- Oxford Handbook of Nutrition and Dietetics; Joan Webster-Gandy, et al., Editors
- Journal of Psychopharmacology: The Effects of Acute Tryptophan Depletion on Neuropsychological Function, Mood and Movement in the Healthy Elderly
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