title: Seasonal variation of the amino acid, L-tryptophan, in interior Alaska.
abstract: The seasonal pattern of L-tryptophan was studied in a Fairbanks, Alaska, population that was unadapted to the extreme light variations of the North. Previously, this population was shown to exhibit seasonal behavior effects such as increases in fatigue and sleep duration, as well as endocrine effects such as increases in melatonin levels and phase shifting. Caloric and macronutrient intake have been reported to vary seasonally in humans, thereby potentially influencing the plasma levels of L-tryptophan, which is a precursor of serotonin and melatonin. Plasma levels of L-tryptophan from volunteers, whose average duration of stay in Alaska was eight months, were determined by automated amino acid analysis. Prominent results included finding increased levels in the winter at several different diurnal time points. These findings support hypotheses which relate underlying physiological adaptations to the North to the increased incidence of behavioral disorders such as depression and alcoholism.
authors: Department of Psychiatry, Fort Sam Houston, Texas, USA.
authors: M E
authors: ME
authors: Levine
authors: L K
authors: LK
authors: Duffy
mesh_terms: D000328:Adult; D000413:Alaska; D000596:Amino Acids / Q000097:blood; D001110:Arctic Regions; D002845:Chromatography; D006801:Humans; D008297:Male; D012016:Reference Values; D012621:Seasons; D012737:Sex Factors; D014364:Tryptophan / Q000097:blood*
chemical_list: D000596:Amino Acids; D014364:Tryptophan