title: Dietary tyrosine benefits cognitive and psychomotor performance during body cooling.
abstract: Supplemental tyrosine is effective at limiting cold-induced decreases in working memory, presumably by augmenting brain catecholamine levels, since tyrosine is a precursor for catecholamine synthesis. The effectiveness of tyrosine for preventing cold-induced decreases in physical performance has not been examined. This study evaluated the effect of tyrosine supplementation on cognitive, psychomotor, and physical performance following a cold water immersion protocol that lowered body core temperature. Fifteen subjects completed a control trial (CON) in warm (35 degrees C) water and two cold water trials, each spaced a week apart. Subjects ingested an energy bar during each trial; on one cold trial (TYR) the bar contained tyrosine (300 mg/kg body weight), and on the other cold trial (PLB) and on CON the bar contained no tyrosine. Following each water immersion, subjects completed a battery of performance tasks in a cold air (10 degrees C) chamber. Core temperature was lower (p=0.0001) on PLB and TYR (both 35.5+/-0.6 degrees C) than CON (37.1+/-0.3 degrees C). On PLB, performance on a Match-to-Sample task decreased 18% (p=0.02) and marksmanship performance decreased 14% (p=0.002), compared to CON, but there was no difference between TYR and CON. Step test performance decreased by 11% (p=0.0001) on both cold trials, compared to CON. These data support previous findings that dietary tyrosine supplementation is effective for mitigating cold-induced cognitive performance such as working memory, even with reduced core temperature, and extends those findings to include the psychomotor task of marksmanship.
authors.affiliation: Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA 01760, USA.
authors.forename: Catherine
authors.initials: C
authors.lastname: O'Brien
authors.forename: Caroline
authors.initials: C
authors.lastname: Mahoney
authors.forename: William J
authors.initials: WJ
authors.lastname: Tharion
authors.forename: Ingrid V
authors.initials: IV
authors.lastname: Sils
authors.forename: John W
authors.initials: JW
authors.lastname: Castellani
mesh_terms: D000222:Adaptation, Physiological; D000293:Adolescent; D000328:Adult; D001831:Body Temperature / Q000187:drug effects* / Q000502:physiology; D003071:Cognition / Q000187:drug effects* / Q000502:physiology; D003080:Cold Temperature; D019587:Dietary Supplements; D004193:Discrimination Learning / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000187:drug effects / Q000502:physiology; D011597:Psychomotor Performance / Q000187:drug effects* / Q000502:physiology; D012016:Reference Values; D018709:Statistics, Nonparametric; D014443:Tyrosine / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D014443:Tyrosine