Testing the Efficacy of Administering Tyrosine for Reducing Environmental Stress (Cold) in Women

摘要

We exposed 18 lean, lightly-clothed women, who were users of oral contraceptives, to cold air to create a stressful situation for evaluating the effects of supplemental tyrosine upon subjective reactions and mental performance. We studied these women, during days 15-26 of their pseudomenstrual cycles, when concentrations of plasma tyrosine would be least and supplemental tyrosine might be most beneficial. Participants were exposed twice to 70C air for 90 min. Tyrosine or maltodextrin (placebo) was incorporated into a specially-developed nutrient bar; tyrosine supplementation (9.3 g) was double blinded. A third condition, 230C and placebo, was a baseline for temperature. We evaluated participants' symptomatology, moods, and cognitive performances with laptop computers; determined plasma levels of tyrosine, epinephrine, norepinephrine, and cortisol; and recorded skin and body temperatures and heart rate. Our nutrient bar methodology was a feasible way to administer the supplemental nutrient, tyrosine, double-blinded. Tyrosine improved ratings of Clear Thinking after 86.5 min of cold exposure. Eight subjective states were affected by cold; only Clear Thinking was improved by tyrosine. Supplemental tyrosine did not improve any measures of mental performance. Substantial cold stress was documented; however, it remains to be determined if the stressful conditions were adequate for a definitive evaluation of supplemental tyrosine.