| The purpose of this study was to determine the effects of a 600 mg dose of soy phosphatidylserine (PS) on cortisol, growth hormone and testosterone response to moderate intensity exercise. Previous research and pilot data indicate an 800 mg dose of soy PS has been effective at attenuating cortisol without adversely affecting growth hormone or testosterone responses to moderate intensity exercise. The lowest effective dose of soy PS has not been determined. A step-down approach to aid in determining a possible lower effective dose was employed by using a 600 mg dose of soy PS. To study the effects, volunteers (N = 9) were recruited to participate and received a placebo and a 600 mg dose of soy PS administered in a double-blind crossover design. The participants recruited were males ages 18 to 35 from The University of Mississippi faculty, staff, and student population. The participants underwent a familiarization session and two experimental sessions. The experimental sessions consisted of a resting phase, a moderate intensity exercise on a bicycle beginning at 65% up to 85% VO2max for 15 minutes in five 3-minute incremental stages, and a recovery phase. Blood samples were taken at specific time intervals throughout the experimental sessions to determine hormonal responses. Pre- and post-supplementation test measures were assessed for cortisol (C), growth hormone, testosterone (T), lactate (L) and T/C ratio using a two-way repeated measures analyses of variances (RMANOVAs) for treatment (soy PS, placebo) by time (-30, 0, 15, 20, 30, 40, 60, & 80 minutes). A Student's paired t-test was performed on the mean T/C ratio. The alpha level for all statistical analysis was set a priori at p = 0.05. Treatment with 600 mg/d PS showed no significant differences for GH, T, L, and T/C ratio. Treatment with PS 600 mg/d resulted in a lower C level showing a significant effect for treatment (F = 12.2, p = 0.008). The final results failed to reject the hypothesis that there will be no significant difference between pre-and post-supplementation exercise-induced response of cortisol. |
