The Effect Of 5-hydroxytryptophan (5-htp) And Intense Exercise On Plasma And Salivary Cortisol

Abstract

Background: Oral administration of 5-hydroxytryptophan (5-HTP), the precursor of serotonin, has been reported to stimulate the Hypothalamic-Adrenal Axis resulting in increased cortisol in healthy volunteers and clinical populations. Exercise is known to stimulate the cortisol secretion, whether pre-exercise 5-HTP enhances the cortisol response to intense exercise is not yet known. PURPOSE: The purpose of this study was to examine the effect of 5-HTP and a graded exercise test to maximal effort (EX) on plasma (PL) and salivary(SA) cortisol in 9 healthy young volunteers (7M/2F). METHODS: Each subject completed an EX trial in the evening spaced at least 5 days apart, one under placebo and another under 5-HTP (200mg capsule 90-120 min prior to testing). The study was randomized double-blinded trial. Capillary and SA samples were obtained at rest before exercise (EX0), at 5 (Post-EX5) and at 20 (Post-EX20) minutes post-exercise. An ANOVA for crossover experimental design and t-tests were used to determine differences in PL and SA cortisol concentrations between placebo vs 5-HTP trials, and to determine if plasma and salivary cortisol increased over time, respectively. Cortisol was analyzed by enzyme immunoassays. RESULTS: There was a significant increase in plasma cortisol in the placebo (EX0: 265 ± 67 nM vs Post-EX20: 664 ± 78 nM; p<0.001) and in the 5-HTP trial (EX0: 349 ± 58 nM vs Post-EX20: 567 ± 81 nM, p< 0.001). Similarly, there was a significant increase in SA cortisol in the placebo (EX0: 1.26 ± 0.20 nM, Post-EX20: 8.63 ± 1.96 nM; p<0.01) and in the 5-HTP trial (EX0: 3.96 ± 1.73 nM vs Post-EX20: 9.57 ± 2.96 nM, p< 0.01). However, there was no treatment effect for cortisol in either media nor was there a treatment effect at baseline (p>0.05). CONCLUSIONS: Under the present experimental conditions, there was no difference between placebo and 5-HTP. There was an increase from EX0 to Post-EX20 for both placebo and 5-HTP. Increasing sample size, and examining higher 5-HTP dosage regimen are warranted.