The influence of vitamin C on the interaction between acute mental stress and endothelial function.

Abstract

To determine whether orally administered vitamin C attenuates expected mental stress-induced reductions in brachial artery endothelial function as measured by flow-mediated dilation (FMD). Fifteen men (21±2years) were given 1000mg of vitamin C or placebo over two visits in a randomized, double-blinded, within-subject design. Acute mental stress was induced using the Trier Social Stress Test (TSST). Saliva samples for cortisol determination and FMD measures were obtained at baseline, pre-TSST, and 30 and 90-min post-TSST. An additional saliva sample was obtained immediately post-TSST. Cardiovascular stress reactivity was characterized by changes in heart rate (HR) and mean arterial pressure (MAP). A significant stress response was elicited by the TSST in both conditions [MAP, HR, and salivary cortisol increased (p<0.001)]. Overall FMD did not differ pre- vs. post-stress (time: p=0.631) and there was no effect of vitamin C (condition: p=0.792) (interaction between time and condition, p=0.573). However, there was a correlation between cortisol reactivity and changes in FMD from pre- to post-stress in the placebo condition (r 2=0.66, p<0.001) that was abolished in the vitamin C condition (r 2=0.02, p=0.612). Acute mental stress did not impair endothelial function, and vitamin C disrupted the relationship between cortisol reactivity and changes in FMD post-stress. This suggests that acute mental stress does not universally impair endothelial function and that reactive oxygen species signaling may influence the interaction between FMD and stress responses.