The effects of L-Citrulline on thermoregulation and vascular function

Abstract

Backround: Nitric oxide (NO) is a vital regulator of vascular function and relevant in conditions such as CVD and stroke. Supplementation to improve NO levels has proven difficult and supplementation with its precursor , L- Arginine, has given minor statistically significant results. L-Citrulline is a precursor of L-Arginine , supplementation of L-Citrulline above 1.5g has the potential to significantly improved vascular parameters. Within both animal and human trials L-Citrulline improves vascular function assessed through PWV, AIx and BP. Objectives : The aim of this study is to asses vascular response after supplementation of L- Citrulline (1.5g/day) compared to supplementation of Vitamin C placebo (120mg/day). Methods: A single blinded, randomised, placebo controlled, trial design was used with 16 normotensive participants that met inclusion/exclusion criteria. Participants were randomly allocated intervention or placebo for 2 weeks were assessed with Pulse wave velocity (PWV), Augmentation index (AIx) , Heart rate (Hr), Blood pressure(BP) and Sympathetic release test ( SRT). Intervention included 1.5g/day of L-citrulline and placebo included 120mg/day. Results : After two weeks SBP reduced significantly (P=0.01)within the intervention group, SBP was also reduced in placebo group,(P=0.05). Between baseline and follow-up sessions SRT found a significant difference in sympathetic release time highlighting improved vasodilation. (P=0.01). No significant changes in PWV, AIx or Hr were found in either arms. No significant differences in skin or aural temperature were found after two weeks in either group. Conclusion : This short term study highlights the significant effects of L-Citrulline on systolic blood pressure and sympathetic release time after a 2 week supplementation period.. Within other parameters; Hr, PWV and AIx no significant effect was found in either of the treatment arms. Larger population studies are needed to further understand any short term effects as well as whether these effects are dose dependant. This study also provides support for the use of SRT which should be considered for further research. Keywords: L-citrulline, Vitamin C, PWV, Sympathetic Release Test, Nitric oxide, Thermoregulation, haemodynamics.