Effect of Oral Caffeine and L-Citrulline Supplementation on Arterial Function in Healthy Males
Status:
Completed
Trial end date:
2014-03-01
Target enrollment:
Participant gender:
Summary
Caffeine is an exceedingly popular and consumed pharmacological agent. Although caffeine is
primarily consumed from coffee and tea beverages, it is also available in other forms such as
sodas, energy drinks, tablets and capsules. Nevertheless, caffeine acutely increases brachial
and aortic systolic blood pressure (BP) and arterial stiffness. Arterial stiffness is an
independent predictor of cardiovascular disease (CVD) and assessed through pulse wave
velocity (PWV). Interestingly, previous studies have proposed that caffeine may increase
aortic BP through increases in aortic PWV and augmentation index (AIx), a measurement of wave
reflection. Yet, these effects were seen in middle-aged adults with treated hypertension and
a wide age range. Therefore, it is imperative to consider that caffeine may cause different
effects in young normotensive individuals than in older adults independently of BP levels.
Importantly, oral supplementation of the amino-acid, L-citrulline has been shown to enhance
the bioavailability of L-arginine levels and nitric oxide (NO) production and, therefore,
improve arterial function. L-citrulline supplementation for 7 days given at 6 g/day has shown
to increase NO levels while improving PWV. Previous studies by our group also demonstrated
that L-citrulline supplementation reduces the BP response to cold exposure; a condition with
an increased vasoconstriction. Therefore, the acute effects of caffeine on central and
peripheral PWV and BP in healthy young men are yet to be fully evaluated. We hypothesized
that acute caffeine intake would increase peripheral and aortic BP and PWV and that
L-citrulline supplementation would attenuate the effects induced by acute caffeine ingestion.