Acute ingestion of 6 g or 12 g citrulline malate did not significantly improve brachial artery flow-mediated dilation at 60 or 120 minutes compared to placebo in healthy young males (p > 0.3).
RCT (n=12)
Double-blind
Randomized, counterbalanced order
No
Does acute supplementation with citrulline malate improve flow-mediated dilation in healthy young males?
Acute supplementation with up to 12 g of citrulline malate does not significantly enhance flow-mediated dilation in healthy young males, despite marked increases in serum markers favorable to nitric oxide production.
Effect estimate: No significant interaction or main effect; p = 0.315 for interaction, p = 0.301 for dose effect, p = 0.649 for time effect
p-value: p = 0.315 interaction, p = 0.301 dose, p = 0.649 time
Introduction The use of ergogenic compounds has gained increasing popularity among individuals who wish to improve performance and recover faster from their workouts. Among these products is citrulline malate (CitMal), a popular dietary supplement that is suggested to enhance nitric oxide (NO)-mediated vasodilation and muscle blood flow. Methods To evaluate effects on arterial function, flow-mediated dilation (FMD) of the brachial artery during active hyperemia was measured in 12 healthy, recreationally active males (23 ± 3 years) before and after (60- and 120-min post) consuming either 6 g CitMal, 12 g CitMal, or a taste-matched placebo. The study used a randomized, double-blind, placebo-controlled, within-subject counterbalanced crossover design with ≥7-day washouts. Results Repeated measures ANOVA revealed no significant interaction (p = 0.315) or time effect (p = 0.649) in corrected FMD% at 60- and 120-min after intake of placebo, 6 g CitMal, and 12 g CitMal. There were also no significant differences (p = 0.301) between doses at any timepoint. A subgroup of six participants completed two additional visits to assess the effect of CitMal ingestion on serum markers involved in NO production. Over 120-min post-consumption, both doses significantly increased peak serum concentrations of citrulline (6 g: 504.7 ± 139.7; 12 g: 881.9 ± 216.7 μM), arginine (6 g: 70.2 ± 20.4; 12 g: 101.8 ± 36.2 μM), and ornithine (6 g: 27.9 ± 14.2; 12 g: 56.5 ± 30.0 μM) from baseline (all p 0.001), with greater increases following 12 g (all p 0.05). Likewise, arginine-to-dimethylarginine ratios (SDMA and ADMA) increased from baseline (SDMA, 6 g: 114.1 ± 24.2; 12 g: 166.2 ± 43.7; ADMA, 6 g: 119.2 ± 31.8; 12 g: 169.1 ± 29.1; all p 0.001), with greater increases following 12 g (p 0.05). Discussion Collectively, these findings suggest that neither 6 g nor 12 g of CitMal significantly enhance FMD within 120 min, despite marked increases in biochemical markers favorable to NO production. To our knowledge, this is the first study to compare acute doses of CitMal up to 12 g in relation to brachial artery FMD. These results indicate that acute vascular responses to CitMal may be limited by physiological ceiling effects and that potential vascular benefits may depend on longer-term supplementation, the presence of an exercise stimulus, or populations with impaired endothelial function.
Grannes et al. (Fri,) conducted a rct in Healthy, recreationally active young adult males (mean age 23 ± 3 years) with normal BMI and no known medical conditions (n=12). Citrulline malate vs. Taste-matched placebo was evaluated on Corrected flow-mediated dilation percentage (corrected FMD%) of brachial artery at 60 and 120 minutes post ingestion (No significant interaction or main effect; p = 0.315 for interaction, p = 0.301 for dose effect, p = 0.649 for time effect, p=p = 0.315 interaction, p = 0.301 dose, p = 0.649 time). Acute ingestion of 6 g or 12 g citrulline malate did not significantly improve brachial artery flow-mediated dilation at 60 or 120 minutes compared to placebo in healthy young males (p > 0.3).