Effects of L‐citrulline on Blood Pressure Response to Exercise in Older and Younger Adults
Authors: Ashley John Devin , Kellawan Jeremy M. , Gonzales Joaquin U. 
Published: June 2021

IntroductionIn humans, L‐citrulline (Cit) supplementation has been shown to increase production of the vasodilator nitric oxide (via arginine), reducing resting mean arterial blood pressure (BP) in several populations. However, there is limited research on the effect Cit has on BP immediately following exercise. Therefore, this study sought to determine the effect Cit can have on BP response to exercise in young and old healthy adults. We hypothesized Cit would reduce BP in both older (Old) and younger (Young) adults, with a greater reduction observed in Old.MethodsTwenty‐six adults, ages of 20–35 years (n=15) and 64–86 years (n=11), completed a 7‐day randomized, double‐blind placebo (Pl) controlled, crossover study with L‐citrulline (6 g/day) and a 14‐day washout. Participants were healthy, un‐medicated, recreationally fit, non‐smokers, and not obese (BMI < 30 kg/m2). Systolic and diastolic pressure measurements were taken pre and post treatments, and used to calculate BP. Resting BP was measured in quadruplicate during the 5 minutes prior to exercise. The two lowest measurements were averaged to represent resting BP. Immediately following exercise, BP was measured in duplicate, with these values averaged to represent post exercise BP. All BP measurements were completed while standing with the left arm just below the heart using an ambulatory pressure device (Oscar 2, AtCor Medical). Subjects completed two, 6‐min exercise protocols at 0% grade. One absolute (1.03 m/s) and one relative intensity (40% HR reserve, HRR) separated by 20‐min rest. HRR was calculated by subtracting measured standing resting HR using a Polar monitor, from age‐predicted HRmax (220‐age for Young, [208‐(0.7*age)] for Old). The BP response was calculated by subtracting resting BP from immediately post exercise BP (Δ mmHg).ResultsMean ± SEM. Pl and Cit did not affect resting BP in Young (p=0.40, 88 ± 2 vs. 88 ± 2 mmHg, pre vs. post Pl; 89 ± 2 vs. 87 ± 3 mmHg, pre vs. post Cit). Resting BP was also unaffected in Old (p=0.27, 95 ± 3 vs. 94 ± 3 mmHg, pre vs. post Pl; 98 ± 3 vs. 94 ± 2 mmHg, pre vs. post Cit). In Young, Pl or Cit did not alter BP responses to exercise at an absolute (p=0.93, Δ1.4 ± 3 vs. Δ3.4 ± 1 mmHg, pre vs. post Pl; Δ3.7 ± 1 vs. Δ5.9 ± 1 mmHg, pre vs. post Cit) or relative intensity (p=0.39, Δ19 ± 4 vs. Δ18 ± 3 mmHg, pre vs. post Pl; Δ19 ± 4 vs. Δ21 ± 4 mmHg, pre vs. post Cit). Surprisingly, BP responses to absolute (p=0.32, Δ12 ± 3 vs. Δ10 ± 3 mmHg, pre vs. post Pl; Δ15 ± 3 vs. Δ11 ± 3 mmHg, pre vs. post Cit) or relative (p=0.74, Δ4.0 ± 2 vs. Δ3.9 ± 2 mmHg, pre vs. post Pl; Δ0.7 ± 4.7 vs. Δ−1.7 ± 4.6 mmHg, pre vs. post Cit) intensity exercise were unaltered by Pl or Cit in Old.ConclusionThe main finding of this study was that Cit did not affect exercise pressure response in Old or Young during the same absolute speed or relative intensity. Therefore, 7‐days of Cit supplementation does not alter BP response to absolute or relative exercise intensities in adults.Support or Funding InformationWork supported by an American Heart Association Beginning Grant‐in‐Aid (award number 15BGIA22710012 to J.G.)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.