L-Citrulline Supplementation Does Not Affect Blood Pressure and Arterial Stiffness at Rest and During Isometric Exercise in Older Adults

Hypertension and arterial stiffness are the main factors contributing to cardiovascular disease. L-citrulline, a nitric oxide precursor, has been proposed as a blood pressure-lowering intervention. This study aimed to investigate the impact of L-citrulline on central and peripheral blood pressure, arterial stiffness, and muscle oxygenation at rest and during an isometric knee extension exercise protocol. Twelve older males received 6 g of L-citrulline or a placebo for six days using a double-blind crossover design. Blood hemodynamics parameters (i.e., arterial and brachial systolic and diastolic blood pressure, mean arterial pressure, pulse pressure, heart rate), arterial stiffness (i.e., augmented pressure, augmentation index, forward, backward wave pressure and carotid-femoral pulse wave velocity) and muscle oxygenation [i.e., oxyhemoglobin (Δ[O2Hb]) and deoxyhemoglobin (Δ[HHb]), total hemoglobin concentration (Δ[tHb]) and tissue saturation index (TSI%)], were measured at baseline, post-supplementation and during isometric exercise. No significant effects of L-citrulline supplementation were observed at rest or during exercise on blood pressure, arterial stiffness, and muscle blood flow. Both central and peripheral blood pressure were increased during the exercise, which is consistent with isometric contractions. The results of the present study question the efficacy of short-term L-citrulline in decreasing blood pressure at rest or attenuating blood pressure increases during isometric exercise.