Acute dietary nitrate supplementation does not change venous volume and compliance in healthy young adults

In this crossover study, we investigated the influence of inorganic nitrate ([Formula: see text]) supplementation on venous volume and compliance in the resting forearm and calf. Twenty healthy young adults were assigned to receive an [Formula: see text]-rich beverage [beetroot juice (BRJ): 140 mL; ∼8 mmol [Formula: see text]] or an [Formula: see text]-depleted control beverage [prune juice (CON): 166 mL; < 0.01 mmol [Formula: see text]). Two hours after consuming the allocated beverage, each participant rested in the supine position for 20 min. Cuffs were then placed around the right upper arm and right thigh, inflated to 60 mmHg for 8 min, and then decreased to 0 mmHg at a rate of 1 mmHg/s. During inflation and deflation of cuff pressure, changes in venous volume in the forearm and calf were measured by venous occlusion plethysmography. Venous compliance was calculated as the numerical derivative of the cuff pressure-venous volume curve in the limbs. The plasma [Formula: see text] concentration was elevated by intake of BRJ (before, 15.5 ± 5.8 µM; after, 572.0 ± 116.1 µM, P < 0.05) but not by CON (before, 14.8 ± 7.2 µM; after, 15.3 ± 7.4 µM, P > 0.05). On the other hand, there was no significant difference in venous volume or compliance in the forearm or calf between BRJ and CON. These findings suggest that although acute inorganic NO₃^- supplementation may enhance the activity of nitric oxide (NO) via nitrite → NO pathway, it does not influence venous volume or compliance in the limbs in healthy young adults.