Nitrate and Nitrite Concentrations in Fingertip Serum Following Beetroot Juice Ingestion Correlate with Those in Venous Plasma.

Dietary nitrate (NO) supplementation can offer health benefit and improve exercise performance by increasing nitric oxide (NO) through NO-nitrite (NO)-NO pathway. Individuals may benefit from dietary NO supplementation by monitoring blood [NO] and [NO], although a simple and practical method for assessing blood [NO] and [NO] has not been established. We examined whether fingertip serum samples could substitute for venous plasma samples in assessing [NO] and [NO]. Ten young adults consumed 140 mL of nitrate-rich beetroot juice. Fingertip serum and venous plasma samples were collected at baseline and every hour for up to 4 h after ingestion. [NO] and [NO] were similar between samples at baseline, whereas they were higher in fingertip serum throughout the post-ingestion periods. Significant correlations existed between fingertip serum vs. venous plasma for both [NO] and [NO] throughout post-drink periods, except [NO] assessed at 2 and 4 h after ingestion of beetroot juice. We show that although fingertip serum [NO] and [NO] overestimate those measured by venous plasma after dietary NO intake (125-141% and 156-183% of venous values), [NO] and [NO] in fingertip serum samples may be utilized for assessing blood [NO] and [NO] levels, although [NO] assessment may lack precision compared to [NO].