Impact of Acute and Chronic Red Beetroot Juice Consumption on Postprandial Endothelial Function and Levels of Nitrate/Nitrite in Plasma and Saliva (P06-113-19)

Abstract

ObjectivesHigh-fat meal (HFM) consumption has been shown to impair postprandial endothelial function. Red beetroot juice (RBJ) contains polyphenols, betalains, carotenoids, ascorbic acid, and inorganic nitrate, and has been shown to improve endothelial function. This study investigated the acute and chronic effects of RBJ and its bioactive components on postprandial endothelial function. We hypothesized that a HFM would impair postprandial endothelial function, and that RBJ would attenuate this, in part, through increased circulating nitrate/nitrite (NOx) levels. MethodsA 4-period randomized, double-blind, placebo-controlled crossover clinical trial was conducted. Fifteen overweight and obese middle-aged/older men and postmenopausal women underwent baseline (T0) assessment of endothelial function (via reactive hyperemia index, RHI) and collection of blood and saliva. Participants consumed one of the following 70 mL treatments (acute exposure): 1) RBJ, 2) nitrate-free RBJ (NF-RBJ), 3) placebo + nitrate (PBO + NIT), and 4) placebo (PBO), followed by a HFM. RHI was measured at 4 hours (T4) post-HFM, and blood and saliva were collected at 1 hour (T1), 2 hours (T2), and T4. Participants then consumed treatments daily for 4 weeks (chronic exposure), and all assessments were repeated before/after the HFM but without consuming treatments. ResultsNo significant time or treatment effects were observed for RHI. Following acute and chronic exposure to RBJ and PBO + NIT, plasma NOx levels were higher at T0 (chronic only), T1, T2, and T4 compared to PBO and NF-RBJ (P < 0.001). After chronic exposure to RBJ, saliva NOx levels were higher at T0, T1, T2, and T4 compared to PBO and NF-RBJ (P < 0.001). Saliva NOx levels for PBO + NIT were higher than both PBO and NF-RBJ at T0 (P < 0.001), but only higher than NF-RBJ at T1 (P = 0.02), and higher than PBO at T4 (P = 0.02). Additionally, there was a time*treatment interaction for plasma and saliva NOx levels following 4 weeks of daily exposure to RBJ and PBO + NIT (P < 0.001). ConclusionsThe preliminary results of this study suggest that HFM consumption does not significantly impair postprandial endothelial function in this population. In addition, acute and chronic RBJ exposure does not significantly improve endothelial function despite increases in plasma and saliva NOx. Funding SourcesColorado Agricultural Experiment Station, NIFA, USDA.