Background: Through effects on nitric oxide bioavailability, vascular endothelial function is improved after the intake of a high amount of nitrate or L-arginine, but decreased after the intake of a high-fat meal. Therefore, we compared the effects of beetroot powder with or without L-arginine on postprandial brachial artery flow-mediated vasodilation (FMD) after consumption of a high-fat mixed-meal.
Methods: Eighteen abdominally obese men completed this randomized, double-blinded, cross-over trial. The study consisted of five test days, each separated by a wash-out period of at least one week. Participants received in random order, a blended meal with a control or nutritional supplement consisting of beetroot powder providing 200 mg nitrate, beetroot with 0.8 g of L-arginine, beetroot with 1.5 g of L-arginine, or 3.0 g of L-arginine. Participants then fasted and 2 h postprandial FMD measurements were performed.
Results: No significant differences between meals were observed for postprandial FMD (p = 0.45) levels. However, there was a non-significant trend towards a more beneficial postprandial FMD response with the beetroot-containing meals as compared with meals without beetroot.
Conclusion: This trial could not provide evidence for beneficial additive effects of a single dose of beetroot powder combined with L-arginine on postprandial endothelial function in abdominally obese men.
Keywords: L-arginine; beetroot; dietary nitrate; endothelial function; flow-mediated vasodilation; nitric oxide.