Evaluating the impact of short-term nitrate-rich dietary supplementation on endothelial function in COPD: A randomized crossover study

Aim: This study aimed to investigate the acute effects of dietary nitrate ingestion through L-arginine supplementation or dehydrated beet consumption on endothelial function in chronic obstructive pulmonary disease (COPD) patients. The secondary outcome was to analyze arterial stiffness, plasma nitrate, and nitrate/protein concentration. Methods: In this randomized crossover study, subjects with COPD underwent three series of supplementation: (1) L-arginine, (2) dehydrated beetroot, and (3) a placebo that appeared like the other supplements. Each intervention lasted 14 days, with a 7-day washout period between series. Participants underwent endothelial function assessment using flow-mediated dilatation (FMD), and plasma nitrate levels were measured at the end of each supplementation series. Results: Seventeen subjects (twelve male) completed the study protocol. Only five subjects presented endothelial dysfunction (RHI <= 0.51) at baseline. The mean baseline characteristics included age 66.5 +/- 9.4 years, BMI 27.5 +/- 4.5 kg/m(2), FEV1, 0.79 (0.67-1.06) L. There were no differences (p > 0.05) between the groups or from pre-to post-interventions for RHI and arterial stiffness index (AIx) values, as well as parameters of endotheliumdependent vasodilation, such as blood flow velocity (BFV), shear stress, shear rate, FMD (mm), and FMD%. There was also no differences (p > 0.05) between the groups or from pre-to post-interventions plasma nitrate levels. Conclusions: Acute dietary supplementation with nitrates, at the doses provided, did not show a significant improvement in endothelial function assessed by FMD, EndoPAT, or plasma nitrate levels in COPD. These findings suggest that a higher dose or prolonged supplementation might be required to achieve a therapeutic effect.