['The aim of this trial was to investigate the influence of a dietetic product consisting of a unique combination of L-arginine with the vitamins B', 'Subjects aged 40-65\xa0years with mild to moderate blood pressure (BP) elevation not treated with anti-hypertensive drugs were randomly assigned to either the dietetic product (n\xa0=\xa040) or a matching placebo (n\xa0=\xa041) for 3\xa0months with open follow-up for a further 3\xa0months. Postprandial change in endothelial function was assessed using the validated reactive hyperaemia index (RHI) at 3\xa0months compared to the study onset (RHI post-pre, visit 3-visit 1; ΔΔRHI). Secondary parameters included BP and plasma homocysteine concentration.', 'The primary efficacy analysis revealed superiority of the nutritional intervention over placebo (p\xa0=\xa00.0349) in reducing the deterioration of endothelial function. While in the active group ΔΔRHI increased (0.371 ±\xa00.122), almost no change could be detected in the placebo group (0.031\xa0±\xa00.100), thus demonstrating a significant improvement in vascular function in the intervention group. Moreover, the intervention reduced BP and homocysteine levels. Non-serious adverse events were equally distributed in both groups, and none of the events were assessed as possibly intervention-related by the investigators.'] Do l-Arginine and B vitamins improve endothelial function in subjects with mild to moderate blood pressure elevation?