Six weeks of daily consumption of a nitrate-rich beetroot juice produced significant increases in flow mediated dilation (FMD), a measure of blood flow and vascular health, according to results of a randomized, double-blind, placebo-controlled parallel study.
Changes to the microbiome in the mouth were also reported by the researchers in the American Journal of Clinical Nutrition.
“In this 6-week trial of daily inorganic nitrate (beetroot juice) ingestion compared with intake of a low-nitrate placebo in patients with hypercholesterolemia, a rise in circulating nitrite was associated with an approximate 24% improvement in the primary outcome measure of the FMD response together with improvements in measures of arterial stiffness. These improvements compared with an approximate 6% decline in the FMD response in the placebo cohort,” wrote the researchers, led by Amrita Ahluwalia from the Queen Mary University of London.
“This effect was also associated with reductions in circulating platelet-monocyte aggregates numbers and reduced platelet P-selectin expression.
“Together, these data intimate that dietary nitrate might be useful in improving vascular and platelet functions in hypercholesterolemic patients.”
The study adds to a growing body of science supporting the potential cardiovascular benefits of beetroot juice, linked to the nitrate content.
Until relatively recently nitrate – which is abundant in green leafy vegetables – had been considered merely as an inert end product of nitric oxide (NO) metabolism or as a potentially toxic constituent in our diet.
However, the last decade has brought understanding of its importance in biological processes, including regulation of blood flow, blood pressure, cellular signaling, glucose homeostasis, and tissue responses to low oxygen levels (hypoxia). In addition, epidemiological studies have linked the intake of green leafy vegetables to a reduction in the risk of cardiovascular disease.
The new study included 67 people with elevated cholesterol levels (hypercholesterolemia) who were randomly assigned to receive 250 mL per day of either nitrate-rich beetroot juice or nitrate-depleted beetroot juice (placebo) for six weeks. Both drinks were provided by James Whites Drinks.
Results showed that participants in the nitrate group had an absolute increase in the FMD response of 1.1%, with an improvement from the start of the study of about 24%. Absolute FMD decreased by 0.3% in the nitrate-depleted beetroot juice group.
A small but significant decrease in platelet-monocyte aggregates was also observed in the nitrate-rich group, whereas a 10% increase was reported for the placebo group.
Changes were also observed for the salivary microbiome, with changes in the proportions observed for 78 bacterial taxa, with increases in N. flavescens and R. mucilaginosa specifically noted by the researchers.
“These findings intimate a shift in the oral microbiome in favor of organisms that are capable of nitrate reduction,” they wrote.
“In conclusion, this study supports the use of dietary nitrate as a safe, well-tolerated, and potentially powerful prevention strategy in CVD in individuals with early vascular dysfunction. This strategy is evidenced by improvements in FMD, vascular stiffness, and the platelet inflammatory profile. Long-term outcome studies are required to test the merits of a dietary nitrate strategy.”
Source: American Journal of Clinical Nutrition
Published online ahead of print, doi:10.3945/ajcn.115.116244
“Dietary nitrate improves vascular function in patients with hypercholesterolemia: a randomized, double-blind, placebo-controlled study”
Authors: S. Velmurugan, et al.