Review of Dietary Nitrate and Cardiovascular Health

Introduction

Researchers in Australia conducted a comprehensive review of existing studies examining the relationship between dietary nitrate intake and cardiovascular health. Cardiovascular diseases, including heart disease and stroke, are leading causes of morbidity and mortality globally. Large population studies have indicated that diets high in vegetables, particularly green leafy varieties, correspond to a reduced incidence of these diseases.

Focus on Dietary Nitrate

A significant amount of research has sought to identify the specific components in vegetables that contribute to improved cardiovascular health. Recently, dietary nitrate has gained attention due to its presence in varying concentrations across all vegetables. This nitrate intake serves as a biological pathway for producing nitric oxide (NO) within the body.

The Role of Nitric Oxide

Nitric oxide is a crucial molecule for maintaining vascular health. It relaxes smooth muscles in blood vessel walls, enhancing blood flow, and it reduces the “stickiness” of certain blood components, which may slow the progression of atherosclerosis, or hardening of the arteries.

Findings from the Systematic Review

The researchers published their findings in the American Journal of Clinical Nutrition in April 2018. They meticulously searched the medical literature, identifying 37 human studies and 14 animal studies that explored the effects of dietary nitrate on cardiovascular health.

Effects of Dietary Nitrate on Vascular Function

Several experimental intervention studies assessed how dietary nitrate impacts blood pressure, arterial stiffness, endothelial function (the health of artery linings), platelet function (related to blood clotting), and cerebral blood flow. The results indicated that nitrate consumption lowered blood pressure and improved endothelial function in healthy individuals. However, the researchers noted that most studies focused on healthy subjects and were of relatively short duration, with few examining high-risk cardiovascular patients, leading to inconclusive results.

Population Studies on Dietary Nitrates

While there is evidence linking diets rich in green leafy vegetables to better cardiovascular health, it remains unclear whether this is attributable to their nitrate content. There are limited population studies specifically addressing nitrate intake in relation to cardiovascular disease.

Two studies conducted by the reviewers in Australia suggested that increased nitrate consumption could reduce atherosclerosis and the risk of stroke in older women. To aid future population studies on dietary nitrate intake, the reviewers have established a reference database detailing the nitrate content in various vegetables.

Conclusion and Future Directions

Experimental evidence supports the notion that dietary nitrate from vegetables can lower blood pressure and enhance vascular function in healthy individuals. However, there is a scarcity of evidence regarding at-risk populations, highlighting the need for long-term observational studies. Additional animal studies may further elucidate the mechanisms by which dietary nitrate influences cardiovascular health.

Reference

Blekkenhorst LC, Bondonno NP, Liu AH, et al. Nitrate, the oral microbiome, and cardiovascular health: A systematic literature review of human and animal studies. Am J Clin Nutr 2018;107:504-522. https://doi.org/10.1093/ajcn/nqx046