Nitric oxide is the primary signalling molecule for vascular dilation. Endothelial cells lining blood vessels produce nitric oxide to regulate blood vessel tone, blood pressure, platelet aggregation, and blood flow. With age, endothelial nitric oxide production declines, contributing to rising blood pressure and reduced cardiovascular capacity. Dietary nitrates from specific vegetables provide an alternative pathway to nitric oxide production that bypasses the age-related decline in endothelial function.
The Nitrate-Nitrite-Nitric Oxide Pathway
Inorganic nitrate from vegetables is absorbed in the upper gastrointestinal tract and concentrated in saliva. Bacteria in the mouth reduce nitrate to nitrite, which is swallowed and further reduced to nitric oxide in the stomach and tissues under low-oxygen conditions. This is why mouthwashes that kill oral bacteria significantly reduce the cardiovascular benefit of dietary nitrate intake. The pathway is sensitive to both the vegetable source and the integrity of the oral microbiome.
The Blood Pressure Evidence
A meta-analysis of randomised controlled trials found that dietary nitrate supplementation, primarily through beetroot juice, reduced systolic blood pressure by an average of 4.4 mmHg and diastolic blood pressure by 1.1 mmHg. These are clinically meaningful reductions equivalent to the blood pressure effect of moderate aerobic exercise training. The effect is most pronounced in adults with elevated blood pressure.
- Highest dietary nitrate vegetables: spinach, rocket, celery, beetroot, Swiss chard, and lettuce
- Aim for at least one high-nitrate vegetable daily
- Raw consumption or light steaming preserves more nitrate than boiling
- Do not use antibacterial mouthwash immediately before or after eating high-nitrate vegetables: it eliminates the oral bacteria that perform the first conversion step