Dietary nitrate (beetroot)

Dietary nitrate (NO₃⁻) is abundant in beetroot, leafy greens, and celery and is converted in the body to nitric oxide (NO) via a two-step cascade. Salivary glands concentrate circulating nitrate; bacteria on the tongue dorsum reduce it to nitrite (NO₂⁻), which is absorbed and further reduced to NO in blood and tissues — particularly under hypoxic conditions in working muscle and ischaemic endothelium. This entero-salivary pathway is distinct from the classical eNOS route and gains importance as eNOS activity declines with age (Lundberg, Weitzberg & Gladwin 2008). Kapil et al. (2015), randomised double-blind trial: 250 ml nitrate-rich beetroot juice daily for four weeks reduced systolic BP by ~8 mmHg and diastolic by ~4 mmHg in hypertensive adults, without significant adverse effects. Bailey et al. (2009): six days of beetroot juice supplementation cut the oxygen cost of moderate-intensity cycling by ~19% and extended time to exhaustion, attributed to more efficient mitochondrial respiration and lower ATP cost of contraction. The oral microbiome is mechanistically essential — antibacterial mouthwash that eliminates nitrate-reducing bacteria nearly abolishes plasma nitrite rise and haemodynamic effects, so antibiotic use and oral hygiene products directly modulate efficacy. Evidence in humans is strongest for acute BP lowering and exercise economy in non-elite populations; effects on all-cause mortality and longevity remain unproven in controlled trials.