Nitrate and nitrite in health and disease

Summary

This narrative review examines the physiological pathway and biological functions of dietary nitrate, primarily sourced from green leafy vegetables. The paper documents the discovery of sialin as the mammalian nitrate transporter and explains the mechanism by which dietary nitrate is converted to nitrite and nitric oxide in the body. The authors argue that dietary nitrate serves as an important endogenous NO reservoir, particularly valuable under hypoxic and ischaemic conditions where conventional L-arginine-dependent NO synthesis is impaired, challenging the earlier assumption that nitrate and nitrite were solely carcinogenic compounds.

Regional applicability

The mechanistic and nutritional findings are universally applicable to UK populations consuming nitrate-rich vegetables. UK dietary guidelines and public health messaging around leafy greens could benefit from emphasis on the bioavailable nitrate content and its cardiovascular and metabolic benefits, particularly relevant to populations at risk of vascular disease.

Key measures

Dietary nitrate source (leafy vegetables), absorption via intestinal mucosa, salivary gland concentration and secretion, conversion to nitrite by oral commensal bacteria, conversion to nitric oxide (NO), endogenous NO production from L-arginine, exogenous NO₃⁻-NO₂⁻-NO pathway activity

Outcomes reported

The review describes the sources, absorption, circulation, and bioconversion of dietary nitrate to nitrite and nitric oxide, and examines their physiological roles in human health. It addresses the shift in scientific understanding from viewing nitrate/nitrite as carcinogenic to recognising their beneficial biological functions, particularly under hypoxic and ischaemic conditions.

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