Nitrate (NO3-) is a small molecule produced in the body to limited amounts (as a byproduct of nitric oxide) and is obtainable via consumption of vegetables, particularly beetroot and other low-calorie tuber vegetables such as turnips and leafy green vegetables such as spinach or rocket (arugula). It appears to be a potent regulator of blood flow and vasodilatation via its metabolite nitric oxide, and has greater relative affinity for areas of the body with poor oxygenation as the conversion of nitrite (NO2-, a metabolite of nitrate) to nitric oxide is undergone by deoxygenated blood.
In regards to cardiovascular health, it appears to reduce blood pressure in instances where blood pressure is raised. This appears to occur in people with hypertension and can occur in otherwise healthy persons undergoing exercise with little effect on resting blood pressure in healthy persons. It may exert endothelial protective effects, and is thought to be a link between vegetable intake and cardiovascular health.
It appears to enhance exercise performance secondary to reducing the oxygen cost of exercise (and thus prolonging time to exhaustion, thought to be due to increased mitochondrial efficiency). There is little to no effect on acute power output, but seems to reduce the rate of fatigue seen with continued muscle contractions and as such seems to have most benefit in exercises ranging from 1 minutes up to 10 minutes and as such exerts most benefit during anaerobic cardiovascular exercise or muscular endurance events (sports requiring anaerobic intervals such as hockey or rugby, some benefit to rowing and crossfit-type exercises) but although it does have benefit to prolonged cardiovascular exercise (5km jogs or 10km cycling events) the magnitude of effect appears to be lesser.
Due to interactions with nitric oxide, it appears to also be kidney protective and may help to regulate blood flow during the aging process (which is associated with reduced nitrate levels in circulation); the anti-aging effects, however, are preliminary at this moment in time. Due to endogenous production of nitrate and some disease states with lower circulating nitrate (cardiovascular diseases and aging) nitrate may have pseudovitamin-like properties but more evidence is required to support this claim.
Nitrate has the potential to form carcinogenic nitrosamines, although the practical significance of this in living systems is not known (epidemiological survey research has failed to show a significant link after controlling for other confounds, but some nitrosamines themselves are proven carcinogenic; practical relevance of nitrates and subsequently forming nitrosamines following supplemental or vegetable intake in a mixed diet is not really known). Although the carcinogenic potential cannot be ruled out at this time, it cannot be supported reliably either.