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What is it?

  • Dietary nitrate may be used to enhance the availability in the body of a molecule called nitric oxide (NO). NO is important for a variety of functions that are essential to life, and important to exercise performance, including the regulation of blood pressure and blood flow, mitochondrial respiration, muscle contraction and immune function.
  • In our bodies, nitrate is produced continuously because it is formed when the amino acid, arginine, is oxidized to generate NO. Until recently, it was believed that this nitrate had no biological function, but it has now been discovered that it can be recycled to form NO. Specifically, nitrate can be converted into nitrite (this process relies principally on the action of bacteria in the mouth) and then to NO. This nitrate-nitrite-NO pathway might be particularly important when oxygen is in short supply such as in muscle during exercise.
  • In addition to the nitrate that is produced within our bodies, the amount of nitrate and nitrite carried in our blood, and stored in our muscles and other organs, can be greatly augmented by the consumption of nitrate in our diet. The main dietary sources of nitrate are vegetables (particularly leafy greens) and some fruits, along with processed meats (where it is added as a preservative) and drinking water.
  • Increasing dietary nitrate intake, or using a nitrate supplement, may increase NO bioavailability and have the potential to enhance exercise performance in situations where NO production might otherwise be compromised.1
  • The average dietary intake of adults in the US, Europe and Australia is 1-2 mmol/d (~60-120 mg/d) with vegetables providing about 80% of the total. Vegetarians are likely to consume higher nitrate intakes and people who follow “heart-friendly” eating plans such as the Dietary  Approaches to Stop Hypertension (‘DASH’) diet are also likely to achieve higher nitrate intakes.
  • Interest in beetroot juice for enhancing sports performance arises principally from research by Professor Andy Jones and colleagues (University of Exeter, UK) which has used this juice as a rich source of dietary nitrate.
  • Nitrate consumed in the diet is rapidly absorbed via the stomach and small intestine, with plasma nitrate levels peaking ~ 1 hour after nitrate ingestion. A significant proportion of the plasma nitrate enters the entero-salivary system and is extracted by the salivary glands and concentrated in the saliva. Bacteria in the mouth convert nitrate to nitrite as part of their metabolism and this nitrite is subsequently swallowed. Some of the nitrite is converted to NO and other reactive nitrogen species in the acidic stomach environment but the remainder enters the small intestine and is absorbed into the blood where it can be transported around the body and reduced to NO if required.
  • Plasma nitrite concentrations peak at ~ 2.5 h following the intake of dietary nitrate. Factors that interfere with salivary nitrate handling - such as the use of antibacterial mouthwashes to reduce mouth levels of bacteria - may markedly limit this rise in plasma nitrite and blunt any  subsequent physiological effects.
  • Nitrate supplementation has been shown to enhance some of the effects of NO, even in healthy people. For example, supplementation with dietary nitrate sources or nitrate salts (such as sodium or potassium nitrate) has been shown to reduce blood pressure even in individuals with  normal blood pressure.
  • Original and subsequent studies have reported that both chronic (3-15 d) and acute (single dose prior to exercise) beetroot juice supplementation can enhance exercise economy (i.e. reduce the oxygen cost of exercise), exercise capacity and sports performance.1
  • Aerobic fitness levels influence the efficacy of dietary nitrate, with highly-trained endurance athletes (with VO2max greater than 65 ml/kg/min) not benefitting significantly from nitrate supplementation.2 Few studies have investigated the impact of nitrate supplementation on female athletes.
  • Recent studies indicate that dietary nitrate supplementation can enhance muscle power, sprint, multiple-sprint, and high-intensity intermittent exercise performance, thereby widening the potential application of nitrate supplementation to a greater number of both individual and team sports.3

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