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Welcome to Part 27, where we finish ‘N’ with nitrates and nootkatone and move onto ‘O’ starting with octacosanol. The first review focuses on what has become quite a hot topic in sport nutrition in the recent years with the BBC leading with a headline in August 2009 that ‘Beetroot Juice boosts Stamina’. The BBC was describing a study from Professor Andy Jones' group: in his brief review for Part 27, he describes the link between supplementing the diet with nitrate-rich beetroot juice to enhance NO availability and the consequential proposed mechanisms that could lead to an improvement in exercise performance. The other two reviews deal with substances that are generally found as plant extracts: nootkatone, a chemical found in the essential oil of grapefruit and other plants including cedars, which is used predominantly as a flavouring compound but also as a natural insecticide; and policosanol, a wheat-germ extract whose main component is octacosanol.
Nitric oxide (NO) is an important physiological signalling molecule that can modulate skeletal muscle function through its role in the regulation of blood flow, muscle contractility, glucose and calcium homeostasis and mitochondrial biogenesis and respiration.1 Until quite recently, it was considered that NO was generated solely through the oxidation of the amino acid l-arginine in a reaction catalysed by nitric oxide synthase (NOS).2 It is now appreciated, however, that NO may also be produced by the reduction of nitrate to nitrite and subsequently of nitrite to NO.3 This pathway may be particularly important in hypoxia. Nitrate and nitrite are present in the body as products of NO production through NOS and are also modulated through the diet. Nitrate in foods (particularly green leafy vegetables) can be reduced to nitrite by oral bacteria, leading to an increased plasma nitrite concentration that serves as a …