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A–Z of nutritional supplements: dietary supplements, sports nutrition foods and ergogenic aids for health and performance—Part 30
  1. N M DiMarco1,
  2. N P West2,
  3. L M Burke3,
  4. S J Stear4,
  5. L M Castell5
  1. 1Institute for Women's Health, Texas Woman's University, Denton, Texas, USA
  2. 2Griffith Health Institute, Griffith University, Southport, Australia
  3. 3Australian Institute of Sport, Canberra, Australia
  4. 4Performance Influencers Limited, London, UK
  5. 5Green Templeton College, University of Oxford, Oxford, UK
  1. Correspondence to Linda M Castell, Green Templeton College, University of Oxford, Oxford OX2 6HG, UK; lindy.castell{at}gtc.ox.ac.uk

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Introductory remarks

Part 30 includes just two supplements: potassium and prebiotics. The role of potassium in exercise metabolism has been well documented in the literature but it seems that its appearance as a component of electrolyte-replacement products is a custom, rather than a necessity, since it is widely found in the diet. By contrast, prebiotics are at the beginning of an investigative story which may conclude by finding some beneficial uses for athletes to promote immune or gastrointestinal (GI) health during times of increased stress.

Potassium

Nancy DiMarco

Potassium (K+) is the major intracellular cation in the body, with ∼98% of the body potassium stores located inside the cells with a concentration maintained at about 145 mM. Its major functions are to promote contractility of ciac, smooth and skeletal muscle and to influence the regulation of nerve conduction through the influx of sodium (Na+) and efflux of K+ on either side of the nerve terminal, occurring at the rate of 107 ions per second. On the surface of a nerve terminal, there are voltage-dependent channels for K+. In humans, at least 15 different K+-specific voltage-dependent channels have been identified. The Na+/K+ ATPase, also known as the Na pump, is the primary active transporter system that maintains the high K+ and low Na+ intracellular concentrations. The plasma membrane ATPase of all mammalian cells catalyses the reaction: ATP→ADP+Pi with obligatory requirements for Na+ and K+ and Mg2+ required for the dephosphorylation of ATP. Muscle has an especially high activity of this P-type Na+ pump which has been estimated to use 60% to 70% of the ATP synthesised in nerve and muscle cells.1 2

For active individuals/athletes, sweat is the …

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