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A–Z of nutritional supplements: dietary supplements, sports nutrition foods and ergogenic aids for health and performance: part 15
  1. D C Nieman1,
  2. S J Stear2,
  3. L M Castell3,
  4. L M Burke4
  1. 1Appalachian State University, Human Performance Laboratory, North Carolina Research Campus, Kannapolis, NC, USA
  2. 2Performance Influencers Limited, London, UK
  3. 3University of Oxford, Oxford, UK
  4. 4Australian Institute of Sport, Canberra, Australia
  1. Correspondence to L M Castell, University of Oxford, Green Templeton College, Oxford OX2 6HG; lindy.castell{at}

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Introductory remarks

The most commonly used dietary supplements are micronutrients. The antioxidant properties of several dietary micronutrients are of particular interest to athletes due to the support of the body's endogenous antioxidant defence systems that allows free radicals to be neutralised to help decrease oxidative damage. Dietary antioxidants include vitamin C, vitamin E, carotenoids (mainly β-carotene), polyphenols (eg, flavonoids), selenium, glutathione and coenzyme Q10 (see part 3 of this series for an excellent overview of antioxidants). Due to the enhanced interest of the role of flavonoids in exercise, both in the media and scientific research, we have dedicated this issue to the topic: the very large number of flavonoids means that an exceptional number of citations is required. In this short review the potential bioactive effects of flavonoids and their efficacy as performance aids and countermeasures to exercise-induced oxidative stress, inflammation, delayed onset of muscle soreness (DOMS) and immune dysfunction are summarised.


D C Nieman

Phytochemicals are chemicals produced by plants, and include tannins, lignins and flavonoids. The largest and best studied polyphenols are the flavonoids, with more than 6000 identified and classified into at least six subgroups: flavonols, flavones, flavanones, flavanols (and their oligomers, proanthocyanidins), anthocyanidins and isoflavonoids (table 1).1 Flavonoids are widely distributed in plants and function as plant pigments, signalling molecules and defenders against infection and injury.

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Table 1

Flavonoid subgroups and food sources

Dietary intake of flavonoids ranges from 50 to 800 mg/day depending on the consumption of fruits and vegetables and the intake of tea.2 3 In the USA, total flavonoid intake averages 210 mg/day,2 and in Spain 313 mg/day,3 with important sources including tea, citrus fruit and juice, beers and ales, wines, melon and berries, apples, onions and bananas.

A high intake of fruits and vegetables has been linked in numerous studies to a reduced …

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  • SS, LC, LB edited this part.

  • Competing interests DCN sits on the Scientific Advisory Board for Quercegen Pharma, Sudbury, Massachusetts, USA.

  • Provenance and peer review Commissioned; not externally peer reviewed.