There is a view in the popular press that caffeinated drinks, such as tea, have an adverse effect on hydration.
While studies on caffeine pills have produced inconsistent results1, those on caffeinated drinks, at caffeine intakes of 114-420mg/d, have found no significant impact on hydration2, 3. However, there have been no randomised controlled trials on tea, as consumed.
The present trial aimed to assess the impact of 4 x 240ml mugs of black, i.e. regular tea, on blood and urine measures of hydration. The control condition was a similar volume of boiled water. Four mugs is slightly above average daily tea intakes in the UK.
1 Ruxton CHS (2008). Nutr Bull 33, 15-25
2 Grandjean AC et al. (2000). J Am Coll Nutr 19, 591-600.
3 Fiala KA et al. (2004). Int J Sport Nutr Ex Metab 14, 419-429.
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