15 Jul 2011 (Updated 7 Jan 2014)

Waterlogged - misguided and misleading

Both the European Federation of Bottled Waters and the Natural Hydration Council have issued rebuttals following an article by Dr Margaret McCartney dismissing how much water we should drink. Here, Thomas A Sanders, professor of nutrition & dietetics at King's College London adds his opinion.

Margaret McCartney's article has spawned headlines in the UK national press suggesting that advice to drink 6-8 glasses of water a day is bad for you.

Appropriate hydration is particularly important for the elderly and the very young and for most people it is better to obtain most fluid intake from water, whether bottled or tap water, than from other beverages (especially sugar containing and alcoholic beverages).

MacCartney focused on the more whacky claims made for water and appeared to cherry pick her references to make a story.

Notable omissions were:

  • any reference to the Dietary Reference Value for Water published by the European Food Safety Authority.
  • or the US Institute of Medicine review of water requirements
  • let alone the guidelines of the National Patient Safety Agency guidelines.

Readers who want an unbiased view are referred to an excellent review in the British Nutrition Foundation Briefing Paper on Hydration.

Six to eight glass of water represents an intake of between 900-1200ml per day (a small plastic cup provides 150ml water). This is not an unreasonable amount of water and is consistent with current guideline of 2 litres and 2.5 litres a day for men and women respectively after allowing for water in food and metabolic water.

The BMJ prides itself in promoting evidence based medicine. Yet this article was commissioned and did not undergo peer reveew. An editorial policy of publishing strong opinion pieces which are not peer-reviewed underthe imprimatur of the BMJ undermines the credibility of evidence based medicine and contributes to public confusion regard dietary advice as discussed by Cooper et al.

Competing interests: Member of Scientific Advisory Committee of the Natural Hydration Council Member of the Scientific Advisory Committee of the Global Dairy Platform Trustee and Governor of the British Nutrition Foundation