You’ve probably heard the advice that if you want to ensure your overall wellbeing, you must include 8 glasses of water in your diet every day. However, according to Glaswegian GP Margaret McCartney, this wellness mantra has no basis in research.
The advice comes from official sources, and the NHS website says you need to prevent dehydration by drinking six to eight glasses of water each day and even more than the 1.2 litres this provides when the weather is hot. However, McCartney writes in her opinion article in British Medical Journal (BMJ), that as there is little research to back this up, the official water advice given is ‘not only nonsense, but is thoroughly debunked nonsense’.
Heinz Valtin published a critique of the evidence for drinking eight glasses a day in the American Journal of Physiology in 2002, and McCartney refers to his conclusion that ‘Not only is there no scientific evidence that we need to drink that much, but the recommendation could be harmful’ as you could become guilt-ridden about not drinking enough water, and if you do get your 8 glasses this could lead to a dip in the sodium levels in your body and leave you more exposed to pollutants.
McCartney wrote her article following the recent Hydration for Health meeting in Evian, France, which warned on their website that ‘40% of 11-18 year-old children are drinking less than 1.2 litres per day’, it is not uncommon for school children to go six or seven hours without a single drink and older people are at particular risk of dehydration because they are less likely to realise they are thirsty than younger people. Not only is McCartney unimpressed by these claims, as they have no quality evidence to back them up, but further points out that Hydration for Health was created and sponsored by Danone.
Danone is a French company which markets Evian, Volvic and Badoit brands of water, and so has a vested interest in getting you drinking more water. Danone warns that even if you have a mild case of dehydration you can have a reduced cognitive and physical performance, fatigue, tiredness, and constipation, as well as developing kidney stones. McCartney concludes, on the other hand, that ‘water is not a simple solution to multiple health problems’.
David Graham, Director of Danone’s Hydration for Health Initiative responded by saying that the company’s advice about water intake was in line with recent advice from the European Food Safety Authority (EFSA), and ‘The amount a person should drink is dependent on personal factors, such as sex and age, and EFSA’s opinion to drink 1.5L to 2L of water per day is sensible for a normal woman or man’.
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