Water is a fine drink. I like it best when frozen into cubes and added to gin, but it is also good when taken fresh from the tap. It is better for teeth than sugary fizz or cordial. It is cooling, refreshing and life-sustaining. In other words, none of what follows should be taken as disapproval of water.

Making water freely available to drink in schools is also good. Though Glasgow’s Refresh campaign (and there are similar around the country) goes a little too far. My children came home from school recently carrying water bottles and leaflets. These informed me that the benefits of water are legion and, therefore, a supply should be given to and carried by my children in order for them to sip freely all day.

I hate to think of myself as jaded and cynical, especially when it comes to something as cheap and vital as water. But I’ve got a few problems with this. Not the least of which is practical, as this initiative has resulted in my children insisting that I should run home to collect the water bottles I have forgotten to pack in their schoolbags in the mornings lest their brains rust.

The Refresh leaflets say that water should be drunk all day long, that “most children and adults do not drink enough water, causing them to become dehydrated” and that “water will help you speed up learning”. Looking into the last claim first, I was sent to wateriscoolinschools.co.uk, a website run by a charity that campaigns for free access to water in schools.

Similar claims are repeated here. “By the time a child feels thirsty, their mental performance may have deteriorated by 10 per cent” is one. Is such a marked effect on mental ability really possible? The website for the water industry, Water UK (water.org.uk), to which I was also referred by the Refresh Campaign, thinks so: “Water reduces tiredness, irritability and distraction from thirst and can have a positive effect on pupils’ concentration throughout the day. An experiment in a Scottish school also found that drinking water contributed to improvements in pupils’ test results.”

At least this website references its claims. For the excerpt above, it provides two. One is a news report from the BBC reporting a school in Edinburgh that had shown that “water improves test results” after primary school children were encouraged to drink water throughout the day. However, at the foot of the cited BBC report, it rather tellingly notes that the deputy headmistress “was reluctant to see the school’s success linked solely to the water experiment – saying that improvements in test results reflected the effectiveness of the teaching and other measures being tried at the Edinburgh primary school”. Contact with the school and the local education authority did not provide any further information about this project.

Water UK provides a lot of other references. In support of its thesis that water improves children’s cognition, it references two other studies. The first is contained within a paediatrics journal. This study showed that “study of the relationship between voluntary dehydration and cognitive performance in elementary school children aged 10-12 years in southern Israel has found that at the beginning of the day there were no significant differences in cognitive performance between the hydrated and dehydrated groups. At midday, however, the hydrated group performed better in four of the five cognitive tests compared to the dehydrated group, especially on a short-term memory task.”

All very well but I don’t think that a small study of children in a “desert town” is enough to provide meaningful data for UK schoolchildren, and this is without picking apart any of the flaws in the study itself. Interestingly, in support of water’s success in “improving the cognitive” ability of children, the academics on this paper cited a BBC news report – exactly the same BBC news report as before, where the deputy head says that maybe it wasn’t just the water that did it.

Water UK also references a review paper published in a journal called Nutrition Review. I went to great lengths to get a copy of this paper, which says that the small study of children in the Israeli school is the only one they found examining the effects of dehydration on children’s cognitive performance. It also points out the shortcomings with the study that mean it cannot be generally applied.

Intriguingly, the authors of this journal paper also report that encouraging water intake in UK students “might” improve student attention and concentration. And what is their source for this? None other than that same BBC news report, the one in which the teacher says that they are not so sure at all…

Margaret McCartney is a GP in Glasgow

margaret.mccartney@ft.com

More columns at www.ft.com/mccartney

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