Myth G: Drinking water

Drinking water is often promoted as a way to improve learning and it is true that even mild dehydration can reduce our ability to think . However, a recent adult study has shown that drinking water when not thirsty can also diminish cognitive ability . Luckily, forgetting to drink water is not usually a problem, because our brains have evolved a sophisticated system that makes us thirsty when our bodies (and brains) need more fluid. So, encouraging and enabling children to drink water when they feel thirsty may be a more sensible approach than constantly monitoring the amount of water they consume. Exercise and unusually hot weather are the exception to this rule, when there is evidence that the body’s own monitoring system becomes less reliable, suggesting children might then need encouragement to drink in order to avoid dehydration .

Apart from these special circumstances, there is no evidence to suggest that normally functioning children are generally prone to voluntary dehydration. Indeed, the only study showing voluntary dehydration in the classroom comes from the Dead Sea region– the lowest point on the planet and notoriously hot . Our survey also revealed 20% of trainee teachers thought their brain would shrink if they failed to drink 6-8 glasses of water a day. Very serious dehydration can do this, as graphically illustrated when a man in Japan tried to commit suicide by overdosing on soy sauce . Three weeks later, after appropriate treatment, the man’s brain was shown to have returned (mostly) to its original dimensions. However, this was a rare case and one caused by vast amounts of soy sauce, not by forgetting to drink water.