An elderly relative of mine who finds himself occasionally forgetting things, was persuaded by his concerned daughter, a nurse, to visit his doctor to enquire about the possibility of alzheimers. He went along reluctantly and was asked a series of questions, the first of which was; “What day is it?” “No idea” he answered, “I don’t work anymore, so I don’t see why that’s relevant.” At 86 he is in good physical shape, but just forgets things he doesn’t think are relevant. At the end of the consultation, the doctor asked him if he ever drank water. He said no and the doctor advised him to drink at least four pints a day. It hasn’t helped his memory, but he does need to go to the bathroom more frequently.
We live in unsettling times. Old certainties crumble daily: Jeremy Corbyn leads the Labour party; colouring books for adults are bestsellers and apparently it’s not even true that you’re supposed to drink eight glasses of water a day. This bombshell comes from Aaron Carroll, a US paediatrician who’s researched hydration and who rounded up the evidence in the New York Times: the notion that most of us walk around dehydrated, he showed, is a myth. The web, which loves a good debunking only slightly less than a good shaming, went wild. Howevever, many people still follow the eight-glass rule.
There is no suggestion eight glasses is bad; you’ll probably drink fewer sugary drinks; and those toilet trips will stop you sitting, unhealthily, at your desk all day. Plus following any such rule makes you more attentive to what you’re putting into your system. In other words: the eight-glass rule is wrong, on its own terms, but still useful. And all sorts of “rules for living” work this way.
Diets are an obvious example: on the rare occasions they work, it’s probably because you’re thinking carefully about food, rather than any specifics. (All manner of eating regimes based on dodgy science – wheat-free, GMO-free etc. – could thus prove healthy if they result in you consuming less crap.) Or take relationships: “once a cheater, always a cheater” plainly isn’t universally true – but in the early stages of dating, it could be an excellent strategy for filtering out jerks. Barack Obama’s trick for avoiding “decision fatigue” – he always picks from a blue or grey suit – doesn’t derive its value from those specific colours, or garments; the point is that, with the rule in place, he needn’t think further about clothes. Drink eight glasses of water a day, and nothing else, and you’ll never have to wonder if you’re dehydrated, or drinking too much Coke: for as long as you follow the rule, those worries are off your agenda.
And scientific research is only so much help in deciding which rules to follow. Christmas came early for debunkophiles in August, when a major effort to rerun 100 psychology studies found more than 60% couldn’t be replicated. For researchers, this is worrying. Even the very strongest studies are true only for the general population, or some subset of it, whereas everyone is unique – so a conclusive finding that running alleviates depression, for example, isn’t much personal use if running always makes you feel worse. Conversely, a debunked finding about, say, the benefits of rising early could still prove transformational – for you. And you’d surely be rather strange if you abandoned that fruitful habit solely to “stay scientific”. Anyway, you can’t stay in bed: you’ve got a busy day of water-drinking ahead.