There are so many rules and regulations in the healthy eating game, you almost need a calculator and a clipboard each time you step into the kitchen. Five portions a day of this, three portions of that, no more than so many units of such and such… and so on. But one that I’ve always been sceptical about is the eight-glasses-of-water-a-day rule. I mean, it sounds like good advice. But people differ hugely when it comes to water intake. Some people I know hardly ever drink a glass of plain water – and they seem perfectly healthy – whereas others are constantly sipping from a bottle that never leaves their side.
Thankfully, these days nutrition experts agree water isn’t the be all and end all when it comes to hydration. In fact, tests show milk is much better at hydrating you than plain water. And let’s face it, adding tea to a cup of freshly boiled water gives it a lovely antioxidant boost, making it healthier – and tastier – than water on its own.
So let’s get over that whole you-must-drink-pure-water-or-you’ll-be-horribly-unhealthy thing already, please.
This week, I came across an interesting study that looks at how the body regulates water intake – because as you probably know, drinking too much of the stuff can be rather dangerous. Some people have even died from drinking too much water. That’s because too much water in the body can cause a condition called hyponatraemia, which is where the levels of sodium in your blood become so low they can trigger a range of symptoms, the most serious of which include convulsions and coma.
Well apparently, your brain tries to control how much water you drink – or, more specifically, tries to stop you from drinking too much – by making swallowing more difficult after you’ve had enough. Researchers from Monash University in Melbourne, Australia, discovered this by asking volunteers to rate how much effort they needed to swallow water when they were thirsty (in this case, after exercising), and then again after they’d already drank to excess. It turns out you have to put in three times more effort to swallow after you’ve drank too much – though whether or not this just applies to water I couldn’t say, it most certainly doesn’t apply to beer from what I’ve seen in my local bar on a Saturday night.
“Here for the first time we found effort-full swallowing after drinking excess water which meant they were having to overcome some sort of resistance,” said associate professor Michael Farrell, who oversaw PhD student Pascal Saker’s study. “This was compatible with our notion that the swallowing reflex becomes inhibited once enough water has been drunk.”
Their findings, say the researchers, challenge the eight-glasses-a-day rule. Why? Because our bodies know how much we need to drink – and in all likelihood it doesn’t conform to a one-size-fits-all recommendation.
“If we just do what our body demands us to we’ll probably get it right – just drink according to thirst rather than an elaborate schedule,” adds Professor Farrell.
In other words, drink when you’re thirsty, and you won’t go far wrong.
Sounds wildly sensible to me.
The study was published in the journal Proceedings of the National Academy of Sciences in the United States of America.