How much water should you drink every day? Roughly two litres sound about right? Perhaps you keep a bottle next to your desk at work and swig from it all day in a bid to stave off all those problems you’ve been convinced will arise the moment your body’s hydration levels dip below “perfect”?
And perhaps you should worry. A poll of GPs this week, carried out by the Natural Hydration Council, found that one in five of their patients were coming into surgeries and clogging up their valuable time with ailments such as feeling tired, headaches or poor concentration, mostly caused by them not drinking enough water. Of course, it’s a not-so-small detail that the Natural Hydration Council is the trade body for the bottled water industry, and it’s in their interest to make you worry about how little water you’re drinking. But surely it’s hard to argue against the basic advice that drinking lots of water is good for you?
Unfortunately, there isn’t much robust scientific evidence to support this simple-sounding advice. The “two litres of water per day” mantra is, at best, an educated guess. For a start, you get water from almost anything you consume – coffee, fruit juices, beer, meals – and you don’t need to gulp down two more litres to make up your daily dose. But more importantly, your body is very finely tuned to keep water levels stable. If you drink too much, your kidneys will get rid of the excess. If you don’t get enough, your body will hold on to what it has, you’ll feel thirsty and you’ll urinate less.
Unless you have health problems that mean you get dehydrated, you’re in a particularly dry place or you’re an athlete halfway through a marathon, you don’t really need to think too much about water. The idea that purposefully drinking litres of it every day will be of great benefit is, while well-meaning, a bit pointless. You might as well breathe more every day because oxygen is just “so good” for you, and more is always better.
We all have an intimate biological relationship with water – two thirds of your body is made of it, and water is an active participant in the functions and organisations of your cells, keeping proteins and DNA working properly, and moving energy and nutrients around. But, as crucial as it is to maintain that balance, this is not the human-water relationship that should be foremost in your mind.
Every aspect of our lives has a water footprint: we need water to grow food, make clothes, build offices and homes, construct cars, and do and make almost everything else we come into contact with. You will never see or touch most of the water you are responsible for using: a kilogramme of beef has a water footprint of 16,000 litres; a cup of tea needs 35 litres. A sheet of paper has a footprint of 10 litres of water; and just one of the microchips in your laptop took 30 litres of water to make.
A kilogramme of cotton comes with a water footprint of 10,000 litres, on average, though this figure varies according to where it comes from – cotton from India can “cost” up to 22,500 litres per kilo. Meanwhile, at home, you will use almost 190 litres for a five-minute shower, 10 litres to brush your teeth, and between 10 and 30 litres for each toilet flush.
Though there are 1.5bn cubic kilometres of water on the surface of the planet, less than 1% of it is useful to us – the rest is salty or locked up in the polar ice sheets. And we have to share that tiny amount with every other plant and animal on Earth. Ever since the beginnings of agriculture, 12,000 years ago, humans have found new and ever-more-wasteful ways to use water to build their growing civilisations. Cities and empires have been built on diverting rivers and moving water over vast distances to feed crops and people in ever-growing numbers. Perhaps it was fine to waste water in 6,000BC when there were only a million people spread across our vast planet. Today, there are 7 billion of us hankering after the same level of resource.
Most of today’s profligate water use occurs in the richer nations – the average American uses around 575 litres of water per day, while Europeans somehow manage on 250 litres per day. Compare that to more than a billion people in developing countries who have to make do with less than 19 litres each, and double that population who don’t have access to basic sanitation.
As rising temperatures around the world, caused by climate change, wreak havoc on agricultural lands, those in the poorest countries will not be able to cope with the impact of disappearing water sources. During the current heatwave in India about 1,800 people are thought to have died, with casualties from dehydration and heatstroke concentrated among the young, the old and the very poor. Water shortages intensified the effects of the heatwave, which in turn made those shortages more acute.
In 1995, the UN predicted that half a billion people would be living in water-scarce or water-stressed areas by 2050. By 2005, the organisation revised that prediction to 4 billion people. We’ve used water to build our world and wasted it without thinking for the entire history of human civilisation, and mostly we’ve got away with it. We’re now racing to the end of that era. Human bodies regulate their water use so well that we don’t need to spend too much time thinking about this precious resource. Human societies, unfortunately, can no longer afford that same luxury.
• Alok Jha is the author of The Water Book: the Extraordinary Story of Our Most Ordinary Substance
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