Nutrition: why it's great to hydrate
Have you noticed that it’s become commonplace to walk around clutching a bottle of water. The notion that we are dehydrated has become increasingly popular (perhaps encouraged by the nice people that sell bottled water).
Although it is potentially overstated, many people don’t get adequate hydration every day. Two thirds of the human body is water and it helps regulate temperature, improve digestive function and regulate blood pressure, so even mild dehydration can manifest itself in a variety of ways, including hunger. Researchers at the University of Washington highlighted that drinking just one glass of water eliminated midnight hunger pangs in virtually 100 per cent of the dieters studied. (I’m sure the benefits extend beyond midnight eating however.)
Dehydration can also impair brain function — you may feel irritable, dizzy or struggle to remember things easily. Other signals that you could be dehydrated include headaches, dry mouth and constipation.
But the answer doesn’t always lie in just drinking more water — excess fluid is limited in what it can do to combat dehydration simply because we can’t absorb much at once. Dietary habits can improve hydration as the fluid contained in food is absorbed more effectively simply because it’s delivery is regulated by the digestive system.
All food contains water, but some more than others. For example, all fruits and vegetables contain plenty of water but even chicken and fish can contain as much as 65 per cent water and so eating fresh food that hasn’t been overcooked will go a long way to preventing dehydration. Don’t forget that juices, smoothies, herbal teas, stews and soups are all excellent sources of water.
As always with nutrition, what we cut out is equally important. Refined sugars and caffeine contribute indirectly to water loss, although the effect is mild, as does eating food that is especially salty (there is a reason why bars put out salted nuts, it helps sales).
The official advice from the Department of Health is to drink 1.2 litres a day, which equates to around eight glasses or mugs a day. In warmer weather or when exercising this increases to two litres (13 glasses or mugs).
A simple way to check if you are adequately hydrated is the colour of urine — pale straw is good, dark yellow suggests you need more fluid.
Ian Marber is one of the UK’s most highly regarded nutrition experts and the author of 11 books. Follow him at Twitter @IanMarber