DR EMMADERBYSHIRE is a public health nutritionist and adviser to the Natural Hydration Council (naturalhydrationcouncil.org.uk)
If you’re thirsty and finding it hard to concentrate, chances are you’re experiencing hypohydration – mild dehydration. Up to 60 per cent of our body weight is water, and our brains are actually 70 per cent water. ‘Every cell needs water to function,’ says registered nutritionist Dr Emma Derbyshire. ‘Most of our blood is water, with the minerals potassium and sodium giving a finely tuned electrolytic balance.’
We lose water daily through breathing, sweating and urination – and that’s not taking into account the extra demands of exercise. ‘The definition of dehydration is when you lose more than wo per cent of your body weight. For a 60kg woman, that means a loss of 1.2kg or more,’ explains Dr Derbyshire. ‘The thirst reflex in our brains detects the lower levels of fluid and tries to hold on to what it can. That’s why you don’t wee as much and urine is darker.’ Causes include not drinking enough fluid, too much alcohol (a diuretic), or losing fluid through illness, such as diarrhoea, fever or heat exhaustion. Babies and the elderly are more vulnerable. The best remedy? ‘Drink water regularly throughout the day, starting at breakfast,’ says Dr Derbyshire.