Electrolyte drinks have become a staple on gym floors and running routes, promoted as essential for better performance and faster recovery.
Long used by elite athletes to cope with hard training in hot conditions, they have now crossed firmly into the mainstream and are marketed to casual gym-goers, office workers and even commuters as an everyday hydration boost.
From sports drinks to sachets and powders, these products can set you back a couple of pounds a day.
Electrolytes - minerals like sodium, potassium and magnesium - help regulate nerves, muscles and fluid balance in the body.
According to Professor Graeme Close, a leading sports nutrition researcher at Liverpool John Moores University, most people are spending money they don't need to.
