Q In some countries fizzy drinks are handed out during races, but they never seem to be in the UK. Will the carbon dioxide make any difference to a drink’s ability to rehydrate me?
A This question has been addressed by researchers at Washington University School of Medicine in the USA. Cyclists were given fizzy or flat drinks containing either 10 per cent carbs or no carbs on four occasions.
Researchers found that the fizzy and flat drinks emptied from the stomach at the same speed and – in the case of the 10 per cent carb drinks – raised blood sugar levels to a similar extent. In other words, carbonation has no detrimental or beneficial effect on a drink’s ability to rehydrate the body during exercise or deliver carbs to exercising muscles.
Perhaps of greater concern to runners is the issue of bubbles. One study did test the effect of fizzy versus flat sports drinks on runners. Again, rehydration was equal but runners were more likely to complain of mild heartburn and stomach discomfort when drinking fizzy drinks containing 8g carbohydrate/100ml as opposed to calorie-free ones.
Cola may be popular with athletes for its taste, which is useful because you’re more likely to drink something you find palatable. The caffeine in cola might also enhance performance by increasing fatty acid levels in the blood and improving endurance.
If you prefer drinking carbonated drinks and the bubbles don’t upset your stomach, then go ahead. If it’s cola you crave, dilute it one or two parts cola to one part water to provide a better carbohydrate concentration (four to eight per cent) for maximum absorption. Bear in mind that it is a very acidic drink which can dissolve tooth enamel, so swish water around your mouth afterwards.
— Anita Bean, RW Nutrition Editor