Parents should not give their children 'flat' carbonated drinks to rehydrate them after sickness and diarrhoea, according to a new study.
Researchers at Watford General Hospital in Hertfordshire suggest that fizzy drinks gone flat should not be used as an alternative for oral rehydration solution to prevent dehydration in children with acute vomiting and diarrhoea.
Oral rehydration solution is a liquid containing the ideal balance of salts and sugars for avoiding dehydration in people with gastroenteritis who are losing fluids, salts and sugars through diarrhoea and vomiting.
It is commonly believed that 'flat' carbonated drinks are an effective alternative to these solutions, particularly for children who don't like their taste.
However, researchers were unable to find any published trials to back this up, so they looked for information about the contents of different types of liquids and compared them.
Carbonated drinks were found to contain too much sugar and not enough salts.
Current World Health Organisation recommendations are for oral rehydration solution to contain 75mmol/l of sodium and the same amount of glucose.
Published biochemical analyses show carbonated drinks have much lower levels of sodium (1.0-9.9 mmol/l) and potassium (0-0.3 mmol/l), but much higher levels of glucose, with branded cola having 550mol/l of glucose (more than seven times the recommended amount).
The authors concluded there was little information available from clinical studies on the effectiveness of using carbonated drinks compared with oral rehydration solution for the prevention of dehydration in children with gastroenteritis, but that there were many scientific analyses demonstrating their inappropriateness.
"Carbonated drinks, 'flat' or otherwise, including cola, provide inadequate fluid and electrolyte replacement and cannot be recommended," the authors said.
The study is published in the May issue of Archives of Disease in Childhood.