A single glass of fruit juice a day is the most anyone should drink, new guidelines say, as a British report warns that families are consuming unsafe levels of sugar.
There is rising concern that sugar is one of the greatest threats to health, creating an obesity time bomb and contributing to spiralling levels of diabetes.
Health officials issued the warning as a nationwide study in England found that children and teenagers are consuming around 40 per cent more added sugar than the recommended daily allowance.
Fruit juices and fizzy drinks are the chief culprit, providing the largest source of sugar for children aged between four and 18, the National Diet and Nutrition Survey by Public Health England found.
The country's most senior nutritionist yesterday advised limiting children and adults to 150ml of fruit juice per day, and always accompanied by a meal. It is the first time health officials have outlined such a limit.
Dr Alison Tedstone, the chief nutritionist at the body, part of the NHS, said: "The best drinks for school-aged children are water and low-fat milk.
"Fruit juice is also a good choice as it can be included as one of your five portions of fruit and vegetables per day.
"However it should only be drunk once a day and with a meal because it can be high in sugar and can cause tooth decay." Some fruit juices and smoothies contain four times as much sugar as is recommended by the World Health Organisation.
Dr Tedstone said the survey demonstrated the need for a change in habits, particularly for children and teenagers.
It found that every age group exceeded the recommendation that added sugar should be no more than 11 per cent of daily calorie intake.
Among children under 10, added sugar made up an average of 14.7 per cent of their intake, while for those aged 11 to 18 it constituted 15.6 per cent.
Among adults, the figure was 12.1 per cent. For boys under 10, fruit juice accounted for 15 per cent of their daily added sugar and other drinks a further 17 per cent.
For girls the same age, fruit juice accounted for 12 per cent and other drinks 16 per cent of added sugar.
As children got older, the proportion from soft drinks including juice rose, to 42pc for boys, and 38pc for girls.
Cereals and cereal bars were the next biggest contributor.