New UK research shows natural fruit juices contain unacceptably high levels of sugar, with smoothies the worst offenders.
The study, published in the British Medical Journal, looked at juice drinks, fruit juices and smoothies which were specifically targeted at children.
Nearly half the products assessed contained at least 19g of sugar, almost five teaspoons -- the entire recommended maximum sugar daily intake for a child.
While many of the juice drinks contained sucrose (table sugar), the fructose naturally found in fruit juices is also classed as 'free sugar'. Free sugars include sucrose, glucose and fructose.
The fructose naturally present in fruit juices and smoothies is as likely to cause dental decay as all other sugars, and increased consumption of sugary drinks has been linked to childhood obesity.
Researchers at the University of Liverpool assessed the sugar content of 203 fruit juice drinks, 100 percent natural juices, and smoothies. Smoothies contained the highest amount of sugar.
In the UK, children aged between four and 10 years are now getting 30 percent of their sugar intake from soft drinks.
The UK government announced last week it will introduce a sugar tax on sugar-sweetened beverages in an attempt to combat childhood obesity, but it excludes natural fruit juices with no added sugar.
In New Zealand a third of children are classed as overweight, and 10 percent are obese.
The Government revealed its plan to tackle childhood obesity last year, but fell short of a tax on sugar and has no plans to introduce one.