Almost half of the fruit juices and smoothies marketed to children contain the equivalent of a child's entire maximum daily recommended sugar intake, new British research has found.

Whether at breakfast or for an afternoon snack, it's better to give kids a piece of fresh fruit rather than fruit juice -- even 100 per cent pure juice -- according to the findings of a study published March 23 in the BMJ Open journal.

Researchers from the Universities of London and Liverpool set out to investigate how much sugar was really contained in pre-packaged fruit juices, juice drinks and smoothies aimed at children.

They analyzed the sugar content of 203 products, including 21 fresh juices, 158 fruit juice drinks and 24 smoothies on sale in seven U.K. supermarkets.

The team calculated the quantity of "free sugar" in a 100 millilitre serving of each drink, defined as sugar added by the manufacturer, including glucose and fructose, and sugars from products like honey and syrups. It did not include the natural sugars found in fruit.

The researchers found an average sugar content of 7grams per 100ml, in a range running from 0g to 16g. This averaged at 10.7g for 100 per cent pure fruit juices. Smoothies contained the highest levels of sugar, with an average 13g per 100ml, while juice drinks contained the lowest, with 5.6g per 100ml.

Of the 203 products, 85 were found to contain at least 19g of sugar, equivalent to the maximum daily recommended sugar intake for children in the UK. Certain smoothies even contained up to eight teaspoons of sugar in a 200 ml serving, which is three times the recommended daily amount.

Nearly 65 of the drinks studied also contained artificial sweeteners without any calories.

The study's authors conclude that these kinds of drinks contain "unacceptably high" levels of sugar, and are calling on manufacturers to stop adding unnecessary sugars and calories to their products.

The World Health Organization recommends a sugar intake not exceeding 10 per cent, or if possible, 5 per cent of the total daily energy intake, to reduce the risk of obesity, weight gain and tooth decay.