Just one single serving of some of the most popular fruit juices for children contains enough sugar for one day, a new study found.

For this study, the researchers examined the levels of free sugar, which included naturally occurring sugar found from different sources, such as honey and syrups, and added sugar, in 203 fruit beverages that were about 7 ounces in size. All of the beverages, which included juices and smoothies, were advertised as 100 percent natural and were marketed to children. Sports drinks, iced teas and carbonated drinks were excluded from the study because these drinks do not target children specifically.

The researchers found that in nearly 50 percent of the beverages studied, one serving met the maximum daily recommended intake of 19 grams or five teaspoons of sugar for children.

"Increasing public awareness of the detrimental effect sugar sweetened drinks have on kids' teeth and waistlines has prompted many parents to opt for seemingly healthier fruit juice and smoothie alternatives," said Simon Capewell, the lead investigator of the study and a professor at the University of Liverpool's Institute of Psychology, Health and Society. "Unfortunately our research shows that these parents have been misled. The sugar content of the fruit drinks, including natural fruit juices and smoothies tested, is unacceptably high. And smoothies are among the worst offenders."

The researchers are recommending parents to find alternative options, such as real fruit that can satisfy children's sweet tooth without all of the added sugar. Whole fruits are provide other healthy nutrients, such as fiber. The researchers added that diluting the juices and making portion changes can also reduce their children's daily sugar intake. Capewell acknowledged that the blame cannot be placed solely on the parents. He stated that food and beverage companies need to step up and make changes as well.

"Manufacturers should stop adding unnecessary amounts of sugars, and therefore calories, to their fruit drink/juice/smoothie products," Capewell said. "Our kids are being harmed for the sake of industry profits. If companies can't slash sugar voluntarily, the government should step in with statutory regulations."

The study was published in The BMJ.