Children who drink one serving of 100 percent fruit juice a day don't appear to gain significantly more weight than kids who consume no juice at all, a research review suggests.
Even though previous studies on fruit juice and weight gain have gotten mixed results, doctors often tell parents to avoid juices with added sugars and other ingredients altogether and to limit 100 percent fruit juice to a single serving a day.
In the current study, one 6- to 8-ounce serving of 100 percent fruit juice was associated with a small amount of weight gain in kids 1 to 6 years old, but the difference was too small to be clinically meaningful because it didn't shift most children from a healthy weight to overweight. Fruit juice wasn't linked to any weight gain in children aged 7 to 18.
"This finding was a little bit surprising," said lead study author Dr. Brandon Auerbach, a researcher at the University of Washington in Seattle. "Our team had thought that drinking one serving a day of 100 percent fruit juice would be linked to a small but clinically important amount of weight gain."
Parents shouldn't take the results as a reason to let kids drink more juice, however.
"Aside from weight gain, there are still other reasons to chose whole fruit instead of 100 percent fruit juice whenever possible," Auerbach said. Too much juice can contribute to problems like poor nutrition, obesity and tooth decay.
Pure fruit juice is also not the same as fruit drinks, which typically have added sugars and can be just as harmful to kids as drinking sodas, Auerbach added.
For the current analysis, researchers examined data from eight previously published studies of juice and weight gain that included a total of more than 34,000 kids. Six were conducted in the U.S., one in Germany and one in the UK. Studies followed children for anywhere from one to a dozen years.
Three of the four studies looking at younger kids found a statistically meaningful association between 100 percent fruit juice and weight gain, researchers report in Pediatrics.
Researchers looked at participants' body mass index (BMI), a measure of weight relative to height, to assess trends in weight gain over time based on how much juice kids drank across all of the studies.
Kids with a BMI anywhere above the 5th percentile and below the 95th percentile in their age group are considered to have a healthy weight.
Among the younger kids in the analysis, one serving of fruit juice was associated with a 4 percent increase in BMI percentile, too little to push most kids from the healthy to overweight BMI category.
For the older kids, there was no difference in BMI percentile based on how much fruit juice children consumed.
The study didn't assess whether kids would be better off eating whole fruit instead of drinking fruit juice, and it also didn't examine what would happen if children consumed more than a single daily serving of juice.
Even so, the findings should reassure parents that a small amount of pure fruit juice is not likely to directly cause obesity in kids - just as long as parents don't confuse these beverages with fruit drinks that, like sodas, often lack nutrients and are full of sugars and empty calories, said Dr. Stephen Daniels of the University of Colorado School of Medicine in Aurora who co-authored an editorial accompanying the study.
Especially for children who don't eat enough servings of fruit and vegetables, 100 percent juice may be a way to sneak in some needed nutrients, Daniels said by email.
"We should all be concerned that children and adolescents do not get enough servings of fruits and vegetables," Daniels added. "There are numerous issues here, but one especially for families of lower socioeconomic status is the availability and shelf life of fresh fruits and vegetables, which means that other forms of fruit such as 100 percent fruit juice can be helpful."
The American Academy of Pediatrics advises against any juice for infants under 6 months of age because it offers no nutritional benefit. AAP recommends kids 1 to 6 years old drink no more than six ounces of juice a day, and older children and teens have no more than 12 ounces a day (http://bit.ly/1Uw2yyQ).