The same marketing techniques used to persuade children to eat junk food are highly effective in promoting fruits and vegetables, a new study has found.

Researchers assigned 10 elementary schools to one of four groups. In the first, they posted vinyl banners around the salad bar depicting cartoon vegetable characters with "super powers." In the second, they showed television cartoons of the characters. The third got both cartoons and banners, and a control group got no intervention. The study, in Pediatrics, went on for six weeks in 2013.

Compared with control schools, TV segments alone produced a statistically insignificant increase in vegetable consumption. But in schools with the banners alone, 90.5 percent more students took vegetables. And where both the banners and the TV advertisements were used, the number of students taking vegetables increased 239.2 percent.

"It's possible to use marketing techniques to do some good things," said one of the authors, David Just, a professor of applied economics at Cornell.