SAN DIEGO — Labeling healthy foods with smiley faces and rewarding children with small prizes may entice students to make healthier food choices in the school lunch line, according to a new study presented April 26 at the Pediatric Academic Societies annual meeting in San Diego.

As part of the study, researchers introduced two successive interventions to improve healthy eating during the same academic year in an inner city school in Cincinnati that had 297 children. During the first intervention, green smiley faced emoticons were posted near the four most healthful foods: fruits, vegetables, plain white fat-free milk and an entree with whole grains. Three months later, researchers introduced the concept of “Power Plate,” which consisted of the four healthy foods. Students who selected the Power Plate could receive a small prize, such as a sticker, temporary tattoo or mini beach ball.

Based on the researchers’ findings, students’ purchases of plain white fat-free milk increased to 48% of total milk sales from 7.4%, while chocolate milk sales decreased to 44.6% from 86.5% of total milk sales. The total amount of milk purchased remained constant from baseline to the end of the study.

Selection of fruits increased by about 20% during the course of the study, to 1.2 items per day from 1. Vegetable selection increased 62% to 1.2 items per day from 0.74 items.

Over a three-month period, the number of students opting for a Power Plate increased 335%, the researchers said.

“It looks like we found a very promising, low-cost and effective way of improving the nutrition of elementary school children,” said Robert Siegel, M.D., medical director of the Center for Better Health and Nutrition of the Heart Institute at Cincinnati Children’s Hospital Medical Center, and lead author of the study. “This type of program may be a useful component in schools trying to improve the nutrition and health of their students.”

The study was supported by the Heart Institute and Population Health Team of Cincinnati Children’s Hospital Medical Center.