Want kids to eat something healthy? Put a smiley face on it.

A new study finds that labeling healthy foods with smiley face emoticons may be an easy, inexpensive way to get kids to make good cafeteria choices such as fruits, vegetables, plain fat-free milk, and entrees with whole grains.

At an inner-city school in Cincinnati, researchers marked healthy foods with a green smiley face for students from kindergarten through sixth grade. Three months later, they created a "Power Plate" featuring four of these healthy foods. Kids who chose the special plate were rewarded with a little prize: a sticker, temporary tattoo or a mini beach ball. Prizes were also given out by researchers whenever they saw students with four healthy choices on their trays.

The smiles and prizes seemed to pay off.

Sales of white milk rose from 7.4 percent to 48 percent — an increase of more than 500 percent. Sales of fruits jumped 20 percent and vegetables increased by 62 percent. Sales of chocolate milk dropped. Power Plate selection increased by 335 percent.

"It looks like we found a very promising, low-cost and effective way of improving the nutrition of elementary school children," said study author 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. "This type of program may be a useful component in schools trying to improve the nutrition and health of their students."

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Mary Jo DiLonardo Mary Jo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.