School lunch programs often get a bad rap for not providing kids with the proper nutrition, but vending machines on campuses are making matters worse, a new study suggests.

The results show school children who consume foods purchased in vending machines take in more calories and fewer essential vitamins and minerals than kids who don't buy foods from these machines.

If kept up, poor dietary choices such as these may put children at risk for obesity and chronic health problems such as diabetes and coronary artery disease , the researchers say.

"Consumption of vended foods and beverages currently offered in U.S. schools is detrimental to children's diet quality," said study researcher Madhuri Kakarala, of the University of Michigan Medical School. "Childhood obesity, resulting from poor dietary choices , such as those found in this study, greatly increases the risk for many chronic diseases. A healthy school food environment can reduce these dietary risks."

Vending machines have tempting offerings

This study is the first to look specifically at "competitive" foods and beverages those sold at snack bars or vending machines, rather than through the USDA lunch program.

Researchers analyzed data from 2,309 children in first through 12th grade from schools across the country. Interviewers administered questionnaires to find out what kids ate over a 24-hour period on a given school day.

Among the children surveyed, 22 percent ate competitive or vended food items in a school day. Usage was highest in high school, where 88 percent of schools had vending machines, compared to 52 percent of middle schools and 16 percent of elementary schools. Kids who ate or drank competitive or vended food and beverages had significantly higher sugar intakes and lower dietary fiber, vitamin Band iron intakes than kids who didn't.

The researchers also found that soft drinks accounted for more than two-thirds of beverages offered in school vending machines and stores. Desserts and fried snacks were the most commonly eaten vended items among elementary school children, and beverages other than milk and fruit juice were the most commonly consumed items among middle and high school students. Other frequently eaten vended foods included candy, snack chips, crackers, cookies, cakes and ice cream.

The results did not show a significant difference in students' consumption of these items based on family income or race and ethnicity.

What can be done

Based on their findings, the study authors recommend school administrators design guidelines restricting vended and competitive foods and beverages to those that are rich with nutrients and not energy-dense. Additionally, school foodservice personnel can prepare point-of-service materials and displays to promote more healthful foods such as fresh fruit, yogurt, low-fat milk, juice and sandwiches.

Establishing healthy dietary habits for children is important because "the foods that children are exposed to early on in life influence the pattern for their eating habits as adults," Kakarala said.

This study is published in the September issue of the Journal of School Health.