Fewer elementary school students can buy soda and other sugar-sweetened drinks at school than could a few years ago, according to a new study.

Researchers called the trend of fewer vending machines and snack bars selling the beverages "encouraging," with soda drinking being one nutrition issue public health experts have tied to childhood obesity.

The Institute of Medicine (IOM), an advisory panel to the U.S. government, recommends schools sell only water, 100-percent juice and fat-free or low-fat milk to kids.

For the new study, Lindsey Turner and Frank Chaloupka from the Institute for Health Research and Policy at the University of Illinois at Chicago analyzed five years' worth of surveys from public elementary schools across the country. Principals and food service workers recorded which kinds of beverages their students could buy and where in the school the drinks were sold.

Between 578 and 748 schools returned surveys every spring between 2007 and 2011.

Researchers found the number of elementary school students who could buy soda or other drinks not recommended by the IOM at school peaked at 47 percent in 2008 and dropped to 33 percent in 2011.

Similarly, close to 16 percent of kids could buy drinks from vending machines at school in 2007, a figure that dropped to 11 percent by the most recent survey year, Turner and Chaloupka reported Monday in the Archives of Pediatrics & Adolescent Medicine.

A representative for the American Beverage Association, a trade group that represents companies including Coca-Cola Co. and PepsiCo Inc., told Reuters Health the industry reduced beverage calories shipped to schools by 88 percent since 2004, due to voluntary national guidelines.

"In fact, when it comes to elementary schools, the guidelines removed full-calorie soft drinks and allow for only bottled water, low-fat milk and 100 percent juice in 8 ounce containers," according to the emailed statement.

"This is an historic effort that was implemented in good faith as a result of a promise to change the school beverage landscape in our nation's schools - and we delivered on our commitment."

Because the researchers didn't survey students themselves, they couldn't tell how the changes in beverages available at kids' schools affected their overall soda-drinking habits.

One study from last year, however, found middle-schoolers drank the same amount of sugar-sweetened drinks, whether or not their schools had banned the beverages (see Reuters Health story of November 7, 2011).

According to the Centers for Disease Control and Prevention, 17 percent of kids and teens in the U.S. are obese - a number that has tripled since 1980 but may be leveling off.

Cutting access to soft drinks and other sugary beverages has been one strategy to address growing waistlines. In May, New York City Mayor Michael Bloomberg proposed a ban on all sugar-sweetened beverages larger than 16 ounces, including those sold at restaurants and movie theaters.

SOURCE: Archives of Pediatrics & Adolescent Medicine, online July 2, 2012.