Banning vending machines form schools may not be enough to reduce soda and fast food consumption among students, according to a recent study.

Researchers from the University of Illinois at Chicago found that 23 percent of students reported drinking at least one soda per day if they had access to vending machines in schools, compared to 28 percent of students who did not have access. This finding suggests that removing vending machines is the only school food policy change implemented, it may increase sodas consumption.

However, these differences were only observed in states where soda was taxed less or students were able to buy soda from the school cafeteria or the school store.

"Policy changes really need to be comprehensive and not just focused on one item such as regular soda or one location such as cafeterias," said Jamie Chriqui, a study coauthor and senior research scientist at UIC's Institute for Health Research and Policy.

For the study, researchers compared student data from the National Youth Physical Activity and Nutrition Study with state-level data on soda taxes, restaurant taxes, and laws governing the sale of soda in schools in 2010.

The research team also found that students eat more fast food when vending machines are removed, particularly when state sales tax rates for restaurant foods are lower, according to the authors.

The study shows that "there may be unintended effects if you only make small-scale changes. When more comprehensive changes were implemented, there were no unintended effects," Daniel Taber, lead author and a former researcher at UIC's Institute for Health Research and Policy, said in a statement

Researchers caution that the study does not necessarily mean bad news for school nutrition policies -- only that an isolated change in the school food environment is not likely to have an impact when kids have access to high-fat, high-calorie foods and beverages from other sources.

Other studies have shown that long-term, comprehensive changes in school food policies, including strengthening school meal standards, can have a positive impact on students' health.

The findings were recently published in PLOS One.