TUESDAY, Feb. 7 (HealthDay News) -- Drinking a lot of soft drinks may increase the risk for asthma and/or chronic obstructive pulmonary disease (COPD), a new study suggests.

Nearly 17,000 people aged 16 and older in South Australia were asked about their consumption of soft drinks such as Coke, flavored mineral water, lemonade, Powerade and Gatorade.

More than 10 percent of the participants said they drank more than half a liter of soft drinks a day, according to the study, published in the February issue of the journal Respirology. That's a little more than two 8-ounce glasses of soft drinks.

The researchers found that 13.3 percent of the participants with asthma and 15.6 percent of those with COPD consumed more than half a liter of soft drinks a day.

People who consumed that amount were 1.2 times more likely to have asthma and 1.7 times more likely to have COPD than those who did not consume soft drinks, the researchers said.

"Our study emphasizes the importance of healthy eating and drinking in the prevention of chronic diseases like asthma and COPD," study leader Dr. Zumin Shi, of the University of Adelaide, said in a journal news release.

The researchers said the risk was dose-related, meaning the more soft drinks consumed, the greater the odds of having COPD or asthma.

However, the study merely points out an association and does not establish a cause-and-effect relationship.

Smoking increased the risk even further, especially for COPD. People who smoked and consumed more than half a liter of soft drinks a day had a 6.6 times greater risk of COPD than those who didn't smoke and didn't consume soft drinks.

More information

The American Lung Association has more about asthma.