A high level of soft drink consumption is associated with asthma and/or chronic obstructive pulmonary disease (COPD). 13.3% of participants with asthma and 15.6% of those with COPD reported consuming more than half a liter of soda per day. Furthermore, smoking makes this relationship even worse, especially for COPD. Compared with those who did not smoke and consume soft drinks, those who consumed more than half a liter of soft drink per day and were current smokers had a 6.6-fold greater risk of COPD.
Respirology, Feb 2012