The study involved more than 40,000 current and former male smokers. The current smokers who consumed five or more servings of fruits and vegetables every day were 40% less likely to develop the lung disease compared to smokers who only ate two servings or less.
Each additional serving of fruits and greens was tied to an 8% risk reduction.
Lead author Joanna Kaluza of the Karolinska Institute in Stockholm suggests that current and former smokers should eat as much fruits and vegetables as possible as each serving significantly decreases the risk of COPD development.
COPD is a category of lung diseases that make breathing difficult and can cause wheezing or coughing. The most common types of COPD are emphysema and chronic bronchitis, and they most often occur in smokers and former smokers.
The antioxidants found in produce might help to protect lungs from smoking damage, the researchers write in the journal Thorax.
The team studied data on 44,335 middle-aged and older Swedish men. None of the men included in the analysis had been diagnosed with COPD at the first assessment.
At the start of the study, the participants completed questionnaires detailing how often they ate different types of foods, including fruits and vegetables, as well as their smoking history. Researchers followed the men from 1998 to 2012 and used a patient registry to determine if they were diagnosed with COPD during the study period.
Almost two thirds of the men were current or former smokers and 1,918 were diagnosed with COPD by 2012.
The research team divided participants into five groups according to how many servings of fruit and vegetables they ate daily. The top fifth ate more than five servings per day, while the bottom fifth ate less than two servings daily.
After separating them again by smoking status, researchers found a significantly lowered risk of COPD tied to high fruit and vegetable consumption among smokers and former smokers, but not among never-smokers.
Ex-smokers with high consumption of greens were 34% less likely to develop COPD than ex-smokers with low fruit and vegetable consumption, and each additional serving was tied to a 4 percent drop in COPD risk.
When researchers analyzed the types of produce tied to lower COPD risk, they found an association with apples, pears, leafy greens and peppers but not with berries, citrus, tomatoes or onions.
We rely on antioxidants, such as those found in fruits and vegetables, to defend our lungs against harmful substances in cigarette smoke and air pollution, said Seif Shaheen, a professor of respiratory epidemiology at Queen Mary University in London who co-authored an editorial accompanying the study.
However, Shaheen stressed that diet is not a cure-all for the effects of smoking. “The most important thing you can do to reduce your chances of getting COPD is not to smoke/to stop smoking,” he said by email.
“Eating more fruit and vegetables is likely to be beneficial for your health in many ways, and for smokers who can’t stop smoking this may help to reduce your risk of getting COPD,” added Shaheen, who was not involved in the study.
“High fruit and vegetable consumption not only reduces the risk of chronic lung disease, but also cardiovascular disease, cancers, helps to keep proper body weight and other benefits,” Kaluza noted.
“It is possible for everyone to include more fruits and vegetables in their diet,” she said.