Increasing daily intake of fruits and vegetables does not improve lung function or other markers of lung health in people with chronic obstructive pulmonary disease (COPD), according to a recent study published in the European Respiratory Journal.
Previous research had shown that people who eat large quantities of fruits and vegetables may have less-severe lung symptoms or may be less likely to die from COPD. Researchers believed this to be true because of the antioxidants present in those food groups and their anti-inflammatory effects. However, those studies were observational, meaning that scientists compared people who were already eating fruits and vegetables to those who did not eat them.
While this type of research is effective for some studies, it does not prove that nutritional habits alone drive changes in lung function. That is because scientists cannot take into account every other health and lifestyle variable that affects breathing and airway function.
For the latest study, researchers attempted to overcome this hurdle by recruiting 75 people with COPD who skimped on fruits and vegetables and randomly assigned half of them to increase their consumption from less than two servings per day to at least five servings. The remaining participants were instructed to eat no more than two daily portions. Participants from both groups had fruits and vegetables delivered to their home for 12 weeks and were advised on how to store and cook them.
While those people assigned to a diet high in fruits and vegetables increased their consumption to more than six servings per day, this did not lead to any improvement in lung function or measures of inflammation in the airway. Further, 35 patients saw their COPD worsen during the study, including six patients who required hospitalization. Participants in both diet groups were equally as likely to have worsening symptoms.
The researchers note that participants in the study may have been too far along in the disease to see any benefit from diet changes. All patients had moderate to severe lung disease and were an average age of 65. However, the researchers believe that a boost in fruit and vegetable intake that lasts longer than just a few months may lead to improvements in lung function for those in the early stages of COPD.