By Nicole MacKee
A high fruit and vegetable intake can help current and former smokers to reduce their risk of chronic obstructive pulmonary disease (COPD), a large prospective study of Swedish men has found.
The study, published online in Thorax, found that current and former smokers who consumed 5.3 or more serves of fruit and vegetables a day had a 40% and 34% lower COPD risk, respectively, than those who consumed fewer than two serves a day.
The researchers identified a dose–response relationship between fruit and vegetable consumption and COPD risk, with each serving per day reducing the risk by 8% in current smokers and 4% in former smokers. However, in never smokers, they found no association between fruit and vegetable consumption and COPD risk.
More than 44,000 men, aged 45 to 79 years and with no history of COPD at baseline, were included in the study. Almost one in four men were current smokers (24.3%), and 38.5% were former smokers. Over 13 years of follow up, 1918 incident cases of COPD were diagnosed.
Professor Christine McDonald, Director of Respiratory Medicine at Austin Health in Melbourne, welcomed the findings and said the data could add weight to Australia’s COPD guidelines.
The COPD-X Plan: Australian and New Zealand Guidelines for the Management of Chronic Obstructive Pulmonary Disease recognises fruit and vegetables as being part of a healthy diet, but evidence of benefit in reducing COPD risk is limited.
‘Perhaps this [new research] will allow us to strengthen the guidelines,’ said Professor McDonald, who is an author of The COPD-X Plan. We know that there are data about physical activity and pulmonary rehabilitation, and now this will add to that information and knowledge.’
The researchers found that in the current and former smokers combined, the type of fruit and vegetables consumed also had a bearing on the COPD risk reduction, with strong inverse associations found between COPD risk and intakes of apples and pears, green leafy vegetables and peppers. They said it was likely that antioxidant-rich fruit and vegetables countered the higher oxidative stress in current smokers and former smokers.
Professor McDonald agreed. ‘If you think about COPD as a chronic inflammatory disease, with elevations of systemic cytokines and the presence of increased reactive oxygen species, you can hypothesise that a diet that is rich in antioxidants could be beneficial,’ she said.
Although the study was observational, Professor McDonald said it appeared robust and there was no ‘downside’ to promoting a diet rich in fruit and vegetables, as long as it did not provide smokers with an excuse to continue smoking.
Thorax 2017; doi: 10.1136/thoraxjnl-2015-207851.
Picture credit: © John Bavossi/SPL