COPD is Ireland's fourth biggest killer and smoking is the main cause. However, a new study has found that former and current smokers may reduce their risk of the disease if they consume a diet rich in fruit and vegetables.

COPD (chronic obstructive pulmonary disease) is an umbrella term for a number of chronic lung disorders, including bronchitis and emphysema. It is a progressive, disabling condition caused by a narrowing of the airways. An estimated 380,000 people in Ireland are affected.

Recent research suggests that diet may have an important role to play in the development and/or prevention of the disease. In order to investigate this further, European researchers monitored the respiratory health of over 44,000 men aged between 45 and 79 over a 13-year period.

The men's diets were assessed, along with other potentially important factors, such as weight, physical activity levels, alcohol consumption and education. Their smoking habits were also included.

Almost two in three had smoked at some point and one in four were current smokers.

The study found that the number of current and former smokers developing COPD was lower among those who consumed plenty of fruit and vegetables. In fact, each additional daily serving was linked with a 4-8% reduced risk.

Overall, those eating five or more daily servings were 35% less likely to develop COPD than those who ate two or less daily servings per day.

However when it came specifically to smokers, current smokers who consumed five or more servings per day were 40% less likely to develop COPD, while former smokers reduced their risk by 34%.

On the other hand, those who currently smoked and consumed less than two portions of fruit and vegetables per day were 13 times more likely to develop COPD than never-smokers who consumed five or more fruit and vegetables per day. Former smokers were six times more likely to develop the disease.

The fruit and vegetables that appeared to offer the biggest benefits were apples, pears, green leafy vegetables and peppers.

While stopping smoking is still widely acknowledged as the main way to reduce the risk of COPD, the potential benefits of a healthy diet should also be promoted, the researchers insisted.

"We would argue that clinicians should consider the potential benefits of a healthy diet in promoting lung health, and advocate optimising intake of fruits and vegetables, especially in smokers who are unable to stop smoking," they said.

Details of these findings are published in the journal, Thorax.