New research has found an association between a diet rich in fruit and vegetables and a reduced risk of chronic lung disease among former and current smokers.

Eating lots of fruit and vegetables is not just good for the heart but also the lungs, especially those of former smokers.

New research has found a diet rich in fruit and veg has been linked to a much lower risk of developing chronic obstructive lung disease (COPD) - a condition that affects up to one in five Australians over the age of 40.

A study published in journal Thorax found each extra daily serving of fruit or vegetables was associated with a four to eight per cent reduction in risk of COPD among former and current smokers.

Smoking is the leading cause of COPD and the World Health Organisation predicts the lung disease is set to become the third leading cause of death worldwide.

The main symptoms of COPD, for which there is no cure, are shortness of breath, coughing, and increased mucus production, while wheezing and chest tightness are also common.

To try to find out if fruit and vegetable intake might have a dietary role in treatment, researchers from the Department of Human Nutrition at the Warsaw University of Life Sciences in Poland tracked the respiratory health of more than 44,000 Swedish men aged between 45 and 79 for 13 years up to the end of 2012.

Almost two thirds of the men had smoked at some point; around one in four were current smokers; and nearly four out of 10 had never smoked.

During the monitoring period, 1918 new cases of COPD were diagnosed.

In all, those eating five or more daily servings were 35 per cent less likely to develop lung disease than those eating two or fewer daily servings.

Each additional serving was associated with a four per cent lower risk of COPD in former smokers and an eight per cent lower risk in current smokers.

Apples or pears; green leafy vegetables; and peppers seemed to exert the strongest influence on risk.

No such associations were seen for berry fruits; bananas; citrus fruits; cruciferous and root vegetables; tomatoes; onions; garlic; or green peas.

It's thought the antioxidants abundant in fruit and vegetables my curb the inflammation smoking causes in the lungs.

Expert on COPD Dr Raphaelle Varraso from French research institute INSERM says while this is only an observational study "there is nothing to be lost by acting now".

"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," he said.