Sulforapane is found in broccoli and brussel sprouts
A substance found in broccoli may limit the damage which leads to serious lung disease, research suggests.
Chronic obstructive pulmonary disease (COPD) is often caused by smoking and kills about 30,000 UK residents a year.
US scientists found that sulforapane increases the activity of the NRF2 gene in human lung cells which protects cells from damage caused by toxins.
The same broccoli compound was recently found to be protective against damage to blood vessels caused by diabetes.
Brassica vegetables such as broccoli have also been linked to a lower risk of heart attacks and strokes.
In the latest study, a team from Johns Hopkins School of Medicine found significantly lower activity of the NRF2 gene in smokers with advanced COPD.
Writing in the American Journal of Respiratory and Critical Care Medicine, they said the gene is responsible for turning on several mechanisms for removing toxins and pollutants which can damage cells.
Previous studies in mice had shown that disrupting the NRF2 gene caused early onset severe emphysema - one of the conditions suffered by COPD patients.
Increasing the activity of NRF2 may lead to useful treatments for preventing the progression of COPD, the researchers said.
In the study, they showed that sulforapane was able to restore reduced levels of NRF2 in cells exposed to cigarette smoke.
"Future studies should target NRF2 as a novel strategy to increase antioxidant protection in the lungs and test its ability to improve lung function in people with COPD," said study leader Dr Shyam Biswal.
A spokeswoman for the British Lung Foundation said: "This is an important study for the 3 million people in the UK with COPD because of its findings about the imbalance of oxidants and antioxidants in the lungs.
"We know broccoli naturally contains important compounds but studies so far have taken place in the test tube and further research is needed to find if you can produce the same effect in humans."