Your lungs have an almost “magical” ability to repair the cancerous mutations caused by smoking – but only if you stop, say scientists.
Smokers have long been told their risk of developing diseases like lung cancer will fall if they can quit, and stopping smoking prevents new damage to the body.
A study published on Thursday in the journal Nature found that the benefits may go further, with the body appearing to draw on a reservoir of healthy cells to replace smoke-damaged ones in the lungs of smokers when they quit.
The effect has been seen even in patients who had smoked a pack a day for 40 years before giving up.
The thousands of chemicals in tobacco smoke corrupt and mutate the DNA in your lung cells – slowly transforming them from healthy to cancerous.
The study’s joint senior author, Peter Campbell of the UK-based Wellcome Sanger Institute, said the results should give new hope to smokers who want to quit.
“People who have smoked heavily for 30, 40 or more years often say to me that it’s too late to stop smoking – the damage is already done,” he said in a statement issued by the institute.
“What is so exciting about our study is that it shows that it’s never too late to quit.”
In people who quit, up to 40% of their cells looked just like those from people who had never smoked.
“We were totally unprepared for the finding,” Dr Peter Campbell, from the Sanger Institute, told BBC News.
He added: “There is a population of cells that, kind of, magically replenish the lining of the airways.
“One of the remarkable things was patients who had quit, even after 40 years of smoking, had regeneration of cells that were totally unscathed by the exposure to tobacco.”
The precise mechanism by which that replacement occurs is not yet clear, but the study’s authors believe there may be a sort of reservoir of cells, waiting for a chance to emerge.
“Once the person quits smoking, the cells gradually proliferate from this safe harbour to replace the damaged cells,” Campbell said.