For years, the conventional wisdom held that your lungs, once damaged by smoking, were about as likely to regenerate as a politician's sense of shame. But Dr Charlotte Dean, head of the lung development and disease group at Imperial College London, has some encouraging news: that's not actually true. "Broadly speaking," she says, "they can repair when you quit smoking."
Your lungs, it turns out, have a substantial capacity to heal themselves - which makes sense, given that they've spent millennia evolving to cope with things like pollution, bacteria, and viruses. "Because they're so vital - you can't survive without your lungs - they needed to have this capacity," Dean explains. So yes, your body knew what it was doing when it designed the organ that keeps you from turning blue.
But before you use this as an excuse to light up, Dean has a word of caution: smoking and vaping expose your lungs to more toxic particles than they can handle. Everyone is different, and some people's lungs will not regenerate as effectively, leaving them more susceptible to permanent tissue damage. "While it's broadly true that if you stop smoking you can revert to having much better lung health," Dean says, "it doesn't mean you're completely out of the woods. You may well have triggered mutations or genetic changes or tissue damage, and those things can affect your overall lung health, meaning that the decline as you age will come quicker or could lead to cancer."
The takeaway: quit as early as possible, because - similar to how your bones stop mending as well when you get older - your lung tissue gets less effective at repairing itself over time. A healthy lifestyle can help, and exercise is particularly important. "Just like how when you exercise you keep your muscles healthy," Dean says, "in a way the lungs are the same. You build up the capacity for gas exchange to happen more effectively, to provide oxygen around the body." So go for a jog. Your lungs will thank you - assuming you haven't already made them too hoarse to talk.