Studies published in Circulation: Cardiovascular Genetics shows that smoking affects human genome. Researchers have conducted a meta-analysis of genome-wide DNA methylation using samples of 16,000 participants.
DNA methylation is an epigenetic mechanism that methyl groups are added to DNA without any interruption of DNA sequence. Methylation can regulate gene expression that involves turning genes on & off. Change of gene expression caused by an acquired lifestyle such as smoking, eating habits, exercise can be inherited to the next generation.
Researchers determined that smoking-associated DNA methylation alters more than 7,000 genes and it may cause some diseases over a long period of time. They found that DNA methylation sites mostly returned to normal level within 5 years after quitting smoking. However, change of some genes can last for people who stopped smoking even after 30 years.
Co-author and an instructor at Harvard Medical School, Roby Joehanes Ph.D. says, “The encouraging news is that once you stop smoking, the majority of DNA methylation signals return to never smoker levels after five years, which means your body is trying to heal itself of the harmful impacts of tobacco smoking.”