Some of the body’s negative reactions to smoking—a risk factor for six of the world’s eight leading causes of death—could be reversible, new research from the American Chemical Society (ACS) states.

Even after using tobacco for years, male test subjects displayed improved lung function and healthier bodies just months after quitting, a team of ACS researchers found. In a study published in the ACS’s Journal of Proteome Research, these scientists noted that their patients’ bodies seemed to self-repair some of the damage caused by smoking, resulting in a decreased risk for heart attacks.

The study’s authors used urine, blood and saliva collection in men who had just quit smoking to determine whether any metabolic damage done to a body because of smoking could be reversed after quitting. The team found 52 metabolites that were “significantly” altered after the smokers quit, shifting metabolite levels to look similar to those of individuals who had never touched a cigarette.

This research provides insight into how well a body can repair itself after seemingly irreversible damage done by an unhealthy habit that kills more than seven million people per year.

Read more about the ACS research here: