"One won't hurt," is what the older students shout to the freshmen who are secretly smoking their first cigarette in the bike shed. A small choice that, without them knowing, leaves a mark on their future. Everyone knows that smoking is bad, but it turns out that the age at which you start smoking can influence the lung health of your future children. Scientists examined the blood of over 800 father-child pairs and took questionnaires about their smoking habits. It turns out that the risk of asthma and obesity in offspring is significantly increased when boys start smoking before the age of 15. This is because smoking leads to an increase in methylation on the offspring's DNA. These groups can suppress the normal DNA function and lead to diseases like asthma and obesity. Children of fathers who started smoking before their 15th birthday have methylation on 19 different sites on their DNA. In contrast, children of fathers who started smoking later only have methylation on 2 sites. This major difference is because the germ cells of teenage boys are not fully developed yet. Therefore smoking not only affects their own lungs but also those of their offspring.
