A new study led by the Harvard university indicates that male fertility is irreversibly damaged due to high consumption of junk food by the time men reach the age of 18. The study found that young men whose diet most closely matched a typical “western diet” had drastically lower average sperm counts than those who relied on more fresher foods. The study used sperm samples from around 3,000 men along with diet surveys. It is the largest study of its kind to examine the impact of diet in a group of young men who wouldn’t otherwise have any reason to check their fertility. It brings to light a serious concern that following a poor diet younger in life could bring about unwanted changes that will stick around forever.