Teenage males following a junk food diet are causing irreversible damage to their sperm, a study has found.
Eating foods such as pizza, sugary drinks, chips and burgers can result in significantly low sperm counts compared to following a healthier diet.
The research, led by Harvard University, looked at nearly 3,000 men who had a compulsory medical exam before entering the Danish army for national service.
The average age among those tested was 19.
Researchers from the US and Denmark found those men following a so-called ‘Western diet’ of these high-fat and processed foods had the lowest average sperm count.
On average, they had 25.6 million fewer sperm per ejaculation compared to those eating the healthiest diets.
While previous studies have focused on older men trying to conceive, this research shows some men have “clinically low” sperm counts despite being at their peak reproductive age.
What’s more, men eating junk food diets were found to have diminished levels of Sertoli cells – a type of cell contained in the testicles which is associated with producing healthy sperm.
Eating a junk food diet causes oxidative damage to these cells, it was found, and this cannot be reversed in later life.
The research will be presented at the European Society for Human Reproduction and Embryology (ESHRE) annual conference in Vienna.
Sperm counts have declined 59.3% among Western men from 1973 to 2011, according to a study by Hebrew University.
While the prevailing reason for this drop in sperm counts is unclear, researchers have suggested it is down to a mixture of chemical and pesticide exposure to modern lifestyles.
Men from Switzerland are among those with the lowest sperm counts in Europe, according to new findings.
Danish, Norwegian and German men were also found to have particularly low sperm counts.
According to the Harvard University study, eating a “prudent” diet high in fish, chicken, fruit and vegetables was associated with the healthiest total sperm counts.
A traditional vegetarian diet – rich in vegetables, soya milk and eggs – was the next best alternative for boosting sperm counts.
Other ways to boost sperm count include wearing loose-fitting boxer shorts and maintaining a healthy weight, according to science.