Stating that only a few studies have looked at caffeine's impact on reproductive health in men, Jensen said that the team decided to study the effect, as Danish youth has been increasing their consumption of caffeine-containing soft drinks over the last decades.

According to researchers from Copenhagen University Hospital in Denmark, the effect is unlikely due to caffeine, as coffee did not have the same effect, even though its caffeine content is higher.

Instead, other ingredients in the beverage or an unhealthy lifestyle could be behind it, the media reported.

For their research, the team studied more than 2,500 young men.

They found that those men who did not drink cola had better sperm quality, averaging 50 million sperm per milliliter semen and tended to have a healthier lifestyle.

In contrast, the 93 men who drank more than one liter of cola a day had only 35 million sperm per milliliter. They also ate more fast foods and less fruit and vegetables.

When looking at caffeine from other sources, such as coffee and tea, the decrease in sperm quality was much less pronounced, the researchers note in the American Journal of Epidemiology.

It is still not clear if the cola or the unhealthy lifestyle, or both, is to be blamed.

While the sperm counts would be considered normal by the World Health Organization, men with fewer sperm generally have a higher risk of being infertile, the report said.

From the April 12, 2010, Prepared Foods E-dition