Fizzy drinks won't just hide your penis behind a belly of sugar and syrup. They can also destroy your manhood.

We all heard the rumour that Doctor Pepper lowered your sperm count (cue gag: what's the worst that could happen?). Scientists at Copenhagen University Hospital have found some truth in the playground myth. A study of young men found that those who drank excessive amounts of cola saw their sperm count drop by a massive 30 per cent.

The study which began in 2009 looked at 2,554 men who drank regular and diet fizzy drinks. When they reach the age of 18 all Danish men are prompted to undergo a medical examination in order to establish their readiness for military service. In addition to a fitness test the selected participants completed a questionnaire about their caffeine and cola consumption.

The scientists found that sperm count could be as low as 35 million per millilitre in excessive cola drinkers, compared with 56 million per millilitre in more moderate consumers. 35 million is within the normal range of sperm, but the study warned that a reduced sperm count increases the risk of infertility. The threshold at which this began to occur was when participants consumed at least one litre of cola per day. That's just over three UK sized (330 millilitre) cans.

The cause of the reduced count was not what one might expect. Published in the American Journal of Epidemiology the study claimed it was not caused by caffeine:

The reduction in semen quality among high quantity cola drinkers, if causal, must be attributed to constituents in cola other than caffeine because the caffeine content of cola is not high.

This suggests the cause is an ingredient in cola, or possibly that drinking cola is an indicator of an unhealthy lifestyle more generally. A previous study by the Copenhagen University Hospital found that stress impaired semen quality.

The report concluded:

We cannot exclude the possibility of a threshold above which cola (and possibly caffeine) negatively affects semen quality. Alternatively, a less healthy lifestyle among these men may explain the findings.

Picture: energyy/iStock

As if this news weren't troubling enough, scientists at Nicolaus Copernicus University, Poland, also found that in some cases cola addicts suffered from erectile dysfunction.

The study by doctors Jan Adamowicz and Tomasz Drewa suggested that a sweetener present in many fizzy drinks damages arteries and prevents blood flow to the penis. This can combine with other physical and psychological factors to prevent an erection.

The study drew attention to the sweetener High Fructose Corn Syrup, which is already considered a primary cause of obesity due to its presence in a variety of food stuffs.

Writing for the Central European Journal of Urology, Adamowicz and Drewa had this conclusion:

Is there a link between soft drinks and ED [erectile dysfunction]? Based on their popularity and its influence on metabolism we think that the probability of such a coincidence is very high.