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Could drinking too much cola alter semen quality?

According to a study carried out on 2,554 young Danish men and published in the American Journal of Epidemiology, men who drink at least a litre of cola a day present alterations in the quality of their sperm with a significant reduction in sperm concentration. These results, nevertheless, remain difficult to interpret...

Coke and semen quality
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Daily caffeine intake can be quite high in today’s society, in particular amongst young people who are often fans of caffeine-filled sodas (Coke, Pepsi or fashionable energy drinks like Red Bull).  Prof Tina Kold Jensen and her team in Copenhagen took an interest in the potential repercussions of this growing caffeine consumption on male fertility.

Cola up… semen count down?

Jensen and her team surveyed 2,554 Danish 18 year old males between 2001 and 2006 during their military service about their dietary habits: consumption of sodas, coffee, tea, and also alcohol, chocolate bars, vegetables, meat, hamburgers, etc. These young men were also clinically examined and provided a blood sample and sperm sample. They also indicated the last time they had had sexual intercourse (something which influences sperm concentration). The scientists then classed the young men into groups depending on their total daily caffeine consumption and cola-based soda consumption.

The results showed that moderate daily cola consumption did not alter semen quality. However, young men who drank 1 litre or more per day had an average sperm concentration of only 35 million per millilitre, compared to 50 million for those who didn’t drink cola at all, and 47 million for those who drank less than a litre a day.

A ‘cola’ lifestyle

Is this because of the caffeine? Probably not just the caffeine. Those young men who consume more than 800mg of caffeine a day (the equivalent of 7 cups of coffee) did not have a significant decrease in sperm count, even though the volume of their sperm was slightly lower. What is more, regular caffeine intake has also been linked by other studies to having a sedentary job, stress or insufficient physical activity, a myriad of factors that can also affect semen quality...

So is it due to a certain lifestyle? These young cola-lovers drink less milk than others, eat less fruit, vegetables and fish. They also consume more alcohol, tobacco and hamburgers than those who drink less than one litre of cola per day. But here still, it’s difficult to categorically interpret these results as one of these types of behaviour or another could itself influence sperm count...

What is certain in all cases however is that colas have very high sugar content, and cola consumption, when excessive, is associated with an unhealthy lifestyle in young people. Furthermore, the study authors - who were unable to definitively conclude on the reasons for the reduction in semen quality observed - emphasise that the fertility of young Danish men is steadily decreasing, while their study showed a clear increase in cola consumption between 2001 and 2005.

While waiting for new scientific studies that confirm or invalidate this data, the Danish researchers insist on moderation and recommend drinking less than a litre of cola per day – which means no more than 3 cans. They also recommend limiting overall daily caffeine intake to less than 800mg per day.

Caffeine Intake and Semen Quality in a Population of 2,554 Young Danish Men’, Jensen TK et coll., American Journal of Epidemiology, March 2010

Posted 04.01.2011


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