A guy may enjoy having a ice cold soda after a hot day of working out, but if he has any concerns about his reproductive prowess, he might want to consider the following: a recent study has found that drinking cola in excess might lower sperm counts by as much as 30%. This effect was initially thought to be the consequence of caffeine consumption, but coffee, which has more caffeine that cola, doesn't have the same effect.

In fact, previous attempts to study the relationship between male fertility and caffeine were inconclusive. In light of these findings, scientists wanted to obtain a clearer picture of the direct effect that regular or excessive consumption of caffeinated soft drinks had on male reproductive health.

In the study, published in the American Journal of Epidemiology, over 2500 young men were recruited over the course of 4 years, from 2001-2005. They were asked to complete a questionnaire regarding lifestyle choices and diet. The information included caffeine intake from various sources, including soda pop, coffee, and tea. Baseline semen samples were also taken.

What researchers found was that a high intake of caffeine and cola corresponded with a decrease in sperm count and concentration, though the effect was only significant for cola consumption. "High intake" was described as over 800 mg of total caffeine every day and more than 7 liters (14 x 0.5 liter bottles) of cola per week. For men who drank at least one liter of cola each day, the sperm counts were much lower than those who drank less cola.

There was no link uncovered between the caffeine in coffee or tea and reduced sperm counts, which implies that the effect on male fertility might be due to some other ingredient in the soda, as well as other lifestyle choices. Furthermore, people who consume large amounts of soda may in fact embrace other unhealthy practices, including eating fewer fruits and vegetables and more junk/fast food. It was not clear how these factors interrelated.

It is also instructive to bear in mind that even the lowest sperm counts in the study are still within what are considered normal limits, as indicated by the World Health Organization. However, even modest reductions in sperm could have a cumulative effect and eventually contribute to the risk of infertility.

Whatever the case, the findings could represent yet another reason to embrace a more wholesome lifestyle, which includes healthier foods and exercise. These choices can impact the way you look and feel, as well as reduce your risk for such chronic conditions as heart disease, obesity, diabetes, and heart disease. Now, apparently, they may also play a role in male fertility.

By some estimates, up to 10% to 15% of couples experience fertility issues when trying to conceive. About half of these cases are due to problems with the man. Male infertility can result from a number of causes, which include physiological problems with sperm production and delivery, environmental factors, and lifestyle choices such as smoking or alcohol, drug usage, obesity and diet.

If you have concerns about your reproductive health, speak with your physician. For more information, visit the website for the Cornell Institute for Reproductive Medicine.