Men who smoke or drink or even do drugs may not be jeopardizing their fertility, says new study. Researchers say that unhealthy lifestyle might not affect the swimming sperms men produce.

"Despite lifestyle choices being important for other aspects of our health, our results suggest that many lifestyle choices probably have little influence on how many swimming sperm they ejaculate. For example, whether the man was a current smoker or not was of little importance. The proportion of men who had low numbers of swimming sperm was similar whether they had never been a smoker or a smoker who was currently smoking more than 20 cigarettes a day. Similarly, there was little evidence of any risk associated with alcohol consumption," said Dr. Andrew Povey from the University of Manchester’s School of Community Based Medicine.

For the study, the researchers recruited nearly 2,300 men from 14 fertility clinics. These men were asked to fill out a questionnaire about their lifestyle.

Some 900 participants in the study group had low sperm counts. Their lifestyles were compared with data from the control group of more than a 1,000 men.

The researchers found that men who have had testicular surgery were more likely to have low sperm counts. Also, men who were engaged in manual labor, who did not wear boxer shorts were more likely to have low sperm count.

Men who had low sperm counts were also more likely to be blacks or not had a previous conception.

They found that smoking, drinking, BMI and recreational drugs did not affect the sperm count in men.

"This potentially overturns much of the current advice given to men about how they might improve their fertility and suggests that many common lifestyle risks may not be as important as we previously thought. Delaying fertility treatment then for these couples so that they can make changes to their lifestyles, for which there is little evidence of effectiveness, is unlikely to improve their chances of a conception and, indeed, might be prejudicial for couples with little time left to lose."

"Although we failed to find any association between common lifestyle factors and the number of swimming sperm men ejaculate, it remains possible that they could correlate with other aspects of sperm that we have not measured. These include the size and shape of sperm (sperm morphology) or the quality of the DNA contained in the sperm head. We need to do further work to look into these aspects," said Dr. Allan Pacey, Senior Lecturer in Andrology at the University of Sheffield and part of the research team.

Dr. Pacey says that men should follow a healthy lifestyle but becoming a monk isn't all that necessary.

"In spite of our results, it’s important that men continue to follow sensible health advice and watch their weight, stop smoking and drink alcohol within sensible limits. But there is no need for them to become monks just because they want to be a dad. Although if they are a fan of tight Y-fronts, then switching underpants to something a bit looser for a few months might be a good idea!" Dr. Pacey said.

"The higher risk we found in manual workers is consistent with earlier findings that chemicals at work could affect sperm and that men should continue to keep work exposures as low as possible," said Professor Nicola Cherry from the University of Alberta.