Sperm has another enemy - marijuana - with new United States researchers reporting that smoking cannabis can jeopardise the fertility of men and women.

The article discusses a study in the February 5, 2010 issue of "Cell" which finds that human sperm relies on an ion channel to reach an unfertilized egg. Also noted in the study was the discovery of a compound similar to one found in marijuana that may interfere with the ion channel suggesting a molecular link between male infertility and habitual marijuana use. An overview of the research, including a discussion on the proton channel Hv1 used by human spermatozoa, is presented.

Taking cannabis doubles the risk of men under 30 producing abnormal sperm which could significantly lower their fertility and prevent them from having children, according to the world’s largest study into lifestyle and sperm quality.

A new study by scientists at the University of Sheffield links marijuana use to sperm abnormalities that could limit men's fertility.

Men who smoke marijuana frequently have significantly less seminal fluid, a lower total sperm count and their sperm behave abnormally, all of which may affect fertility adversely, a new study in reproductive physiology at the University at Buffalo has shown.

Around 40% of infertility cases are due to problems with the size, shape, motility, and/or count of the man’s sperm. A recent study seeking to explore lifestyle factors that may influence sperm morphology discovered that young men who smoked marijuana were more likely lower amounts of normally-shaped sperm. The study was led by Allan Pacey of the University of Sheffield and the paper was published in the journal Human Reproduction.

''Cannabis doubles younger men's risk of infertility, study finds,'' reports The Independent. The same study also found a drop in sperm quality during the summer months.

Young men who use cannabis may be putting their fertility at risk by inadvertently affecting the size and shape of their sperm, according to new research. In the world's largest study to investigate how common lifestyle factors influence the size and shape of sperm, a research team found that sperm size and shape was worse in samples ejaculated in the summer months, but was better in men who had abstained from sexual activity for more than six days.