MARIJUANA SMOKING DAMAGES SPERM

Men who smoke marijuana frequently damage their fertility in several
different ways, research suggests.

Scientists at Buffalo University found regular smokers had significantly
less seminal fluid, and a lower sperm count.

Their sperm were also more likely to swim too fast too early, leading to
burn-out before they reach the egg.

Lead researcher Dr Lani Burkman said: "The bottom line is, the active
ingredients in marijuana are doing something to sperm."

Marijuana contains several chemicals known to have an impact on human
physiology, including THC (tetrahydrocannabinol).

The researchers believe that THC may disrupt the way sperm swim, or it may
block mechanisms designed to weed out malfunctioning sperm.

Key receptors

It is known that human sperm contains receptors which are stimulated by
substances like THC and other cannabis-related chemicals.

Tests have shown that sperm exposed to high levels of THC began to swim in
an abnormal fashion, and were less able to attach to an egg so that
fertilisation could take place.

In the current study, Dr Burkman's team carried out a battery of tests on
sperm samples taken from 22 men who had smoked marijuana on average 14
times a week for at least five years.

In particular, the scientists assessed the sperm to see when they began to
swim in a very vigorous fashion.

It is vital that a sperm begins to swimming vigorously as it approaches the
egg to improve its changes of successful fertilisation. However, if it
begins to swim too fast too soon its changes of reaching the egg are
significantly reduced.

Dr Burkman said: "The sperm from marijuana smokers were moving too fast too
early.

"The timing was all wrong. These sperm will experience burnout before they
reach the egg and would not be capable of fertilization."

Long-term impact

Dr Burkman conceded that many men who smoke marijuana have fathered children.

However, she said that smoking the drug may tip the balance against men
whose fertility was borderline to start with.

"THC from marijuana may push them over the edge into infertility."

Dr Burkman said it was unclear whether fertility would recover after men
stopped smoking marijuana.

But she warned that THC remained stored in fat for a long period.

"We can't say that everything will go back to normal.

"I definitely would advise anyone trying to conceive not to smoke
marijuana, and that would include women as well as men."

Professor Alison Murdoch, chair of the British Fertility Society, told BBC
News Online the results were not surprising as marijuana was a potent drug
which was likely to have an effect on many systems in the body.

However, she said many other factors, such as diet, alcohol consumption,
cigarette smoking and exercise also had an impact on fertility.

"Male fertility is quite complicated. The partners of men with low sperm
counts can sometimes achieve pregnancy, and it is only when men produce
very, very small amounts of sperm that they can be considered infertile."

Details of the study were presented to a meeting of the American Society of
Reproductive Medicine in San Antonio.