CANNABIS LINK TO DOPEY SPERM

Smoking cannabis slows more than just your thoughts and speech - men may
find their sperm also in low gear.

Research shows that sperm swim much more slowly when heavily exposed to the
drug's active ingredient, increasing the chance of infertility among dope
smokers.

American scientists have studied the effects of cannabis on the chemical
signals in the reproductive organs.

A small amount of the active ingredient in marijuana smoke -
tetrahydrocannabinol (THC) - makes sperm more alert and increases the chance
of the egg being fertilised. But a large dose of THC leaves sperm sluggish
and dopey and less likely to penetrate the egg.

The scientific director of Auckland's Fertility Associates, Dr Bert Stewart,
said THC could affect fertility but only in large doses.

"If you expose sperm to huge quantities of the active ingredient in cannabis
then it does affect sperm," he said.

"But the amount of THC introduced would have to be huge - a lot more than
even a chronic dope abuser."

Professor Herbert Schuel, of the University of Buffalo in New York, carried
out the research.

He said sperm swam hyperactively and rapidly, waving their heads
side-to-side when subjected to a low dose of THC.

"But when the concentration was 10 times higher, the number of sperm showing
hyperactivity decreased."

Professor Schuel examined the role of THC in the cells of the male and
female reproductive systems and focused on its relationship with a similar
set of chemicals produced by the body.

Known as anandamides, these signal to sperm and nearby cells to become
hyperactive by latching onto receptors on the outside walls of cells.

But the THC latches onto the receptors instead, leaving the anandamides
adrift to build up around the sperm. Too many anandamides give the sperm an
excess of signals, making them confused and sluggish.

Dr Stewart said that while it was not the case that smoking cannabis would
lead to infertility, "if you are on the edge of becoming infertile it could
push you over."

Factors which lowered sperm production were usually reversible.

"If you see patients who smoke heavily and ask them to stop, sperm
production will eventually return to normal," Dr Stewart said.

"Sperm is constantly being produced - the production line is happening all
the time.

"If you are a chronic user of anything it is bound to have an effect on your
fertility but occasional cannabis use probably has no effect.

"Twenty cigarettes will do you more harm in the baby stakes."