Cannabis link to dopey sperm

By KATHERINE HOBY

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."