By Caroline Ryan
BBC News Online health staff in Berlin
A chemical found in the khat plant could boost the power of men's sperm, researchers have found.
Khat is chewed for a 'high'
Lab tests by King's College London found treated sperm became fertile faster, and stayed fertile for longer, than untreated sperm.
Khat is mild narcotic, producing a high when chewed, but its use has been linked to long-term problems.
The study was presented at the European Society of Human Reproduction and Embryology conference in Berlin.
The researchers say their findings could lead to products to help couples conceive.
Chewing khat leaves, which is particuarly popular in parts of East Africa, releases cathinone, a stimulant that produces the feelings of euphoria linked with the plant.
When cathinone is broken down in the body, it produces chemicals including cathine and norephedrine, which have a similar structure to amphetamines and adrenaline.
The researchers from the Centre for Reproduction, Endocrinology and Diabetes at King's College examined the effect of cathine on mouse sperm.
They found that the chemical accelerated the development of sperm, so it reached the stage where it was fertile more quickly.
It then remained in this stage for longer than normal.
This is important because, when sperm meets an egg, it needs to connect using a "lock and key" system.
If is past its 'peak', and its membranes are no longer intact, sperm will not have its part of this mechanism, meaning fertilisation cannot take place.
Early tests on human sperm suggest it is affected by cathine in the same way.
Other studies in rabbits have shown chewing khat leaves could also increased sperm production.
However, there is some concern that prolonged use could actually damage sperm.
Around seven tonnes of khat leaves are estimated to be imported into the UK each week.
The Home Office is currently investigating the plant's long-term health effects, following concern it may be linked to heart and mental health problems.
It is due to report later this year.
'Not a high dose'
The researchers say they will now carry out more analysis of human sperm.
Lynn Fraser, Professor of Reproductive Biology at King's College London, told BBC News Online: "It might be relatively easy to develop products.
"Compounds related to the ones we studied are being used in over-the-counter and prescription medicines, for dietary treatments and asthma."
"And the amount that's required isn't that high, so it's not a question of taking very high doses and therefore becoming overstimulated."
She said khat-based products could be used to help couples who are having trouble conceiving naturally, and in clinics as additives to sperm used in IVF or artificial insemination.
Professor Fraser said if the research on cathine improving sperm production was proven: "We could give it to men to improve sperm production, and to women because it is in the female reproductive tract that the sperm go through this process to become fertile."