Male circumcision is many things: mark of cultural identity, hygiene measure, medical necessity. And now it's a new front in the HIV war

One of the most famous supporters of male circumcision was the cereal magnate John Harvey Kellogg. "The operation should be performed by a surgeon without administering an anaesthetic, as the brief pain attending the operation will have a salutary effect upon the mind, especially if it be connected with the idea of punishment," wrote the doctor who invented wheat flakes.

Kellogg's enthusiasm for the practice was the spurious belief that it would deter masturbation, but now the operation is being hailed as a lifesaver for millions. Last week, American scientists announced that circumcision can halve the risk of a man picking up HIV through heterosexual intercourse.

The National Institutes of Health closed major trials in Kenya and Uganda early after deciding that it was unethical to continue after a review of the data showed the halving of risk. All uncircumcised participants will now be offered the operation. In 2005, another randomised trial in Africa was stopped for the same reason.

It is estimated that in the next 10 years, male circumcision in Africa could avert two million new HIV infections and 300,000 deaths. In 20 years, it could avert 5.7 million new infections and three million deaths.

"I have no doubt at all that a number of African countries will now scale up the provision of male circumcision," says the British urological surgeon Timothy Hargreave, who has co-authored a World Health Organisation technical manual of surgical techniques for circumcision. "Already some of the African countries are asking for help."

Will Nutland, the head of health promotion at the HIV and Aids charity the Terrence Higgins Trust, says: "We have known for some time that male circumcision can reduce the risk of men picking up sexually transmitted infections, including HIV. However, circumcision will not reduce onward transmission of HIV if a man is already infected with the virus. [Circumcision] should not be a substitute for investment in education programmes, condom provision and HIV vaccine and microbicide research."

Research indicates that HIV (the human immunodeficiency virus) enters a man's body by binding to receptors on Langerhans cells, which are found in large numbers in the moist skin on the underside of the foreskin. When the foreskin is pulled back during intercourse, these cells are exposed to the virus. After circumcision, the skin of the head of the penis and just under the head becomes dryer and thicker, covering up the Langerhans cells and denying the virus an easy point of entry. However, there are some Langerhans cells in the skin near the tip of the inside of the urethra, so a condom is still necessary.

The foreskin is designed to protect the penis, to ease penetration, and to stimulate friction and thus arousal. It has its own lubrication and sensory nerve-endings.

Circumcision is likely to have arisen in the ancient societies of the Middle East as an early health measure to prevent inflammation caused by sand underneath the foreskin. It was part of early Egyptian culture and is represented on the tomb of Ankhmahor at Sakkara. It has been a religious rite in Judaism and Islam for thousands of years. During the world wars, Australian soldiers in North Africa and the Middle East suffered sand-induced inflammation on such a scale that many required circumcision.

The Victorians were keen on infant circumcision, believing it would deter masturbation. It is estimated that one in three boys was circumcised in the 1930s, but the procedure fell out of favour from the 1940s onwards. Today, in non-Jewish and non-Islamic sectors of British society, fewer than 5 per cent of men are circumcised, mostly for medical reasons. But the practice still flourishes elsewhere, particularly in North America, owing to Jewish and fundamentalist Christian influences, and for "hygiene" reasons. In Morocco last year, 7,000 prisoners were pardoned to celebrate the circumcision of King Mohammed VI's two-year-old son. It has been reported that Madonna, a follower of Kabbalah, an offshoot of Judaism, wants to hold a traditional circumcision known as a bris for her adopted baby David.

There are several medical reasons why the operation is carried out. The opening of the foreskin may be damaged, so that it can no longer be pulled back. This can be the result of minor injury, or of inflammation. Infection of the head of the penis is a particular problem in diabetic men.

Circumcised men are at less risk of harbouring or transmitting syphilis, chlamydia and chancroid. It also limits urinary tract infections, and early circumcision can reduce the risk of cancer of the penis in older age.

One argument against circumcision, usually based on anecdotal evidence, is that it reduces sensation during intercourse. Men circumcised at birth have nothing to compare it to, and those who had the operation as adults for medical reasons will have suffered reduced sensation before. Doctors in Israel currently offering circumcision to healthy adult Jewish immigrants from Belarus and Ukraine claim their patients do not report a reduction of pleasure.

Some men bitterly regret having been circumcised. "Some say the head of the penis becomes desensitised and they don't feel very much when they have sex," says Dr John Warren, chairman of the charity NORM-UK. The association started as a self-help group, and now operates also as an information service. "Some men complain of discomfort from the head of the penis rubbing on clothing. Some don't like the appearance. We hear from a lot of young men who don't do sports because they don't want to be seen in the changing room. Some have complications and ugly cosmetic results."

Measures can be taken to restore the foreskin, but none is entirely satisfactory. Some men resort to a skin graft. "We have yet to hear of someone who has had a good result from this," Warren says. "One or two surgeons in America and Australia have apparently been able to produce good results."

The alternative is stretching the skin with weights, a traction device or straps, or manually. Enough skin can be produced to cover the head of the penis, which becomes more moist and sensitive as a result. "But you never get back all those nerve endings that are lost," Warren adds.

'There are three genders: male; female; and with a foreskin' - David Schneider

I have a Jewish friend who's so assimilated that he's joined a church and even had himself baptised. This might be to do with getting his daughters into the local church school (I'm sure St Paul only converted because there was an excellent C of E primary just off the road to Damascus), but you have to admire his commitment. Nevertheless, when his first son came along, even this hardcore convert to school-league-table Christianity had him circumcised.

Circumcision is the last thing a Jew abandons, probably because it's the most primitive and tribal of our rituals, a mark of belonging. But it's not just a religious/ethnic issue. For me, it's like there are three genders: male; female; and with a foreskin. The last is a mystery to me, even more than the female. It's inevitable that I'd want my son to be like me in that crucial area (plus possibly a bit bigger). But why would a right-on parent who'd never dream of smacking his child think nothing of cutting off a piece of his penis?

There are plenty of reasons not to circumcise. The internet tells me that circumcised men enjoy considerably less sexual pleasure than uncircumcised. One article says 35 per cent less, though you wonder how they reached such an exact figure, especially as any shortfall in their Jewish subjects is more likely to be due to their relationships with their mothers.

Then there was the actor I worked with who was "restoring" his foreskin through an eye-wateringly painful process of tape, "manual tugging" and - God help us - a system of O-rings and weighted foreballs, whatever they are (I didn't ask). For him, circumcision was abuse, the mutilation of an innocent child without consent. We're opposed to female circumcision, so why allow it with males? You could say the guy had issues.

Still, generations of circumcised Jews have turned out all right, give or take the odd few years of therapy. It's meant to be cleaner and, as the announcement by the World Health Organisation's Kevin de Cock (surely not his real name) seems to prove, healthier. I'm told the Royal Family are circumcised, though whether that's a recommendation, I'm not sure.

I'm told that Jews are circumcised when they're eight days old because the nerve endings aren't yet fully developed so the baby doesn't feel pain like we would. It may be crying for other reasons - discomfort or hunger. Well, I'm no Lord Winston (who's Jewish and so, I presume, circumcised) but I don't think the sound the baby made at a circumcision I attended was because it felt a bit peckish.

Luckily, my very thoughtful girlfriend has so far provided me with two girls. I'm not sure what I'd do if I had a boy. It's a big statement for a Jew not to circumcise, but whether I could risk condemning him to a future of O-rings and foreballs, I just don't know.

David Schneider is a comedian