Why Circumcision Protects Against HIV

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Uncircumcised David has a higher risk of contracting HIV than the average circumcised man. At least he would if he were sexually active and not made of marble.

On LWON’s first birthday, Richard Panek asked me to explain why being circumcised makes a man less likely to catch HIV. So I will. Here you go, Richard.

Let’s be honest. Foreskin is weird. The rules of evolution suggest that it once conferred an advantage, but I can’t fathom what that advantage might have been. These days, it seems like having foreskin may be more of a hindrance than a help. Not only does foreskin have a tendency to get painfully caught in pants zippers. It also substantially increases a man’s chances of contracting sexually transmitted diseases like HIV.

Researchers have long observed that HIV rates are generally higher in countries where male circumcision is not common practice. This correlation between circumcision and HIV is intriguing, but any scientist will tell you (ad nauseam) correlation does not equal causation.

So three research groups set out to test whether having foreskin could really influence a man’s risk of contracting HIV. The teams conducted three separate randomized clinical trials — one in South Africa, one in Uganda, and one in Kenya. In each study, they enrolled between 2,000 and 5,000 HIV-negative men and circumcised half. Taken together, the studies found that circumcision reduced a man’s risk of contracting HIV by about 60%. “It’s just a slam dunk,” Maria Wawer, an HIV researcher at Johns Hopkins, told me in 2007.

Now that I’ve convinced you that circumcision does provide protection against HIV, let’s turn to the question Richard asked—why?

I’ve written a decent amount about male circumcision as a means of preventing HIV (see this, and this, and this), so I thought I knew the answer. But when I delved into the latest research to write this post, I found far less consensus than I thought I would. So perhaps I can’t answer Richard’s question (hangs head in shame), but I can give you a short tour of the main hypotheses and the latest evidence. (For more info, see this 2011 review article).

Hypothesis #1: The top layer of skin on the inside of the foreskin is thin and delicate, thus more easily penetrated by HIV. Skin’s top layer contains a tough protein called keratin, the very same protein found in teeth, hair, and fingernails. At least one study found that this keratin-containing layer of skin was thinner on the inside of the foreskin compared to the outside. And researchers hypothesized that this might explain the foreskin’s role in HIV. Thinner skin would likely be easier for the virus to penetrate than thicker skin. But the evidence is mixed. A study published last year found that the inner skin was just as thick as the skin found on the outside of the foreskin.

Hypothesis #2: The foreskin is rife with special immune cells that are susceptible to HIV. To infect a cell, the virus must bind to particular proteins on the cell’s surface. Only certain immune cells have these proteins. So it makes sense that if the foreskin had more of these cells than, say, the rest of the penis, it would be an attractive entry point for the virus. But researchers can’t seem to agree on whether that’s true. Some studies have found more of these specialized cells on the inside of the foreskin, others have not. The jury is still out.

Hypothesis #3: The space between the foreskin and the head of the penis is populated with bacteria that make it easier for HIV gain entry. To study this, researchers collected swabs from the penises of HIV-negative men before and after circumcision. They found two entirely different communities of bacteria. Before the surgery, most of the microbes were anaerobic. A year after the foreskin was removed, the bacteria were mainly aerobic. One group of researchers posits that the anaerobic bacteria can cause inflammation, attracting the very immune cells that HIV likes to infect.

A number of other hypotheses exist as well. Foreskin is more prone to tearing during sex than the rest of the penis. Foreskin traps HIV, giving the virus more time find a way in. The genital ulcers characteristic of some sexually transmitted diseases can provide a doorway for HIV to enter the body. Circumcised men are less likely to get these infections. Clearly, more research is needed.

In the meantime, the countries most heavily impacted by HIV and AIDS are working to roll out mass circumcision as an HIV prevention strategy, offering the procedure for little or no money. According to UNAIDS, at least 450,000 men have been circumcised in Africa since 2007. It’s a start.

Image credit: Wikimedia commons. Note that I have spared you the more graphic images that come up when you search on “foreskin” and “circumcision” in Wikimedia commons. You’re welcome.

Note: Circumcision, in case you didn’t know, is a highly controversial topic. Many people believe circumcision is mutilation. Obviously, adults can make their own choices about whether they want to keep their foreskin. But babies don’t have that option. I’ve often wondered what I would do if I had a son, and whether my decision would differ if I were South African instead of American.

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18 thoughts on “Why Circumcision Protects Against HIV

  1. Erm, in reference to the photo above *David* is made of marble. Michelangelo not so much. Thanks for the post though. It’s a debate I will be going through if I have a boy later this year.

  2. Ed, Doh!!! Thanks for catching my dumb mistake. I’ve corrected the error.

    Rebecca,
    The fact that circumcision protects against herpes fits in with the ulcer idea. And it also seems like the thinner skin hypothesis would fit, but I don’t know enough about HPV and herpes infection to say for sure.

    I am intrigued by the idea that the microenvironment under the foreskin (and the bacteria that live there) could contribute to HIV infection. To me, it seems plausible that something about that microenviroment makes HPV and herpes infection more likely too. Any experts out there have thoughts?

  3. Hi Cassandra,

    Nice post. I would however want to point out that the results found in Africa may not necessarily be representative of the relationship between circumcision and HIV in other parts of the world.

    Additionally, in one of the studies you cited, the men already had HIV, and it tested whether or not the virus was transmitted to their partners. This isn’t the same as testing whether or not circumcision prevents the men from becoming infected. Another study was also terminated early, for reasons which aren’t clearly described and therefore may be missing any potentially equalizing effects that happened after the study was prematurely stopped.

    I agree with you that circumcision seems to lower transmission rates in parts of the world where HIV are rampant, such as in Africa, but I would caution against interpreting this as a direct effect, and against extrapolating this data to the rest of the world.

  4. “The Biblical technique of circumcision designed to fulfill the Covenant with Abraham removed only preputial tissue that extended beyond the tip of the glans penis…”

    “The wonderful statue of David by Michelangelo appears intact but is in fact correctly represented because the future King David has been circumcised by the accepted procedure of the Biblical era. Only the tip of his foreskin has been removed, fulfilling the Covenant with Abraham (Genesis 17).”

    See:
    http://www.doctorsopposingcircumcision.org/virtual_journal/v1n1.html#article1

  5. Wouldn’t the inside of the foreskin be similar to the tissue on the inside of the labia or vagina? And the tough outer part be the outside of the labia? I am trying to remember where all the parts shift to when the hormones raise during the pregnancy… I am trying to compare it to something I am familiar to. I always thought the foreskin was there for protection so that the penis didn’t all dried out like the keretinized outside of the foreskin.

  6. Michelle,
    There actually were three trials where they tested the ability of circumcision to prevent HIV acquisition in men. I linked to the wrong study (in HIV-positive men), but I’ve fixed that now. And you’re right that male circumcision does not protect women from contracting HIV.

    Also, it is my understanding that all the trials were stopped early because they saw such a dramatic effect, and it would have been unethical to continue to withhold the intervention from the men in the study who didn’t receive circumcision. And, though they stopped the trials early, they continued to follow the men. The effect appears to be lasting (see here: http://i-base.info/htb-south/1276/).

    And I’m not sure that I buy that the results aren’t applicable to other parts of the world. A penis is a penis is a penis, no? The World Health Organization recommends circumcision as a HIV prevention strategy in all countries with a high prevalence of HIV, and says high-risk groups (such as sex workers and injection drug users) in low-prevalence countries may benefit too.

  7. I am circumcised and HATE it! No one has the right to surgically mutilate my body. It’s my body and it should be my choice. I have been left scarred for life emotionally, physically and mentally. 

    I have to live in this body, no one else. I have to live with the zig zag scar line, skin tags, skin bridge, scar and missing flesh from my glans (head) and the tight cut that causes my turkey neck. No one did me any favors!

    Parents should not have the right to surgically inflict their religious, sexual or cosmetic preferences on their children. It’s for the child to decide, when old enough. Until then, they must be legally protected from this assault and mutilation.

    HIV/ AIDS, HPV, STDs are all diseases of sexually active adult men. This has nothing to do with an infant boys healthy penis. 

    Condoms, safe-sex and hygiene prevent disease. NOT circumcision. 

    My parents religion is not my religion. And a boys penis has nothing to do with religion. Your religious freedom stops at another persons body. You are free to do and say what you please for your religion with your own body. That is your religious freedom. But don’t force your beliefs and religion on non-consenting infants!

    I am the only mutilated male in my family.  My mother learned better so she did better. My Father, 4 brothers, 2 nephews, my partner and other male family members are all whole and intact. None have had any issues with their foreskins. 

    Circumcision Ends with Me!

  8. Yes, a penis is a penis, but public health strategies are highly context-dependent. Circumcision is promoted as a way to reduce the risk of HIV (and other STDs) contraction in parts of the world that lack easy access to more efficient prophylactics (like condoms and sex education), which is why most studies of this type are done in Africa. In societies where prophylactics like condoms are cheap and readily available, there are diminishing returns on the benefits of circumcision.

    I am also not entirely convinced that circumcision provides a great physiological barrier to HIV infection. It is very likely that there’s a behavioral component as well. The act of having the surgery might influence the sexual practices and behaviors of the men in the study. I imagine that if you have surgery done on your penis, it isn’t a stretch to imagine that you’ll start using it differently. Do any of these studies address this? Frequency of sex, duration of sex, number of partners, types of sex acts, etc?

  9. Michelle,
    The studies have actually addressed this question of whether men use their penises differently after they get circumcised. One of the big fears related to circumcision was that men would get circumcised, think they are fully protected from HIV, and engage in riskier behaviors. So the researchers actually examined this issue very closely.

    Let’s look at the Uganda study as an example (http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2807%2960313-4/fulltext). Before the study began, the two groups were similar in terms of number of partners, condom use, alcohol consumption with sex, and sex for money or gifts. And the surgery didn’t appear to change anyone’s behavior. The authors report, “At the 12 and 24 months follow-up visits, the number of sexual partners, non-marital relationships, and condom use were much the same in the two groups.” So you can’t attribute the protection seen in the Uganda study to changes in behavior.

    The other two trials found that the circumcised group actually engaged in slightly riskier sexual behavior, which doesn’t fit with your hypothesis that the protection is due to differences in sexual practices.

    Also, for the record, I think belly buttons are weird too ;)

  10. You say that male circumcision is recommended to prevent HIV. I would challenge you to find a medical body that recommends it for those of us in developed nations. There isn’t one. The reason for this is that all the studies that have been done in Europe or North America have found no benefit from circumcision, in prevention of HIV acquisition. 

    Further to that, male circumcision has been shown to increase the HIV acquisition in women who have circumcised partners by the same 50% touted for male protection, negating any benefit.If we are to accept the protective factor from male circumcision, we must also accept the protective factor from FGM. Despite their best attempts to show a negative in protection for women, studies have shown that FGM provides protection for women in preventing HIV acquisition. 

    Why then, do we not allow FGM for protection?

  11. “Let’s be honest. Foreskin is weird. ”

    Only to a twisted mind. 80% of the world’s male population has one firmly in place so it is common.

    “The rules of evolution suggest that it once conferred an advantage, but I can’t fathom what that advantage might have been.”

    The advantage still exists. The foreskin protects the glans keeping it soft and sensitive making for a better sexual experience for the man. It also provides a mobile skin sleeve reducing damaging friction with the vaginal sphincter. Women who have long term sex with circumcised men are at risk of “female arousal disorder” which affects post menopausal women making normal sexual activity extremely painful or impossible.

    “Researchers have long observed that HIV rates are generally higher in countries where male circumcision is not common practice.”

    This is not true. Six countries in Africa where circumcision is not common have lower HIV rates than countries where circumcision is common. Additionally, The US with the highest male circumicison rate of all industrialized nations also has the highest HIV rate. Those are confounding problems that no one has explained.

    “So three research groups set out to test whether having foreskin could really influence a man’s risk of contracting HIV.”

    No, there was only one research group that conducted their research in three different places. The leaders of this group have been very public circumcision advocates for more than 30 years. It appears the research was to validate their agenda. This is highly suspect.

    “Taken together, the studies found that circumcision reduced a man’s risk of contracting HIV by about 60%”

    This is also highly suspect. If this were true, HIV would be rare in The US with an adult circumcision rate of 80%. We can look at other communicable diseases and interventions to see this. For instance, the polio vaccine only had a 70% effective rate yet wiped the disease from the populace in The US and around the world in a single generation. Male circumcision has not shown anywhere near this success rate. In fact, the HIV/AIDS rate is the same in both circumcised and genitally intact men in The US inferring circumcision offers no protection.

    “And researchers hypothesized that this might explain the foreskin’s role in HIV. Thinner skin would likely be easier for the virus to penetrate than thicker skin. But the evidence is mixed.”

    A hypothesis is the same thing as a SWAG (scientific wild a** guess). The inner skin is unbroken so it is a barrier just like any other skin. There is also a hyopthesis/SWAG that it is highly populated by langerhans cells but this is also highly improbable. The lining of the mouth is also highly populated by langerhans cells and an official at The CDC told me that there is no known case of oral infection.

    “The foreskin is rife with special immune cells that are susceptible to HIV.”

    These are the langerhans cells.

    “The space between the foreskin and the head of the penis is populated with bacteria that make it easier for HIV gain entry.”

    Females also have this same bacteria. If this were true, female circumcision would provide the same protection. Are you ready for that????

    “Before the surgery, most of the microbes were anaerobic. A year after the foreskin was removed, the bacteria were mainly aerobic.”

    These two words simply mean bacteria that can only live in an oxygen rich environment and those that can live in a low oxygen environment. If this were true, female circumcision could provide the same levels of protection. Are you ready for your circumcision so you will be protected from HIV/AIDS? ? ? ?

    “Foreskin is more prone to tearing during sex than the rest of the penis.”

    Yes, and the female vulva, specifically the vaginal sphincter is prone to abrasion/tearing. Let’s start circumcising female babies to protect them, right?

    “Foreskin traps HIV, giving the virus more time find a way in.”

    Yes, maybe but the labia would have the same effect. I’m building a stronger and stronger case for female circumcision with your help.

    .

  12. @ Cassandra Willyard: “To me, it seems plausible that something about that microenviroment makes HPV and herpes infection more likely too. Any experts out there have thoughts?”

    Interesting! A study of 14 – 1 6 year old school girls found that 54% of them had already been infected with HPV. The researchers concluded that they were infected as they passed through their mother’s birth canal. Another justification for female circumcision. I’m building quite a case.

    Incidentally, The website, National Campaign for HPV and Cervical Cancer states that of all people infected with HPV, 97% will build/develop a natural immunity to the virus rendering it a toothless lion. But, we should circumcise all girls, shouldn’t we? Just to get the other 3%?

    Back 5 or 6 years ago, a vaccine against HPV was developed and has been available since for both boys and girls. Back when it/they were announced, I accurately predicted that circumciison advocates would completely and entirely ignore this important development and continue to advocate male circumcision. They have not disappointed me or proven me wrong.

    .

  13. Why not just distribute free condoms and teach proper sex ed. in these countries? It would be cheaper and more effective. Why all this pushing of circumcizion? I’m sure cutting off the whole penis would reduce the risk of HIV infection too but you don’t see anyone advocating that.

    I present Hypothesis #4-Since the foreskin is sensitive it increases pleasure in sex. The circumsized men found they liked sex less after the procedure, had less sex, so they got less HIV. Plus, people recovering from medical procedures are unlikely to want much sex during that period of healing.

    They really ought to commission a study of the psychological effects of receiving circumcision in adulthood(and preferably several studies in different parts of the globe). Doing that could rule out a psychological route of causation or show one. If the reason is psychological(it’s not like you can do a double-blind study on circumcision) then it would be even more pointless to circumcize, instead educate safer behavior.

  14. Several women want the law on male circumcision to ensure that the practice is compulsory.

    “Susan Akello from Orom sub-county says government should pass a legislation that will compel all men to be circumcised and those who refuse be punished.

    Jane Adokorach, a self styled women activist agrees with Akello. Adokorach says women should deny sexual rights to men who are not circumcised. She also proposes a law that will include punitive measures for men who refuse to be circumcised. She says this reduces the rate of infection for men and transfer of the disease to their spouses.”

    Read more: http://ugandaradionetwork.com/a/story.php?s=33903#ixzz1Y9HgjBya

  15. Well, I have a foreskin and

    1. I have never had a problem with it getting caught in my zipper.

    and 2. I’m a Muslim, so my religion prohibits me from partaking in fornication (so no HIV for me).

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