This was a preliminary version of the article. Click HERE for the current version or visit CircumcisionChoice.com/single-post/16Functions
The 16 Foreskin Functions - what are they? Anti-circumcision activists claim that the foreskin provides 16 essential functions. They say that circumcision eliminates these irreplaceable functions, rendering a man physically harmed and sexually crippled. Intactivists claim that anyone unaware of these functions must be ignorant of the incredible value of the foreskin! Woe to doctors and nurses who are unaware of these valuable foreskin benefits!
One of our first actions on the Circumcision Choice Facebook page was to publish a weekly series on the 16 Functions of the Foreskin. We devoted a post to analyzing each function. Where possible, we used explanations provided by leading intactivists to understand a function and its value. We've compiled the entire series here for easy reference. The entries are updated and include links to studies, articles, and other sources.
FUNCTION #16: MAKES THE GLANS A VISUAL SIGNAL OF SEXUAL AROUSAL
This function requires a bit of explanation. The glans (head) of a circumcised penis is always uncovered. By contrast the foreskin covers the glans of an uncircumcised penis in its flaccid state. When an uncircumcised man starts to get sexually aroused, the foreskin usually retracts to expose his glans.
Apparently the argument is that since the glans on a circumcised man isn't covered by foreskin, a partner can't determine whether he's sexually aroused just by seeing his glans. Whereas the partner of an uncircumcised man can tell. If the she can see the head of her partner's penis, then she knows that he's getting aroused.
This "function" is laughably ridiculous. The glans is not the most visual sign of male sexual arousal. His growing erection is the universal signal that a man is ready to perform in bed.
Those who promote this "function" mistakenly presume that in order for a woman to be aware that her partner is feeling erotic, he must be naked, or at least have his penis peeking through his briefs. In fact the presence of an erection can be clearly visible even when he's fully clothed.
Moreover, there are many signs that show arousal beyond the physical appearance of genitals. The look in his eyes, the tone of his voice, and a change in his body stance are just a few of the sensory signals that alert a partner that her man wants some action.
(NOTE: Although this post assumed a female partner, the signs of sexual arousal would be no less apparent to a male partner.)
FUNCTION #15: PROTECTS THE GLANS FROM FROSTBITE AND OTHER WEATHER-RELATED CONDITIONS
An anti-circumcision website explains that the foreskin, "rich in blood vessels that bring heat to the tissues ... protects the less vascular glans against frostbite." The website quotes Sir Ranulph Fiennes, an English explorer, in a book detailing his exploration of Antarctica.
"...my private parts were nipped and swelled up. When I mentioned this to Mike, it turned out he was having the same problem only worse, with a blistered end. He was circumcised and therefore, in effect, had one less layer of insulation. I made a note of this factor in terms of selecting future candidates for polar expeditions."
There is no apparent awareness among circumcision opponents of the implausibility of this "function."
Incidents of severe frostbite are rare. A 2009 study by Mäkinen reported that the annual incidence of severe frostbite in men in Finland was 1.6%. Men were more likely than women to suffer severe frostbite based on "employment in certain industries, high physical strain, and weekly cold exposure at work." 
A 2006 article in a science journal reports that a many cases of severe frostbite occur in men serving in harsh weather conditions in the Finnish military.  We were unable to find ANY study that mentioned frostbite of the glans or listed circumcision among the risk factors. Severe frostbite is so rare in the United States that with no standardized reporting system, it's difficult to get a definitive number on the frequency among American males.
Let's assume that the Fiennes quote is true and accurate. While it's possible that the foreskin lessened the swelling of his penis, it didn't prevent injury. And we don't know whether Fiennes wore additional protection than his partner. We don't know whether Mike spent more time outside their shelter. And even if all other factors were identical for both, the comparison involves just two men living in a rare, severe environment, and cannot be extrapolated to the general population.
Moreover, in case a man was unprotected, the foreskin would suffer the same or more serious frostbite than the glans. If you’re the one-in-a-billion man on earth who will spend months traveling on foot in Antarctica  - then you may benefit from having a foreskin. If you’re not a polar explorer, your glans will probably be fine as long as you’re not a long-term outdoor nudist in winter. 
Finally, a polar explorer is unlikely to have access to warm running water for washing. An uncircumcised man may run into hygiene issues, which would cancel any benefit of a tiny extra layer of insulation. The idea that the foreskin must be treated as sacred - because a baby may grow up to become a polar explorer lacking adequate protection from the elements, and that circumcision will be the reason why he gets frostbite - is so ludicrous that we can only laugh at this entry on the list.
 Mäkinen TM; "Occurrence of frostbite in the general population - work-related and individual factors"; Scand J Work Environ Health; October 2009
 Juopperi, Kimmo; "The occurrence of frostbite and its risk factors in adolescents and young adults"; International Journal of Circumpolar Health; 2006
 Modern technology is now used to travel to the Antarctic bases.
 Melanie Lindwall Schaab of Circumcision Facts and Science is credited with this paragraph.
FUNCTION #14: PIGMENTED, IT PROTECTS THE UNPIGMENTED GLANS AGAINST SUNBURN
The fabulous foreskin delivers all-weather protection. It shields the rugged male genitals from the bitter cold of the Arctic tundra and the unrelenting heat of the Sahara desert.
Seriously, there isn't much to say about this supposed "function." Most circumcised men don't burn their glans because they aren't foolish enough to expose themselves for a significant period of time on a sunny day.
Shorts or a swimsuit will provide plenty of protection for the private parts. Nude sunbathers should check with a dermatologist regarding the use of sunblock products on certain body parts. It probably isn't a good idea to spend a long time sunbathing in the nude. You don't want to increase your risk of melanoma, particularly in the pubic region.
FUNCTION #13: PROVIDES LYSOSOMES FOR BACTERIOSTATIC ACTION AROUND THE GLANS
In the foreskin, there are lysosomes that kill bacteria. However, in spite of this fact, uncircumcised males acquire more bacterial infections than circumcised males. 
The foreskin also contains white blood cells. However, HIV specifically attacks white blood cells, so their presence makes a man at greater risk of contracting HIV. 
Several studies show that the foreskin is prone to infection. There is evidence that the warm, moist space under the foreskin becomes colonized by bacteria associated with UTIs , and one study shows that circumcision changes the microbiome of the glans by reducing harmful anaerobic bacteria. 
So it’s more accurate to look at the lysosomes as a stop-gap measure against infection, not an actual infection prevention. Lysosomes in the foreskin provide a pyrrhic benefit whose value is negated by the increased overall risk of infection. 
 For a list of studies, see Summary of Circumcision Research at Facebook.com/groups/ElephantInTheHospital.
 Irkilata L.; "Preputial bacterial colonisation in uncircumcised male children: Is it related to phimosis?"; JPMA; 2016
 Liu, Cindy M; "Male Circumcision Significantly Reduces Prevalence and Load of Genital Anaerobic Bacteria"; mBio; 2013
 Melanie Lindwall Schaab of Circumcision Facts and Science contributed to this post.
FUNCTION #12: IN INFANCY, IT PROTECTS THE URETHRA AGAINST CONTAMINATION, UTIs, AND MEATAL STENOSIS
PART 1: Protects against contamination and UTIs
We embarked on an elaborate scavenger hunt to uncover the source for this protective function. The starting point was a 2009 article posted on a popular anti-circumcision website. The article states:
“The foreskin contains muscle fibers arranged in a whorl to form a sphincter at the tip of the foreskin. The sphincter holds the foreskin protectively closed except when the child urinates and the pressure of the urine stream forces the sphincter to open, allowing outflow of the urine. Then the sphincter closes again and prevents entry of foreign matter, such as fecal material that contains bacteria. The sphincter of the foreskin keeps contaminants away from the urethra and is added protection against UTI.” 
So we're looking for a series of muscle fibers that act as a sphincter. The article cited a 1998 article published in a British medical journal, authored by a trio of academics whose names we recognized as scholars with a long trail of anti-circumcision advocacy. According to the authors, “The sphincter action of the preputial orifice functions like a one way valve, blocking the entry of contaminants while allowing the passage of urine.” 
To support this assertion, the 1998 article cited two other articles: one in a 1980 Indian medical journal, the other in a 1916 American medical journal. The 1980 article describes the structure of the foreskin, but does not indicate that the foreskin contains or functions as a sphincter or a one-way valve. Nor does the article suggest that the foreskin acts to protect the urethra from contamination, infection, or complications. 
The 1916 article describes the dartos fascia based on examinations of ten foreskin specimens. The author didn’t detect a sphincter, but referred to a passage from a 1902 medical book. “Woolsey remarks that the dartos fibers at the end of the prepuce are circularly arranged, forming a kind of sphincter. There was no special collection of fibers such as might be thought to indicate a sphincter in any of the specimens I examined, but the sphincteric possibilities of any part of the preputial portion of the muscle cannot be denied.” 
Searching the internet we were fortunate to locate a scanned copy of the 1902 Woolsey book. The key passage was hidden deep within a detailed description of the male urethra and external genitals. “At the end of the prepuce the muscular fibers are arranged circularly, forming a kind of sphincter.” The author did not indicate that these fibers provide any protective function for the urethra. Interestingly, he reported that the foreskin is responsible for inflammation and other penile complications. And he noted that some cases of phimosis “require circumcision” as the appropriate treatment. 
So the promised reward for our trek resembled the illusive treasure at the end of the rainbow; these sources provided no evidence that the foreskin protects the urethra against infections.
On the contrary, several studies show that uncircumcised boys have more urinary tract infections than circumcised boys. Although the foreskin can be tightly fused to the glans, bacteria, viruses, and yeast can and do infiltrate the space between the foreskin and the glans. In comparative studies, uncircumcised boys consistently have more UTI-causing microorganisms than circumcised boys. 
PART 2: Protects against meatal stenosis 
Meatal stenosis is the narrowing of the urethral opening. Estimates for the frequency of this complication vary by orders of magnitude. Circumcision opponents typically cherry-pick studies with the highest rates, and ignore others. The study with the largest sample size found about 80 cases per million in circumcised boys, and 71 per million in uncircumcised boys in the first 6 months of life. The rate is less than 0.05 % risk for boys up to three years. 
The cause of meatal stenosis is currently uncertain. Theoretical causes in the circumcised male include irritation from the ammonia (in urine) in the diaper, resulting in meatitis, resulting in meatal stenosis; congenital meatal stenosis resulting in meatitis; abrasions; and diet (Belman et al, 1978). However, ammoniacal dermatitis and meatitis are more common in uncircumcised males.
One study suggested that meatal stenosis occurs symptomatically in 3-8% of circumcised boys. A 2015 study found that only half of symptomatic cases will require treatment (i.e., 1.5-4% of circumcised boys may require treatment). Furthermore, severe complications of meatal stenosis are extremely rare (Godley et al, 2015).
The idea that meatal stenosis is more common in circumcised boys is based on studies like one by Robert Van Howe, a physician with an extensive background promoting an anti-circumcision agenda. Van Howe’s study lacked a sufficient number of uncircumcised boys to obtain a statistically significant result. On the other hand, one study found that applying petroleum jelly to the penis following circumcision reduced the meatal stenosis incidence from 6% to 0% (Bazmamoun, Ghorbanpour, & Mousavi-Bahar, 2008), which seems to suggest that circumcision may indeed play a role.
In any case, meatal stenosis is a simple problem to fix.
The bottom line is that the available evidence doesn’t support this “function,” as circumcised boys generally have lower rate of complications of the urethra than their uncircumcised peers.
 “How the Foreskin Protects Against UTI”; Peaceful Parenting; December 2009
 Fleiss, P, Hodges, F, Van Howe, R; “Immunological functions of the human prepuce”; Sexually Transmmitted Infections, Volume 74, Number 5, pp 364-367, October 1998
 “Human prepuce: some aspects of structure and function”; Indian Journal of Surgery; Volume 44: Pages 134-137, 1980
 “Surgery, Gynecology, and Obstetrics”; Volume 23, Number 2, pp 177-181; August 1916
 Woolsey, George; Applied Surgical Anatomy, pp 406-407; 1902.
 Tuesday Topic: Circumcision Reduces UTIs Week 01; Circumcision Facts and Science; August 30, 2016
 Melanie Lindwall Schaab of Circumcision Facts and Science contributed to this section.
 El Bcheraoui, Charbel; "Rates of adverse events associated with male circumcision in U.S. medical settings, 2001 to 2010"; JAMA Pediatrics; July 2014
FUNCTION #11: PROTECTS THE NERVES OF THE GLANS AND THEIR EROTIC FUNCTIONS
The three items on the list beginning with Function #11 can be condensed into a single function: protect the glans. Circumcision opponents seem to be fixated on the number 16 for some reason. A second list of fabulous foreskin functions (which we'll analyze next year) also has 16 items. So whoever created this list may have felt the need to expand “protecting the glans” into three distinct bullet points.
Be that as it may, we found no evidence to prove the validity of this function. Few studies exist that compare the nerves of the glans that provide erotic pleasure for neonatally-circumcised men with the corresponding nerves in the glans of uncircumcised men.  Bossio compared glans sensitivity and reported her conclusions:
“This study provides no evidence that neonatal circumcision decreases penile sensitivity, and no evidence that the exposed glans penis in circumcised men becomes less sensitive over time... If differences in sexual functioning or sexual dysfunction are related to circumcision status, these differences are not likely the result of changes in penile sensitivity resulting from neonatal circumcision.” 
The authors recommended additional research to determine the effect of circumcision on glans sensitivity and male sexual pleasure. Until such research is presented and evaluated, the claim that circumcision harms the nerves of the glans has no scientific basis.
 In a 2007 Sorrells study, the uncircumcised men were younger and from different ethnic backgrounds than the circumcised men. And the authors admitted that their survey was plagued by self-selection bias. A 2007 Payne study used a small sample size (40 men, half of whom were circumcised) and did not indicate whether the subjects were circumcised during infancy.
 Bossio, Jennifer; "Examining Sexual Correlates of Neonatal Circumcision in Adult Men"; Queen’s University; 2015
FUNCTION #10: PROTECTS THE THIN-SKINNED GLANS FROM INJURY
This is the second of three consecutive functions that should be combined into a single function: “protects the glans.”
The foreskin forms a physical barrier to things like sticks and thorns that would harm the glans. It’s true that the foreskin protects the glans from injury when a boy is naked and running through the underbrush. It's quite possible that for primitive men, the foreskin may have served a valuable purpose protecting the glans from foliage. However, this protection is hardly relevant in modern societies in which men wear undergarments.
The foreskin, in fact, may be more prone to injury than the glans. Uncircumcised boys are significantly more likely to experience zipper injuries than their circumcised peers. And some couples have reported foreskin injuries during sexual intercourse. Any protective function for the glans would be negated by injury to the foreskin itself.
(NOTE: Melanie Lindwall Schaab of Circumcision Facts and Science composed the text for this post, with some editing by an admin.)
FUNCTION #9: PREVENTS THE GLANS FROM DRYING OUT (KERATINIZATION) AND KEEPS IT SOFT AND MOIST
Those who tout this function seem to think that the moist environment in an uncircumcised penis provides lubrication to better facilitate vaginal intercourse. According to O'Hara, “the skin of the circumcised penis rubs against the vaginal wall, increasing friction, abrasion and the need for artificial lubrication.”  However the survey on which the study was based was fraught with methodological flaws and bias.  Bossio reported that women with circumcised and uncircumcised partners “did not differ significantly on their self-reported responses ... measuring ... vaginal lubrication ... or lubrication ... or pain with penetrative intercourse.” 
Intactivists seem to be confused over the difference between a dry organ and one that is dried out. Dry means free from moisture. A dry penis is a good thing, as harmful bacteria thrive in a moist environment. In a recent medical advice column, urologist Dr. George Lee explained that "the moist glans of the penis can create the ideal environment for pathogens to incubate, making it susceptible to infections. This may include bacteria, fungus and sexually transmitted infections such as herpes and HIV.” 
Keratinization - dried out - refers to a thickened skin. The only study on keratinization found no difference between circumcised and uncircumcised men.  Although the glans does become dry after circumcision, this condition doesn’t appear to affect sexual sensation and function. It’s been demonstrated that a dry glans is less susceptible to infection than a wet glans, even with good hygiene.    (There is speculation that this is the reason that uncircumcised men in certain cultures routinely wear their foreskins pulled back to expose and dry the glans.)
Thus we are unable to verify a benefit of having a glans that is soft and moist.
NOTE: Melanie Lindwall Schaab of Circumcision Facts and Scence contributed to this post.
 Ohara, K and O’Hara J; “The effect of male circumcision on the sexual enjoyment of the female partner”; BJU International, pp 79-84; January 1999
 Gross, Andrew; “Sex as the researcher intended it " at https://www.facebook.com/groups/elephantinthehospital
NOTE: The author is an admin of this website.
 Bossio, Jennifer et al; “You either have it or you don’t; The impact of male circumcision status on sexual partners”; Canadian Journal of Human Sexuality; 2015
 Lee, George, “To cut or not to cut?”; The Star Online; November 20, 2016
 Szabo, R and Short, R; “How does male circumcision protect against HIV infection?”; BMJ; 2000
 Krueger, H., & Osborn, L.; “Effects of hygiene among the uncircumcised”; The Journal of Family Practice; 1986
 O’Farrell, et al; . (2006). “Association between HIV and subpreputial penile wetness in uncircumcised men in South Africa”; Journal of Acquired Immune Deficiency Syndromes, pp 69–77; 2006
 O’Farrell, N et al (2007). “Low prevalence of penile wetness among male sexually transmitted infection clinic attendees in London”; Sexually Transmitted Diseases, pp 408–409; 2007
FUNCTION #8: PROVIDES A SEAL AGAINST THE VAGINAL WALL TO CONTAIN SEMEN
This function is a little confusing, as we aren’t sure what is the purpose of containing semen. We’ll consider a couple of possible interpretations.
Foreskin promoters lecture us that condoms, not circumcision, provide protection. It's our understanding that the condom's raison d'être is to contain the semen - in order to prevent pregnancy and transmission of infections. So why would the foreskin also be needed to contain the semen? Is that an extra measure in case the condom breaks?
Other points: If it's enclosed inside the condom, how can the foreskin provide a seal against the vaginal wall? And if a man isn't wearing a condom during vaginal sex, then presumably infection isn't a concern, and pregnancy is an acceptable possibility. So what's the target which the semen need to be prevented from reaching?
Perhaps this is simply a misunderstanding of the function. Perhaps during unprotected sex, the foreskin acts as a goaltender, keeping the semen in play in order to increase the chances of conception. Alas, we were unable to find a study that compares the fertility rate of circumcised and uncircumcised men of similar demographics. And containing semen would be detrimental to certain alternative sexual practices (which we won’t discuss here.)
On a related note, we’ve come across the claim that circumcision decreases the fertility rate by reducing the sperm count. The reasoning: The temperature of a circumcised penis is higher than that of an uncircumcised penis. The flaccid penis rests on or by the testicles. The warmer the penis, the warmer the testicles will become, damaging the sperm.  Yet Muslims and Orthodox Jews, two groups that tend to produce large families, are the leaders among all demographic groups in terms of circumcision prevalence. That would suggest that circumcision has no significant effect on procreation.
 Von Newmann, Georg; "Does Circumcision Decrease the Fertility of Sperm in the Male?"; Ezine; January 24, 2010
FUNCTION #7: STORES, RELEASES, AND HELPS DISTRIBUTE NATURAL LUBRICANTS (SMEGMA/PRE-EJACULATORY FLUID)
Smegma is a pleasant hobbit who was transformed by a balanitis infection into a gaunt, slimy, nasty creature with a murderous obsession for a band of jewelry...
Whoops! That's Sméagol from The Lord of the Rings.
Smegma is a combination of dead skin cells, body oils, and moisture that collects beneath the foreskin. This crusty substance typically emits an unpleasant odor. It’s often referred to by the derogatory slang “dick cheese.” According to one source smegma “helps ensure that the foreskin can easily slide on and off the glans, or head, of the penis without irritation.” 
Smegma is associated with certain infections. A buildup of smegma can cause balanitis. And smegma is more common in men with phimosis, which can lead to penile cancer. 
Foreskin advocates downplay the possibility of infections, saying that smegma can be easily removed with regular cleaning. Unfortunately it’s often easier said than done. While it’s certainly true that a boy can be taught proper hygiene, many boys don't take hygiene seriously and don't clean themselves regularly. (Even adult men are notoriously lazy about cleanliness. Despite the health risks, a British study showed that 63% of men didn’t wash their hands after using a public toilet.)  Anecdotal evidence suggests that even when a man does clean thoroughly under his foreskin, a foul odor often persists.
Circumcision opponents seem to have a schizophrenic relationship with smegma. On the one hand they dismiss it as easily removed with proper hygiene. On the other hand, here we see that they claim that smegma provides an essential function as a lubricant. We observed with Function #9 that the female partner provides the lubrication for smooth penetration, and a moist genital area attracts infections.
So which is it? Should smegma be stored or removed? Confused intactivists can’t seem to make up their minds.
 Cara, Ed; "Just What Is Smegma And Why Does It Make Us Cringe?"; Medical Daily; May 21, 2015
 "What Are the Risk Factors For Penile Cancer?"; American Cancer Society; Revised October 19, 2017
 Ferris, Izzy; "Majority of men don't wash hands after using toilet study finds - as expert warns over spread of bugs"; Mirror; September 23, 2015
FUNCTION #6: STORES PHEROMONES AND RELEASES THEM ON AROUSAL
What the heck is a pheromone, what does it do, and why should you care?
Humans possess arousal-stimulating chemical messengers. The term pheromone is derived from two Greek words: pherein, which means to transfer; and hormon, which means to excite. When released some of the pheromones become sexual stimulants to attract members of the opposite sex. The chemicals “signal sexual desire, sexual readiness, hormone levels, fertility and the deepest emotions.” 
It turns out that smegma contains pheromones. So there you have it. This essential and irreplaceable foreskin function is to produce a scent to arousal sexual partners. Right?
Well, not exactly. It turns out that pheromones are secreted by several areas of the body. These include the skin, sweat glands, and saliva. Men primarily release pheromones through their skin and hair. Surprisingly, even urine contains pheromones.
We were unable to locate any research studying whether circumcision has any significant effect on the level of pheromones that are released and that a woman would perceive through her sense of smell. A prominent anti-circumcision website even admitted that “the effect of their absence on human sexuality has never been studied.”  So there’s no evidence that circumcision would affect the release of a significant amount of sexual stimulants to attract female partners.
 “Human Pheromones: The Science Behind the Scent of Attraction”; Smart Publications
 “Foreskin and its 16 Functions; Not 'Just Skin'”; Saving Our Sons; September 2015
FUNCTION #5: SUPPLIES SKIN TO COVER THE SHAFT DURING ERECTIONS WHILE PREVENTING TIGHTNESS
Whoever composed this list may have set a goal to create a nice even number of items. He may have conceived of this entry when he had exhausted all other possibilities. That’s the only explanation we have for the existence of this “function.”
Circumcision usually removes the excess foreskin and leaves ample skin to properly cover the shaft. Most circumcised men have ample mobility in the skin covering the shaft.
This “function” suggests that foreskin provides some sort of functional or protective benefit to the shaft during an erection. Despite an internet search we were unable to locate any source that would explain such a benefit. We have no choice but to conclude that #5 is not a serious entry on the list of Fabulous Foreskin Functions.
FUNCTION #4: STIMULATES PARTNER’S GENITALIA (PROVIDING EROTIC PLEASURE)
Having reviewed 12 of the 16 functions on the list, we're now in the homestretch. Today we analyze whether the foreskin provides erotic pleasure for a man's female partner.
In a 1999 article Kristen O’Hara explained that when the uncircumcised penis
thrusts in the vagina, it does not slide, but rather glides on its own ‘bedding’ of movable skin, in much the same way that a turtle’s neck glides in and out of the folded layers of skin surrounding it. The underlying corpus cavernosa and corpus spongiosum [erectile tissues that are filled with blood during an erection] slide within the penile skin, while the skin juxtaposed against the vaginal wall moves very little. This sheath-within-a-sheath alignment allows penile movement, and vaginal and penile stimulation with minimal friction or loss of secretions.” 
O’Hara failed to provide any citation for this description.
The article was based on her own survey that violated several methodology standards. 
She did provide anecdotal comments by some of her respondents, who reported that sex was more pleasurable with uncircumcised partners. One woman’s sexual experience, however, cannot be applied to every other woman. Many women have reported that circumcised partners provided equal or superior pleasure. For example…
“Being with an uncircumcised man was uncomfortable. Being with a circumcised man it was easier; his ‘head’ rubs against my g spot better… The foreskin is useless to me.”
“When my ex was thrusting in and out, his penis would naturally go in and out of the foreskin which was securely planted in my vagina. Therefore you only get half the thrust sensation.”
“Uncut feels like a spear stabbing me. Plus I've been with larger then average men (8+ inches) – and the ones that were cut were pleasurable. The uncut man felt like he was assaulting my cervix because he couldn't tell when to stop pushing in.” 
Bossio reported that women with circumcised and uncircumcised partners “did not differ significantly on their self-reported responses to ... experiences of sexual arousal, vaginal lubrication, orgasm, or pain with penetrative intercourse.” 
The bottom line is that foreskin can help or hinder a partner's sexual pleasure. In most cases, however, it has no significant effect.
 Ohara, K and O’Hara J; “The effect of male circumcision on the sexual enjoyment of the female partner”; BJU International, pp 79-84; January 1999
 Gross, Andrew; “Sex as the researcher intended it" at https://www.facebook.com/groups/elephantinthehospital
NOTE: The author is an admin of this website.
 Bossio, Jennifer et al; “You either have it or you don’t: The impact of male circumcision status on sexual partners”; Canadian Journal of Human Sexuality; 2015
FUNCTION #3: PREVENTS DYSPAREUNIA (PAINFUL INTERCOURSE)
A 2008 parenting book explained this function, using the precise wording. “The glans covered by a foreskin has a natural moist lubrication thought to have a beneficial effect to women during sexual intercourse by providing a moist gliding action that lubricates the vagina and prevents dyspareunia (painful intercourse.) The penis with an uncovered glans is dry because the foreskin serves to keep the glans moist, which is the natural state.”  The author did not provide any citations to support her assertion.
One study found that circumcised men engaged in a wider array of sexual behavior, so one would expect that circumcised men would