Men circumcised either as children or adults report less intense sexual pleasure and orgasm than their uncircumcised counterparts, according to a new study from Belgium.
"We're not saying less sexual activity or satisfaction, but sensitivity," said the study's senior researcher Dr Piet Hoebeke, from Ghent University Hospital.
The new study surveyed 1369 men over the age of 18, who responded to leaflets handed out in train stations across Belgium.
The men were asked whether they were circumcised, and were then asked to rate how sensitive their penis was, how intense their orgasms were and whether they experience any pain or numbness when they are aroused.
Overall, 310 men who took the survey were circumcised, and 1059 were not. Each rated how sensitive their penis was on a scale from 0 to 5, with higher numbers being the most sensitive.
Overall, uncircumcised men reported between 0.2 points and 0.4 points higher sensitivity and sexual pleasure when their penis's head - known as the glans - was stroked during arousal, compared to circumcised men.
For example, uncircumcised men reported an average sensitivity score of 3.72 when they or their partner stroked the top part of their penis's glans, compared to 3.31 amongst circumcised men.
Uncircumcised men also reported more intense orgasms.
"It's not a very big difference in sensitivity, but it's a significant difference," Hoebeke said.
Currently, about half of US baby boys have their foreskin surgically removed at birth, and about 30 per cent of men around the world are circumcised. According to the Royal Australasian College of Physicians an estimated 10 to 20 per cent of newborn boys are circumcised in New Zealand and Australia.
Some religions, such as Judaism and Islam, consider circumcision part of religious practice, while other people choose circumcision for possible health benefits - including a reduced risk of urinary tract infections.
Hoebeke and his colleagues write in BJU International that there are few studies researching whether foreskin plays a role in sexual pleasure. But Dr Aaron Tobian, who studies circumcision but was not part of the new study, said that previous randomised controlled trials - considered the gold standard of medical research - looked at sexual performance and satisfaction. Those studies, he said, did not find a difference.
One possible explanation for any potential difference in sensitivity is that a man's foreskin may protect his penis's head from rubbing against underwear and clothing. It's possible, the researchers write, that friction makes the head of the penis thicker, drier and ultimately less sensitive.
The researchers also found circumcised men were more likely to report more pain and numbness during arousal than uncircumcised men, which Hoebeke said is likely due to scar tissue.
"I'm amazed that people report pain during sexual pleasure... That's very amazing and that was unexpected," he said.
'ABUNDANTLY CLEAR' EVIDENCE
Tobian, from Johns Hopkins University in Baltimore, said the findings are missing important context.
"The medical evidence and the benefits of male circumcision are abundantly clear," Tobian told Reuters Health.
"If there was a vaccine out there that reduces the risk of HIV by 60 per cent, herpes by 30 per cent and the penile cancer causing HPV by 35 per cent, the medical community would rally behind it," said Tobian.
The American Academy of Pediatrics says the benefits of male circumcision outweigh the risks, but stops short of recommending universal circumcision