updated 3/4/2011 11:57:24 AM ET 2011-03-04T16:57:24

It seems the popularity of foods made from human breast milk is on the rise.

Last week, a London ice cream shop unveiled a "Baby Gaga" flavor made with human breast milk. So many people clamored for it that the shop ran out of the flavor on the day of its debut. And last year, a New York University graduate student started making human breast milk cheese, in varieties such as "City Funk" and "Wisconsin Bang."

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What is it that attracts people to these strange comestibles? And why do others find them absolutely revolting?

It's easy to pinpoint what's repelling about the products: We all have an innate disgust for bodily secretions hardwired into our brains, said Gavan Fitzsimons, a professor of marketing and psychology at Duke University in North Carolina.

"You get the same reaction whether it's breast milk, whether it's blood, whether it's saliva, and at some level, there's logic to it," Fitzsimons told MyHealthNewsDaily. "If another person is ill in any way, oftentimes they could pass those germs to you through the bodily secretions."

Even when it is not used to make foods, people just find human breast milk inherently disgusting, said Andrea Morales, an expert in disgust and associate professor of marketing at Arizona State University.

All milk comes from female nipples, and though researchers are not clear as to why, people are more likely to associate breast milk with women's nipples than to associate other types of milk with animal nipples, Morales said. This may up the ick factor.

"The risk of contracting a disease from a cow or goat seems higher than the risk of contracting a disease from a human, but for some reason people don't perceive it that way," Morales told MyHealthNewsDaily. "I think it's driven a lot by our associations with regular milk coming from a carton or jug, rather than a cow's nipple and the fact that this is the norm versus unusual."

But even though we're nursing some primal grudge against body fluids, there's still appeal in the idea that we'd elicit an emotional response from an onlooker that gets us to take that first taste, Fitzsimons said.

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"My speculation is anyone who is buying the breast milk ice cream would not be buying it to take it home and put it in the freezer, and consume it by themselves that night at home," Fitzsimons said.

People have a natural desire to prompt emotional reactions in others. If you're eating something astonishing, and those around you witness it, you're going to elicit a disgust response — one of the most reliable responses you can get, he said.

In addition, Fitzsimons' own work has revealed that sometimes people are drawn toward disgusting items because they usually elicit a unified response and bond us together.

"If you go to see a disgusting movie, everyone reacts the same way at the same time," he said, "and so our emotional response is basically simultaneous and intense."

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We like it when others engage in the same physical behaviors we're doing, he said. With emotions, the concept is the same, whether we're screaming at the same time as other people watching a scary movie in a theater, or trying "Baby Gaga" with your pals and hundreds of other strangers at an ice cream shop, Fitzsimons said.

Pass it on: People try strange edibles like breast milk ice cream and breast milk cheese because of the need for an emotional response and for the feeling of being part of something bigger than themselves.

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Follow MyHealthNewsDaily staff writer Amanda Chan on Twitter @ AmandaLChan.

Vote: Would you try a food made with breast milk?