U.S. researchers who compared samples from a breast milk-sharing website with samples donated to a milk bank say milk purchased online was often contaminated with disease-causing bacteria. 

Health Canada, the U.S. Food and Drug Administration, and Canadian and U.S. pediatric societies warn of potential health risks of giving babies human breast milk obtained online or directly from unscreened individuals.

Researchers in Ohio weren't aware of any previous studies that evaluated the safety of human milk sold online.

To quantify bacterial contamination, they compared 101 internet milk samples with 20 unpasteurized samples of milk donated to a milk bank.

They found 74 per cent of internet milk samples had detectable pathogens or were colonized with levels of bacteria like E.coli that would have failed the Human Milk Banking Association of North America's criteria for feeding without pasteurization.

With internet sites, "you have very few ways to know for sure what you are getting is really breast milk and that it's safe to feed your baby," said Sarah Keim, lead author of the study in Monday's issue of the journal Pediatrics and a researcher at Nationwide Children's Hospital in Columbus, Ohio.

"Because the consequences can be serious, it is not a good idea to obtain breast milk in this way."

Milk banks in Canada

Human milk protects against bacterial illnesses. But previous studies have reported cases of preterm and immune-compromised infants developing illnesses and deaths linked to raw human milk, and they called for more research into the potential risk of milk sharing for these babies in particular.

"Just imagine if the donor happens to be a drug user. You don't know," said Dr. Kenneth Boyer, pediatrics chief at Rush University Medical Center in Chicago, who was not involved in the study.

In Canada, there are human milk banks that screen and pasteurize donated milk for preterm and high-risk infants in Vancouver, Calgary and Ontario. Quebec is also planning a bank, said Dr. Sharon Unger, medical director of the Rogers Hixon Ontario Human Milk Bank.

Unger thinks internet sharing of breast milk is dangerous for many reasons, including microbial contamination. In contrast, milk at the Ontario bank is tested for bacterial culture and must have no growth before it is dispensed.

"I think that this study highlighted an important issue," Unger said in an email. "There is simply no quality control in purchasing over the internet (particularly a product from the human body)."

Potential sources for bacteria found in the study could include donors' skin, breast pumps used to extract milk or contamination from improper shipping methods, Keim said.

Unger agrees with the study authors, who recommend lactation support for mothers who want to provide breast milk to their infants but who have difficulty making enough. Keim's team recognized that not all women access or are referred for support early.

Milk-sharing websites post guidance on how to minimize health and safety risks, because the onus is on individuals to protect themselves and their children. Besides sales, several sites also advertise free milk.

With files from The Associated Press