Breast milk may be best for baby, but ordering it over the Internet is not necessarily such a good idea.

Researchers recently bought more than 100 samples of expressed breast milk from two milk-sharing websites and then took them to the lab to see what might be growing in them. The results, published this week in the journal Pediatrics, were fairly disturbing.

Three quarters of the purchased human milk was contaminated with gram-negative bacteria that can pose serious health risks in babies, the researchers found. Three of the samples were contaminated with salmonella. E. Coli was also detected in some samples, an indicator of fecal contamination.

“Even at modest levels these bacteria are closely associated with disease,” said Sarah Keim, an epidemiologist at Nationwide Children’s Hospital in Columbus, Ohio, and the lead author of the study.


The contamination levels of the milk weren’t so bad that they would make every baby sick, said Keim. A healthy baby could drink some of the purchased milk and feel no adverse effects, or perhaps just get a little diarrhea. But a baby with a weak immune system or a healthy baby that was exposed to salmonella could end up in the hospital with meningitis after drinking some of the milk samples.

“While there may be some milk out there that is fine, so much of the milk we saw was contaminated,” said Keim. “As a buyer you have no idea what you are getting unless you have a laboratory to test for this.”

As of now, the sale of human milk via the Internet is almost entirely unregulated. Based on the postings on the milk-sharing sites, the sellers are mostly mothers who have a freezer full of expressed milk and aren’t sure what to do with it, Keim said. The buyers are mostly women who have had trouble producing enough milk -- or any milk -- and were determined to feed their babies breast milk.

“It wasn’t everyone, but I saw a number of ads posted where women who were looking for milk said, ‘I just don’t want to feed my baby formula,’” she said.


In 2011, Keim and her team counted a total of 13,000 postings across the four most popular milk-sharing websites from both buyers and sellers.

“We believe there is probably a lot more sharing between friends and relatives that is offline,” she said. “That is likely more common, but it hasn’t been extensively studied yet.”

As far ask Keim can tell, there is no way to vet that the milk you buy from a stranger is safe for your baby. While most sellers are probably well meaning, they may not be collecting their milk or storing it in a way that is sanitary. For example, making sure that the breast pump is thoroughly washed after each use might eliminate much of the bacteria the researchers found.

“If people are going to participate, there are safer ways to do this,” she said.


Follow me on Twitter for more stories on the science of parenting.

ALSO:

Hope for the balding? Scientists trigger new hair growth

Researchers: Regular bedtimes lead to better behaved kids


Spanking your kids could affect their vocabulary down the road