Selling breast milk is big business.

It really is, ‘Buyer beware.’ When you’re purchasing milk from a source you’re not familiar with, you can’t tell by looking at it if it’s safe. It’s really a risky activity.

Each year tens of thousands of women post ads on websites, offering their extra milk for $1 to $3 an ounce: "My rich milk makes giants!" promises one seller. "Organic and Gluten Free Breastmilk," claims another. Then there's this one: "470 oz. of breastmilk must go!!!"

A small but growing market exists on the internet for Human Breast Milk. Buyers should really beware—some purveyors of breast milk might be adulterating their product with cow's milk. 

Such bovine contamination is more than just a scam: it can be a health risk for infants who are allergic to or intolerant of cow’s milk. The study, the first to document this milk fraud, is in the journal Pediatrics. (Sarah A. Keim et al, Cow’s Milk Contamination of Human Milk Purchased via the Internet)

Some women online aren't delivering what they're advertising. Researchers purchased 102 samples of supposed human breast milk online. Tests found that ten of these samples had enough bovine DNA to indicate that at least 10% of the milk in the sample actually came from cows. 

And we're not talking about just a smidge. The tainted samples contained at least 10 percent cow's milk, the team reported Monday in the journal Pediatrics. That's too much to be an accidental contamination. Sellers are diluting the breast milk, the researchers speculate, to make more money.

Dilution with cow's milk is clearly dangerous to babies with milk allergies. Human milk is an ideal source of nutrients for infants—when it’s safe. If the option is buying breast milk online from an unscreened donor, and not from a reputable milk bank, I would recommend formula.

Prior studies on breast milk purchased online have revealed dangerous amounts of bacterial growth that make it unsuitable for infant consumption. About 75 percent of the samples had high levels of bacterial contamination or detectable levels of disease-causing pathogens, such as salmonella and E. coli. In other words, the same kind of bacteria found in human waste. So these samples were unsuitable for a baby to drink. Since no one typically screens these internet-sold milk products for pathogens or other contamination it’s up to consumers to protect themselves. 

It really is, 'Buyer beware,'.  When you are purchasing milk from a source you're not familiar with, you can't tell by looking at it if it's safe. It's really a risky activity that we don't recommend.

The U.S. has a network of nonprofit milk banks that screen donors, pasteurize the milk and test it for pathogens. But Keim says this milk is very expensive — about $4 per ounce or more. And almost all that milk is fed to preemies in hospitals.

It's still a new method for feeding preemies, but there's a lot evidence that it protects them against a devastating intestinal disease, called necrotizing enterocolitis, and helps their immune systems.

I would urge mothers, if they have an excess supply of breast milk, to consider donating it for premature infants.  We're just trying to procure enough human milk for the tiniest babies — who have the most need.