Ten percent of breast milk samples purchased online have added cow’s milk or formula— which may pose health risks to babies with allergies and expose children to infectious disease— reveals a study published Monday in the journal Pediatrics.

A team led by Nationwide Children’s Hospital, including researchers from The Ohio State University and Cincinnati Children’s Hospital Medical Center, purchased and tested 102 samples of breast milk advertised on milk-sharing websites. They found that all purchases contained human milk, but 11 also contained bovine DNA.

The team made their own mixtures of human and bovine milk, and created a reference curve from which they estimated what proportion of milk may have been cow’s milk.

Researchers used a molecular test that not only differentiated between human milk and cow’s milk, but also detected the level of cow’s milk in the liquid, which allowed them to exclude accidental contamination from their findings. Of the 11 contaminated samples, one tested for minor, accidental contamination, which suggests a notable number of sellers intentionally added cow’s milk or infant formula to the human milk. Infant formula can also be made from cow milk.

“In all honesty, I’m not that surprised. Sellers charge per ounce of milk. Cow’s milk is about 100 times cheaper than breast milk you can buy online,” study co-author Jesse Kwiek, an associate professor of microbiology at The Ohio State University Wexner Medical Center, told FoxNews.com. The team paid between $1 and $4 per ounce.

Experts have seen increased momentum of women purchasing breast milk online, and while the reason for the growing trend hasn’t been studied, say it’s not a fad to follow. According to Kweik, an estimated 12,000 breast milk transactions were made in 2012, but now that number may be roughly more than 50,000.

“I would not recommend, under any circumstance, for a family to purchase unscreened donor milk online,” Dr. Amy Hair, neonatologist and director of the Neonatology Nutrition Program at Texas Children’s Hospital, told FoxNews.com. Hair, who was not involved with the study, focuses specifically on neonatal nutrition, human milk and growth for infants.

Previously, the research team found that breast milk is not always packaged properly to arrive in good condition— a significant proportion were not between freezer and fridge temperature, some arrived much colder because of dry ice, and some were so warm they exploded in transit.

“You don’t really know what you’re getting.”
Purchased milk with unknown additives may pose various hazards for babies.

“The primary risk of this is if a child has a cow’s milk allergy, there could be an allergic reaction, but also that the child is not getting all the benefits of human breast milk,” Kweik said.

Another concern is that the online donors are completely unknown to buyers. The Nationwide Children’s-led team has an upcoming study that has found that breast milk sellers who advertise that they are caffeine- or nicotine-free may not be telling the truth, as researchers tested for those metabolites in the milk.

The American Academy of Pediatrics recommends breast milk for all infants. Breast milk provides immune factors and antibodies that pass through the baby, which may prevent infection early in life, a time when the child’s own immune system is developing. Human milk also provides important nutrients— such as brain-boosting DHA— and minerals that a growing baby needs.

“Breast milk diluted with cow milk or milk you buy at the store may not have the full nutrition content that an infant would need,” Hair said. “If they can’t get a full amount of breast milk, I would recommend supplementing with formula to meet nutrition needs.”

Severe malnourishment could lead to poor outcomes in a child’s development, including missing milestones such as walking, talking and learning, she added.

Another concern is if a donor mother has an infection or illness they are unaware of, it could pass to the baby. A heavy smoker could pass high levels of nicotine; an illicit drug user could pass along the chemicals they ingest.

“You would hope that someone wouldn’t be selling milk if it could potentially harm a baby, but you just don’t know. It can be very dangerous; you just don’t know if it’s unknown,” Hair said.

Hepatitis is another risk with donor milk. If a mother has a liver infection and is unaware, the infectious virus could transfer to the recipient baby.

Cow’s milk is not recommended until one year of age, and mothers who can breast-feed are generally advised to do so for as long as possible. If that is not an option, formula should be used for the first year because of the baby’s nutrition and protein needs, Hair said.

“The take-home message is you really don’t know what you’re getting,” Kweik said of Internet milk purchases.

Milk banks as the safest option
Both Kweik and Hair recommend that women who are unable to breast-feed their children use non-profit milk banks as the safest resource. The Human Milk Banking Association of North America (HMBANA), a professional association for supporters of nonprofit donor human milk banking, assesses each of their 15 accredited U.S. locations annually for adherence to guidelines. Donor milk is pasteurized, tested for bacteria growth, and shipped frozen overnight to hospitals and individual recipients.

At Texas Children’s, the hospital’s state-of-the art facility uses DNA fingerprinting to ensure their donor milk comes from their pool of screened mothers, a unique feature, Hair said.

“Donors go through extensive screening for health conditions, disease. They are more heavily screened than blood donors,” Hair said.

Both Hair and Kweik noted that while there are not enough non-profit milk banks as they’d like to see, they are the best resource for  families— and for women with excess breast milk, who can donate.

Kweik noted the Food and Drug Administration (FDA) currently does not regulate donor human milk. The FDA recommends that if a woman needs to get milk from a source other than herself, then she should consult her health care provider or pediatrician. She also advised against using donor breast milk acquired directly from individuals or through the Internet.

For many women, it can be frustrating not to be able to provide milk for their newborn, but turning to the Internet is not the solution, Hair said.

“While I’m a proponent of breast milk, for a term baby, if it was an option between unscreened donor milk that has potential risk, or formula, I would choose formula,” Hair said.