Cows produce version of human breast milk

You've probably read plenty of stories about the risks of eating chicken. But the most important protein to buy organic may well be beef. <br><br>"Research suggests a strong connection between some of the hormones given to cattle and cancer in humans, particularly breast cancer," says Dr. Samuel Epstein, professor emeritus of environmental and occupational medicine at the University of Illinois at Chicago School of Public Health. Specifically, the concern is that the estrogen-like agents used on cattle could increase your cancer risk, adds Dr. Ted Schettler, science director at the Science and Environmental Health Network.<br><br>More from Health.com: <a href="http://www.health.com/health/gallery/0,,20471203,00.html">5 surprising things you don't have to buy organic</a><br> istockphoto

Chinese researchers say they have genetically engineered dairy cows to produce milk more akin to human breast milk.

The key is a particular protein — called lysozyme — that is abundant in human breast milk. As an enzyme that attacks certain bacteria, it helps protect nursing babies from infection. Lysozyme, however, is found  in only trace amounts in cow's milk.

"Despite the benefits [human lysozyme] provides to breast-fed infants, mothers do not always desire to lactate and sometimes situations prevent lactation," write the researchers in an article that appeared on March 16 in the journal PLoS ONE. "Therefore, the development of alternative sources of [human lysozyme] would be beneficial to infant health."

The researchers, led by Bin Yang of the State Key Laboratory for Agrobiotechnology at the China Agricultural University in Beijing, created calf embryos with the genes to produce the protein and raised them once they were born. They examined the milk produced by the four transgenic cattle that were lactating during the time of the study.

They concluded that the protein produced by the transgenic cattle was identical to that of human breast milk and had similar bacteria-killing activity. The altered cows' milk also had fat, protein and lactose contents similar to that of regular cows' milk.

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