by Florence Williams

Bruce German, a food chemist at the University of California, Davis, had been studying red wine when a life-changing thought hit him. He knew that humans have to ferment, cook, mash and otherwise manipulate foods like grapes because plants didn’t evolve to feed us. Cooking, mashing and manipulating make the inedible edible and the unpalatable palatable, or even delicious. Prior to processing, many plants often contain toxins and other defenses in order not to be eaten. To truly learn about promoting health, he thought, he needed to be studying a food that did evolve to feed us. There is only one: human milk.  And hardly anyone was researching it. (For one thing, there was a lot more industry funding to study wine or cow’s milk.)

German forged ahead, and now, 20 years later, he runs the university’s Foods for Health Institute.  He is passionate about the subject. “Milk is personalized, dynamic, active and structured,” he says, “all of the things we’d like to be able to give people to gain control of their health. And, oh, by the way, it’s delightful.” He means not just the substance, but the act of lactation itself, which enabled social learning, brain growth and the subsequent global flourishing of mammals that began about 55 million years ago.

But back to health. German chuckles about what he calls the dark ages, the years in which scientists thought human milk was merely a food, a delivery system for sugars, fats and proteins. Now we understand lactation evolved as much for immune support as for nutrition. Milk contains immune factors, including antibodies, and anti-infective proteins, but also over 800 species of live bacteria all customized to a baby’s particular environment. In other words, breast milk contains natural probiotics – healthy bacteria – just like yogurt. Many of these bacteria have never even been named, but German’s favorite one has and it comes with a bit of history. If he has his way, it also will have a glorious future: Bifida infantis.

B. infantis is one of dozens of subspecies of the genus Bifida, whose members are found all over the human body (even occasionally in your belly button). Bifidobacteria make up only about 3-6 percent of the adult gut microbiome, but they constitute 90 percent of the intestinal bacteria of infants who are breastfed. The largest population of all are of B. infantis, which is rare in both older children and adults. Bifida were named for their Y-shaped structure (bifid means two) in 1899 by the French pediatrician Henry Tissier, who noticed that babies filled with B. infantis suffered fewer gastrointestinal problems. But he didn’t know why.

In an effort to find out, German’s lab decoded (sequenced) the genome of the bacteria and tried to figure out what made it grow. It turns out that B. infantis has special genes that make an enzyme to help it digest its main food source: human milk, or more specifically, a major milk ingredient, human milk oligosaccharides. These are unique sugars, and human milk is teeming with them, so much so that they make up 21 percent of the volume of milk.  Clearly the mother’s hard-working mammary glands go to a lot of trouble to make these, even though the infant can’t digest them at all. Their main beneficiary is Bifida, baby’s guests of honor.

German realized that Bifida infantis must be really important. “This bacterium co-evolved with us. It’s our true symbiont.” Bifida helps the infant in a number of clever ways. When it breaks down the sugars in the infant gut, it appears to reduce local pH levels, making it more difficult for disease-causing bacteria to grow. It’s also such an efficient eater of these sugars that there aren’t many leftovers for other bacteria. It starves them out.

The mother’s body, by producing this spectacular milk, is recruiting other life forms that help keep her baby safe.  Bifida is part of a biological security system. All of this health-giving makes sense. Among babies who are born too early, the ones who are fed breastmilk survive better than the ones given formula. They are about half as likely to suffer from fatal gut infections, especially one called necrotizing enterocolitis, which causes part of the intestines to shrivel up. Among full-term babies, the ones who are breastfed get fewer infections and go to the doctor less often.

Because not every baby receives breast milk, German is proposing that babies receive a dose of B. infantis when they are born, like a vitamin. The bacteria is currently difficult to grow outside the human body, but the laboratories at UC Davis are working on it. First they need to make the special oligosaccharides to feed it. Then they need to put it in an oxygen-free chamber. And then they have to test the product in humans.

Having learned so much about Bifida, now German also wants to study the other healthful components of milk.  He thinks they will likely provide clues to help prevent both childhood and adulthood diseases from infections to cancer. If scientists learn how these other ingredients work, they can develop new and better drugs. “We can act quickly and with confidence if we use human milk as the inspiration,” he says.

About the Author

Florence Williams writes for the New York Times, Discover, Mother Jones and other publications. Her book, BREASTS: A Natural and Unnatural History (W.W. Norton, 2012) won the Los Angeles Times Book Prize in Science and Technology. She lives with her family in Washington, DC and serves on the board of her favorite nonprofit, High Country News.