Not nearly enough people know about this mind-blowing characteristic of breast milk: It changes daily based on signals from the baby.
To produce breast milk, mothers melt their own body fat. Are you with me? We literally dissolve parts of ourselves, starting with gluteal-femoral fat, aka our butts, and turn it into liquid to feed our babies.
Before and after giving birth to my daughter 10 months ago, I was inundated with urgent directives from well-meaning, very insistent health practitioners, parenting book authors, mommy bloggers, journalists, and opinionated strangers that “breast is best.” The message was clear: In order to be a good mom, I had to breast-feed.
But breast-feeding is more than being a good mom. And breast milk is much more than food: It’s potent medicine and, simultaneously, a powerful medium of communication between mothers and their babies. It’s astonishing. And it should be—the recipe for mother’s milk is one that female bodies have been developing for 300 million years.
Breast-feeding leads to better overall health outcomes for children, which is why the World Health Organization and the American Academy of Pediatrics recommend that babies be exclusively breast-fed for a minimum of six months.
Those outcomes, though, are relative: A premature infant in the neonatal intensive-care unit or a baby growing up in a rural African village with a high rate of infectious disease and no access to clean water will benefit significantly more from breast milk over artificial milk, called formula, than a healthy, full-term baby born in a modern Seattle hospital.
We’re also told that breast-feeding leads to babies with higher IQs and lower rates of childhood obesity than their formula-fed counterparts. I understand why people find this appealing, but I don’t plan to raise my daughter to understand intelligence in terms of a single test score, or to measure health and beauty by body mass index.
More compelling to me are the straightforward facts about breast milk: It contains all the vitamins and nutrients a baby needs in the first six months of life (breast-fed babies don’t even need to drink water, milk provides all the necessary hydration), and it has many germ- and disease-fighting substances that help protect a baby from illness. Oh, also: The nutritional and immunological components of breast milk change every day, according to the specific, individual needs of a baby. Yes, that’s right, and I will explain how it works in a minute. Not nearly enough information is provided by doctors, lactation counselors, or the internet about this mind-blowing characteristic of milk.
I made the choice to breast-feed around the same time I was offered a full-time job writing about food. Every morning at 7 a.m., I nurse my daughter. At the office, I pump milk two times a day. When I come home, we nurse, and then at 7 p.m., we nurse before she goes to bed. A few nights a week, I go out to dinner for work.
For six months straight, I woke up every night at 3 a.m. and pumped milk for half an hour in order keep my supply ahead of her demand. (Three a.m. is possibly the darkest, loneliest, and most quiet hour of the night, but I had the reassuring, rhythmic sound of my pale-yellow breast pump to keep me company.) For the last 10 months, there hasn’t been one minute of my life when I wasn’t thinking about, writing about, eating, and/or producing food.
Food points to who we are as animals—human beings with a fundamental need for nourishment, survival—but also to who we are as people: individuals with families, histories, stories, idiosyncrasies. Every day, calories, vitamins, and even clues about the culture I live in flow, drip, leak, and squirt out of my boobs, staining my clothes and making my skin sticky. And every day, I wonder what exactly goes into this miraculous substance.
“People tend to underestimate what milk is,” says Katie Hinde, a biologist and associate professor at the Center for Evolution and Medicine at the School of Human Evolution & Social Change at Arizona State University. She also runs the very funny, highly informative, and deeply nerdy blog Mammals Suck… Milk!
“That’s in part because you go to the store and there’s an entire aisle dedicated to buying milk that is literally a homogenized, standardized food. It leads us to take mother’s milk for granted.”
But right now, researchers like Hinde—a mix of evolutionary biologists, dairy scientists, microbiologists, anthropologists, and food chemists—are examining milk, and the more closely they look, the more complexities they find.
Nutritionally, breast milk is a complete and perfect food, an ideal combination of proteins, fat, carbohydrates, and nutrients. Colostrum, the thick golden liquid that first comes out of a woman’s breasts after giving birth (or sometimes weeks before, as many freaked-out moms-to-be will tell you) is engineered to be low in fat but high in carbohydrates and protein, making it quickly and easily digestible to newborns in urgent need of its contents. (It also has a laxative effect that helps a baby pass its momentous first poop, a terrifying black tar-like substance called meconium.)
Mature breast milk, which typically comes in a few days after a woman has given birth, is 3 to 5 percent fat and holds an impressive list of minerals and vitamins: sodium, potassium, calcium, magnesium, phosphorous, and vitamins A, C, and E. Long chain fatty acids like DHA (an omega-3) and AA (an omega-6)—both critical to brain and nervous-system development—also abound in mother’s milk.
The principal carbohydrate in breast milk is lactose, which provides copious calories and energy to fuel babies’ relentless round-the-clock growth. (No, new parents, you are not hallucinating—your baby did just grow out of her pajamas sometime in the middle of the night.)
Other sugars are also present, including some 150 oligosaccharides (there may be even more, scientists are really just beginning to understand them), complex chains of sugars unique to human milk. (I repeat: unique to human milk.) These oligosaccharides can’t be digested by infants; they exist to feed the microbes that populate a baby’s digestive system.
And speaking of microbes, there’s a ton of them in breast milk. Human milk isn’t sterile—it’s very much alive, filled with good bacteria, much like yogurt and naturally fermented pickles and kefir, that keep our digestive systems functioning properly. So mother’s milk contains not only the bacteria necessary to help a baby break down food, but the food for the bacteria themselves to thrive. A breast-feeding mother isn’t keeping one organism alive—but actually hundreds of thousands of them.
Like a glass of red wine, breast milk has a straightforward color and appearance, but it possesses subtleties in flavor that reflect its terroir—the mother’s body. And it turns out that like any great dish of food, mother’s milk holds a variety of aromas, flavors, and textures.
The flavors of breast milk are as dynamic as a mother’s diet. In the 1970s, researchers at the University of Manitoba obtained samples of breast milk from lactating women and had them evaluated by a trained panel for taste, quality of sweetness, and texture. There were variations across all samples in all categories, most notably that the milk of a woman who had recently eaten spicy food was described by tasters as being “hot” and “peppery.”
The flavors of food ingested by breast-feeding mothers—kimchi, carrots, mint, blue cheese—are transmitted to their milk and, in turn, tasted by their babies.
Based on her more recent research, Julie Mennella of the Monell Chemical Senses Center in Philadelphia believes that these early breast-milk experiences help infants develop their own personal taste preferences, as well as increase their enjoyment of particular flavors.
“The types and intensity of flavors experienced in breast milk may be unique for each infant and serve to identify the culture to which the child is born,” writes Mennella.
I find this thrilling. My job allows me to explore the diversity of Seattle’s food scene, and my body allows my baby to discover it as well. My daughter began dabbling in solid foods at five months, and since then, much to my delight, has eagerly scarfed down pork ribs smoked by her grandfather, roasted zucchini from Local Roots Farm, lechon and bagoong at a Food & Sh*t pop-up dinner on Beacon Hill, Neah Bay king salmon at Capitol Hill’s Marjorie, and deep-fried hush puppies from Jackson’s Catfish Corner in Rainier Valley.
I love the idea that even before her first encounter with solid food, her taste buds had already begun telling her that she is part of a city filled with the cuisines of many nations, a household that supports local farmers, and a Filipino family with an abiding love of pork and fermented shrimp paste.
Just as exciting as the possibility that breast milk may help my daughter develop a healthy appetite in the future, though, is the reality that it is helping her live a healthier life right now, and that without my knowing it, my milk has already been adapting itself to her needs.
Breast-fed babies have lower instances of colds and viruses. When they do get sick, they are often able to recover more quickly because the mother’s body produces antibodies specific to the baby’s infection. This is an idea that has literally kept me up for hours at night. How exactly is my body able to write my daughter a prescription for her illness without a diagnosis?
When I ask Hinde, she pauses, looks straight through the Skype interface of her computer and directly into my eyes/soul, then says: “If I tell you, you can’t unknow it. Are you sure?” (Answer: yasssssss.)
According to Hinde, when a baby suckles at its mother’s breast, a vacuum is created. Within that vacuum, the infant’s saliva is sucked back into the mother’s nipple, where receptors in her mammary gland read its signals. This “baby spit backwash,” as she delightfully describes it, contains information about the baby’s immune status. Everything scientists know about physiology indicates that baby spit backwash is one of the ways that breast milk adjusts its immunological composition. If the mammary gland receptors detect the presence of pathogens, they compel the mother’s body to produce antibodies to fight it, and those antibodies travel through breast milk back into the baby’s body, where they target the infection.
At the same time that it is medicine, breast milk is a private conversation between mother and child. While my daughter lacks words, breast-feeding makes it possible for her to tell me exactly what she needs. The messages we are sending each other are literally made of ourselves, and they tell us about what is going on in our lives at that very moment.
Even before babies have any concept of time, breast milk helps them understand certain hours from other hours, night from day.
“Milk is so incredibly dynamic,” says Hinde. “There are hormones in breast milk, and they reflect the hormones in the mother’s circulation. The ones that help facilitate sleep or waking up are present in your milk. And day milk is going to have a completely different hormonal milieu than night milk.”
Mother’s milk informs babies of not just the present, but also the past. Returning to the maternal fat-melting thing, Hinde explains that mothers who are vegetarians in adulthood, but ate meat as teenagers, have stored fatty acids that are specific to animals. When they mobilize that fat to produce breast milk, their babies receive those nutrients.
“You have information about your whole life span that could be in your milk,” says Hinde. “Milk is telling the baby about the world its mother has lived in.”
But even more than the world I have lived in, I am moved by the idea that, without words, I am telling my daughter about myself, my life.
Breast milk also points to a future of exciting possibilities. Recently, researchers discovered that pluripotent stem cells, stem cells that have the ability to form any of the more than 200 different types of cells found in adult human bodies, are present in breast milk. The only other place these cells have been found is embryonic tissue.
“There are lots of ethical issues with embryonic stem cells,” says Hinde. “But breast milk could become a source of stem cells that can potentially be turned into any cell in the human body. There’s huge potential for regenerative medicine.”
And while science is a very long way off from being able to engineer and grow replacement tissue for people with degenerative diseases, these things are being discussed because of breast milk.
“It sounds like science fiction, but these are things that are now on the table as plausible,” Hinde says.
To get to that future, our society will need to place real value on breast milk. But as it stands, there are many economic, cultural, and political obstacles that stand between a baby’s mouth and its mother’s breast.
During the 20th century in America, feminism, aided in part by the convenience of formula, helped bring more women into the workforce. While this was a great thing for gender equality, it shifted focus away from breast milk, which meant that medical and governmental institutions turned away from it too.
“You have two generations that lost the cultural knowledge and the social capital of this information,” says Hinde. “We’re really grappling today with the erosion of social knowledge and social support networks that facilitate breast-feeding and information about what breast milk is.”
There’s a resurgence in prioritizing breast-feeding because we know for certain that it’s what’s best for a baby, all other things being equal.
But when is anything ever equal?
I breast-feed because I am lucky, have choices, and am physically able to. I have a supportive husband, an incredible mother who watches her granddaughter three days a week for free, and a workplace that allows me to exercise all of my breast-feeding rights as laid out by the Affordable Care Act. (For the record, mothers, you are entitled to these things: reasonable break time to express breast milk for one year after your child’s birth each time you experience the need to express milk, and a place to pump, other than a bathroom, that is shielded from view and free from intrusion from coworkers and the public.)
But many women literally cannot afford to work and send their children to day care, as they can’t get a job that pays enough to justify the cost. And some mothers meet with resistance when they exert their Affordable Care Act–supported rights.
We can’t expect the value of breast-feeding to just trickle down to mothers in the trenches, pumping away in cramped offices and broom closets, working multiple jobs, forking over significant portions of income to day care, and, yes, tired and close to the breaking point, cursing their own desire to continue feeding their children their milk. We have to make an effort to reach all mothers, not just those actively seeking support and information.
There’s much more at stake than infant health. “Breast-feeding is one of the key public-health interventions that we can actually do,” says Hinde. “Because we know that a lot of our metabolism, neurobiology, and immune function are shaped in huge ways by it—and that these have lifelong influences on how our bodies function.”
We know that breast-feeding can help children avoid diseases that manifest later in life, like type 2 diabetes and high cholesterol. We also know that black people are 2.2 times more likely than white people to develop type 2 diabetes, while Native Americans are 2.8 times as likely. Black and Native American people have the two lowest initiation rates of breast-feeding of all racial and ethnic groups in the United States.
Right now, we lack the societal, institutional, and cultural support structure to help mothers meet their breast-feeding goals. If we’re telling women that they should breast-feed exclusively for six months, then we should give them—at minimum—the same amount, six months, of paid family leave. Seemingly everything about breast-feeding, which for the first few months easily takes up eight hours a day, is at odds with holding down full-time work.
What stories that our bodies tell each other are lost when we’re forced to spend every day apart?
My daughter was born under the gray blanket of Seattle’s fall, but now that she is eating solid foods, I think of her as a summer babe. She’s been obsessed with Yakima nectarines and cherries, as well as the Skagit strawberries and blueberries of early summer. Her first tomato—a small, beautiful Sweet 100 plucked from our garden—was still sun-warm when she bit into it, squirting seeds and juice onto her clothing and face. She seems to like the taste of the Italian plums that our neighbor John lets us pick from his tree, purple as bruises, even more than I do.
Breast-feeding is an intense relationship, but ultimately one that lasts only a short period of time. As my daughter eats more, she breast-feeds less. We introduced her to some cow’s milk the other week, and she barely seemed to notice the difference.
Last weekend, though, she developed a 101-degree fever. She was miserable, unable to sleep, and uncharacteristically disinterested in eating even the beloved blackberries we pick from the brambles a few blocks from our house. So we nursed instead.
As I held her close, her body fiery and fragile, I tried to picture her saliva entering my body, my mammary glands interpreting it, my body producing her medicine, my breasts giving some defense against what she was fighting. And while I understood that these things were happening, it didn’t feel any different, just the same soft, familiar tickle of her tongue against my nipple.
From the moment my girl exited my body, I’ve understood that being her mother would be a lifelong process of separation, letting go. But in that moment, I pulled her closer. I leaned in, as though I might actually hear her body whispering to mine. 