Since it’s hard to see big bangs from breast-feeding in countries where kids are generally healthy and well taken care of, I wanted to look elsewhere. The data start to get really electric when you peer farther over the fence into areas of poverty or the world of preemies and sick babies.
I owed it to breasts to check it out. So I headed for Peru.
• 9 •
HOLY CRAP:
HERMAN, HAMLET, AND THE
ALL-IMPORTANT HUMAN GUT
O, thou with the beautiful face, may the child Reared on your milk, attain a long life, like The gods made immortal with drinks of nectar.
—SUSRUTA SAMHITA,
fourth to second centuries BC
LIMA HOSTED THE FIFTEENTH MEETING OF THE INTERnational Society for Research in Human Milk and Lactation during a cool austral spring week in October. The society’s cochair, Professor Peter Hartmann, welcomed me heartily. “We’ve never had a journalist before! Maybe you can tell people about our work!”
Hartmann, an Australian now in his seventies, is perhaps the world’s foremost expert in lactation. Even so, he bears the demeanor of someone whose work is largely unacknowledged outside this crowd. He’s a little bent over, and quiet, and a bit harried. He spent the week in Lima clutching his briefcase and scurrying from meals to meetings wearing his beret and a leather jacket. His son, Ben, is also here, not quite as stooped or as sartorial. Ben, thirty-four, runs a milk bank, collecting and storing donated human milk for use in the preemie ward of King Edward Memorial Hospital on the edge of Perth. (What is it with fathers and sons dove-tailing careers around breasts? Ben’s infant, Arlo Peter, has actively benefited from the Hartmann male tradition. “As my poor wife has indeed been subjected to the full barrage of tests by the research group, we certainly had a lot more information at our fingertips than most,” said Ben.)
I sat down with the elder Hartmann during one of the numerous café breaks in a heavily tiled, open-air meeting room at our faux-Renaissance lodge. Originally, he told me, he intended to study dairy science. He got a Ph.D. in bovine lactation. But then Britain changed its export policy, and the Australian dairy market “disappeared overnight,” he said. He secured a lectureship in biochemistry at the University of Western Australia in Perth, and in 1971, his first child was born. That event piqued his interest in the human side of things. He started studying progesterone withdrawal in women after birth, and found a large pool of enthusiastic breast-feeding volunteers through the Australian version of La Leche League. Human lactation was a tough academic sell, though. “Nobody was really interested when I applied for grants. It wasn’t a good career choice.” He smiled impishly, then added, “I proved them wrong.”
Still, he said, “It’s amazing how few people are interested in this incredible organ. The breast is the only organ without a medical specialty. It represents 30 percent of a woman’s energy output, and it’s not represented by a specialty! It’s absolutely appalling!” What he meant by the energy bit is that while a woman is lactating, the metabolic energy required to feed her infant is 30 percent of her total output—or the energy equivalent of walking seven miles—every day. Looked at another way, a male baby requires almost 1,000 megajoules of energy the first year of life. That is the equivalent of one thousand light trucks moving one hundred miles per hour. As the ecologist and writer Sandra Steingraber has put it, “Breastfeeding is a form of matrotropy: eating one’s mother.” No wonder so many women are ambivalent about doing it.
“It’s a magnificent organ to study from a molecular standpoint,” Hartmann continued, occasionally smoothing his trim white beard. “It’s easy to get access to it and harvest molecules. The problem lies with the view of it as an aesthetic breast. You only have to go to the local newspaper and see breasts hanging all over the place.” (Hartmann must be one of the few Western men on the planet who see this as unfortunate.) “The problem is the view of the aesthetic breast gets in the way of the view of the breast-feeding breast. The guys at the tennis club joke they wish they had my job, but no one is doing my job. At other [biological] meetings, you see thousands of scientists. We’ve got less than a hundred.”
He’s right that breasts are often overlooked, at least for noncancer scientific research. The Human Microbiome Project, for example, is decoding the microbial genes of every major human gland, liquid, and orifice, from the mouth to the skin to the ears to the genitals. It neglected to include breast milk, the life-giving, lifesaving, older-than-mammals-themselves elixir. Oops.
There is at least one entity very interested in Hartmann’s research, and that is Medela, the Swiss maker of breast pumps. The company sent a number of representatives to Lima, and they presented a poster explaining their latest product. It’s a new artificial “teat”—that’s Australian for nipple—based entirely on Hartmann’s lab studies regarding flow and suction. I know a thing or two about suction. Just talking about it makes me wince. The new teat is meant to be used with Medela bottles filled with pumped human milk.
The Hartmann lab in Perth is well regarded for upending prior notions of how sucking—technically, suckling—works. Experts used to think the infant squeezed the nipple with her tongue, rhythmically releasing milk through this peristaltic action, a bit like wringing a washcloth. But Hartmann and his colleagues, using high-tech ultrasound videos, showed that the baby forms a strong suction with her lips, and it’s when she releases the nipple that milk flows down her throat (and moreover, this being a specialized human infant, she can suck and breathe at the same time, unlike adults).
One day some years ago, Hartmann was flying over Australia, and he found himself gazing out at giant ore piles near the mines. They were large mounds of salt and minerals, smooth and gently rounded. They looked like … his favorite organ. From high in the sky, a stockpile looked just like a breast from a few feet away. It occurred to him that it might be possible to apply giant-earth stereoscopic measuring techniques to the human breast. But he wasn’t merely interested in measuring the volume of a breast; he wanted to measure the synthesis of milk.
“Humans do not produce milk at full capacity, like a dairy cow,” he said. “They down-regulate to match the baby’s appetite. So we had to learn about those differences. How do you measure milk synthesis in a woman? I thought maybe if you could measure the volume of the breast, you could measure synthesis.” So he approached an expert in a mine-measuring technology called Moiré topography, and together they figured out how to calibrate units in something other than metric tons. They call it CBM, for computerized breast measurement, and it has to do with projecting light stripes at an angle onto the breast. “The distortion of the stripes could let you work out the volume of breast!” said Hartmann. “We could do it before and after feeds over a twenty-four-hour period. The difference in volume is the short-term synthesis [of milk] from one breast-feed to another!”
In the old days, people used to measure milk output by simply weighing the baby before and after a feed, but that didn’t reveal information about the workings of each breast independently, or about how much milk a breast could make from hour to hour or day to day. These data could be useful to hospitals, doctors, and, of course, Medela, which funded the research. In a paper describing the work, Hartmann and colleagues found that each breast of the average new mother produces approximately 454 grams, or 16 ounces, every twenty-four hours. Each breast can store about half of that, and both actions are determined by the demand of the infant (one baby in the study ate twice the average). Check this out: even after fifteen months of lactation, each breast can still make 208 grams of milk, even though the breast has returned to its pre-pregnancy size. In other words, the breast becomes more efficient, possibly owing to a “redistribution of tissues within the breast,” according to the paper by Hartmann’s lab. Breasts should get an Energy Star rating.
In any case, thanks to Hartmann, no longer is the dairy machinery such a mystery.
But the dairy product still is. I wanted to find out more. What makes m
ilk so special, if it really is? A lot of Hartmann’s work is in the liquid physics arena, but many of the Peru attendees were molecular biologists, biochemists, or geneticists who are deconstructing the components of milk bit by bit. They’ve been doing this for well over thirty years, and you’d think they’d have figured it out by now. Until very recently, it was thought that breast milk had around two hundred components in it. These could be divided into the major ingredients of fats, sugars, proteins, and enzymes. But new technologies have allowed researchers to look deeper into each of these categories and discover new ones altogether.
Scientists also used to think breast milk was sterile, like urine. But it turns out it’s more like cultured yogurt, with lots of live bacteria doing who knows what. These organisms evolved to be there for a reason, and somehow they’re helping us out. One leading theory is they act as a sort of vaccine, inoculating the infant gut so it can recognize bad actors and fight them when the need arises. At the conference, Mark McGuire, another former dairy scientist recruited to the human lactation field, described how he took forty-seven samples of milk, extracted DNA, and identified eight hundred (yes, eight hundred) species of bacteria living there, including small amounts of staph, strep, and pneumonia, all of which normally live in our bodies. An individual milk sample has anywhere from one hundred to six hundred species of bacteria. Most are new to science.
Then take the sugars. There’s a class of them called oligosaccharides, which are long chains of complex sugars. Scientists have identified 140 of them so far, and estimate there are about 200 of these alone. The human body is full of oligosaccharides, which ride on our cells attached to proteins and lipids. But the mother’s mammary gland cooks up a unique batch of “free,” or unattached ones and deposits them in milk. These are found nowhere else in nature, and not every mother produces the same ones, since they vary by blood type. Even though they’re sugars, the oligosaccharides are, weirdly, not digestible by infants. Yet they are a main ingredient, present in milk in the same percentage as the proteins and in higher amounts than the fats. So what are they doing there?
They don’t feed us, but they do feed many different types of beneficial bacteria that make a home in our guts and help us fight infections. In addition to recruiting the good bugs, these sugars prevent the bad bugs from hanging around. They act as “anti-adhesives,” kicking the bad guys off the gut surface. Some also seem to handcuff themselves to the criminals and escort them off the premises like a micro paddy wagon. “I think the benefits of human milk are still underestimated,” said Lars Bode, an immunobiologist at the University of California, San Diego. “We’re still discovering functional components of breast milk using new technologies and using smaller amounts of milk.”
Bode told me it’s well established that premature infants do remarkably better—as in, an order of magnitude better—on breast milk than on formula. As we’ve been able to keep younger and younger preemies alive, they’re more likely to be very sick. About 10 percent of preemies will suffer from a dreadful disease called NEC, or necrotizing enterocolitis, and about a fourth of those will die from it. NEC is a gut infection that causes the lower intestine to shrivel up and die. Babies who survive this often must have the necrotic portion surgically removed, leaving them with a condition called shortgut syndrome. Because they can no longer adequately digest food, they spend the rest of their lives attached to an IV. But the incidence of NEC is 77 percent lower in breast-fed babies than in formula-fed babies. This is why neonatal units work so hard to get mothers to pump breast milk for their preemies’ feeding tubes. In lieu of that, they use donated milk from milk banks, and in lieu of that, they can buy a newfangled “fortifier” made from concentrated human milk by a company called Prolacta Bioscience. It costs $12,000 per baby.
Naturally, conventional formula companies are falling all over themselves to synthesize these unique human sugars and add them to their cow-milk products. So far, they’ve been able to re-create only a few of the simpler ones, and to not much effect. These newly enriched formulas, for example, do not alter preemie NEC rates, according to Bode. This is because the most “bioactive” molecules are the bigger, more complex oligosaccharides, which are incredibly difficult to make in a lab. “Take one of these special monosaccharides? If you wanted to supplement human milk with it, the package would cost half a million dollars,” he said.
Bode said his lab has also shown that a simpler chain, called GOS, is effective at fighting amoebiasis, a parasite that kills 100,000 people a year. It’s likely GOS could help adults as well as babies.
THE GUT, IT TURNS OUT, IS INCREDIBLY IMPORTANT NOT JUST TO infant health but to adult health as well. Bruce German, a food chemist from the University of California, Davis, drove this point home for me. Picking up the breast ball where the Human Microbiome Project dropped it, German is spearheading the Infant Microbiome Project at the university’s Foods For Health Institute. The idea is to map and characterize oligosaccharides, as well as other human milk components, for eventual infant and adult medical applications. As German put it in a recent video, “We’ll take little tiny droplets of milk and disassemble them completely, understand every single molecule in it … and how they function when ingested by infants… We’re confident it will teach us how to prevent diseases like diabetes and heart disease and ultimately even cure diseases like cancer.”
German speaks in superlatives and alluring metaphors even when he’s not being filmed. “The genomic tree of life is a compelling one,” he told me in a private mini-lecture on microflora over breakfast one morning. A wiry, almost hyper speaker, he began to turn red. “We’re just a tiny branch! The rest of it is all microbial! We’re just a small part of the mass of microbial life. To a large extent, we live our life at their say-so. We have to form a pact with the world around us. Recruiting protective microflora is the very first thing we do in life.” He wasn’t eating, but now he sipped his coffee. “Put yourself in the mindset of an infant. You’re born, you are dropped in the mud, literally, where the microbial community thinks of us as lunch. So you must develop a community that protects you for life.”
He continued in his riveting, pretend-you’re-a-baby mode. Clearly he’s a man used to speaking to glassy-eyed undergraduates. “If you’re a preemie and you probably came out by C-section and you’re not breast-fed, you’re acquiring bacteria in your gut from the hospital that will reside there for the rest of your life.” He winces. “That’s not the way you want to do it. Normally, the mother hands down bacteria to her infant by means we still don’t fully understand. If there’s a successful transfer, it will be handed down mother-todaughter for generations. Now we think one C-section could break that chain.” He plunks down his coffee cup. “You’ve lost touch with your genetic ancestry.”
Could another way to break the microbial chain occur if the mother herself was not breast-fed? Are we now looking at a couple of generations of orphaned intestines, cut off from their full bacterial legacy? I asked German and he nodded. “Exactly.” He said he’d like to see every baby (who doesn’t receive breast milk) get a dose of Bifidus infantis at birth, like a vitamin K shot.
This bacterium is one of German’s favorites. Bifidus infantis has seven hundred genes, all of which evolved to live and thrive in a unique microbial environment: the infant gut. There, B. infantis eats the oligosaccharides that rain down in breast milk. The bacterium produces proteins that pull those special sugars inside it, where they get broken down and digested so that they are unavailable for other (worse) bacteria. Furthermore, said German, “Bifidus can overwhelm bad bacteria. It recruits a whole schoolyard of supportive organisms.” As I’ve said, these human milk oligosaccharides are not found anywhere else in nature. “It’s clear that these bacteria co-evolved with our oligosaccharides,” continued German. “It’s our true symbion.”
It’s good to know all this, but it’s also another intense failing for modern mothers to feel guilty about. I couldn’t help but wonder if I’d somehow flubbe
d the important microbial hand-off to my children. Some of the blame I could cast to my mother, who might not have given me the adequate goods in just four weeks of nursing. But I get a pit in my stomach when I think of the repeated rounds of antibiotics I took for mastitis while nursing my son: cephalexin, amoxicillin, dicloxicillin. Was I killing off everything good in his gut as well as in mine?
The adult gut can recover from antibiotics within a few months because of mysterious reserves of bacteria in our bodies, our housemates, and to some extent, our food. But the infant, who is bacterially “naive” and building colonies for the first time, might not. These thoughts snowballed in my mind, because my son has had gastrointestinal trouble for most of his life. The poor guy is chronically constipated. One pediatric gastrointestinal specialist I took him to shrugged off a search for root causes, saying, “Well, some people just have slow motility, like a sloth.” That’s my son, the sloth.
I sought out David Newburg, a biologist from Boston who has been studying the connections between breast milk, intestinal microflora, and disease for over two decades. A tall, tanned man with a trim goatee, I often saw him enjoying the Peruvian pastry table, as did I.
“Can I ask you a personal question?”
Newburg raised his eyebrows. “In that case, I’m going to need two tea sandwiches,” he replied.
I told him the story of my mastitis and the antibiotics. Was my son’s problem my fault?
“It’s definitely possible,” he said, making me feel wretched. Good tests to diagnose the gut’s array of normal and abnormal microflora are still a few years out, he explained. Changing the microflora is even harder. Someday, though, these things will be a routine part of medical care. In the meantime, Newburg recommended Ben regularly take probiotics (such as the lactobacillus found in yogurt and supplements) as well as eat foods rich in prebiotics (the complex carbohydrates that beneficial bacteria need to thrive). Although breast milk is the world’s best source of prebiotics for humans, they can also be found in Jerusalem artichoke, Belgian endive, onions, asparagus, and some other plants not terribly alluring to a nine-year-old.
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