By now, you’ve likely heard that breast-feeding is good. Women hear the mantra “breast is best” practically from the moment they conceive — both the World Health Organization and the American Academy of Pediatrics recommend exclusively breast-feeding babies for six months. With this kind of endorsement, which any nursing mother will tell you requires a mammoth commitment, you would think we know everything there is to know about the practice.

In reality, we don’t. We aren’t even close.

Breast-feeding is perhaps the oldest human activity that we know the least about. Scientists know more about what’s in a tomato than what’s in human milk, according to Katie Hinde, a lactation researcher and associate professor at Arizona State University. (And we know twice as much about erectile dysfunction.) We have yet to discover the full catalogue of breast milk’s ingredients, how they get there and what babies do with them. Most lactation research is dietary, but nursing is an intricate and complicated function. Science barely understands it, much less the doctors and nurses who are supposed to aid new mothers — who are often overwhelmed by breast-feeding struggles and left to fend for themselves. Eight out of 10 parents believe breast-feeding troubles contribute to postpartum depression in new moms, according to a recent survey. No wonder 60 percent of women don’t meet their own breast-feeding goals.

Science has uncovered far more about breast-feeding’s advantages for babies than it has about its benefits and challenges for moms. Studies have tied breast-feeding to postpartum weight loss, protection against some cancers and, most recently, Type 2 diabetes prevention. There are hormonal rewards, likes oxytocin boosts. But milk supply remains a mystery — there is no clear answer to why some women produce too little milk while others make so much that it causes them extreme pain. It’s not obvious who is most at risk for agonizing breast-feeding-related infections that can impede nursing, like MRSA, mastitis or thrush. Drugs that increase milk supply are imperfect and under-prescribed. Women with oversupply are told to apply cabbage leaves and hot compresses, or to ingest herbal supplements, as if they have given birth in Westeros or an ancient civilization, not the United States in 2018. The answers to these questions matter if we’re ever to fully understand breast-feeding and ensure that women who want to can.

We don’t even use the right words to describe what actually happens during nursing: a baby’s milk drawing is still called “suckling,” but, as biomechanist Katy Bowman explains, it’s actually a complex series of movements that includes compression and creating a vacuum. When a baby extracts milk from a breast, she’s shaping her jaw, bite and facial muscles, which affect chewing, breathing and swallowing, Bowman says.

Why has the lightning pace of technology and scientific discovery left breast-feeding behind? Lactation biology is not new, having emerged in the late 1800s. Yet funding priorities for research lie elsewhere today. The gender of the majority of legislators appropriating research dollars may shed some light. “The fact that we don’t have this thing can only be attributed to the fact that people do not perceive it as being necessary,” Hinde told me. The existence of formula suggests that we have the recipe for an exact copy of breast milk, but we don’t. Noel Mueller, an assistant professor of epidemiology who studies the contents of human milk at Johns Hopkins School of Public Health says, “The evidence is still mixed as to whether or not formula can be a substitute for human breast milk and give the same type of nutrition to infants.”

It might not matter much to a new mom if she can’t find a detailed medical study of the contents of breast milk. But it matters a great deal if she can’t properly breast-feed her baby, and science shrugs its shoulders. Breast-feeding is assumed to be easy because it’s “natural,” but it can be downright Sisyphean for some moms, due to factors like milk supply, nipple and breast shape and size, and infant’s ability to latch on to the breast. The Internet is rife with stories of breast-feeding woes and message boards where desperate moms seek help. One pediatrician, who says she spent hours advising parents to breast-feed, wrote in this essay that she expected breast-feeding to be a cinch when she had her own child. The reality was far different.

Nursing is physically, emotionally and psychologically consuming, even to women for whom it comes “easy.” The intense pressure to breast-feed combined with the lack of support can put mothers in an impossible situation; nursing difficulties can become a life-or-death matter for women experiencing postpartum depression, which affects up to 1 in 7. And when women struggle with breast-feeding, the medical system often fails them.

Health systems are more likely to thwart the establishment and practice of breast-feeding than to teach it. “The vast majority of hospital staff members can’t provide the education about how to breast-feed just after birth that so many women want, so instead, women receive conflicting advice or none at all,” wrote Malika Shah, an assistant professor at Northwestern University who specializes in breast-feeding medicine.

Only 23 percent of U.S. births take place in “baby-friendly” certified hospitals, meaning they encourage nursing by allowing mothers and newborns to stay together immediately after birth to establish breast-feeding. Breast-feeding can be forestalled in these places, too. They prioritize practices like “rooming in,” “skin-to-skin” contact and avoiding formula, but labor and delivery nurses who care for women typically aren’t trained lactation specialists with expertise to troubleshoot specific problems. About half a dozen women have told me they received little to no feeding help after delivery in baby-friendly hospitals, and that was my own experience twice. Some hospitals employ enough certified lactation specialists, but they don’t work around the clock, and often there aren’t enough of them to meet postpartum women’s needs.

Who picks up the slack? Enter the field of private lactation consultants who exist outside the medical system, and often aren’t covered by insurance. They know far more about how to establish and correct breast-feeding than hospital staff, and play a vital and uninhabited role in teaching women to breast-feed. Lactation consultants can be godsends, but they are not part of routine postpartum care and can be prohibitively expensive for many women.

Jada Shapiro, a lactation counselor and the founder of Boober, an on-demand breast-feeding support service in Brooklyn, says she is contacted by four to seven women each day who need more breast-feeding guidance than they received in their hospital. “What I see the most is that women are told they don’t have enough milk,” Shapiro says.

She explains that women are alarmed by colostrum, the first milk they produce, because it doesn’t seem like much. In fact, that’s all a newborn needs for the first few days until the breast and nipple are stimulated enough for more breast milk to be produced. Hospitals still whisk newborns off to the nursery and give them formula, a practice that Shapiro says interferes with the establishment of milk supply. “What is done in the hospital to mothers is completely counterintuitive to how breast-feeding works,” she says.

Misunderstandings like these are not new. Mainstream medicine has historically paid little attention to breast-feeding. The American College of Obstetricians and Gynecologists first formally recommended that breast-feeding be part of their practices only in 2016. Hinde points out that hospitals standardize the assessment and diagnosis for major organs, but not for the mammary glands and milk production. The standard postpartum protocol — one visit more than a month after hospital discharge — is insufficient on many levels, but it’s definitely too late to help a new mother figure out how breast-feeding works.

While research on human lactation and breast-feeding is far from a priority of any significance, much more has been conducted in the past decade, spurring more questions and highlighting what we don’t know. In 2015, for instance, researchers identified that the specific interaction between human milk and baby saliva creates hydrogen peroxide, which kills bacteria. New initiatives, like Rush Mothers’ Milk Club in Chicago, are trying to increase human milk feeding for NICU newborns, and asking whether human milk could be matched to a baby the way we match blood based on blood type. That this all sounds like science fiction reveals how much we have to learn.