Why do some women struggle to breastfeed? A UCSC researcher on what we know, and don’t

Lindsay Hinck
UC Santa Cruz researcher Lindsay Hinck.

UC Santa Cruz stem cell biologist Lindsay Hinck wants to solve a global and deeply personal problem: Why do some women struggle to make enough milk for their babies? The former breast cancer researcher switched her research focus after she struggled to breastfeed her daughter 22 years ago. As the nationwide baby formula shortage drags on, Guananí Gómez-Van Cortright spoke to Hinck about what we do and don’t know about why breastfeeding can be so difficult.

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Like many moms, UC Santa Cruz stem cell biologist Lindsay Hinck struggled to make enough milk to feed her infant daughter.

A Q&A with Lindsay Hinck

Frustrated by her low supply, she went to a lactation consultant, who advised her to wake up every night at 3 a.m. — an optimal time in the hormone cycle — to pump precious drops of “liquid gold” for her baby.

Hinck did it, but she also wondered, why was she having so much trouble and losing so much sleep while other moms had no problem feeding their newborns?

After many exhausting early hours with the pump, Hinck did what she does best: research. She found something remarkable: More than 25% of women worldwide struggle to produce enough milk to feed their infant children.

But when she looked to scientific literature for an explanation, it came up empty.

Hinck, who got a master’s degree in biochemistry from UC Davis and her Ph.D. in cancer biology from Stanford University, was shocked to realize scientists have barely studied human lactation. There was almost no information for scientists or moms about how human breast tissue makes milk.

Hinck decided to change that.

She switched her UCSC lab’s research focus from breast cancer to lactation, specifically looking into how stem cells in breast tissue create milk — and why some women’s supply comes out low.

It’s a topic some view with skepticism; lactation and breastfeeding are still treated by many as uncomfortable or inappropriate. In fact, in the early days of her research, Hinck had to get funding from an animal health firm interested in increasing milk production in cows.

“We sexualize breasts in the most amazing ways, and people don’t seem to have a problem talking about that,” says Hinck, who has been at UCSC since 1998 and serves as co-director of the university’s Institute for the Biology of Stem Cells. “Yet when it gets down to their biological function — which is to provide nutrition for infants — somehow the world clams up.”

With the a nationwide baby formula shortage having affected millions of families, Hinck’s work — funded by the National Institutes of Health — takes on even greater importance. Parents whose infants have allergies or metabolic conditions rely on formula, and women — particularly those who are already struggling to breastfeed — can’t suddenly build a milk supply overnight when formula is not available.

Hinck spoke with Lookout from her office at UCSC; this interview has been edited for clarity.

Lookout: What is lactation insufficiency?

Lindsay Hinck: Lactation insufficiency is the inability of a woman to produce the breast milk in daily volumes that meet the nutritional needs of her infant.

The statistics that we have are very broad. Somewhere between 25% and 67% of women will experience this worldwide. And this statistic is so broad because lactation insufficiency is understudied, and it’s hard to study.

A lot of scientists would agree that breast milk does confer an immunological advantage, and that it is filled with immune cells that the mother is giving to her infant; milk is also filled with microbes. Those are two of the major deliveries to children that come through breast milk, not to mention all the comfort of the breastfeeding cycle, psychological comfort and connectedness through the skin on skin feeling of being fed that way.

Lookout: How do you feel about your research in the context of the baby formula shortage?

Hinck: A lot of women rely on formula because they have trouble building a milk supply. Currently there are no FDA (U.S. Food and Drug Administration)-approved drugs in the United States for lactation insufficiency. My research is identifying therapeutically relevant drug targets, so that maybe we will be able to address this issue. We hope that one day women can take a drug to better build a milk supply.

We’re working on a nonhormonal drug. The current drugs work on the hormone prolactin, whereas my lab studies stem cells. None of the drugs targeting prolactin have been approved, because they have terrible side effects.

Hormones have wide-ranging effects. They’re released and they spread throughout the body. I think maybe we have an opportunity to identify a therapeutic that won’t have so many deleterious side effects.

A woman who has received the COVID vaccine breastfeeds her child
(Mel Melcon / Los Angeles Times)

Lookout: Because of the baby formula shortage, an easy answer might be to tell mothers they should just breastfeed. Why might that not be a compassionate or realistic response?

Hinck: No, that’s not a compassionate or realistic response. I mean, especially if you haven’t built your milk supply, it’s not a trivial thing. If you didn’t build a milk supply from the beginning, and even if you are breastfeeding, if you can’t meet the daily needs of your infant, you simply don’t have the milk. It’s just not there.

Building a milk supply doesn’t occur over 24 hours, you can’t just latch the child on more often and have more milk in a day. Eventually the milk supply will increase, but it’s complicated. It’s hard for some women to initiate and build a milk supply.

Lookout: In the U.S., lactation and breastfeeding seem to be treated as somewhat taboo or uncomfortable topics. How do you respond to that?

Hinck: We don’t want to see women doing it. It seems to make people uncomfortable, so at best we provide women a room somewhere, and at worst there are no accommodations. We certainly don’t appear as a society that welcomes breastfeeding in public. I am bemused at this, and find it tragic at the same time.

I myself, when I breastfed, I just breastfed. I just got to the point where — tough, you know? I know I made people uncomfortable. My mother-in-law would try to drape a huge blanket over me and my child in the summer in the heat, and it was like 100 degrees underneath that blanket. I would just be like, “This is crazy!” It’s just an infant at my breast eating. Seems fine to me. And I don’t think the climate has dramatically changed in many places in the world. My daughter is 22 years old, and in 22 years I have not seen that needle budge. It still seems like breastfeeding makes people uncomfortable, and I don’t know why.

Lookout: Have you faced any skepticism about this as a research topic, or faced any particular challenges in studying lactation compared to other topics, like cancer?

Hinck: I would say that I have had a harder time getting my lactation research funded. But recently, I received a NIH grant from the National Institutes for Child Health and Human Development, so that’s been terrific. There has been a gaining interest in a number of what’s been classified as “women’s diseases” that have been understudied for a long time.

But in the early days, I got money from an animal health firm because they were interested in increasing milk supply in cows. The biology is the same, however. So that worked out for me, and we were able to have a project that involves looking to see if this would work for building milk supply in cows, and then we were able to unravel the basic pathways, and now we’re applying that.

Lookout: What would you say are the big questions driving your current research?

Hinck: How does the breast tissue know how many progenitor cells to release or recruit to expand and to build the milk supply?

Breast stem/progenitor cells have to last a whole lifetime, and they have limited potential. They’re stemlike in that they undergo an asymmetric cell division, which is a special type of cell division that recreates the stem/progenitor cells and gives rise to daughter cells that can go on to expand and become the milk producing cells.

So how many of those asymmetric cell divisions occur? How many cells are recruited to undergo those asymmetric cell divisions? All of that is unknown. Remember, the stem cell, the progenitor cell, wants to divide as infrequently as possible. Every time they replicate their DNA, it is opening up the possibility of damage that could lead to cancer.

Lookout: How would understanding these progenitor cell pathways help improve people’s lives, or pursue a solution to lactation insufficiency?

Hinck: It’s early days. We don’t understand a lot, and of course giving drugs to women who are pregnant is tough. There are drugs on the market for lactation — domperidone is the best medicine to build milk supply, but it’s not approved by the FDA in America. It has side effects, cardiac side effects.

So it’s not unheard of that there would be drugs that could help build a milk supply. I think that would be the ultimate goal of our research, to understand if there is any pharmacological intervention that could help.

Lookout: What do you think nursing mothers who are struggling with lactation need? What can we do as a society to support them?

Hinck: Well, in the short term, certainly make workplace rules that change the climate. I mean, even if the rules are in place, if women don’t feel welcome to take the breaks to pump then it doesn’t happen. I mean, we all know how that goes.

Give mothers more time off. Create more welcoming environments when they come back to work to support them and their desire to breastfeed their child.

And in the longer term, we could understand the biology of building milk supply, which is still quite mysterious in humans. What are some of the factors that may impinge on that during pregnancy or after pregnancy?

Lookout: What did you have to do in order to feed your child when you were having trouble making enough milk?

Hinck: I saw the lactation consultant and I was told to pump at 3 a.m. when prolactin levels are the highest. I would set the alarm and get up and pump every night. I was also working full time, pumping every four hours. But I could barely pump the amount of milk for the next day.

That’s a burden, you know? It’s just hard to balance. You’ve got an infant, and you’ve got this other role, but you’re also providing all the food for them. It doesn’t always work seamlessly, that’s for sure. I went to work to do my science, and I did the best I could.

It was a lot of work. It’s so much to expect of mothers. And we just don’t give parents, mothers, the space and time to breastfeed at work. It’s also underappreciated that there could be other people who want to breastfeed, and we need to open doors for them — for non-birth moms, trans people. Why do we keep lactation in just the realm of women? I think that if we understood lactation physiology better, we could help people breastfeed.

Guananí Gómez-Van Cortright is a 2022 graduate of the UC Santa Cruz Science Communication master’s program. She has written for Good Times, KQED radio and the San Jose Mercury News.

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