Illustration: Angie Wang

The Race to Recreate Breast Milk Without the Breast

Companies are harnessing biotech to make bespoke milk

For many new mothers, the “breast is best” advice given by doctors can seem hopelessly unrealistic. Not all women have the time or support they need to breastfeed, and some have trouble producing enough milk or getting their baby to latch.

Although health experts recommend that babies be exclusively breastfed for the first six months of life, only about 25% in the United States are. The vast majority of mothers start breastfeeding but don’t keep it up. Before the coronavirus pandemic, many women stopped breastfeeding because they simply couldn’t do it at work. With no federally mandated maternity leave policy in the United States, women return to work much sooner than they do in other countries. Pumping at work can be onerous, and some workplaces may not be accommodating to new mothers.

“This is a huge burden both physically and emotionally,” Sarah Reyes, PhD, a postdoctoral researcher at the University of Manitoba who studies breast milk, tells Future Human.

Amid this less-than-ideal situation, a handful of startups are trying to engineer better formula that more closely resembles breast milk. While some are focusing on recreating a few important compounds found in human milk to give standard formulas a boost, others are attempting to grow actual breast milk in the lab from just a couple of cells. In the future, breast milk and baby formula could even be turned into a drug to help treat sick babies.

There are plenty of infant formulas on the market, but none get close to real breast milk. Most formula is made with cow’s milk, which doesn’t contain the same components found in human milk. Beyond providing nutrition, breast milk helps build up babies’ immune systems and lowers the risk of infections, diarrhea, and allergies. It may also aid early brain development. The formula found in stores today provides the basic nutrients babies need, like sugars and carbohydrates, but breast milk is a far more complex mixture.

“This is a huge burden both physically and emotionally.”

Companies have long sought to improve baby formula. “There’s always been interest,” says Casey Lippmeier, vice president of innovation at Conagen, a Massachusetts-based biotech company that manufactures food additives. “What has changed is technology. Our ability to actually meet these demands for infant nutrition is improving tremendously.”

Scientists made a breakthrough a decade ago when they figured out how to brew up large vats of complex sugars known as human milk oligosaccharides (HMOs) — the third most abundant component of breast milk. Over the past few years, formula manufacturers have started adding HMOs to infant formula. These sugars promote the growth of healthy gut bacteria and are thought to lower the risk of intestinal infections. They’re found in cows’ milk too, but are much less abundant and are structurally different than human ones.

To make the human version, formula manufacturers need to genetically modify bacteria to produce these human sugars, which is a complicated process. Using simple enzymes, Conagen says it has figured out a more efficient way to make a key HMO that’s similar to how cheese is made. The resulting product is a non-GMO, something the company hopes will make it more appealing to parents. The company has also developed a fermentation process to produce human-like lactoferrin, an immune protein that contributes to healthy infant digestion. Cow lactoferrin has been added to formula as a specialty ingredient in recent years, but Conagen claims its protein is much closer to the lactoferrin in human breast milk.

Formulas with other “designer” ingredients — additives that haven’t traditionally been added to formula — like fatty acids and probiotics—have also become available as companies have figured out how to produce them at commercial scale. In theory, these ingredients are supposed to make formula more like breast milk. But there’s not enough evidence to know what health benefits, if any, these formulas with extra ingredients might have for babies compared to more traditional recipes.

For example, about 20% of women don’t produce 2'FL, one of two HMOs now mass-produced by formula companies. It remains unclear whether babies whose mothers don’t produce 2'FL should receive it. “We should understand these and other health implications before recommending it to the general public,” Reyes says.

No matter how many nutrients biotech companies add to formula, it will never be exactly like breast milk. “Breast milk is a custom product,” Lippmeier says. “Infant formula has to make big batches for lots of babies at a time.”

One reason is because human milk isn’t just a food source; it’s actually a tissue that’s rich with living cells, explains Lars Bode, PhD, a professor of pediatrics who studies human milk at the University of California, San Diego.

“You have living components in there — certain microbes or bacteria, immune cells and antibodies that come with the mom that are very specific to the environment,” Bode tells Future Human.

Startups like Biomilq of North Carolina and TurtleTree Labs of Singapore think they can more closely imitate breast milk by growing it from cells in the lab.

Biomilq has developed a way to extract cells from the mammary gland, the organ that produces milk, and propagate those cells in a lab by feeding them a cocktail of nutrients and special chemicals. When those cells grow, they should pump out human milk, which will be tested to make sure it’s safe and resembles real human milk.

Earlier this year, Biomilq announced that it had succeeded in growing two key components of human milk — lactose and casein — from human cells grown in a bioreactor. Formula contains animal versions of both of these molecules, but Biomilq’s mimic human ones, bringing the company closer to replicating real human milk.

The company’s founders, Michelle Egger and Leila Strickland, PhD, have since raised $3.5 million in funding from Bill Gates’ Breakthrough Energy Ventures and other investors. In an emailed statement, the company told Future Human that it hopes to have a product to market by 2025.

TurtleTree Labs has developed a similar cell-culture process that uses “cells as biofactories,” says Fengru Lin, the company’s founder and CEO. The startup, which has raised $3.2 million in seed funding, plans to eventually market its product in the United States and Asia. Lin told Future Human that lab-made milk could allow mothers to focus on other things rather than “worrying about the safety and nutritional composition of the food given to their growing baby.”

Biomilq and TurtleTree Labs also think lab-produced breast milk would be better for the environment than cow-based formula since dairy farms contribute to greenhouse gases.

“It sounds like science fiction, but it is certainly very exciting,” Bode says of the idea of lab-made human breast milk.

“Breast milk is a custom product.”

Still, both companies are a long way from fully reproducing human breast milk, which has other characteristics that could prove challenging to copy in a lab.

Breast milk varies from person to person, and its nutritional contents change throughout the day and over the course of weeks to meet a baby’s needs. For instance, a 2009 study in Nutritional Neuroscience showed that breast milk made in the evening contained higher concentrations of certain molecules called nucleotides that relax the central nervous system. The findings suggested that milk made in the evening helps babies fall asleep, and the authors concluded that milk should be given at the same time of day that it’s produced.

Environmental factors can also affect the composition of breast milk. If a mother is exposed to a virus, for example, she might start making antibodies against it and pass on those antibodies in her milk.

“We haven’t really fully understood what is in human milk and what benefits the infant and what benefits the mom,” Bode says, “and we’re now talking about reproducing that.”

One researcher thinks breast milk could be more than just a food source but also a treatment for sick infants. Kathryn Whitehead, PhD, an associate professor of chemical and bioengineering at Carnegie Mellon University, is working on genetically engineering cells found in breast milk to treat diseases in babies.

Whitehead has found that breast milk contains millions of human cells in addition to nutrients. These cells have a fascinating property: They can squeeze through the small spaces of the gastrointestinal tract and take up residence in the body’s tissues — a perfect system for drug delivery, if it can be harnessed.

Because of these small spaces, our intestines typically only allow the passage of small-molecule drugs, like aspirin. Once a drug gets to be a certain size, it can’t fit through the gaps and has to be administered another way, like in an injection or infusion. But Whitehead has found that the cells in breast milk are able to squeeze through those gaps even though they are pretty large, which suggests that they have special properties that allow them to get out of the gastrointestinal tract and go elsewhere in the body.

What Whitehead and her team are trying to discover now is where, exactly, in the body these breast milk cells go, and how long they stay there. The answer could reveal what diseases may be treatable by these cells.

“As for what diseases we’ll treat, we actually have no idea yet,” Whitehead says. “We need to understand more about where the cells are going and what type of cells within the milk are the ones that are going there.”

Whitehead imagines that, in the future, scientists could modify a mother’s milk cells to match the specific needs of the baby. Those cells would be added back to the milk then fed to the baby as a treatment.

“It sounds like science fiction, but it is certainly very exciting.”

“However, it may very well be that these cells have some other properties that are important to healthy babies,” she says. “If we do find that there is some kind of nutritional element to these or something that’s really beneficial to healthy babies, there’s always a possibility of trying to incorporate that into formula.”

Incorporating living cells into formula could be a challenge though since live cells die quickly. It might be easier to isolate only the most beneficial parts of the cell to add to formula, says Whitehead.

These efforts are supposed to provide parents with more options for their babies, but there could be one big limiting factor to tailor-made treatments or bespoke milk: cost.

Formula already costs families about $1,500 to $2,000 a year in the United States, and organic brands or those that contain specialty ingredients can cost even more. Personalized milk will almost definitely come with an even higher price tag. And as formulas get more complex, they could get more expensive, too.

Some worry these products could come with other downsides. “It could discourage moms from breastfeeding because they think it’s not necessary,” says Steven Abrams, MD, a neonatologist and professor of pediatrics at the University of Texas, Austin who serves on the American Academy of Pediatrics’ nutrition committee. “There’s no evidence right now that these will be the equivalent of receiving breast milk.”

Women could also lose out on some of the well-known physical and emotional benefits that come along with breastfeeding, like promoting weight loss after birth and helping baby bonding through skin-to-skin contact. Breastfeeding also causes the release of a hormone called oxytocin in the blood, which helps contract the uterus back into its prepregnancy size.

If more parents opt for these new products, says Abrams, it could make society even less friendly toward breastfeeding. “What we don’t want is for society to give up on breastfeeding because now formula is the same as breast milk,” he says.

Even as these new and improved baby formulas are developed, Reyes says people who want to breastfeed must feel supported. This requires friendlier parental leave policies and greater acceptance of breastfeeding in public. Even though it’s legal in all 50 states, breastfeeding in public remains controversial in certain places in the United States, and many mothers are still reluctant to do so.

Access to lactation consultants that coach women on breastfeeding would also help new moms, Reyes says. Not all insurance covers these services though.

“If we can have something that is a better alternative to formula, that would be great,” Reyes says. “But we’re miles away from even understanding the science of breast milk itself. It’s hard to replicate something you don’t completely understand.”

Former staff writer at Medium, where I covered biotech, genetics, and Covid-19 for OneZero, Future Human, Elemental, and the Coronavirus Blog.

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