In recent years, the common advice that "breast is best" for newborns has become increasingly challenging for many new mothers to follow. Time constraints, lack of support, and difficulties with milk production or latching can create significant hurdles.

Health officials advocate for exclusive breastfeeding during the initial six months of life, yet only around 25% of infants in the U.S. are exclusively breastfed. A substantial number of mothers initiate breastfeeding but do not maintain it. Before the COVID-19 pandemic, many women ceased breastfeeding due to workplace challenges. The absence of a nationwide maternity leave policy in the U.S. often forces women back to work sooner than in other countries. Furthermore, expressing milk at work can be cumbersome, and some employers may not provide adequate facilities for new mothers.

"This presents a significant physical and emotional strain," notes Sarah Reyes, PhD, a postdoctoral researcher at the University of Manitoba who specializes in breast milk.

In light of these challenges, several startups are attempting to develop infant formulas that more closely mimic breast milk. Some are focusing on replicating key components found in human milk to enhance standard formulas, while others are exploring the possibility of cultivating actual breast milk in laboratories from just a few cells. In the future, it might even be possible to create therapeutic formulas for sick infants.

Although a variety of infant formulas exist, none can truly replicate the complexity of breast milk, which is derived from cow’s milk lacking the same beneficial components. Beyond nutrition, breast milk is crucial for strengthening infants' immune systems and reducing the likelihood of infections, diarrhea, and allergies. It may also support early brain development. While store-bought formulas provide essential nutrients like carbohydrates and sugars, they lack the intricate balance found in breast milk.

"There's always been interest in enhancing baby formula," states Casey Lippmeier, vice president of innovation at Conagen, a Massachusetts biotech firm. "What has evolved is technology; our capacity to meet infant nutrition needs is advancing significantly."

A pivotal discovery was made a decade ago when scientists learned to produce large quantities of human milk oligosaccharides (HMOs) — the third most abundant component of breast milk. Over recent years, formula producers have begun incorporating HMOs into their products, as these sugars support the growth of beneficial gut bacteria and may decrease the risk of intestinal infections. While HMOs can also be found in cow’s milk, they are less prevalent and structurally different from those in human milk.

To create human-specific HMOs, formula companies must genetically alter bacteria, a complex endeavor. Conagen has developed a more efficient method to produce a key HMO using simple enzymes, akin to cheese production. The resulting product is non-GMO, which the company hopes will appeal to parents. Moreover, they have created a fermentation process to generate lactoferrin, an immune protein vital for infant digestion, which is more aligned with the lactoferrin found in human milk compared to cow's lactoferrin.

Other "designer" ingredients, such as fatty acids and probiotics, are now being added to formulas as companies refine their production methods. While these additions aim to make formulas more similar to breast milk, evidence regarding their health benefits compared to traditional formulas remains limited.

For instance, around 20% of women do not produce 2'FL, one of the two HMOs now mass-produced by formula companies. It is still uncertain whether infants whose mothers lack 2'FL should receive this compound. "We need to understand these health implications better before making recommendations," Reyes states.

Regardless of how many nutrients biotech firms incorporate into formulas, they will never replicate breast milk perfectly. "Breast milk is a customized product," Lippmeier explains. "Infant formula is produced in large batches for many babies."

A significant reason is that human milk is not merely a food source; it comprises living cells, as Lars Bode, PhD, a pediatrics professor at the University of California, San Diego, explains.

"There are living components, including specific microbes, immune cells, and antibodies from the mother, tailored to the environment," Bode shares.

Startups such as Biomilq from North Carolina and TurtleTree Labs from Singapore are pursuing the goal of producing human-like breast milk through cell culture techniques.

Biomilq has devised a method to extract cells from the mammary gland and cultivate them in a lab using a blend of nutrients and specific chemicals. These cells are expected to produce human milk, which will undergo testing to ensure safety and similarity to real breast milk. Earlier this year, Biomilq announced the successful cultivation of two essential components of human milk — lactose and casein — from human cells in a bioreactor. While conventional formula contains animal-derived versions of these molecules, Biomilq’s products aim to mimic the human variants, moving closer to recreating authentic breast milk.

The founders of Biomilq, Michelle Egger and Leila Strickland, PhD, have secured $3.5 million in funding from Bill Gates’ Breakthrough Energy Ventures and others, with hopes to introduce a product by 2025.

TurtleTree Labs employs a similar cell-culture approach, using "cells as biofactories," according to founder and CEO Fengru Lin. The company has raised $3.2 million in seed funding and aims to market its product in both the U.S. and Asia. Lin envisions that lab-produced milk could relieve mothers from worrying about the safety and nutritional quality of their baby's food.

Both Biomilq and TurtleTree Labs believe that lab-generated breast milk could be more environmentally friendly than cow-based formulas, as dairy farming contributes to greenhouse gas emissions.

"It may sound like science fiction, but it's genuinely thrilling," Bode remarks about the prospect of lab-created human breast milk.

Despite the excitement, both companies face considerable obstacles in fully replicating human breast milk, which has unique characteristics that may be difficult to reproduce in a lab setting.

Breast milk varies among individuals, and its nutritional profile shifts throughout the day and over weeks to cater to a baby's evolving needs. A 2009 study in Nutritional Neuroscience indicated that evening-produced breast milk had higher concentrations of nucleotides, which may aid in calming the central nervous system, thus helping infants sleep. Researchers suggested that milk should be administered at the same time of day it is produced for optimal benefits.

Environmental factors also influence breast milk composition. For instance, if a mother encounters a virus, she may start producing antibodies that she passes on through her milk.

"We haven't fully grasped what constitutes human milk and its benefits for both infants and mothers," Bode comments. "Now we're discussing the possibility of reproducing it."

One researcher, Kathryn Whitehead, PhD, an associate professor of chemical and bioengineering at Carnegie Mellon University, believes that breast milk may serve not just as nutrition but also as a treatment for ill infants.

Whitehead has discovered that breast milk harbors millions of human cells, in addition to nutrients. These cells possess a remarkable ability to navigate through the small gaps in the gastrointestinal tract and integrate into the body's tissues, presenting a unique potential for drug delivery.

Typically, only small-molecule drugs can traverse the intestinal gaps, necessitating alternative administration methods for larger drugs. However, Whitehead's findings suggest that the cells in breast milk can pass through these spaces, indicating they have unique properties that allow them to exit the gastrointestinal tract and travel throughout the body.

Whitehead's team is currently investigating where these breast milk cells migrate within the body and their duration of residency, which may unveil potential treatments for various diseases.

"As for which diseases we might treat, we currently have no idea," Whitehead admits. "We need to learn more about where the cells go and which specific cells within the milk are involved."

She envisions a future where scientists could modify a mother’s milk cells to meet her baby's specific needs. These tailored cells could then be reintroduced to the milk and fed to the infant as a form of treatment.

"It may seem like science fiction, but it’s genuinely exciting," she asserts. "However, these cells could possess other important properties for healthy infants. If we discover significant nutritional benefits from these cells, there may be opportunities to integrate that into formulas."

Incorporating live cells into formula could pose challenges due to their short lifespan. Whitehead suggests it might be more feasible to isolate the most beneficial components of these cells for formula enhancement.

While these advancements aim to provide parents with more options for their infants, the potential cost of personalized milk could be a significant barrier.

In the U.S., families already spend approximately $1,500 to $2,000 annually on formula, with organic and specialty options costing even more. Tailored milk products will likely carry even higher price tags, and as formulas become more sophisticated, their costs may rise as well.

Concerns have been raised that these innovations could deter mothers from breastfeeding, as they may perceive it as unnecessary, warns Steven Abrams, MD, a neonatologist and pediatrics professor at the University of Texas, Austin, who serves on the American Academy of Pediatrics' nutrition committee. "There’s no current evidence that these alternatives equate to the benefits of breast milk."

Moreover, mothers might miss out on the well-documented physical and emotional advantages associated with breastfeeding, such as aiding postpartum weight loss and fostering bonding through skin-to-skin contact. Breastfeeding also stimulates the release of oxytocin, a hormone that helps the uterus return to its pre-pregnancy size.

If more parents opt for these new products, Abrams warns that society could become increasingly unsupportive of breastfeeding. "We want to ensure society doesn't abandon breastfeeding simply because formula is perceived as equivalent to breast milk," he cautions.

As new and improved formulas emerge, Reyes emphasizes the necessity of providing support for those who wish to breastfeed. This involves establishing more accommodating parental leave policies and fostering greater acceptance of public breastfeeding. Although breastfeeding is legally protected in all 50 states, it remains a contentious issue in certain areas, and many mothers still hesitate to do so.

Access to lactation consultants for guidance on breastfeeding would also benefit new mothers, Reyes adds, though not all insurance plans cover these services.

"If we can create a more effective alternative to formula, that would be a positive step," Reyes concludes. "However, we still have a long way to go in comprehending the complexities of breast milk itself. Replicating something we don’t fully understand is a formidable challenge."