When it comes to feeding infants, the much-used dictum is ‘breast is best’. Breast milk represents the optimal nutrition for babies, containing all the energy and nutrients a growing child needs along with antibodies to boost their immunity. The WHO and Unicef recommend that babies are exclusively breastfed for the first six months of life and continue breastfeeding for 18 months after that as other foods are introduced.

As well as helping the baby fend off illnesses, such as ear infections, studies suggest that breast milk could improve long-term health outcomes. It may lower the child’s risk of developing asthma and allergies and even raise their intelligence. It is more easily digested than formula on the whole and appears to lower the risk of sudden infant death syndrome in the first year of life.

“Fundamentally, breast milk is designed for that specific infant,” says Dr Steven Abrams, a Dell Medical School professor at the University of Texas and chair of the American Academy of Pediatrics committee on nutrition. “It contains a huge number of what we call bioactives. Those are different types of compounds that are believed to have immunological functions. There’s also some evidence for decrease in maternal disease, including maternal breast cancer.”

Abrams also points out that it is hard to conduct research in this field. Ethically speaking, researchers cannot randomly assign some babies to a formula milk group and others to a breast milk group as they would if they were trialling medication. That said, the available evidence, largely based on population data, does show advantages for breastfeeding.

“Especially in lower and middle-income countries, the evidence for a decrease in infections and improved immune function for breastfed babies is pretty strong,” adds Abrams.

The real question, then, is can formula milk ever match up? Many parents are unable to meet the breastfeeding recommendation – be that due to poor milk supply or an unforgiving schedule. And whatever the data may show about the respective benefits, stigmatising this group is not helpful. The most important thing is simply that the baby is fed.

“I often caution against using terms like ‘breast is best’, because families can become very upset and disappointed in themselves if they are unable to breastfeed,” says Abrams. “We’ve tried to get away from this kind of slogan so as to represent families who make whatever choices.”

Shake it up

It is clear that formula milk is a safe and healthy choice in its own right. While there are various types of formula milk available, many are based on purified cow’s milk with modifications. They come in two varieties: powdered feed that is mixed with water or a ready-to-feed liquid formula.

The milk has been adapted to resemble breast milk as much as possible. As a result, babies can thrive on formula, especially in places where water is clean and healthcare resources are good. It is a far cry from early infant formulas, first marketed in the 19th century, which consisted of diluted cow’s milk enriched with cream and sugar.

To give some background to how the field has developed, the modern age of formula milk really began in 1980, when the US passed the Infant Formula Act. Along with the European equivalents that followed it, this act established a set of nutritional requirements and quality control procedures for formula milk.

“The government made a list of nutrients that had to be in [the] formula – let’s say iron or zinc – remembering that in the first four to six months of life, you can’t leave anything out,” says Abrams. “This list still exists everywhere in the world where formula milk is sold. It is very slightly different on [the] European side than the American side, but not massively so.”

By the turn of the 21st century, the idea of adding bioactives had become commonplace. Both the FDA and the European standards agencies were inundated with requests from formula companies: was this or that ingredient OK to use?

“These were added largely for competitive advantage,” says Abrams. “A company could advertise that they had added a compound found in breast milk, and then of course they could sell it for more money. This quest to identify different bioactives has dominated the formula fields over the last 25 years.”

Two commonly used additions are omega-3 and omega-6 fatty acids, compounds that are normally present in breast milk and are associated with healthy brain development. (Whether they perform the same job in formula milk is not clear.)

Another is human milk oligosaccharides (HMOs), the third most abundant ingredient in breast milk. HMOs serve a prebiotic function (meaning they feed the ‘good’ bacteria in infants’ guts) and have been added to certain formula brands since 2016. More recently, manufacturers have focused on some of the proteins present in breast milk, such as lactoferrin – an antimicrobial that also helps with iron absorption.

Tell the difference

At least on paper, these developments do appear to bring formula one step closer to breast milk. However, Abram believes that the two are not strictly comparable.

“I often caution against using terms like ‘breast is best’, because families can become very upset and disappointed in themselves if they are unable to breastfeed.”

“The problem is that even though manufacturers can duplicate the bioactives, they cannot duplicate them in the exact way in which they’re provided in breast milk,” he says. “In breast milk, the amounts vary over time, whereas in formula they’re all very constant. There are literally hundreds of bioactives in human milk and they can only replicate some of the more common ones. And they can’t replicate the type of proteins and mineral mixtures that exist.”

On top of that, the authorities are primarily focused on consumer safety when approving ingredients and are less interested in whether these compounds are as efficacious as claimed.

“In a competitive marketplace, people will simply add whatever gets approved and away we go,” Abrams explains.

“Each manufacturer claims their ingredient makes the formula perfect, or closest to breast milk, but we don’t have the types of long-term studies needed.”

Dealing with data

In terms of the research that has been conducted, a 2021 Brazilian literature review, published in the International Journal of Food Science, found that “although the infant food industry has advanced in the last years, there is no consensus on whether novel bioactive ingredients added to infant formulas have the same functional effects as the compounds found in human milk”. In other words, further studies are needed.

“The World Health Organisation has very strict limits on how infant formula can be marketed, but the United States is not following that marketing.”

Another recent meta-analysis from University College London compared babies who were given nutritionally modified formula milk with those who were given standard formula. Both groups had the same academic performance by age 16, indicating that the added ingredients had no long-term benefits for brain development.

It should be stressed that the data was collated several decades ago, and new types of formulas have been developed since then. However, this study does suggest that some of the more extreme marketing claims should be treated with a measure of caution.

This point was made more emphatically by the WHO and Unicef in their recent joint report ‘How the marketing of formula milk influences our decisions on infant feeding’. The report stated that more than half of parents and pregnant women had been exposed to aggressive formula milk marketing, which undermined women’s confidence in their ability to breastfeed successfully.

The WHO maintains that much of this marketing is in breach of international standards on infant feeding practices and is based on “false and misleading messages”. For instance, an unscrupulous brand may claim that breast milk is inadequate for infant nutrition, that formula keeps infants fuller for longer or that specific formula ingredients are proven to improve child development or immunity.

“The World Health Organisation has very strict limits on how infant formula can be marketed, but the United States is not following that marketing and many other countries often don’t follow it fully,” says Abrams. “That gives us problems trying to gain information so that paediatricians and the like can make good decisions. There isn’t any good, unbiased way to get good advice.”

Abrams would like to see the WHO’s guidelines followed more closely, and thinks the US and Europe could benefit from dedicated organisations that take an impartial look at the evidence. After all, if the new bioactives really are as important for infant health as many manufacturers claim, surely all formula brands should include them?

“Because these ingredients are only added at the highest end of the marketplace, those who get their formula from public assistance will not benefit,” says Abrams. “If something is important enough to be there, it’s important enough that the government should provide it. It’s an equity issue.”

There can be no doubt that, as and when breastfeeding is impossible, and for whatever reason, formula milk is the next best thing. It is a good nutritional approximation for human milk and has been carefully designed to meet babies’ needs. However, when it comes to the latest hype ingredients, there is a lot we still do not know. More research needs to be done before they can be unequivocally recommended.