What's really inside babies' first foods

Scientists are discovering the extraordinary power of human milk and the benefits it brings to infants, but there are also some hidden contaminants that can lurk in breast and formula milks.

Throughout the first year of their lives, I breastfed my two children without the use of infant formula. Breast milk has been shown to be an ideal source of nutrition for babies, with many benefits for their developing brains, immune systems and digestive tracts, and I was glad to be able to offer them that boost. But when I had my blood tested for persistent toxic chemicals while researching a book on pollution, I discovered that some pesticides banned more than 40 years ago could still be detected in my body. There is also evidence that low levels of some chemical contaminants can be ed from a mother into her breast milk. Yet formula milk is also prone to contamination with toxic chemicals or potentially harmful bacteria, which have led to high-profile food scares and recalls in recent years.

It made me wonder what's really in the first foods our children consume – from the most beneficial ingredients, to hidden, undesirable or even toxic ones. And given what we know about some of the dangers, what can be done to improve all the available options for babies, be they breast- or formula-fed, and offer them the best possible start in life?

The milk that changes every day

Breast milk is considered the top choice for a baby's first food (the World Health Organization recommends that infants should be exclusively breastfed for the first six month of life). It mainly consists of water, fat, protein, as well as vitamins, minerals, digestive enzymes and hormones. It is rich in maternal antibodies, and has anti-infective properties. Breast milk is also a dynamic, adaptable food – it is fattier in the afternoon and evening than in the morning, for example. It also varies during a feed. When the baby latches onto the breast, the first gush of milk, or foremilk, is thin and high in lactose, making it thirst-quenching and easy to drink. The so-called hindmilk that follows is creamier and fattier, making it more filling. This dynamic aspect is one reason why breast milk is hard to replicate, despite considerable advances in the quality of infant formula.

"Human milk varies over the course of lactation, over the course of a day, from the start to the end of the feed, and to some extent on maternal factors such as her diet," says Mary Fewtrell, a professor of paediatric nutrition at University College London, who published a peer-reviewed study of lactation. "That all makes it difficult to decide on a precise amount that should be included in a formula whose composition doesn't change with the baby's age."

Fewtrell highlights non-nutrient ingredients in breast milk such as hormones, cells (including stem cells), microRNAs (small strands of genetic material), which give it unique properties. "We still don't fully understand the role of all these components but… quite probably they allow the mother to transmit information to the infant about her own experiences and the environment, which is why breastfeeding is sometimes described as 'personalised nutrition'."

However, while more than 80% of babies in the US are breastfed at the start of their life, according to the Centers for Disease Control and Prevention, that rate falls to 58% at six months. Health authorities have tried to increase that rate, for example by offering more breastfeeding to mothers. Diagnosing and treating conditions such as tongue-tie in babies can also help. But in the meantime, parents who do use formula may also wish to understand more about it, including what might be done to improve it.

"Whilst human milk is the biological norm for human infants and provides benefits for both mother and infant, some women may be unable to breast-feed or choose not to do so, and some choose to partly breast-feed," says Fewtrell. "For young infants, the only safe alternative if an infant is not breast-fed (or not fully breast-fed) is an infant formula which is designed to meet the nutritional needs of infants and normal growth and development." Flexibility is expected – there's no "one size fits all" approach to infant nutrition, she says.

Towards better formula

The manufacture of infant formula has come a long way over recent decades. Throughout the 19th and early 20th centuries, bottle-feeding was not a safe option. In orphanages during the early 1900s, as many as 80% of bottle-fed babies died during the first year of life due to infections from unsterilised bottles, or malnourishment. Since infant formula was first commercially produced in 1865 using just four key ingredients (cows' milk, wheat and malt flour, and potassium bicarbonate), its nutritional contents have been refined in remarkable ways.

So what's in formula today?

Multiple fat sources are often used in formula, including cows' or goats' milk (often skimmed, which isn't as fatty as breast milk) and vegetable oils such as palm, sunflower or rapeseed, plus fatty acids. One fatty acid called DHA (docosahexaenoic acid, a type of omega-3 fat), which plays an important role in infant development, is now a mandatory ingredient in the European Union.

In breast milk, the main carbohydrate is lactose. In formula, this is usually added into the skimmed dairy milk powder base. Maltodextrin (a carbohydtrate derived from maize or potatoes) is also added. In the UK, glucose (a sugar) isn't routinely added but in the US, glucose sugars such as corn syrup are more commonly used. One problem is that this can increase the risk of dental decay in infants when their teeth come through.

The major breast milk proteins are whey and casein, which change in proportion as the baby grows, plus lactoferrin which is found at higher concentrations in colostrum, the first milk a mother produces after birth. The protein quantity and composition differs in formulas based on cows' and goats' milk, which have a higher casein to whey ratio than human milk. Plant-based ones are often made with soya protein. Formula also contains a mix of vitamins (including A, D, B and K), minerals such as calcium, magnesium, iron, zinc and many other trace elements.

Unfortunately, formula can also contain lurking, unwelcome ingredients: just like I discovered pollutants in my own body, toxic substances can make their way into infant formula, too. 

Heavy metal mix

In 2017, the Clean Label Project, a US-based not-for-profit that tests products for toxic substances such as pesticides and heavy metals, found that almost 80% of 86 infant formula samples tested positive for arsenic. It also discovered that soy-based formulas had seven times more cium, a carcinogenic metal found in batteries, than other formulas.

Two years later, researchers from the Clean Label Project and the department of neurology at the University of Miami published a study into the heavy metal content of 91 infant formulas. They found that 22% of infant formula samples tested exceeded the lead exposure limit set by Californian state law, while 23% exceeded the state's limit for cium. The study concluded that "low-level heavy metal contamination is widespread" in baby foods and formulas and that "further research is needed to understand the long-term health effects of this chronic daily low-level heavy metal exposure in babies". Another study of baby foods in Sweden found that the dietary cium exposure of children fed infant formula was up to 12 times higher than those who are breast fed, although the levels were still within weekly tolerable limits set by the WHO and FAO.

Jackie Bowen, an environmental biologist and executive director of Clean Label Project, co-authored the study. She campaigns for greater transparency about the hidden contaminants that end up in our food, including infant formula. According to Bowen, food safety regulation can miss those contaminants since it focuses primarily on microbial pathogens such as E. coli that cause acute, short-term food poisoning.

Food safety regulators, however, insist they are actively trying to tackle the issue of heavy metals in baby foods. The US Food and Drug istration (FDA), for example, insists it routinely monitors baby foods for toxic elements and takes action if they present a health concern. It says it is working with food companies and other stakeholders in an attempt to reduce the levels of heavy metals and other toxic substances in baby foods to as low as possible. But a recent report by the Committee on Oversight and Reform at the US House of Representatives criticised the FDA and food companies for not doing enough.

The FDA, however, says it is continuing to issue guidance to industry that will help lead to "meaningful and lasting reductions in exposure to toxic elements from foods", alongside its sampling and enforcement work.

"As parents and caregivers ourselves, we recognise and understand concerns about toxic elements and how they could impact the health of children," a spokesperson told the BBC.

"Consumers are increasingly concerned about how the foods they eat are linked to long-term chronic diseases like cancer or infertility that can take decades to manifest," explains Bowen who adds that, in the US, this food safety regulation is 'silent' when it comes to heavy metal contamination. "There's a growing divide between the court of law and the court of public opinion of what it means for food to be safe.".

Heavy metals like cium and lead naturally occur in the Earth's crust, so it's impossible to totally eliminate them. But human activities such as mining, fracking, industrial agriculture and the use of waste water for irrigation, exacerbate the presence of heavy metals in air, water and soil in the form of pollution, Bowen argues. Unlike microbial pathogens which can be destroyed by high heat and other methods, there's no way to get rid of such contaminants once they are in a product, she says. Instead, the problem has to be addressed at the start of the process, by beginning with clean, uncontaminated soil. After all, formula starts with farming, since key ingredients come from dairy livestock or crops.

"If you want a high-quality finished product, that comes from high-quality ingredients. That comes from healthy nutritious soils and that comes from good environmental policy that isn't going to allow for that level of pollution that contributed to the problem," says Bowen who explains that certain formula ingredients are at higher risk of heavy metal contamination. Soy, a mainstream plant-based substitute for cows' milk, tends to bioaccumulate heavy metals, as does hemp, whereas pea protein doesn't have that same tendency.

Hidden formula contaminants are only one part of the problem. Powdered formula gets mixed with tap water to create infant milk. That poses a health risk in areas where that water is contaminated by old, flaking lead pipes, which happened in Flint, Michigan, for example (lead exposure can also affect breastfeeding mothers). While lead piping is gradually being replaced, water testing typically focuses on microbes, rather than high levels of heavy metals, Bowen says.

"It's one thing to solve the problem for infant formula, but unless you solve heavy metal contamination of the drinking water that gets mixed with powdered milk to give to baby, you're only fixing half the problem," she says. "What are we doing to prevent these problems in the first place">window._taboola = window._taboola || []; _taboola.push({ mode: 'alternating-thumbnails-a', container: 'taboola-below-article', placement: 'Below Article', target_type: 'mix' });