Kiwi kids take a lot of antibiotics – here’s why that’s a problem

2026-03-15 - 16:06

Comment: You don’t have to read many Victorian novels to understand the toll infectious diseases took on children before antibiotics came along. Charles Dickens’ Tiny Tim (A Christmas Carol) dies, most likely of tuberculosis; half of Jane Eyre’s schoolmates succumb to typhus, the disease that killed two of the author Charlotte Brontë’s sisters in real life. Anne, of Green Gables fame, is seen as a hero after saving the life of her best friend’s sister, Minnie May, when she gets diphtheria. In 19th century England and America, something like 40 percent of children died of an infection before their fifth birthday. Penicillin was first discovered in 1928 and antibiotic use became widespread in the mid-1940s. Since then, the lives of millions of children have been saved every year; millions more would benefit from wider distribution in developing countries and a solution to antimicrobial resistance. But over the past decade, researchers looking at the gut microbiome have discovered something concerning about antibiotics. They aren’t just killing off bad bacteria, they are also depleting the network of beneficial microorganisms inside our gut. It’s not surprising. Bacteria (trillions of them) make up about 90 percent of our gut microbiome. These gut bugs end up as collateral damage for antibiotics prescribed for problems in totally different parts of the body, such as respiratory or ear infections. This matters. It’s increasingly clear the gut microbiome plays a huge role in maintaining our health, not just in terms of digestion, but regulating the immune system, even brain and mental health. Babies aren’t born with a gut microbiome, but during the first three years of life they develop one quickly which begins to look like the adult microbiome. However, this is a vulnerable phase for this developing system, when disruptions can impact its long-term structure and activity. Antibiotics have a negative effect on this fragile early gut ecosystem, depleting it more than with older children or adults. And Kiwi kids take a lot of antibiotics. Our team at the Liggins Institute have shown that in a cohort of more than 150,000 New Zealand toddlers, two thirds had received two or more courses of antibiotics by the time they turned two and one third had received more than five courses. That same study also showed taking antibiotics in the first two years of life was associated with an increased risk of obesity at four or five years of age. Other studies have shown that early antibiotic exposure increases the risk of asthma, eczema and frequent infections in later childhood. The link between early antibiotics and these conditions is thought to be disruption to the developing microbiome, given the important role that the gut microbiome plays in the development of fat tissue and the immune system. No one is suggesting returning to a Dickensian pre-antibiotic era. But what if there was a way to bolster the gut microbiome in young children taking antibiotics? Let me introduce you to human milk oligosaccharides, or HMOs, or (an easier word to remember), oligos. These are big complex sugars found in breast milk – in fact they are one of the most abundant components of breast milk. They don’t provide nourishment to the baby and aren’t absorbed. Instead they pass into the large bowel, where they feed and nourish the developing microbiome. Which led me to the question: given that human milk oligos are so important to the developing microbiome, what if we provided them to weaned children in parallel with taking courses of antibiotics? Could that protect and aid the recovery of the toddler gut microbiome? So we have launched what we call the OAK (human milk Oliggosaccharides and Antibiotics for Kids) Study at the Liggins Institute. We are now recruiting toddlers (12-18 months of age) who are about to receive antibiotics. We aim to see whether treating toddlers with human milk oligos alongside antibiotics will protect these children from later obesity, asthma and eczema. If indeed this is shown, in the future, children given antibiotics could be co-treated with these amazing oligos. Find out more about Liggins Institute research and clinical trials around the gut microbiome at the next Liggins Public Lecture on Thursday March 19. The Good Sh*t: turning microbiome science into therapy. Check out the OAK study into antibiotics, toddlers and human milk oligosaccharides.