Complementary feeding during the first six months of life. Yes or no?

For years, children’s healthcare centres in the Netherlands advised young parents to feed their baby only breast milk for the first six months of life. Exclusive breastfeeding was thought to reduce the risk of infants developing food allergies (such as cow’s milk, egg and peanut allergies) and eczema. “A substudy of our KOALA study found that the reality is a bit more nuanced.” says Carel Thijs, associate professor in the Department of Epidemiology at Maastricht University. The guidelines have since been updated.

Carel Thijs is the initiator of and lead researcher on the KOALA study. “KOALA is a longitudinal cohort study of the health and development of approximately 2,800 children born between 2000-2003. We’ve been following these children, who are now young adults, from pregnancy. During pregnancy, during the first years of the children’s lives and during their teenage years, their parents have been completing questionnaires about their health, diseases and all kinds of relevant factors such as diet and lifestyle. The children, now 17 to 20 years old, recently completed a questionnaire themselves. We’ve also taken blood, breast milk and stool samples at various points in time. I initiated this study more than twenty years ago because I was interested in the development of allergies and asthma, partly in the context of the hygiene hypothesis. Simply put, the hypothesis suggests that our immune systems don’t get enough exposure to stimuli due to better hygiene. It doesn’t learn to distinguish between relatively harmless and more harmful stimuli (like microbes and food components), resulting in overreactions and allergies.”

Subproject: complementary feeding during the first six months of life

“The aim of the KOALA study is to gain a better understanding of what causes allergies, eczema and asthma”, explains Monique Mommers, a fellow researcher, biologist and epidemiologist who is an assistant professor in the Department of Epidemiology at Maastricht University. “It looks at factors such as exposure to microorganisms (vaccinations, gut microbiota, infections), diet, exercise, lifestyle and genetics. The cohort includes parents and children who follow the ‘standard way’ (including vaccinations etc.) as well as parents who, for example, hold a more anthroposophical worldview, who choose not to vaccinate their children and are more cautious about the use of antibiotics. The KOALA study has produced a wealth of data over the course of more than two decades. Subprojects developed over time, one of which was research into complementary feeding during the first six months of life.”