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What is the best time to introduce solid foods to infants and why are the guidelines always changing?

In the last few decades, food allergy – which used to be relatively unknown in the community -  has become a major concern for parents, teachers, clinicians, and policy makers. Hospital admissions for life-threatening allergic reactions to foods (known as anaphylaxis) increased five-fold in Australian children under the age of five over the last decade. Food allergy now affects up to 10% of infants at 12 months of age, although only a small portion of these will have the most severe type of reaction. Most children will grow out of allergies to foods like egg and milk, while allergies to nuts and seafood are often lifelong. The foods an infant eats in the first year of life has long been thought to play a role in whether or not they develop a food allergy, although it is only recently that people have started to study this more thoroughly.

Historically, infant feeding practices were the domain of child and maternal health nurses, and were heavily influenced by cultural and historical norms. Medical intervention, with some notable exceptions, was limited to management of feeding sick and hospitalised infants. Although cultural influences still heavily predominate in developing countries such as Africa and India, Westernised countries have gradually seen a shift as the ‘science’ of infant feeding has moved into the field of public health, with greater involvement of doctors and epidemiologists (people who study the patterns, causes, and effects of health and disease).

The study of infant feeding practices is now regarded as essential to the evolving field of ‘Early Determinants of Health and Disease’ as we understand that nutrition in early life plays a critical role in a wide variety of health outcomes in childhood and beyond into adulthood. Infant feeding guidelines in developed countries like Australia therefore take into account not only the readiness of infants of various ages for specific foods and the requirement for adequate intake of specific nutrients like iron, but also the potential impact of feeding practices on health outcomes that include obesity, cardiovascular disease and allergies.

The history of infant feeding guidelines – how have they changed over the last 50 years and what impact has this had on allergies?

While in the 1960s infants were often given solid foods in the first three months of life, the 1970s saw the introduction of guidelines recommending delayed introduced of solids until after four months of age. This was because of a potential link between early introduction of gluten and risk for coeliac disease. By the early 1990s, experts began to recommend delaying solids until after six months of age, with further delay in the introduction of foods such as egg and nuts, which can cause allergies, until at least two years of age, especially for infants with a family history of allergy.

By 2008, however, it became clear that delayed introduction did not have the desired effect of reducing the prevalence of food allergy, and recommendations were changed internationally to not delay the introduction of any foods beyond four to six months of age. Despite widespread interest and research into the area of infant feeding and allergic disease, to date we still lack sufficient evidence to provide definitive recommendations around the best time to introduce solids and particularly foods that may cause allergies in infants.

What more information do we need to inform these guidelines?

Studying the relationship between infant feeding and health poses numerous challenges. Usually clinical trials in which participants are randomly assigned to either a certain food or medication, or a placebo  (and do not know which one they are taking), provide the best level of evidence to inform guidelines. However, infant feeding has historically been difficult to randomise in the same way due to both practical and ethical considerations.

Several intervention studies currently in progress, which compare early and late introduction of allergy-inducing foods such as egg and peanut, have the potential to provide high-quality evidence about the role of infant feeding in food allergy. Changes in the timing of food introduction may contribute to but are unlikely to completely explain recent increases in the prevalence of food allergy. Current evidence supports the involvement of other environmental and genetic factors in the development of food allergy. 

As more evidence becomes available across various fields of research, we might see further changes to infant feeding guidelines in Australia and internationally as we continue to develop our understanding of how to provide the best possible start to life for infants. Watch this space.

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