The benefits of a varied diet from early childhood
Published on 15/7/2014
A wide range of foods consumed in a child's first year of life can help to prevent the development of allergic diseases.
A team of European researchers studied parents' child-feeding practices in Austria, Finland, France, Germany and Switzerland to measure the diversity of diets in relation to diagnoses of asthma, food allergies and allergic rhinitis.
[This is the first study to show an association between greater exposure to certain foods in the first year of life and protection against the subsequent development of allergies.]
Nutrition is able to influence the development of children's immune system. Early exposure to a range of different foods could increase the immune system's acceptance of the antigens present in those foods, possibly also through the acquisition of a beneficial gut microbiota.
The study is part of a larger study aimed at assessing risk factors and preventive measures against allergic diseases.
The mothers were recruited in the five European countries during pregnancy and, after birth, kept a monthly diary of the food given to their children from the age of three months up to twelve months. A series of questionnaires and blood tests were used regularly up to the age of six years to determine whether the child had developed an allergy (defined on the basis of medical diagnosis).
The "dietary diversity" score was defined as the number of different food products included in the child's diet. In total, 856 children were included in the study.
The results showed that children with a higher dietary diversity score (that is, more different types of food in the diet) had a lower risk of allergic diseases. In particular, the introduction of certain specific foods proved able to bring about a lower risk of disease; dairy products and fish introduced in the first year of life appeared to have a high protective effect against asthma and food allergies, respectively.
At the children's check-up at six years, a less varied diet led to a reduction in the proteins involved in the production of the immune cells that suppress the immune response against our own cells (reduced tolerance). Children with lower "dietary diversity" scores were also more likely to present high levels of IgE antibodies, involved in the type I immune response.
The age at which foods were introduced also proved important. Assessing the "dietary diversity" scores after six months and one year, the researchers observed a significantly greater protective effect after one year. Therefore, the period between the first six months and one year of life may be an important window for exposing children to a variety of different foods so as to reduce the risk of allergic diseases.
The levels of allergic diseases were significantly higher in children with two allergic parents compared to children without allergic parents, and a greater proportion of children with one or both allergic parents presented a low diversity score (less varied diet) compared to that of children whose parents had no history of allergies.
A possible bias could be caused by the "reverse causality" effect; in other words, if children begin to show symptoms of allergic disease or have parents with allergies, they may begin to introduce certain foods only later for precautionary reasons. This would result in a lower dietary diversity score and, consequently, a greater likelihood of an allergic disease.
The current recommendations for children are to introduce solid food at about six months and, in any case, not before four months. Ensuring that children can introduce a wide variety of foods in early childhood, in particular between six and twelve months, may have a preventive effect against the child's risk of developing an allergy.
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