A seven-year study of Spanish children has revealed that giving kids a diet rich in fish and 'fruity vegetables' can reduce asthma and allergies.
The findings also support the researchers' earlier study that found that a fish-rich diet during pregnancy can help to protect children from asthma and allergies.
"We believe that this is the first study that has assessed the impact of a child's diet on asthma and allergies and also taken into account the food their mother ate during pregnancy," said lead author Dr Leda Chatzi from the Department of Social Medicine at the University of Crete, Greece.
"Because we studied the children from pregnancy to childhood, we were able to include a wide range of elements in our analysis, including maternal diet during pregnancy, breastfeeding, smoking, the mother's health history, parental education and social class," Dr Chatzi added.
Researchers followed the progress of the children, on the Spanish island of Menorca, at regular intervals from before they were born until they were six-and-a-half.
They discovered that children who consumed more than 40 grams of "fruity vegetables" a day - namely tomatoes, eggplants (aubergines), cucumber, green beans and zucchini (courgettes) - were much less likely to suffer from childhood asthma.
And children who consumed more than 60 grams of fish a day also suffered less childhood allergies, echoing the protective effects they experienced when their mothers ate fish during pregnancy.
However, the researchers noted that the dietary effects were quite specific and that other fruits and vegetables examined did not provide the same protective effect. Nor did other food groups included in the study, such as dairy products, meat, poultry and bread.
The mothers of 232 boys and 228 girls, who had been recruited during antenatal classes, completed detailed questionnaires on their children's health, weight, diet and any breathing problems every year until their child was six-and-a-half.
90 per cent of the children also underwent allergy testing - skin prick tests were used to check their response to the six most common allergens, including grass pollen and cats.
The researchers found that just under nine per cent of the children suffered from some degree of wheezing, including six per cent with an allergy-related wheeze. And 17 per cent reacted to at least one of the allergens in the skin prick test.
"After adjusting the results for a wide range of variables, we concluded that the link between symptom-free children and a diet rich in fruity vegetables and fish was statistically significant" says Dr Chatzi.
"The biological mechanisms that underlie the protective affect of these foods is not fully understood, but we believe that the fruity vegetables and fish reduce the inflammation associated with asthma and allergies.
"The interesting thing about this study is that it followed a large number of children from the womb to the age of six-and-a-half and incorporated a wide range of dietary, social and health factors" says the Journal's Editor, Professor John Warner, Head of the Department of Paediatrics at Imperial College London.
"It provides parents with specific advice about the health promotion benefits of including fish and fruity vegetables as part of a balanced diet for both their children and the rest of the family."
The study is published in the September issue of Paediatric Allergy and Immunology.