Children who eat a diet rich in fruit, vegetables and fish have a lower risk of asthma and wheezing, but eating three or more burgers a week can increase the risk, scientists have concluded.
Researchers from Germany, Spain and London examined data from 50,000 children aged eight to 12, from 20 different countries, collected between 1995 and 2005.
Parents were asked about their children's usual diet and whether they had ever been diagnosed with asthma or suffered wheezing.
Almost 30,000 children were given a skin-prick test to see if diet directly affected their chances of developing common allergies. The experts found diet did not increase the risk of allergies to grass and tree pollen but did have an effect on asthma and wheeze.
Overall, children who ate a Mediterranean diet rich in fruit, vegetables and fish had a lower chance of developing asthma or wheeze over their lifetime.
Eating three or more burgers a week was linked to a higher risk of asthma and wheeze but a diet that was generally high in meat did not increase the risk.
The authors, writing in the journal Thorax, said: "Fruit and vegetables contain antioxidants and other biologically active factors which may contribute to the favourable effect of fruit consumption in asthma.
"In particular, foods rich in vitamin C have been reported to relate to better lung function and fewer asthma symptoms."
They said carotenoids – contained in fruit and vegetables such as sweet potatoes and carrots – and vitamins C and E also have a positive effect on lung function.
The authors concluded that "adherence to a Mediterranean diet may provide protection against wheeze and asthma in childhood".