A study of almost 700 children on the Greek island of Crete found that those who enjoyed foodstuffs like olive oil and whole grains suffered fewer symptoms.
Researchers asked parents to complete a questionnaire about their children's diet and respiratory problems.
They found eight out of 10 children ate fresh fruit -- and over two thirds of them fresh vegetables -- at least twice a day.
The effect of diet was strongest on allergic rhinitis -- which results in a runny or blocked nose -- but it also afforded protection against asthma symptoms and skin allergies.
The study found children who ate nuts at least three times a week were less likely to wheeze.
Grapes in particular seemed to protect against wheezing and allergic rhinitis.
But high consumption of margarine doubled the chances of asthma and allergic rhinitis, the findings showed.
The report stated, "Children in Crete consume high quantities of locally produced fruits and vegetables; regular and frequent consumption may have a beneficial role against wheezing and rhinitis symptoms.
"A high consumption of nuts also had a protective effect, while margarine intake was positively associated with reported symptoms."
It added, "Our findings indicate that a high dietary intake of commonly consumed fruit and vegetables and nuts may have a protective role on the prevalence of asthma-like symptoms and allergic rhinitis."
The research was carried out by the Royal Brompton Hospital, in London; the University of Crete; Venezelio General Hospital in Crete and the Centre for Research in Environmental Epidemiology, in Barcelona.
The full report is published in the British medical journal Thorax.
Leanne Male, assistant director of research at Asthma UK, said, "The results of this study add to the existing evidence which indicates that a healthy diet can play an important role in the control of asthma symptoms.
"The results demonstrate that the Mediterranean diet, which traditionally contains higher levels of fresh fruit and vegetables, can have a beneficial effect on asthma symptoms in children.
"This benefit is thought to be linked to the vitamins and antioxidants which they contain and Asthma UK is currently funding a number of research projects to further explore this association.
"5.2 million people in the UK currently have asthma, and one in 10 children are affected.
"Therefore Asthma UK encourages all children and adults with asthma to lead a healthy lifestyle, which includes eating plenty of fresh fruit and vegetables, as this may help with the control of their asthma symptoms."
From the April 9, 2007, Prepared Foods e-Flash