April 6 (HealthDay News) -- A Mediterranean-style diet loaded with fruits, vegetables and nuts may help prevent allergic rhinitis and asthma symptoms in youngsters, a British study suggests.

Researchers at the National Heart and Lung Institute, London, looked at almost 700 children, ages 7 to 18, on the Greek island of Crete. Their parents filled out questionnaires on their children's eating habits and on their allergy and asthma symptoms.

Eight out of 10 children in the study ate fresh fruit and more than two-thirds of them ate fresh vegetables, at least twice a day. Diet appeared to have the strongest protective effect against allergic rhinitis but also helped protect children against asthma and skin allergies, the study found.

Children who ate nuts at least three times a week were also less likely to wheeze. The researchers noted that nuts are rich in vitamin E, which protects against cellular damage caused by free radicals. Nuts also contain high levels of magnesium, which may protect against asthma and improve lung power.

The study also found that a daily diet of oranges, apples, and tomatoes protected children against wheezing and allergic rhinitis. Grapes appeared to be especially effective in preventing wheezing and allergic rhinitis. Red grape skins contain high levels of antioxidants and a potent polyphenol called resveratrol, which is known to reduce inflammatory activity, the researchers said.

They also found that eating lots of margarine doubled the risk of asthma and allergic rhinitis.

The study was published in the journal Thorax.