Junk food and ready-made packaged meals may be causing the alarming rise in the world's childhood asthma rates.

Junk food and ready-made packaged meals may be causing the alarming rise in the world's childhood asthma rates.

Scottish researchers found children who have diets low in vegetables, vitamins and minerals are three times more likely to suffer from wheezing, infections and other asthmatic symptoms.

Children who eat less processed or frozen food and more locally grown fresh vegetables are far less likely to be asthmatic.

In Britain, the number of children developing asthma before the age of five has doubled in less than a decade. One in seven children suffers from asthma, around 1.5m children. Asthmatic children have coughing and wheezing and in extreme cases their asthma attacks can be fatal. In 1997, they killed 1,500 people.

The disease had been associated with prosperous urban lifestyles, rising pollution levels and a greater prevalence of fitted carpeting and central heating, increasing children's contact with dust mites.

Although doctors suspected diet might also play a role in the increasing levels of asthma in western societies, the research, in the journal Thorax, shows that children who had the lowest intake of vegetables, milk and vitamin E were at a significantly greater risk of developing asthma.

The study, led by Professor Anthony Seaton, of the department of environmental and occupational medicine, at Aberdeen University, was done in Saudi Arabia where modern and traditional communities live side by side.

Over the past 30 years, as prosperity in the country has increased because of the oil boom, the diet has become increasingly westernised, particularly in the cities.

The researchers found a large difference in the diet between children from the fast-moving "westernised" capital, Jeddah, and those in several rural villages. They compared the diets of more than 300 children, aged 12, a third of whom has asthmatic symptoms.

After taking family history and allergic tendencies into consideration they found eating at fast food outlets was identified as a significant risk factor for wheezing.

Children with the lowest consumption of vegetables, milk, fibre, vitamin E and essential minerals were at significantly greater risk of suffering a wheezy illness. A lack of vitamin E on its own was associated with a threefold increase in risk.

Professor Seaton said the traditional Arabic Saudi diet bore little superficial resemblance to the average western diet. In rural communities, Saudis still ate a diet based on cows' and goats' milk, rice, vegetables, lamb, chicken, dates and local fruits.

"With increasing prosperity and commercial exposure, there has been an influx over some three decades of western-type frozen and prepared foods in supermarkets and restaurants," he said.

"This study suggests that dietary factors during childhood are an important influence in determining the expression of wheezy illness."

Dr Martyn Partridge, the chief medical adviser for the National Asthma Campaign, said: "This is an interesting finding and one consistent with other studies that suggest taking fresh fruit and a balanced diet protects against asthma and some other lung diseases.

"It is another point towards lifestyle as the cause of the increasing asthma."