The research, led by Dr Nariman Hijazi, focused on communities in Saudi Arabia where there are striking differences in lifestyle and rates of allergies across the country.
114 children, drawn from Jeddah and several rural villages, and with symptoms of asthma and wheeze, were compared with 202 non-asthmatic children. Their average age was 12 years.
Family history, allergic tendency (atopy) and a poor diet were significantly associated with wheeze in the children with symptoms.
When dietary components were analyzed more extensively, those children who had the lowest intakes of vegetables and milk, vitamin E and certain minerals, were at significantly greater risk of wheeze, even after adjusting for other factors.
Children eating a diet relatively low in vegetables and vitamin E were around three times as likely to suffer wheeze.
"Dietary factors are associated with a 2-3 fold increase in risk of having asthmatic symptoms."
Dr Nariman Hijazi.
Family size, numbers of infections, level of affluence and parental smoking-all of which are considered to be risk factors for asthma-were not associated with wheeze, the research showed.
As prosperity has increased in Saudi Arabia over the past 30 years, so has the tendency towards a Western diet, say the authors, a trend that is more marked in urban areas.
Poor diet is likely to be an important risk factor for asthma and allergies, they conclude. And a change in diet may, therefore, largely explain the increase in prevalence of these conditions in developed countries.