Asthma lives in cities

Rural folk breathe easier because of their diet, writes KATHERINE HOBY.

City children are at greater risk of being asthmatic than their counterparts who grow up in the country.

A comprehensive Australian study has shown that the high proportion of margarine and vegetable oil found in the diet of a city lifestyle may double the risk of asthma in young children.

And New Zealand experts agree that big-city ways may be responsible for the high number of asthmatics among preschoolers.



Asthma New Zealand president Dr Allen Liang said experts had long used the "fast-food index" when taking into consideration factors which determine who gets asthma and why.

"Having a lot of deep-fried foods can contribute," he said.

Polyunsaturates did not cause asthma but inflammation of the airways would be worse from the reaction to a high-fat diet.













Dr Liang said the countryside-dwellers' diet of fresh fruit and vegetables and less fats and salt seemed to reduce the chances of asthma.

"Kids off farms are less likely to have the allergy response. It has been shown time and time again," he said.

Dr Liang said children were most at risk in their first year. Other contributing factors included obesity and a family history of asthma.

The Australian study on risk factors among preschoolers involved parents of nearly 1000 children aged 3 to 5 years filling in questionnaires covering the family's medical and dietary history.

Around one in five children was found to have asthma.

Dr Michelle Haby, researcher at the Centre for Community Child Health at the Royal Children's Hospital in Melbourne, said it was the first time the link to polyunsaturated fats was shown.

"The study showed that children who usually have margarine on their bread and toast, and eat food cooked in vegetable oils, have twice the risk of asthma," she said.

"However, I wouldn't advise people to stop using them on the basis of this study alone because we have not shown that polyunsaturated fat actually causes asthma or that avoiding it stops asthma."

More research was needed to understand the role of polyunsaturated fats, but a likely explanation is that the increased levels of omega-6 fatty acids they produce promotes inflammation, the underlying cause of the condition.

Other studies have shown that consumption of omega-3 fatty acids, such those found in oily fish, is associated with reduced risk of asthma.

The questionnaires enabled Dr Haby and research colleagues from the Institute of Respiratory Medicine at the University of Sydney to compare the use of polyunsaturated fats with the use of saturated fats such as butter and lard and monounsaturated fats such as olive oil.

The questions on fats were included because of a theory that the increasing prevalence of asthma in countries such as Australia may be linked to higher consumption of polyunsaturates by consumers rejecting saturated fats known to raise cholesterol and increase heart disease risk.

The study, published in Thorax, an international journal on respiratory medicine, also shows that having a parent with a history of asthma doubles the risk for a child.

ASTHMA FACTS

About one in three children and one in seven adults in New Zealand have asthma.

About 600,000 New Zealanders suffer from asthma.

Asthma means the breathing tubes (bronchioles) in your lungs are oversensitive and become irritated easily. Irritation results in the narrowing of airways.

There are a number of symptoms: coughing, wheezing, shortness of breath, chest tightness, raised shoulders, blueness around the mouth.

Common triggers include: house dust mites, cat hair, pollen, strong perfume, exercise, cold air, stress, viral infection, and cigarette smoke.