Margarine linked to dramatic asthma rise
09:35 19 July 01
Emma Young [NewScientist]
Campaigns to reduce heart disease by promoting polyunsaturated margarines and cooking oils could be partly responsible for the recent dramatic increase in childhood asthma in the developed world, say researchers in Australia.
They found that a diet high in polyunsaturated fats more than doubles a child's risk of asthma.
Polyunsaturated fats are found in sunflower and vegetable oil. They contain high levels of omega-6 fatty acids, which can boost inflammation of tissues in the body. This is one possible explanation for the link with asthma, says a team led by Michelle Haby of the Royal Children's Hospital in Melbourne.
"But at this stage, children should not be changing their diet," Haby told New Scientist. "We do not know whether changing the diet will reduce the risk or severity of asthma - that is the subject of ongoing investigation."
The role of changing dietary fat habits on the recent increase in asthma is also unclear, she says. "I expect the increase in asthma is due to a combination of factors, one of which may be diet."
Martyn Partridge, medical adviser to the UK's National Asthma Campaign, says: "This new evidence that suggests a reduction in consumption of polyunsaturated fats may also reduce the likelihood of developing asthma is helpful, but we are still a long way from being able to explain why this common disease is becoming more common."
Spreading risk
The team studied more than almost 1000 children aged between three and five living in two rural towns in Australia.
Parents completed a questionnaire, which included questions on asthma diagnosis, number of children in the family and whether the child was breastfed. It also asked parents to name the type of fat the child normally had on toast and bread, and what type of oil was usually used for cooking.
Haby says she was surprised by the results. Before her study, there had only been speculation that polyunsaturated fat might be a factor, she says.
But the team estimates that a high level of polyunsaturated fats in the diet could account for 17 per cent of asthma cases in the children they surveyed.
Inflammatory findings
An increased consumption of polyunsaturated fats leads to a high intake of omega-6 fatty acids, but a relatively low intake of omega-3 fatty acids.
Omega-6 fatty acids boost the synthesis of Prostaglandin E2, a chemical that increases inflammation in tissues in the body. Increased inflammation is linked to asthma. Omega-3, on the other hand, inhibits the formation of Prostaglandin E E2, and so helps protect against inflammation.
Omega-3 fatty acids are found in high quantities in canola oil, for example, which contains high levels of monounsaturated fats.
More work is now needed to establish the role of dietary polyunsaturated fat on asthma, says Hoby. Several recent studies have found a near doubling of childhood asthma in developed countries in the past 10 years.
Journal reference: Thorax (vol 56, p 589) |
