A research group led by Seif Shaheen from the Department of Public Health Sciences at King's College, London, UK, in collaboration with colleagues from Bristol University, studied 3000 babies to see whether prenatal exposure to the nutrients iron and selenium might play a role in the inception of early childhood wheezing and eczema.

The researchers discovered that children with the highest exposure to selenium, as estimated by concentrations in the umbilical cord tissue at birth, were less likely to wheeze than children with lower exposure, and those with the highest exposure to iron were less likely to wheeze and to have eczema in early childhood.

Shaheen and his group noted they decided to carry out the research as past studies have suggested that foetal nutrition might influence the inception of wheezing and atopic disorders in childhood but specific nutrients have not been implicated.

"A lot of chronic diseases have their origins before birth, in the womb," said Dr Shaheen.

Similarly, it has been proposed that in later life dietary intake of antioxidants might influence the risk of these disorders.

In the UK, intakes of selenium have been falling at the same time as asthma has been increasing. The mineral occurs naturally in fish, meat, cereals and dairy products but a study published in the Journal of Food Sciences and Agriculture last year showed that levels of selenium in British bread-making wheats are up to 50 times lower than their American and Canadian counterparts and levels of selenium in the blood of the British population has been dropping since the 1970s. This is when grain began to be sourced from EU countries where soil is depleted of selenium.

Asthma is the most common long term condition in the UK today, according to Philippa Major, assistant director of research at the National Asthma Campaign.

"One of our most urgent research priorities is to address the primary prevention of asthma in children," she said.

Dr Shaheen together with Dr John Appleton from the University of Liverpool Dental School have previously analysed the mineral content of the milk teeth of 250 children with asthma and 250 children without asthma to record a baby's exposure to elements and minerals before birth.

The new study is published in the August edition of the European Respiratory Journal .