British scientists are hoping to discover if a lack of iron and selenium in the womb increases our risk of asthma later on. The study could lead to pregnant women increasing their use of supplements to prevent wheezing in their offspring.
Dr Seif Shaheen at King's College London suspects that deficiency in the trace minerals iron and selenium could be responsible for a growing incidence of asthma among the UK's children. Previous research on umbilical cord samples showed a possible connection between the level of exposure to iron and selenium before birth and subsequent risk of wheezing, according to Dr Shaheen.
"A lot of chronic diseases have their origins before birth, in the womb. Clues are emerging to suggest that factors which influence the development of the lung and immune system of a baby in the womb are likely to play an important part in determining whether they subsequently suffer from wheezing and asthma as children," said Dr Shaheen.
"We have preliminary evidence to suggest that babies exposed to higher levels of selenium in utero have a lower risk of persistent wheezing in early childhood, and those exposed to higher levels of iron have a lower risk of later onset wheezing and eczema," he added.
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, which is funding the research. "One of our most urgent research priorities is to address the primary prevention of asthma in children," she said.
Dr Shaheen and Dr John Appleton from the University of Liverpool Dental School will analyse the mineral content of the milk teeth of 250 children with asthma and 250 children without asthma. The teeth have been collected from the Avon Longitudinal Study of Parents and Children (ALSPAC), running at the University of Bristol.
"Milk teeth begin to develop before birth and the enamel takes up trace elements and minerals, thus capturing a permanent record of exposure. When milk teeth drop out the enamel can be analysed to look back in time and tell us about a baby's actual level of exposure to trace elements and minerals before birth," said Dr Shaheen.
Dr Appleton added: "I've done a lot of work to monitor environmental pollution with animal teeth - but this will be the first time we've done this in relation to human disease."
Human upper central deciduous incisors (the first to fall out, at about six years of age) begin to calcify between 14 and 19 weeks in utero and finish at about 8-12 weeks after birth. Tooth enamel therefore encapsulates a permanent record of prenatal and very early postnatal exposure to trace elements and minerals.