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Study linking breastfeeding to nut allergy 'ridiculous'

News analysis Claims that exclusive breastfeeding and eating nuts during pregnancy are leading to an increased incidence of allergies are ridiculous and run counter to the bulk of allergy research, according to an Australian expert.

Even though breastfeeding can be a controversial topic, few would think that a mother's milk could actually harm her baby. In fact, the World Health Organisation recommends infants be exclusively breastfed for the first six months of life.

But a recent study from the Australian National University's (ANU) medical school made international headlines when it concluded that children who were exclusively breastfed for their first six months were at an increased risk of developing potentially fatal peanut allergies.

In a press release on the university's website, the study's lead author, Professor Marjan Kljakovic, says the results contribute to the argument that breastfeeding does not protect against allergies, and "may, in fact, be causative of allergy".

According to the press release, Kljakovic says "Despite breastfeeding being recommended as the sole source of nutrition in the first six months of life, an increasing number of studies have implicated breastfeeding as a cause of the increasing trend in nut allergy."

Last year, an Australian study found that food allergies are on the rise; with one in 10 infants being diagnosed with an allergy - one of the highest rates in the world.

Paediatric gastroenterologist and food allergy researcher with Murdoch Childrens Research Institute Professor Katie Allen has concerns about the research and the coverage it has received.

"The conclusions drawn do not match the results of the study, therefore the implications that he has been discussing [in the public domain] are ridiculous and inappropriate," says Allen.

According to Allen, families with an increased risk of allergies tend to breastfeed longer, and their children more likely to have allergies because of family history.

"So it is true that it looks like mothers who breastfeed for longer are more likely to have [children with] allergies, but it's the fact that they are more likely to have allergies that makes them breastfeed for longer," she says.

"Breastfeeding is best, there's absolutely no risk about that. We don't think it will prevent allergies, but it certainly won't increase the risk of allergies."

Self-reported data

The ANU research, published in the latest edition of the International Journal of Pediatrics, was conducted in the Australian Capital Territory where all children are offered a health check when they start school.

Between 2006 and 2009, more than 15,000 parents of children were asked to fill in a Health Check Questionnaire, which covered a range of health issues including infant feeding practices and peanut allergies.

In relation to feeding, parents were asked whether the child, as a baby, had been breastfed, how long they had been breastfed for, and at what age other foods or drinks had first been introduced. Parents were also asked whether their child had a "strong allergic reaction to peanuts/peanut products, and/or other nuts/nut products". If they answered yes, it was recorded as a self-reported nut allergy.

What the researchers found was that the more children below the age of six months had been given food and fluids that weren't breast milk, the less likely they were to be reported as having a nut allergy.

"At one end you have the breastfeeding only lot, which was 5 per cent nut allergy rate. At the other end, where they were only given other foods and fluids, it was a rate of 2.7 per cent and in between where there was breastfeeding and other food then it was 3.7 per cent," says Kljakovic.

"You've actually got a dose response going on there. It's not the breastfeeding that's the dose response so it must be something to do with nuts. But clearly we have to prove that and you have to do further research."

Nut avoidance

Despite this, Kljakovic believes women should avoid nuts and peanuts while pregnant or breastfeeding.

Allen points out that the researchers failed to ask any questions about the mother's diet when she was pregnant or breastfeeding.

"The report only asked [about] breastfeeding, not about maternal dietary practices. Therefore the authors cannot conclude in any way whatsoever about maternal dietary practices including exposure to nuts and its risk of peanut allergy," says Allen.

Moreover, recent research into food allergies suggests the complete opposite. This includes a Danish study, published last week, that found babies born to women who ate nuts during pregnancy were less likely to develop asthma.

"We think exposure to small amounts [of allergens] helps to train the immune system and is safe and may even protect against allergy. However, we need some more formal evidence for us to be sure of it," she says.

But Allen is confident that eating nuts, and other foods known to cause allergies, during pregnancy and while breastfeeding is not going to increase a child's risk of developing allergies.

"Parents can be reassured that what they eat during pregnancy and lactation, at this point in time, appears to have no effect whatsoever on their allergic risk."