Dry-roasted peanuts more likely trigger for allergy
Date: Sep-22-2014In the West, peanut allergy stands out more so than anywhere else. Yet,
Easterners consume as many peanuts as Westerners - perhaps the explanation lies in differences in
peanut preparation. For example, East Asians tend to eat more raw, boiled and fried peanuts,
whereas Westerners tend to eat more dry-roasted peanuts.
Some reactions to peanuts can lead to anaphylaxis, where breathing becomes difficult.
Now, a UK team that carried out a study in mice, has found roasted peanuts are more likely to
trigger an allergy to peanuts than raw peanuts and suggests dry-roasting produces chemicals that
sensitize the immune system to both dry roasted and raw peanuts.
The study is published in the journal Allergy and Clinical Immunology.
According to Allergy UK, allergy to peanut and tree nuts is the most common food
allergy, and allergy to peanuts affects around 1 in 50 young children.
Most allergic reactions to peanuts and tree nuts are mild, but some can be severe and can lead
to anaphylaxis, where breathing becomes difficult due to asthma-like symptoms or throat swelling,
and blood pressure can also drop.
High-temperature roasting of peanuts changes their proteins
Children are more likely to develop allergy to peanuts if they already have a known allergy such
as eczema or an intolerance to another food, or if their immediate family has a history of
allergies such as asthma, eczema or hay fever. However, allergy to peanuts can also involve a
trigger of some sort, as first author Dr. Amin Moghaddam, a senior postdoctoral research scientist
at Oxford University says:
"Allergies in people are driven by multiple factors including family genetic background and
exposure to environmental triggers. In the case of peanut allergy, we think we may have discovered
an environmental trigger in the way that peanuts are processed by high-temperature roasting."
There is already evidence that roasting peanuts changes their proteins, in turn changing the way
the immune system recognizes them. But until this study, we did not know that those changes can
trigger an allergic response.
For their study, Dr. Moghaddam and colleagues exposed groups of mice to purified proteins from raw
peanuts or dry-roasted peanuts - for instance by applying
to broken skin or via skin injection, or directly into the stomach.
They then measured the immune responses in the mice to further peanut extracts given later.
The mice previously exposed to dry-roasted peanut proteins had a much stronger immune reaction
to peanut extracts than mice that had only previously been exposed to raw peanut proteins.
First direct demonstration of a potential trigger for peanut allergy
Senior author Quentin Sattentau, a professor of immunology at Oxford, says:
"This is the first time, to our knowledge, that a potential trigger for peanut allergy has been
directly shown."
But he adds the research is still at an early stage, and it would be premature to urge people to
avoid roasted peanuts until the findings have been more robustly confirmed.
He says he and his team have identified the chemical reactions that occur in dry roasting
proteins that trigger allergic reactions, and they are now looking for ways the food industry can eliminate the proteins.
Dry roasting involves heating the peanuts to temperatures of 160 to 170°C and higher. Above
130°C, peanuts undergo a reaction that changes the chemical composition of specific groups of
proteins. The team suggests it is these products that trigger the strong immune reaction.
Funds for the study came from the National Institute for Health Research (NIHR) Oxford
Biomedical Research Centre, the US National Institutes of Health and the Swiss National Science
Foundation.
Meanwhile, in January 2014, a trial conducted by another UK team showed exposure to peanuts builds immunity in
allergic children if they consume increasingly larger amounts of peanut protein on a regular
basis.
The researchers in that study strongly urged people not to try it at home and reminded parents
and child carers that currently, the only way for children allergic to peanuts to avoid severe
reactions is for them to completely avoid foods that contain them.
Written by Catharine Paddock PhD
View all articles written by Catharine, or follow her on:
Courtesy: Medical News Today
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