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Dry-roasted peanuts more likely trigger for allergy

Date: Sep-22-2014
In 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
Note: Any medical information available in this news section is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.