Missing out on a protein source? Study says people allergic to one legume are often sensitive to others

17 Mar 2023 --- Dutch researchers found that patients allergic to green peas, lupines, lentils and beans had a high co-allergy for peanuts (prevalence of 64.7%-77.8%) and soybean (50%-64.7%). Patients allergic to soybeans had a high co-allergy to peanuts (63.3%). 

In peanut and soybean-allergic patients, allergies to green peas, lupines, lentils and beans were uncommon.

“Legumes are an attractive, sustainable protein source, but allergic reactions in the already legume-allergic population cannot be excluded as antibodies in the blood of legume-allergic patients frequently react to different legumes,” warns Dr. Thuy-My Le, senior author of the study.

“We showed that a large number of patients produced antibodies against more than one legume,” notes Dr. Kitty Verhoeckx, second author of the study. “However, clinical data showed that only a small part of these patients had actual symptoms.”

The researchers caution that follow-up research with more participants is crucial to confirm the co-allergies found and determine how clinically relevant co-sensitization is in practice. 

The study found that many patients produced antibodies against more than one legume. Co-sensitization vs. co-allergy 
Food allergies occur when a person’s immune system sees food proteins as a threat and produces Immunoglobulin E (IgE) antibodies. This process is called sensitization and can lead to allergic symptoms if people are re-exposed to the same food. 

As proteins from multiple foods have similar structures, co-sensitization may occur where people produce IgE antibodies against several foods. Co-sensitization can lead to co-allergy, where someone allergic to one food has a reaction to other similar foods. 

The researchers found that patients with allergies to peanuts, soybeans, green peas, lupins, lentils and beans had co-sensitization to other legumes. Almost a quarter of patients were sensitized to all legumes. Patients with bean allergies were nearly all sensitized to other legumes. 

Nearly all people with allergies to other legume groups were also sensitized to peanuts, while mono-sensitization was only found in patients allergic to soybean, peanut and green peas. 

Alternative protein market 
Plant-based proteins offer a more sustainable option than traditional protein sources and demand and offer are rising. The researchers note that peanut, soybean and lupine allergy are among the most prevalent food allergies and require mandatory labeling. 

“Both protein consumption and the world’s population are increasing, which leads to an urgent demand for sustainable protein sources,” says Le. 

“An increase in the consumption of legumes may increase the number of allergies to these foods. Furthermore, these new legumes may cause allergic complaints in already legume-allergic patients.”

Le notes that although co-sensitization does not always lead to a clinically relevant food allergy, “Introduction of novel foods into the market should be accompanied by an appropriate assessment of the risk of developing (new) food allergies.”The researchers warn that introducing novel foods should include an assessment of the risk of developing new food allergies. 

Research set-up 
The researchers at the University Medical Center, Utrecht, the Netherlands, recruited legume-allergic patients and divided these into groups for peanuts, soybeans, green peas, lupines, lentils and beans. The results are published in Frontiers in Allergy. 

The allergies were validated by an oral food challenge or positive Immunoglobulin E (IgE) antibodies test combined with a history of reactions. Each group was also tested for IgE antibodies against the other legumes. 

The researchers measured IgE binding to total extracts, protein fractions (7S and 11S globulin, 2S albumin and albumin) and 16 individual proteins from 10 legumes (black lentil, blue lupine, chickpea, faba bean, green lentil, pea, peanut, soybean, white bean and white lupine). 

The team found that the 7S and 11S globulin fractions likely contributed to the co-sensitization between legumes. There was a more intensive IgE binding for these fractions than for the 2S albumin and albumin fractions and a high frequency of co-sensitization between 7S/11S globulin fractions of all legumes. 

By Jolanda van Hal