As more and more people strive to reduce their meat consumption, an increasing number of them are looking towards legume-based substitutes as a source of protein, vitamins, and fiber.

However, there is a significant issue at play for those with allergies to legumes like soy or peanuts, as such allergies are both common and can be life-threatening.

A team of scientists, led by Dr. Mark Smits, from the University Medical Center Utrecht, have taken up the task of investigating whether individuals who are allergic to certain legumes are susceptible to meat-free proteins derived from other legumes that may contain different legumes.

“Both protein consumption and the world’s population are increasing which leads to an urgent demand for sustainable protein sources,” explains senior author Dr. Thuy-My Le. “An increase in the consumption of legumes may increase the number of allergies to these foods. Furthermore, these new legumes may elicit allergic complaints in already legume-allergic patients. Therefore, we investigated how often sensitization and allergy to different legumes occurs in these patients.”

Food allergies occur when the immune system mistakenly identifies certain proteins in food as harmful and produces Immunoglobulin E (IgE) antibodies. This can lead to a range of allergic reactions when the food is consumed again. In some cases, people who are allergic to one type of food may also react to other foods as well. This phenomenon is called co-allergy.

Co-allergies are often accompanied by co-sensitization, where the body produces IgE antibodies against multiple foods. This can occur due to cross-reactivity, a process where IgE antibodies bind to similar protein structures in different types of food. As a result, individuals who are allergic to one food may develop allergies to other foods that contain similar proteins.

According to experts, cross-reactivity is a common factor in the development of co-sensitization. People who are sensitive to certain types of food may be at a higher risk of developing allergies to other foods that share similar protein structures. This can make it challenging for individuals with food allergies to identify and avoid all the foods that may trigger an allergic reaction.

Co-sensitization, which refers to the production of IgE antibodies against multiple foods, can sometimes result in a diagnosed co-allergy. However, it’s worth noting that co-sensitization does not always lead to an allergic reaction. In some cases, a person may be sensitized to a particular food but not experience any symptoms upon consumption.

Legume-allergic patients were recruited by Smits and his team from the Allergology Clinic at the University Medical Center Utrecht, and subsequently categorized into six groups based on their specific allergies, which included peanuts, soybeans, green peas, lupines, lentils, and beans. These patients had previously undergone an oral food challenge or had a confirmed allergy through a positive IgE test and history of reactions. The team then conducted IgE antibody testing on each group for the other legumes.

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

Additional legume co-sensitization was observed in all six patient groups, with almost 25% of patients exhibiting sensitization to all legumes. The bean allergy group demonstrated a high prevalence of sensitization to other legumes. Similarly, patients allergic to green peas, lupines, or lentils showed a likelihood of co-sensitization with other legumes. In contrast, patients diagnosed with allergies to peanuts or soybeans did not exhibit a similar trend.

The team also examined the occurrence of documented co-allergies in the patient groups. While the high co-sensitization rate was observed in a significant number of patients, only a relatively small percentage displayed clinical symptoms. Peanut and soybean-allergic patients had fewer co-allergies for green peas, lupines, lentils, and beans. However, patients who had allergies to this second group of legumes were more likely to have co-allergies with peanuts or soybeans. Patients with peanut allergies were often co-allergic to soybeans, and vice versa. Co-sensitization for peanuts was linked to clinically relevant co-allergy in almost all other legume groups. Nonetheless, the team emphasized the need to expand the study to a larger cohort and confirm co-allergies through oral food challenges to establish the clinical significance of this co-sensitization in practice.

“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,” adds Le. “However, this reaction does not always lead to a clinically relevant food allergy. Introduction of novel foods into the market should be accompanied by appropriate assessment of the risk of developing (new) food allergies.”

Source: 10.3389/falgy.2023.1115022

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