Meatless Proteins May Trigger Soy & Peanut Allergy

Many people who want to consume less meat are switching to protein-, vitamin-, and fiber-rich replacements composed of legumes. Yet, soy allergy and peanut allergy are both prevalent and harmful. Are patients who have allergies to specific legumes, even if they contain diverse legumes, in danger from meat-free proteins comprised of legumes? Researchers at University Medical Center Utrecht led by Dr. Mark Smits began their investigation.

Both protein consumption and the world’s population are increasing which leads to an urgent demand for sustainable protein sources,” said Dr. Thuy-My Le, senior author of the study published in Frontiers in Allergy.

“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 occur in these patients.”

When immune systems mistake food proteins for a threat and create Immunoglobulin E (IgE) antibodies, people develop food allergies. When exposed to the same food again after becoming sensitized, some people may experience allergy symptoms. A co-allergy is when a patient who reacts to one food may also react to another.

Co-sensitization, in which individuals generate IgE antibodies against many foods, occurs in conjunction with co-allergies. Cross-reactivity, in which IgE antibodies attach to proteins from other diets because the proteins have similar structures, may be the source of co-sensitization.

It’s conceivable for someone to get co-sensitized to food yet not have a reaction to it when they consume it. Co-sensitization can result in a co-allergy diagnosis, but it doesn’t always. What about other legumes? Do people with specific legume sensitivities react to them?

Smits and colleagues gathered patients with legume allergies from the University Medical Center Utrecht’s Allergology Clinic and divided them into six groups based on their allergies to peanuts, soybeans, green peas, lupines, lentils, and beans. An oral food challenge or a positive IgE test along with a history of responses confirmed allergies in all individuals. The presence of IgE antibodies against the other legumes was examined in each unique group.

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

Over a quarter of patients were sensitized to all legumes, and all six patient groups had co-sensitization to other legumes. The majority of the individuals with bean allergies had developed a sensitivity to other legumes. Individuals with confirmed soybean or peanut allergy were less likely to become sensitized to other legumes than those with allergies to green peas, lupines, or lentils.

The scientists also examined which of these patients had co-allergies to multiple legumes that were reported. The high co-sensitization rate was associated with clinical symptoms in only a relatively limited percentage of patients.

Green pea, lupine, lentil, and bean co-allergies were uncommon in patients with peanut and soybean allergies, but these individuals were also more likely to have soybean or peanut allergies. Individuals with peanut allergy frequently also have allergies to the latter food.

Nearly all of the other legume groupings had clinically significant co-allergy and co-sensitization for peanuts. To ascertain how clinically significant this co-sensitization is in actuality, the team did provide a word of caution, stating that it would be important to increase the study’s sample size and confirm co-allergies with oral food challenges.

“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,” said 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 an appropriate assessment of the risk of developing (new) food allergies.”

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