2025.06.17
Legumes, such as peanuts, soybeans, lentils, chickpeas, common beans, and others, are a group of plants belonging to the Fabaceae or Leguminosae family. Legume seeds play a fundamental role in providing energy and healthy nutrition for humans, and they are the second most important food source after cereals. The European Food Safety Authority (EFSA) has stated that legumes are a recognized source of protein and are essential for a healthy diet.
Global legume consumption
According to market data and an annual growth rate of 3.5%, the legume market was valued at $13.43 billion in 2024. If the approximate average price of legumes in 2024 is considered to be around $1200 per ton, it can be said that global legume consumption increased by approximately 11 million tons in 2024, and the market is projected to grow to $22.51 billion by 2034. The increasing demand for plant-based products and awareness of the health benefits of legume consumption are the main drivers of this market growth.
Legume sensitivity
Over the past decade, there has been a growing trend towards plant-based diets. In addition, more reports of allergenic reactions associated with legume consumption, especially meat substitutes based on them, have been observed. The reasons for this are complex and can involve several factors, such as cultural factors, dietary habits, genetic factors, and more.
- Cultural Factors: sensitivity to legumes can be related to cultural factors and has different patterns in different regions of the world. For example, in India, due to the widespread consumption of lentils and chickpeas in the diet, sensitivity to these legumes is more common, while in Europe, the use of lupin flour in bread and food products has made lupin sensitivity prevalent. Lupin, also known as Egyptian bean or termis, is a plant whose non-starchy seeds are used as a source of protein, minerals, vitamins, etc., in baked goods such as bread and biscuits.
- Dietary Habits: dietary habits can also play a significant role in the development of allergies. Frequent consumption of a food substance can lead to sensitivity in some individuals, depending on their specific conditions and the functioning of their immune system. This means that with the frequent consumption of a particular type of legume by the people of a society, the prevalence of sensitivity in that society becomes more apparent.
- Genetic Factors: genetic and ethnic differences can also play a role in the development of legume sensitivity. Some individuals are genetically predisposed to allergic reactions to legumes such as soybeans and peanuts.
Understanding these factors can help in more accurately identifying allergenic sources. While peanuts and soybeans are the most common allergenic legumes, beans, peas, lentils, and lupin also cause severe allergic reactions. European Union laws and regulations mandate the labeling of allergenic sources such as peanuts, soybeans, lupin, etc. However, some allergenic legumes may be less known, and reported cases about them may be more limited. With the increasing incidence of legume sensitivity and their greater inclusion as food ingredients, there may be grounds for additional labeling regulations.
Mechanism of legume allergy
Legumes contain potent allergenic proteins. These proteins may include storage proteins responsible for providing amino acids needed for the growth and development of sprouts or seeds, structural proteins involved in creating the plant's cellular structure, and transfer proteins responsible for the movement of various substances within the plant. These protein compounds are usually resistant to heat (such as cooking processes) and digestive enzymes, meaning they retain their structure and can still stimulate the body's immune system.
In individuals sensitive to legumes, the body reacts abnormally to the proteins in these foods and effectively fights them off. The immune system mistakenly identifies these proteins as dangerous agents and produces antibodies (specific molecules responsible for identifying and fighting pathogens) called Immunoglobulin E (IgE) to combat them. These antibodies remain in the body and, in a way, sensitize the immune system to that specific protein. This means that if the person consumes the same protein again, the antibodies quickly recognize it and trigger a defensive reaction in the body. This reaction causes the release of specific chemical substances in the body, which are the cause of allergy symptoms.
On the other hand, an allergic reaction occurs when the body's immune system reacts to similar proteins found in two or more food substances due to structural similarities. For example, the proteins in lupin are very similar to peanut proteins, so a person's immune system may identify the proteins in lupin as similar to peanut proteins and react to them. Therefore, people who are allergic to peanuts may also react to lupin. This phenomenon is called cross-reactivity.
Difference between legume sensitivity and bloating
While the mechanism of legume sensitivity results from the body's immune system reacting to allergenic proteins present in them, bloating caused by legume consumption is not related to this immune reaction. Instead, it is related to carbohydrate compounds called oligosaccharides (such as raffinose) that the human digestive system cannot digest in the small intestine. Therefore, these compounds enter the large intestine undigested, where gut bacteria ferment them. In this process, gases such as hydrogen (H2), methane (CH4), and carbon dioxide (CO2) are produced, leading to feelings of bloating, abdominal distension, and more. Soaking legumes dissolves and removes some of these oligosaccharides. Soaking activates natural enzymes present in legumes that can break down some of these compounds, making them easier to consume and less likely to cause bloating but, soaking does not significantly affect legume allergies, as the structure of these proteins remains stable.
Some of the most important allergenic proteins in legumes
- Peanuts: in peanuts, allergenic proteins Ara h 1, Ara h 2, and Ara h 3, are identified as foreign agents by the immune system of sensitive individuals and cause allergic reactions.
- Soybeans: in soybeans, proteins Gly m 4, Gly m 5, and Gly m 6, are considered allergenic factors in some individuals.
- Beans: in individuals sensitive to beans, the protein phaseolin may cause allergic reactions.
- Lentils: allergenic proteins in lentils include phytin and lentinin, which can cause allergic reactions in some individuals.
- Chickpeas: the main proteins in chickpeas include vicilin and legumin, which, similar to other allergenic proteins in legumes, may cause allergies in some individuals.
- Lupin: proteins Lup an 1, Lup an 2, and Lup an 3, are among the main allergenic substances in lupin and may cause allergies in some individuals.
Symptoms of legume allergy
Priority legumes (as a primary and common source of allergies), such as peanuts and soybeans, are on the list of the 9 major food allergens described by the U.S. Food and Drug Administration (FDA). Other non-priority legumes (legumes with lower allergenicity), such as beans, peas, lentils, chickpeas, and lupin, can be considered important and emerging sources of allergic reactions, given numerous reports of allergic reactions. Consumption of legumes by some sensitive individuals can show symptoms ranging from mild to severe, depending on the intensity of their immune system's reaction.
In mild reactions, symptoms such as hives (red bumps on the skin), itching, skin redness, digestive problems (abdominal pain, nausea, etc.), and mild respiratory symptoms (such as sneezing, runny nose, etc.) are usually observed. Severe symptoms may include swelling of the lips, tongue, or throat with itching and swelling in these areas, and respiratory symptoms including shortness of breath, wheezing, coughing, and may progress to a very severe and dangerous allergic reaction (anaphylaxis) that can be life-threatening. This very severe reaction may be accompanied by symptoms such as a sharp drop in blood pressure, feelings of weakness and dizziness, difficulty breathing, loss of consciousness, and more.
Conclusion
Given the increasing trend towards vegetarian diets and the identification of new sources of legumes that can cause allergies, more cases of allergic reactions have been reported in consumers. Since legume sensitivity is usually not resolved by methods such as soaking or even by an individual's digestive enzymes, it is recommended that individuals sensitive to legumes choose their diet more carefully.