Soybean ( Glycine max ) is a legume belonging to the Fabaceae family that contains about 38 to 40% protein. Its consumption has increased in Europe in recent years. In vegetarian cuisine, soy is consumed in different ways, and is also widely used in the food industry due to its technological versatility and low cost (1,2).
The World Health Organization (WHO) identifies 8 allergenic proteins in soy, 7 of which can cause food allergy (3). These proteins are usually resistant to high temperatures and to the action of acidic gastric juice and digestive enzymes. Cooking increases its allergenic potential (1).
The various forms of soy food allergy can be classified into:
a) mediated by IgE antibodies - the most common, with immediate reactions up to 2 hours after ingestion, contact or inhalation, and with very varied manifestations from the most localized and mild to the most generalized and severe (anaphylaxis);
b) not mediated by IgE - usually later, after 2 hours, and more difficult to diagnose. It can be manifested by gastrointestinal symptoms such as vomiting and diarrhea.
c) mixed – involves both IgE and cell-mediated mechanisms, as in atopic dermatitis and eosinophilic esophagitis (1).
Cross-reaction of soy with other allergens
Although food allergy to more than one legume is common, for example, the association of allergy to peas, chickpeas and lentils is common, most soy allergy sufferers tolerate the remaining legumes. For this reason, in soy allergies, restriction of other legumes is not usually recommended, unless there is a high level of suspicion (1).
Some studies report the occurrence of adverse reactions to soy in patients allergic to cow's milk fed soy-based formulas. This is due to a soy protein that is similar to casein in milk, with cross-reaction occurring between them, that is, the body mistakenly identifies it as the milk protein causing the same type of allergic reaction (2).
Soy and soy-based products are part of the list of allergenic ingredients that are subject to mandatory and prominent mention on labels, in accordance with current European legislation on food labeling. This list excludes fully refined soybean oil and its derivatives (4). See below for an explanation of these exceptions.
See which foods may contain soy and how to identify soy and its derivatives on labeling.
Foods that have or may contain soy: (1,2,4,5)
How to identify soy and derivatives on labeling:
Soybeans, soy beans, soy sprouts, tofu, soy sauce, soy sauce, miso, soy flour, soy oil, soy lecithin (E 322), hydrolyzed vegetable protein, hydrolyzed vegetable protein, textured vegetable protein, soy albumin, soy fiber, mono-diglycerides, dofu, kori-dofu, soy curd, edamame, kinako, natto, nimame, okara, yuba (4,5,6).
a) fully refined soybean oil and fat;
b) natural mixed tocopherols (E 306), natural D-alpha-tocopherol, natural D-alpha-tocopherol acetate and natural D-alpha-tocopherol succinate derived from soy;
c) phytosterols and phytosterol esters derived from vegetable oils produced from soy;
d) vegetable stanol ester produced from soybean vegetable oil sterols (7).
The exclusion of these soy-derived products from mandatory labeling is justified by scientific studies that indicate that fully refined soy oil and its derivatives are practically free from allergenic proteins, as they are almost entirely removed by the refining process. However, it is not certain that the remaining proteins cannot also cause allergy in atopic patients, and it is recommended, as a precaution, to avoid soy oil and products containing this oil until consulting an allergist (2,6).
Fidu products do not contain soy. We do not handle any ingredient that may be contaminated with soy in our facilities. In this way, we guarantee that there is no cross-contamination by traces and that our products are safe even for the most sensitive.
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IMPORTANT NOTE: The content of this article is merely informative and should not replace medical indications. If you suspect that you suffer from this type of allergy, you should seek medical advice.
(1) SPAIC Food Allergy Interest Group, 2017. Food Allergy: Concepts, Advice and Precautions , 1st Edition. Lisbon: Portuguese Society of Allergology and Clinical Immunology with support from Thermo Fisher.
(2) NDA (2016). Scientific Opinion on the evaluation of allergenic foods and food ingredients for labeling purposes . EFSA Journal, 12(11).
(3) Allergen Nomenclature WHO/International Union of Immunological Societies Allergen Nomenclature Sub-Committee. Allergen Nomenclature . Available at: www.allergen.org
(4) Vieira, R. (2015). Food Allergens: A Synoptic Study . New University of Lisbon.
(5) Nunes, M., Barros, R., Moreira, P., Moreira, A., Almeida, M. (2012). Food Allergy . Ministry of Education and Science - Directorate-General for Education & Ministry of Health - Directorate-General for Health.
(6) Government of Canada. (2017). Soy: A priority food allergen 2017 .
(7) Regulation (EU) No. 1169/2011 of 25 October 2011 of the European Parliament and of the Council of the European Union.