Soy allergy

Soy allergy
Blocks of tofu, prepared by coagulating soy milk and then pressing to remove excess water
Specialty	Immunology

Soy allergy is a type of

Soy allergy is usually treated with an exclusion diet and vigilant avoidance of foods that may contain soy ingredients.^[1] The most severe food allergy reaction is anaphylaxis,^[1] which is a medical emergency requiring immediate attention and treatment with epinephrine.^[1]

Signs and symptoms

Acute soy allergy can have fast onset (from seconds to one hour) or slow onset (from hours to several days), depending on the conditions of exposure,^[1][3] whereas long-term soy allergy may begin in infancy with reaction to soy-based infant formula.^[4] Although most children outgrow soy allergy, some may have the allergy persist into adulthood.^[4]

IgE allergy

Symptoms may include: rash,

Non-IgE mediated allergic reactions are slower to appear, and tend to manifest as gastrointestinal symptoms, without cutaneous or respiratory symptoms.^[8][9] Within non-IgE reactions, clinicians distinguish among:^{[citation needed]}

• food protein-induced enterocolitis syndrome (FPIES)
• food protein-induced allergic proctocolitis (FPIAP)
• food protein-induced enteropathy (FPE)

The most common trigger-foods for these types of reaction are cow's milk and soy.^[9][10][11] FPIAP is considered to be at the milder end of the spectrum, and is characterized by intermittent bloody stools. FPE is identified by chronic diarrhea which resolves when the allergenic food is removed from the individual's diet. FPIES can be severe, even leading to anaphylaxis characterized by persistent vomiting 1–4 hours after an allergen-containing food, to the point of lethargy. Other symptoms may include headache and abdominal swelling (distension).^[6][11][12] Watery and sometimes bloody diarrhea can develop 5–10 hours after the triggering meal, to the point of dehydration and low blood pressure. Infants reacting to soy formula may also react to cow's milk formula.^[10][13] International consensus guidelines have been established for the diagnosis and treatment of FPIES.^[13]

Mechanisms

Conditions caused by food allergies are classified into three groups according to the mechanism of the allergic response:[14]

1. IgE-mediated (classic) – the most common type, manifesting acute changes that occur shortly after eating, and may progress to anaphylaxis
2. Non-IgE mediated – characterized by an immune response not involving immunoglobulin E; may occur hours to days after eating, complicating diagnosis
3. IgE and non-IgE-mediated – a hybrid of the above two types

In the early stages of an acute IgE-mediated allergic reaction,

Allergenic proteins from soy are named under a nomenclature decided by IUIC, which is also responsible for numbering many of the proteins. Proteins numbered by IUIC include:[18]

• Gly m 1, a hydrophobic protein
• Gly m 2, defensin
• Gly m 3, profilin
• Gly m 4, PR-10
• Gly m 5, vicilin, a cupin
• Gly m 6, legumin, a cupin
• Gly m 7, seed biotinylated protein
• Gly m 8, 2S albumin

These proteins are recognized by the immune system as antigens in susceptible individuals. As many as 8 other soy allergenic proteins are known.^[19]

Diagnosis

Diagnosis of an IgE-mediated soy allergy is based on the person's history of allergic reactions,

A diagnostic laboratory test is not available for non-IgE-mediated allergies, reflecting the obscure pathophysiology of these conditions.^[1] Instead, a person's history of symptoms is studied, and if the symptoms cease with the removal of soy, the diagnosis is made.^[22][23]

Treatment

Treatment for accidental ingestion of soy products by allergic individuals varies depending on the sensitivity of the person. An

Products containing soy protein:^[3][29][30]

• edamame (boiled or steamed immature soybean pods)
• hydrolyzed vegetable protein (HVP)
• hydrolyzed plant protein^[4]
• miso
• nattō
• okara: pulp consisting of insoluble parts of the soybean that remains after pureed soybeans are filtered in the production of soy milk and tofu
• shoyu sauce
• soy
  (Glycine max, soy albumin, soy fiber, soy flour, soy grits, soy nuts, soy sprouts)
• soybean (curd, granules)
• soybean butter (product similar to peanut butter)
• Soybean margarine (vegetable shortening)
• isolate
  )
• soy milk
• soy sauce (tamari, teriyaki sauce)
• tempeh (fermented whole soybeans)
• textured vegetable protein (used as meat substitute or extender in school and prison meal programs)
• tofu (prepared from soy milk, coagulated, pressed to remove excess water)

The following food additives may contain soy protein:

• artificial
  )
• prepared broths, including chicken broth, vegetable broth, and bouillon cubes^[30]
• vegetable gum^[29]
• fruit wax: Potentially allergenic proteins (soy, peanut, dairy, wheat) may be combined with shellac to create a shiny coating on some fruits and vegetables.^[31]
• vegetable starch^[29]
• Mono- and diglyceride^[4]
• Monosodium glutamate (MSG)^[4]

Less-allergenic soy derivatives

Many foods that contain soy are exempt from being labelled as a major allergen under US FDA regulations because they contain negligible soy protein, and individuals with a mild allergy may not experience any symptoms when exposed.^{[citation needed]}

• Highly refined soybean oil (vegetable oil): When tested, this product contains little to no soy proteins. Note that soybean oils extracted using only mechanical means (pressed or extruded) should still be avoided.^[28]
• Soy lecithin: Usually derived from soybean oil, presents minimal amounts of soy protein. However, with few exceptions, the US FDA does not exempt soy lecithin containing foods from its mandatory allergenic source labeling requirements.^[32]

Protein contact dermatitis may occur in some individuals when a product containing soy protein contacts skin.^{[citation needed]}

Cross-reactivity with dairy

Infants – either still 100% breastfeeding or on infant formula – may be prone to a combined cow milk and soy protein allergy referred to as milk soy protein intolerance (MSPI).^[37] The Nebraska government states that soy proteins from processed foods in the breast milk of nursing mothers may cause intolerance in infants.^[37] In opposition, one review stated that there was not yet sufficient clinical evidence to conclude that maternal dietary food avoidance during lactation would prevent or treat allergic symptoms from soy in breastfed infants.^[38]

Another review concluded that milk allergy occurred in 2-3% of infants, and declined with age, while soy allergy had an incidence of less than 1% in young children.^[39] The review indicated that 10-14% of infants and young children with confirmed cow milk allergy may also be sensitized to soy, but did not address whether the cause was two separate allergies or a cross-reaction due to a similarity in protein structure.^[39] There is no medication to treat MSPI or a soy sensitivity in infants, but rather the breastfeeding mother can remove soy foods from her diet.^[37]

Dosage tolerance

People with a mild soy allergy can tolerate small or moderate amounts of soy protein: the typical dose needed to induce a strong allergic response in a person with a mild soy allergy is about 100 times higher than for many other food allergens.^[40] Individuals with a severe soy allergy may experience allergic reactions to even trace amounts of soy, such as found in soy lecithin, but will rarely go into anaphylactic shock unless they have asthma, a peanut allergy or other complications.^[4]

Society and culture

With awareness about the potential for food allergy increasing during the early 21st century, the quality of life for families and caregivers was affected.^{[41][42][43][44]} Soy is one of the most widely used food additives worldwide as one of eight foods having mandatory precautionary labeling.^[45] School systems have protocols about foods with potential allergenicity.^[3] Despite these precautions, people with serious allergies are aware that accidental exposure can easily occur in family homes, school or restaurants.^[3][46] Food fear has a significant impact on quality of life.^[43][44] For children with allergies, their quality of life may be affected by peers. Bullying may occur, including threats or acts of deliberately being touched with allergenic foods.^[47] Despite these trends and concerns, most children having soy allergy during their early years will outgrow soy sensitivity.^[1]

Regulation of labelling

In response to the risk that certain foods pose to those with food allergies, some countries have established labeling laws that require food products to clearly inform consumers if their products contain major allergens or byproducts of major allergens among the ingredients intentionally added to foods. Except in Canada and Brazil, there are no labeling laws to declare the presence of trace amounts in the final product as a consequence of cross-contamination.^{[45][48][49][50]}

Ingredients intentionally added

In the United States, the

FALCPA applies to packaged foods regulated by the FDA^[50] and by the Food Safety and Inspection Service (FSIS), which requires that any ingredient be declared in the labeling only by its common or usual name.^[53][54] Neither the identification of the source of a specific ingredient in a parenthetical statement nor the use of statements to alert for the presence of specific ingredients, like "Contains: soy", is mandatory, according to FSIS.^[53] FALCPA does not apply to food prepared in restaurants.^[55][56] The EU Food Information for Consumers Regulation 1169/2011 requires food businesses to provide allergy information on food sold as unpackaged in public food outlets.^[57]

Products that are not allergen labeled

While many countries require allergen warnings on

Labeling regulations in the European Union require mandatory labeling of certain ingredients, and allow voluntary labeling, termed Precautionary Allergen Labeling (PAL) for "may contain" statements to account for product ingredients included as inadvertent, trace amount or cross-contamination during production.^[45][61] PAL labeling may be confusing to consumers, possibly due to variations of wording on labels.^[61][62][63] The European Union initiated a process to create labeling regulations for unintentional contamination, although it may not be official until 2024.^[64] The US FDA requires reporting by government inspectors and manufacturers to reduce or eliminate the potential cross-contact of product ingredients, including soy, and to state possible cross-contamination on food labels, using the words "may contain".^[51]

Genetically modified soybeans

Although there have been concerns that GMO soybeans might produce new or more allergic reactions than conventionally grown soybeans,^[65][66] a 2017 review, reporting on 20 years of analysis on GM crops, showed that allergenic proteins were unchanged in GM soybeans, indicating GM soybeans were safe, nutritious, and had similar low-allergenicity for food consumption in the general public as conventional soybeans.^[67] The same review concluded that consuming GM foods, including foods derived from GM soy, does not cause new allergies to develop.^[67]

In 2018, a

• Allergy (has diagrams showing involvement of different types of white blood cells)
• Food allergy (has images of hives, skin prick test and patch test)
• List of allergens (food and non-food)

References