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Soy allergy belongs to the group of food allergies. Increased contact with this legume means that the number of people reacting with an allergy to soy is systematically increasing. Importantly, soy allergy affects not only children (including the youngest), but also adults.

Soy allergyis more and more often diagnosed, which is probably due to the fact that more and more people have intensive contact with soy already in childhood.

Soybeans, like beans, peas and peanuts, belong to the botanical family of legumes ( Leguminosae ).

Soybeans are a cheap source of protein and therefore are used as animal feed.

In addition to classic soybeans, there are also various types of soybean products on the market, including the most famous in Poland, such as:

  • soy milk
  • soy sauce
  • tofu
  • soy chops
  • soybean pate
  • miso
  • tempeh

Soybeans themselves are famous for being an excellent source of protein, which makes them an ideal substitute for meat. It is also a good source of B vitamins and many minerals as well as dietary fiber.

Most concerns about the consumption of soybeans and their products, however, stem from the soy isoflavones they contain.

Soy allergy - isoflavones

The isoflavones found in soybeans and products derived from it are primarily daidzein and genistein. They belong to the flavonoids, i.e. polyphenols, which are very common compounds in the plant world.

They show high antioxidant activity, which means that they have the ability to scavenge free oxygen radicals in the body, thus demonstrating a protective effect on tissues against oxidative stress. As a result, regular consumption of these compounds may reduce the risk of certain diseases, including cardiovascular diseases, type 2 diabetes and certain cancers.

Isoflavones are often interchangeably called phytoestrogens because their structure resembles female sex hormones and, therefore, they show estrogenic activity.

These properties of isoflavones mean that they can be potentially used as compounds lowering the risk of hormone-dependent diseases. And in fact, research showsthat regular consumption of soy and products derived from it may reduce the risk of breast cancer in women and may be used in the prevention and relief of menopausal symptoms.

There are also studies that show that the consumption of soy and soy products also affects the male hormonal balance.

Soy allergy - threats

Soybeans have a good reputation in Europe. But there is also controversy as there are voices about the harmful effects of soy on he alth. As of 2008, three significant caveats to soybean have been mentioned.

The first is that relatively high levels of phytoestrogens in soybeans can act as endocrine disruptors and negatively impact fertility.

The second objection to soy is that reports of severe allergic reactions are increasing.

It is also said that many children who were given soy-based milk substitutes because of cow's milk allergy also developed soy allergy.

Why is soy allergic?

The allergenicity of individual soy products varies. Sufficient unchanged soy protein must be present in the diet for an allergic reaction to occur. There aresoy allergens .

For example, ripe soybeans most often containGly m 4 . In addition, significant amounts of the Gly m 4 allergen were also found in milk, yoghurt, cereals, tofu and soy protein powder, which are used in dietary supplementation.

In fermented foods such as soy sauce and miso, studies have shown no significant amounts of Gly m 4 allergen.

Nevertheless, allergy sufferers should be careful with these products. Depending on the production method,fermented soybeansmay also contain sufficient soy allergen to cause an allergy.

Soy allergy - types

There are two types of soy allergies - primary and secondary.

Primary allergy to soyis when our body is sensitized after the first contact with its proteins, which are strong allergens, but it does not cause any noticeable disease symptoms .

As a result of repeated exposure to these allergens, the body's immune system reacts with overstimulation and a full-blown allergic reaction develops.

In an allergic person, re-consumption may cause an allergic reaction, which manifests itself:

  • diarrhea
  • nausea
  • vomiting
  • deterioration of the appearance of the skin

In extreme cases, anaphylactic shock may also occur. It is most common in infants and young children who are taking soy-based milk replacers because of an allergy to cows' milk.

The main allergens in primary soy allergy are proteinsGly m 5andGly m 6 . The latter is thermostable and is processed for a long time by the body.

Secondary soybean allergyoccurs in people who suffer from other types of allergies - most often these are patients allergic to birch pollen.

The so-calledcross-reaction , which takes place between the soybean and birch allergens, plays a major role in this case.

The occurrence of a cross-reaction results from the fact that both allergens are structurally similar, which means that our immune system, which is responsible for identifying compounds that are harmful to us, may confuse them with each other.

In this situation, symptoms of soybean allergy occur after the first contact with it. Gly m 4 soy protein has a strong chemical similarity to the allergenic birch pollen protein.

Gly m 4 is thermostable and is no longer detectable after four hours of cooking. In birch pollen allergy sufferers, an allergic reaction may already occur during the first consumption of a soy product, as the sensitization is not caused by the soy product, but by pollen.

An allergic reaction occurs unexpectedly. The symptoms are similar to the primary allergy. May be

  • swollen lips
  • burning in the mouth
  • swelling of the tongue and larynx which may cause shortness of breath

In extreme cases, anaphylactic shock may also occur.

Soy allergy - symptoms

The symptoms of soy allergy are not unique to soy. Similar ailments occur in almost all types of food allergies. Most often, patients complain of:

  • lack of appetite or its marked reduction
  • nausea
  • vomiting
  • diarrhea (sometimes it can be diarrhea with some blood)
  • burning sensation in the mouth after eating certain foods
  • redness around the lips
  • swollen lips and tongue

In children, especially small ones, an allergy to soy may be additionally manifested by a lack of proper weight gain, as well as by the restless behavior of the child during feeding and reluctance to eat. It is also possible to slow down or even inhibit a child's development, both physically and mentally.

In the case of soybean allergy, the following occurrence is less frequent:

  • skin lesions (mainly in the form of papular eruptions, redness combined with itchy skin, swelling)
  • headaches
  • irritation
  • sleepiness and constant fatigue
  • respiratory symptoms (dyspnoea, asthmatic attacks)

Soy allergy - diagnosis

The diagnosis of soy allergyrequires the exclusion of other causes of the patient's symptoms. It is not easy, because the symptoms of most food allergies are very similar to each other, and sometimes even identical.

It is for this reason that a properly conducted medical history plays such an important role. During such a conversation, the doctor asks not only about the type of our ailments, but also about the circumstances in which they appear or worsen, as well as about similar symptoms occurring in our family members.

To confirm the initial diagnosis, performprovocation tests , which are also often called provocation and elimination tests. These tests are performed in two stages. In the first one, the patient is administered a substance that is suspected of causing discomfort. In the second, this substance is excluded from the diet.

During the examination, the patient's symptoms are observed - if, after contact with a given substance, the patient develops any side effects, and they disappear or decrease after the elimination of this substance, the diagnosis has been confirmed.

So far, provocation trials are the only way to make a confident diagnosis of soy allergy. There are no laboratory tests enabling such a diagnosis to be made unequivocally.

Doctors often order the level of IgE antibodies, but this test only allows to identify the allergic basis of the changes. The survey does not answer the question of what is responsible for their occurrence.

Sometimes it is also ordered to measure the level of IgG antibodies specific for soy allergens. However, from a medical point of view, this test is of little use, as the presence of these antibodies is only indicative of exposure to soy (to which all of us are exposed), not of a soy allergy.

During the diagnosis of soy allergy, the doctor may also order skin tests to exclude rather than confirm the presence of this allergy. The test consists in administering a solution containing a properly prepared allergen under the skin and observing the appearance of skin changes. If such changes occur, there is a diagnosis of this type of allergyprobable, but not certain, but the lack of such changes on the skin excludes the possibility of allergy to soy proteins.

Soy allergy - treatment

The only effective and primary treatment for soy allergy, as with all other food allergies, is to avoid plant-based foods, i.e. follow aelimination diet .

Following such a diet, i.e. completely excluding seeds of this plant from our daily diet, is not so easy. This is mainly because soybeans are commonly added to many foods, which is not always indicated on the food label.

About the authorAnna Jarosz A journalist who has been involved in popularizing he alth education for over 40 years. Winner of many competitions for journalists dealing with medicine and he alth. She received, among others The "Golden OTIS" Trust Award in the "Media and He alth" category, St. Kamil awarded on the occasion of the World Day of the Sick, twice the "Crystal Pen" in the national competition for journalists promoting he alth, and many awards and distinctions in competitions for the "Medical Journalist of the Year" organized by the Polish Association of Journalists for He alth.

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Allergies