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What are the Causes, Symptoms & Treatment for Soy Intolerance?
Updated on September 21, 2023
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Diet / Weight Loss
What are the Causes, Symptoms & Treatment for Soy Intolerance?
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Soy intolerance and soy sensitivity are when the body struggles to digest or reacts negatively to soy products.

A soy intolerance happens when your digestive system finds it difficult to digest soy. The symptoms that arise include:

  • Bloating
  • Gas
  • Diarrhea

On the other hand, a soy allergy occurs when your immune system overreacts to soy.1 It mistakenly activates a defensive response to soy. This can lead to symptoms such as: 

  • Vomiting
  • Stomach cramps
  • Indigestion

When individuals have either of these conditions, consuming soy-based foods can lead to discomfort and other unwanted symptoms.

Understanding the signs and symptoms of soy intolerance and sensitivity can help you better comprehend how your body responds to soy consumption.

What Does a Soy Intolerance Feel Like?

Soy intolerances often feel uncomfortable and painful, especially in the abdominal area.

Soy intolerance involves the difficulty in breaking down soy. Unlike a food allergy, the immune system does not produce antibodies in response to soy.2

Individuals who have a soy intolerance can often consume small quantities of soy.

However, when soy is consumed in large quantities, soy intolerance can lead to various unpleasant symptoms. Common signs include:

  • Digestive Issues – Indigestion, gas, diarrhea, or stomach cramps may occur as the body struggles to break down soy.
  • Nausea and Vomiting – Feeling queasy or experiencing an upset stomach after soy consumption is not uncommon.

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What are the Symptoms of Soy Sensitivity?

The symptoms of soy allergies can be mild or severe. Common signs of soy allergies include:1

  • Digestive Discomfort – Similar to soy intolerance, you may experience indigestion, stomach cramps, or diarrhea.
  • Skin Issues – Eczema, redness, hives, or general skin irritation can be linked to soy sensitivity.
  • Respiratory Problems – Some individuals may notice mild respiratory issues like a cough or a tight throat.
  • Dizziness or Confusion – Feeling mentally foggy, dizzy, or confused might be a symptom of soy sensitivity.3
  • Anaphylaxis – In extreme cases of soy allergies, individuals may experience anaphylaxis. This involves difficulty breathing, increased heart rate, drop in blood pressure, dizziness, and confusion. Anaphylaxis can be life-threatening if not addressed immediately.

Soy sensitivity can sometimes manifest as a food allergy. An allergy is the immune system's response to foreign substances deemed a threat. Often, these substances are harmless to most people.4

Soy allergies are most common in infants and children.5 Most people can outgrow soy allergies by the age of 3. However, a soy allergy can develop at any age.1

If you suspect you have soy intolerance or sensitivity, it's essential to consult with a healthcare professional for proper evaluation and advice. They can guide you in managing your diet and finding suitable alternatives to soy products.

How is Soy Intolerance and Soy Sensitivity Diagnosed?

To diagnose soy intolerance and soy sensitivity, doctors use a combination of methods:1,6

  • Medical History – Your doctor will ask questions about your symptoms and diet to identify potential patterns. They can also ask about your family history, if you have over-the-counter medications, or when you noticed your symptoms began appearing.
  • Elimination Diet – You might be asked to avoid soy for a while to see if your symptoms improve.
  • Food Diary – Keeping a record of what you eat and any symptoms can help in the diagnosis.
  • Graded Oral Challenge – In some cases, you might be given small amounts of soy under medical supervision to observe allergic reactions. A graded oral challenge can take approximately four hours.
  • Blood Tests – Blood tests can measure specific antibodies called IgE antibodies related to soy allergies. A laboratory will analyze the results of these tests.
  • Skin Prick Test – Tiny amounts of soy extract are applied to your skin with a small needle to check for allergic reactions. This test takes less than an hour.

How Can I Test for a Soy Allergy at Home?

While some at-home tests check for soy allergies, some may not feel they’re fully accurate. Others may feel that their home environment is not controlled enough to test properly either.

It’s important to note that many at-home tests are actually very reliable and accessible. They’re also handy in case you don’t have time to go to a professional lab.

There are two reliable types of tests you can take at home to determine if you have a soy allergy:

  1. IgE Home Tests – These test for specific antibodies.7 They require a small blood sample to be examined for IgE antibodies.
  2. Skin Tests at Home – It is recommended to conduct a skin prick test with medical supervision. This can help lower risks and increase accuracy.8 However, at-home skin tests can be conducted, provided that the instructions are followed closely and correctly. It is best to reach out to a medical adviser for any questions or clarifications about the process.

For further testing and interpreting results, it's crucial to see an allergist or healthcare specialist.

Remember, while lab tests are not perfect either and can sometimes lead to false positives, self-diagnosis comes with its own risks. Make sure you carry out at-home tests properly and according to all the instructions.

If you’re not feeling confident about home testing, a healthcare professional can provide accurate and safe testing for soy allergies or intolerances.

What Foods to Avoid if You Are Soy Intolerant

If you have soy intolerance, it's essential to steer clear of certain foods that contain soy or soy-based ingredients:1

  • Soybeans – Avoid whole soybeans and edamame.
  • Tofu – Tofu is made from soybean curds and should be avoided.
  • Soy Milk – Opt for non-dairy milk alternatives like almond or oat milk instead.
  • Soy Sauce – Regular soy sauce contains soy. Consider replacing them with alternatives like tamari or coconut aminos.
  • Miso – This paste is made from soybeans and is a no-go for soy-intolerant individuals.
  • Tempeh – It's a fermented soy product and should be avoided.
  • Soy-based Processed Foods – Check labels for soy flour, soy protein, soy lecithin, or other soy derivatives.

What Foods Can Cause a Reaction to Soy?

Make sure to check whether the food you eat has soy content.

For example, these foods can still cause an allergic reaction due to hidden soy content:6,9

  • Baked Goods – Some bread, cookies, and cakes may contain soy flour or additives.
  • Processed Meats – Sausages, deli meats, and vegetarian meat substitutes might have soy-based fillers.
  • Cereals and Granola Bars – Check labels, as some may contain soy protein or additives.
  • Fast Foods – Sauces, dressings, and fried items could contain soy or soybean oil.
  • Desserts Soy ice cream, soy pudding, and soy yogurt should be avoided.
  • Sauces – Sauces such as teriyaki, shoyu, and Worcestershire may contain soy. Some marinades, gravies, and dressings might also have it in small amounts.

What Foods are High in Soy?

Some foods are naturally high in soy. Avoid them if you have soy intolerance:

  • Soy Protein Isolate – Found in protein bars, shakes, and supplements. Though they come from soy, they have been linked to cancer growth.10
  • Soy Nuts – Roasted soybeans are often used as snacks.
  • Soy-based Ice Cream – Some non-dairy ice creams use soy as a base.9
  • Energy Bars – Certain energy bars may contain soy protein.
  • Soy Oil – Used in cooking and salad dressings.

Always read food labels carefully. Be aware of possible cross-contamination in food preparation. Being mindful of your diet will help manage soy intolerance and prevent uncomfortable allergic reactions.

How Do You Treat Soy Sensitivity?

Avoiding soy is the only way to prevent symptoms associated with soy sensitivity.1 

However, there are various ways to manage and treat soy sensitivity.

Treating soy sensitivity involves simple steps to manage symptoms:3

  • Avoid Soy – Eliminate soy and soy-based products from your diet.
  • Read Labels – Check food labels for hidden soy ingredients.
  • Dietary Alternatives – Replace soy with non-soy options like almond or coconut milk.
  • Medications – Over-the-counter antihistamines can help with mild reactions.
  • Consult a Dietitian – Get expert advice on soy-free meal planning.
  • Monitor Symptoms – Keep track of how your body responds to different foods.
  • Epinephrine – Epinephrine is the initial treatment for anaphylaxis. Your doctor may prescribe an epinephrine auto-injector in case of an anaphylactic shock. They will teach you how to use this device.

Can You Overcome a Soy Intolerance?

In some cases, soy intolerance might improve over time. Some factors can influence this:

  • Individual Variability – Tolerance levels vary; some may tolerate small soy amounts. Try avoiding soy food for a few months, then gradually reintroduce it in small amounts.11 You can start with a teaspoon of soy milk.
  • Children vs. Adults – Children might outgrow soy intolerance12 as their immune systems get stronger.13 Most infants with soy intolerance can outgrow them by the age of three.5 However, some adults have a soy intolerance for the rest of their life.
  • Lifestyle Changes – A healthy lifestyle could positively impact soy tolerance. Make sure to be mindful of the food you consume to prevent ingesting unknown sources of soy.
  • Medical Monitoring – Work with a healthcare professional to track progress. They can help monitor and manage your soy intolerance.

Common Questions About Soy Intolerance and Soy Sensitivity

Why am I Suddenly Sensitive to Soy?

It is not always clear why allergies may arise.14 However, several factors could trigger sudden soy sensitivity, such as:15

Gut Health – Changes in gut bacteria can influence food sensitivities.16
Age – Food sensitivities can develop or change as you age. This is because as you age, your immune system naturally weakens.17
Genetics – If you have a family history of soy sensitivity, you may be more likely to have it.13

Can Soy Cause Gas?

Yes, soy can cause gas for some people. Three factors can contribute to this:

Fermentation: Undigested soy can be fermented by gut bacteria, leading to gas.18
High Oligosaccharides: Soy contains complex carbohydrates19 that contribute to gas.
Individual Differences: Some people are more sensitive to gas-producing foods like soy.

Can You Eat Eggs with a Soy Allergy?

Some people believe that if you eat eggs, it can trigger your soy allergy. This is because most chickens eat soy from their feed.

However, having a soy allergy doesn't mean you must avoid eggs. In most cases, people with a soy allergy can eat eggs.

For example, soy and eggs are distinct allergens.20 It's unlikely that cross-reactivity can trigger a soy allergy.

It's best to consult your doctor or allergist before reintroducing eggs into your diet.

How Serious is a Soy Allergy?

Soy allergies can vary in severity. Some individuals may experience minor symptoms such as rashes or an upset stomach. Other cases can trigger life-threatening reactions like anaphylaxis.

The reactions to soy allergies may differ per individual. Always be cautious with soy consumption. Consult a professional to prevent any adverse reactions from consuming soy.

What is the Difference Between Soy Protein and Soy?

Soy and soy protein are related but not the same.

Soy refers to whole soybeans or soy-based products. Meanwhile, soy protein is an isolated protein extracted from soybeans. 

Unfortunately, soy protein isolate is not as healthy as whole soy. Soy protein isolate is often used in processed foods and supplements. It has been shown to increase insulin-like growth factors linked to cancer growth.10

Always seek medical advice if you suspect soy sensitivity or experience adverse reactions after consuming soy products.

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Updated on September 21, 2023
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20 sources cited
Updated on September 21, 2023
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  2. Soy Allergy”. Baptist Health.
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  6. Soy Allergy”. Allergy & Asthma Specialists of North Florida.
  7. Blood Test: Allergen-Specific Immunoglobulin E (IgE)”. Nemours KidsHealth.
  8. Allergy skin tests”. Mayo Clinic.
  9. Soy”. Food Allergy Canada.
  10. Soy and Health”. Physicians Committee for Responsible Medicine. 
  11. Allergic To Soy?”. Weil.
  12. Soy Allergy”. Food Allergy Research and Education. 
  13. What Are Common Risk Factors for Allergies?”. Ear, Nose and Throat of Georgia. 
  14. Suddenly Have Allergies As An Adult? Here's What You Need To Know”. Henry Ford Health.
  15. Allergies and the Immune System”. Johns Hopkins Medicine.
  16. Gut Microbes May Be Key to Solving Food Allergies”. Scientific American.
  17. Midlife intolerances: signs you may be developing a food intolerance or allergy”. Sanitarium.
  18. Nourish Your Digestive System”. North Dakota State University.
  19. Plant based – A simple, trendy food for healthy eating”. MedPark Hospital.
  20. Ask the RD: If I’m Allergic to Eggs, Is Soy OK?”. MyFitnessPal.
Cristine Santander
Cristine Santander
Content Contributor
Cristine Santander is a content writer for KnowYourDNA. She has a B.S. in Psychology and enjoys writing about health and wellness.
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