Are Food Intolerance Tests Unreliable? Understanding the Science Behind Different Testing Methods

When searching online, you’ll often find claims that “food intolerance tests are unreliable” – but this sweeping statement doesn’t tell the whole story. The reliability of food intolerance testing depends entirely on which type of test you’re discussing and what condition you’re trying to identify.

The Problem with Generalising Food Intolerance Tests

Not all food intolerance tests are created equal. The confusion around whether food intolerance tests are unreliable stems from people lumping together completely different testing methods that serve different purposes:

• True food intolerance tests (enzyme deficiency testing)
• Food allergy tests (IgE testing)
• Food sensitivity tests (IgG testing)

Each addresses different immune responses and symptoms that occur at different timeframes after food consumption.

Which Food Intolerance Tests Are Actually Reliable?

Highly Reliable Tests

Enzyme Deficiency Tests:

• Lactose intolerance breath test: Highly reliable for diagnosing lactose intolerance
• Fructose intolerance breath test: Accurate for fructose malabsorption
• DAO blood test: Reliable for histamine intolerance diagnosis

These tests are considered the gold standard because they measure actual enzyme deficiencies that cause food intolerance symptoms appearing 30 minutes to 2 hours after eating.

IgE Food Allergy Tests:

• Skin prick tests: Highly reliable for immediate allergic reactions
• Specific IgE blood tests: Accurate for Type 1 allergies causing symptoms within minutes to 30 minutes

The Controversial Area: IgG Food Sensitivity Testing

This is where the “food intolerance tests are unreliable” debate primarily focuses. IgG testing measures delayed food reactions occurring 3 hours to 3 days after consumption.

Why Some Consider IgG Tests Unreliable:

• Mainstream medicine has historically questioned their clinical relevance
• Symptoms are delayed, making cause-and-effect relationships difficult to establish
• Not all elevated IgG levels correlate with symptoms

Growing Evidence for IgG Testing: Recent research suggests IgG testing may be more reliable than previously thought when used correctly:

• Studies show effectiveness in migraine patients when IgG-guided elimination diets are used
• Research demonstrates benefits for Crohn’s disease, IBS, and other inflammatory conditions
• Evidence supports use in chronic conditions where conventional treatments have failed

The Critical Distinction: What Each Test Can and Cannot Do

Understanding why people claim food intolerance tests are unreliable requires knowing the limitations:

What Each Test CANNOT Identify:

• Intolerance tests cannot identify allergies or IgG food hypersensitivity
• IgE allergy tests cannot identify food intolerance or IgG food hypersensitivity
• IgG food sensitivity tests cannot identify food intolerance or IgE allergies

Common Mistakes Leading to “Unreliable” Results:

1. Using the wrong test for the wrong symptoms
2. Expecting one test to identify all food-related issues
3. Not understanding the different timeframes for reactions

When Are Food Intolerance Tests Most Reliable?

For True Food Intolerance (Enzyme Deficiencies):

Symptoms: Bloating, cramps, diarrhea 30 minutes to 2 hours after eating Reliable Tests: Breath tests for lactose/fructose, DAO blood test for histamine

For Food Allergies:

Symptoms: Sneezing, itchy eyes, skin rashes, throat swelling within 30 minutes Reliable Tests: IgE blood tests, skin prick tests

For Food Sensitivities:

Symptoms: Chronic symptoms or reactions 3 hours to 3 days later Potentially Reliable Tests: IgG testing when used with clinical assessment

The Research Supporting IgG Testing Reliability

Recent studies challenge the notion that all food intolerance tests are unreliable:

Migraine Research:

Study 1: IgG Food Sensitivity Testing with Migraine Headache Patients

Geiselman, J. F. (2019) conducted a comprehensive literature review examining the relationship between IgG food sensitivities and migraine headaches. The research found that while food sensitivities can be challenging to diagnose due to delayed symptoms (hours to days), IgG food sensitivity testing may prove beneficial for healthcare practitioners treating migraine patients. The study noted that foods such as chocolate, cheese, cow’s milk, eggs, and red wine may trigger migraines, and IgG testing could help create customisable dietary recommendations, potentially treating migraines without medications.

Reference: https://doi.org/10.1007/s11916-019-0819-4

Study 2: IgG Elimination Diet Combined with Probiotics

Xie, Y., Zhou, G., Xu, Y., et al. (2019) studied 60 patients with both migraine and irritable bowel syndrome (IBS). The researchers tested IgG antibodies against 266 food varieties using ELISA and found that IgG elimination diet combined with probiotics significantly improved both migraine and gut symptoms. The study showed reduced use of over-the-counter analgesics and increased serum serotonin levels in subjects treated with elimination diets. This research demonstrates the intricate relationship between migraine and gastrointestinal diseases.

Reference: https://doi.org/10.1155/2019/7890461

Mental Health Applications:

Study 3: Major Depressive Disorder and Food Hypersensitivity

Aucoin M., Bhardwaj S. (2019) reported on a 34-year-old female patient with Major Depressive Disorder (MDD) whose symptoms improved significantly following dietary elimination of common food allergens. When foods were reintroduced, mood symptoms worsened, and serum IgG testing results were consistent with the reintroduction challenges. This case study suggests that food hypersensitivity reactions may play a role in mental health conditions.

Reference: https://www.karger.com/Article/Abstract/502963

Study 4: Food Antigen-specific IgG and Adolescent Depression

Tao R., Fu Z., Xiao L. (2019) evaluated 184 adolescent patients experiencing their first episode of depressive disorder compared to healthy controls. The study found significantly higher serum food antigen-specific IgG positive rates in depressed patients, along with elevated histamine levels (12.35 μM vs 9.73 μM in controls). Over 80% of patients exhibited prolonged food intolerance with elevated histamine levels, leading to blood-brain barrier hyperpermeability, which has been implicated in MDD pathogenesis.

Reference: DOI:10.1016/j.gpb.2019.05.002

Inflammatory Bowel Disease Research:

Study 5: Food-specific IgGs in IBD Patients

Xiao N., Liu F., Zhou G., et al. (2018) analysed 301 IBD patients (201 Crohn’s disease, 100 ulcerative colitis) and found that food-specific IgGs against egg, milk, wheat, corn, rice, tomato, codfish, and soybean were significantly increased in Crohn’s disease patients compared to UC patients and healthy controls. Importantly, infliximab (IFX) therapy was able to down-regulate food-specific IgG-mediated immune responses in active CD patients, suggesting these antibodies play a clinically relevant role in disease pathogenesis.

Reference: DOI:10.2169/internalmedicine.9377-17

Autoimmune Disease Applications:

Study 6: Food Allergy and Ankylosing Spondylitis

Niu Q., Wei W., Huang Z., et al. (2018) studied 75 ankylosing spondylitis (AS) patients compared to 78 healthy controls. AS patients had significantly higher serum levels of beef-, crab-, and pork-specific IgG antibodies. Notably, pork-specific IgG levels were significantly and positively correlated with C-reactive protein (an inflammatory marker), suggesting that α-Gal (the predominant natural antigen in mammalian red meat) might play a role in AS pathogenesis.

Reference: DOI:10.1097/MD.0000000000014421

Obesity and Metabolic Health:

Study 7: Baker’s Yeast Antigen in Obesity

Salamati S., Martins C., Kulseng B. (2015) compared 40 obese individuals (BMI > 35) with 18 healthy controls and found that more than one-third of obese individuals (35%) showed elevated antibodies to baker’s yeast (ASCA) compared to only 5% in the control group. These antibodies were positively associated with weight, BMI, and waist circumference, suggesting that Saccharomyces cerevisiae or related antigens may play a role in obesity.

Reference: DOI:10.1111/cob.12079

Making Food Intolerance Tests More Reliable

To improve reliability:

1. Match the test to your symptoms and timeline
2. Work with healthcare providers experienced in food sensitivity
3. Use IgG testing alongside clinical assessment, not in isolation
4. Consider elimination diets to confirm test results
5. Understand that elevated antibodies don’t always equal symptoms

The Bottom Line: Are Food Intolerance Tests Unreliable?

The answer is nuanced:

• Enzyme deficiency tests are highly reliable for true food intolerances
• IgE allergy tests are very reliable for immediate allergic reactions
• IgG sensitivity tests show growing reliability when used appropriately for delayed reactions

The key is using the right test for the right condition. When people claim “food intolerance tests are unreliable,” they’re often referring to misused testing or unrealistic expectations about what a single test can reveal.

Conclusion

Rather than dismissing all food intolerance tests as unreliable, focus on:

• Understanding which test addresses your specific symptoms
• Working with knowledgeable healthcare providers
• Using test results as part of a comprehensive approach including clinical assessment and elimination diets
• Recognising that different tests serve different purposes in identifying food-related health issues

The reliability of food intolerance testing continues to improve as research advances our understanding of food-immune system interactions. While not perfect, when used appropriately, these tests can provide valuable insights for managing food-related symptoms and improving quality of life.