Food sensitivity testing has become an increasingly important tool in modern health care, especially considering that these subtle yet impactful reactions may affect up to 65% of the American population. Unlike food allergies that cause immediate and often dramatic symptoms, food sensitivities can be more elusive, quietly contributing to chronic inflammation and systemic health problems over time. These hidden triggers can lead to a variety of persistent health issues, from digestive disturbances to headaches and fatigue. Identifying specific food sensitivities through diagnostic testing can help alleviate these symptoms.
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Understanding Food Sensitivities
Food sensitivities are a type of immune-mediated adverse reaction to dietary proteins. They are mediated by IgG antibodies and can cause a wide variety of symptoms up to several days after exposure.
Some of the most common symptoms associated with food sensitivities include:
- Gas
- Bloating
- Abdominal pain
- Constipation
- Diarrhea
- Skin problems
- Joint pain
- Headaches
- Anxiety
- Depression
- Fatigue
Over time, chronic exposure to food sensitivities can cause chronic, low-grade systemic inflammation. Chronic inflammation has been identified as a driver of chronic diseases, including autoimmune diseases, cardiovascular disease, diabetes, and cancer.
To better understand food sensitivities, it can be helpful to recognize how they differ from food allergies and intolerances:
Food allergies are IgE-mediated immune responses that cause immediate adverse reactions (seconds to minutes) after exposure to the culprit food. Symptoms associated with food allergies include hives, itching, shortness of breath, difficulty swallowing, and anaphylaxis. (19)
Food intolerances are non-immune-mediated reactions that result from the body's inability to digest certain food components due to enzyme deficiencies or other non-immune-related factors (13). For example, lactose intolerance occurs when digestive symptoms such as abdominal pain, bloating, and diarrhea arise after consuming dairy products due to insufficient levels of the lactase enzyme needed to break down lactose.
Common Triggering Foods
According to the American College of Allergy Asthma and Immunology, the following nine foods are responsible for causing 90% of adverse food reactions in the United States:
- Eggs
- Milk
- Peanuts
- Tree nuts
- Fish
- Shellfish
- Wheat
- Soy
- Sesame
It's important to remember, however, that just because these foods are the most common triggers, they are not universal to everyone. This is why testing can be so informative – it takes the guesswork out of identifying food triggers in symptomatic individuals.
For example, a study published in 2000 by an otolaryngologist demonstrated significant improvement in chronic symptoms (including asthma, coughing, fatigue, headaches, digestive symptoms, nasal congestion, and skin problems) for patients unresponsive to other treatments. After eliminating foods identified through IgG food sensitivity testing, 70% of patients saw a 75-100% improvement in symptoms. The most common sensitivities were cow's milk, garlic, mustard, egg yolk, tea, and chocolate. (10)
Biomarkers in Food Sensitivity Testing
Biomarkers are measurable indicators used to diagnose and monitor various health conditions. Here's a brief explanation of the key biomarkers measured to identify food sensitivities:
Immunoglobulin G (IgG)
IgG antibodies account for 80% of serum antibody levels. IgG blood tests are the most common for food sensitivities because they are the most studied in this context. Elevated levels of IgG antibodies against a specific food suggest the presence of an immune response and sensitivity to that food.
Immunoglobulin G4 (IgG4)
IgG4 is a subclass of IgG that elevates in response to chronic exposure to non-infectious allergens. Some evidence suggests that IgG4 antibodies can indicate food sensitivity. For example, one study found that patients with IBS experienced improvements in digestive symptoms after three months by eliminating foods that caused elevated IgG4 antibody levels.
Immunoglobulin A (IgA)
IgA antibodies are found in mucous membranes, particularly in the gastrointestinal and respiratory tracts. Elevated IgA levels against certain foods can indicate that a particular food induces a mucosal immune response and localized inflammation.
Immunoglobulin E (IgE)
You may consider ordering a panel that measures IgE antibodies to rule out allergic reactions to foods that can sometimes mimic food sensitivity symptoms. High levels of IgE antibodies indicate an acute immune response to specific allergens, necessitating strict avoidance of the offending foods.
Complement (C3d)
C3d is a fragment of the complement system, a part of the immune system that enhances antibodies' ability to clear pathogens by upregulating inflammation. In the context of food sensitivity testing, the presence of C3d alongside IgG or IgA antibodies can indicate a particular food is causing inflammation. According to one study, patients who followed a C3d/IgG-specific dietary elimination experienced a significant reduction in their symptoms.
If you're interested in testing for food sensitivities, consider doing so with one of these panels:
- foodANALYZER IgG Food Sensitivity by Access Med Labs
- IgG Food MAP with Candida + Yeast by Mosaic Diagnostics
- 96 IgG Food Sensitivity Panel by Alletess Medical Laboratory
- P88-DIY Dietary Antigen Test by Precision Point
- 96 General Food Panel: IgA/IgG/IgG4 by US BioTek
- Food Allergy and Sensitivity Testing (FAST 88 Foods: IgE, IgG4, IgG, C3b/d) by Infinite Allergy Labs
- FIT 132 by KBMO Diagnostics
Types of Lab Tests for Food Sensitivities
Food sensitivity tests can be conducted using different methods of blood collection: venipuncture or blood spot. Both methods are effective for identifying food sensitivities, and the choice often depends on patient preference, convenience, and the specific tests required.
Venipuncture
Venipuncture involves using a needle to draw blood from a vein, typically in the arm. This method collects a larger blood volume, allowing for more comprehensive testing and multiple assays from a single sample. Venipuncture is highly accurate and reliable but requires a trained healthcare professional to perform the procedure, making it less convenient for some patients.
Blood Spot
The dried blood spot method involves pricking the finger with a lancet to collect small drops of blood onto a filter paper or into a small vial. This method is minimally invasive, can be performed at home, and is convenient for younger patients or those who may have difficulty accessing a healthcare facility. However, the smaller blood volume may limit the number of tests that can be performed.
The Role of Elimination Diets
Elimination diets remain the gold standard for identifying food sensitivities. The benefit of elimination diets is that they are both diagnostic and therapeutic. Four steps are involved in the process:
Plan
First, determine which foods you are going to eliminate. This should be individualized based on laboratory testing, clinical history, and symptomology. To be successful during an elimination diet, patients should take the time to create meal plans, gather necessary pantry items, and remove tempting foods from the kitchen. Working with a nutritionist, dietician, or other qualified healthcare provider is helpful to ensure patients can meet their dietary needs while restricting certain foods from their diet.
Avoid
Once you are adequately prepared, begin the elimination diet. The length of elimination diets can vary, but food avoidance is recommended for at least three weeks, as the circulating half-life of IgG is 10-21 days. Patients should mindfully observe how their symptoms change during this phase.
Challenge
This step is perhaps the most important of the elimination diet. Patients should be advised to reintroduce each food previously eliminated with a three-day challenge. Each food challenge should be performed in the following way:
- Day 1 (Reintroduction): Eat a serving of food with each meal
- Day 2-3 (Observation): Eliminate selected food as you observe for adverse reactions
Foods that are reintroduced without problem can be reincorporated into the patient's diet regularly. If a food causes symptoms at any point during the food challenge, it should continue to be avoided.
Maintain
Based on the results of the food challenge, patients should customize their diet to their tolerances and preferences. Foods that induced symptoms during the challenge can be rechallenged again in 3-6 months.
Patients should continue working with their doctors to ensure they meet their nutritional needs with balanced dietary plans. Supplements may be recommended to prevent nutrient deficiencies associated with the long-term elimination of certain foods.
At-Home vs. Clinical Testing
The accuracy of food sensitivity testing has been a topic of significant debate within the medical community. Many health organizations, such as the American Academy of Allergy, Asthma, and Immunology, advise against using IgG tests to diagnose food sensitivities due to a lack of robust scientific evidence supporting their reliability (24). These organizations argue that elevated IgG levels indicate food exposure rather than an adverse reaction. This ambiguity can lead to unnecessary dietary restrictions and potential nutritional deficiencies.
For patients opting for food sensitivity testing, clinical testing is generally preferred over at-home test kits available without a doctor's order. Doctor-ordered tests use validated and clinically approved testing methods, ensuring higher accuracy and reliability compared to many over-the-counter kits. In contrast, at-home test kits often lack rigorous validation and quality control. Results may be invalid, leading to misguided dietary changes and unnecessary anxiety. (15)
Interpreting Test Results
Interpreting food sensitivity test results requires careful consideration and should involve a healthcare provider to ensure accurate understanding and appropriate action. Elevated levels of measured antibodies, such as IgG, indicate an immune response to specific foods. However, these antibodies alone do not always signify a problematic sensitivity.
Healthcare providers can help interpret the results in the context of the patient's overall health, medical history, and symptom patterns. They can distinguish between significant and insignificant findings. Various factors, such as recent illnesses, medications, or other dietary components, can impact test results. A provider can help identify and account for these variables to avoid false conclusions. From there, patients should collaborate with their healthcare team to develop a personalized elimination diet and plan for food reintroductions. Regular follow-up will help ensure that dietary changes are effective and sustainable.
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Key Takeaways
- Food sensitivities play a significant role in the health and well-being of many individuals, often contributing to a range of inflammation-driven health issues. Identifying these sensitivities can help manage symptoms and improve overall health.
- The validity of food sensitivity testing is an important factor to consider. Working with a healthcare provider who can order a clinically validated and accurate test panel ensures test results are correctly interpreted and effectively acted upon.
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