Does a 2-year adherence to a carnivore diet affect the accuracy of Immunoglobulin G (IgG) food sensitivity testing in an adult with a history of gastrointestinal issues or autoimmune disorders?

IgG Food Sensitivity Testing After Prolonged Carnivore Diet

IgG food sensitivity testing will be significantly affected—and essentially invalidated—by two years of adherence to a carnivore elimination diet, as IgG antibodies to foods require ongoing dietary exposure to remain detectable. 1

Why the Test Becomes Unreliable

IgG antibodies are exposure-dependent markers, not true indicators of food intolerance. The British Society of Gastroenterology explicitly states that IgG antibodies have "poor specificity and applicability" for identifying problematic foods, noting that 87% of IBS patients tested positive for IgG antibodies to yeast despite these foods rarely causing symptoms on rechallenge. 1

Mechanism of Test Invalidation

• Antibody levels decline with food avoidance. When specific foods are eliminated from the diet for extended periods, the corresponding IgG antibodies naturally decrease or disappear entirely, as these antibodies reflect recent dietary exposure rather than true immunologic sensitivity. 1

• A carnivore diet eliminates most testable antigens. After two years of consuming only animal products, you will have minimal to absent IgG antibodies to plant-based foods (grains, legumes, fruits, vegetables, nuts), dairy (if excluded), and other commonly tested items—not because you tolerate them, but because you haven't been exposed to them. 2

• The test cannot distinguish between tolerance and non-exposure. A negative or low IgG result after prolonged elimination could mean either: (1) you genuinely tolerate the food, or (2) you simply haven't eaten it recently enough to mount an antibody response. 1

Clinical Evidence Against IgG Testing

Multiple gastroenterology societies recommend against using IgG antibody testing for food elimination decisions. 1

• The British Society of Gastroenterology conducted an RCT showing only modest symptom improvement (10% greater reduction) with IgG-guided elimination versus sham diet, and concluded that "food elimination diets based on IgG antibodies are not recommended" due to poor specificity. 1

• The American Gastroenterological Association notes there is "insufficient evidence to support routine use" of IgG testing in clinical practice, with only "limited, older data" suggesting any predictive value. 1

• Even when IgG testing showed some correlation with symptom improvement in one 150-patient RCT, the effect was modest and the test's poor specificity (detecting antibodies that don't correlate with actual food reactions) undermines its clinical utility. 3

What Happens If You Test Now

Testing after two years on carnivore will likely show:

• Absent or very low IgG antibodies to all eliminated plant foods (grains, vegetables, fruits, legumes, nuts, seeds), regardless of whether you actually tolerate them. 1

• Potentially elevated IgG antibodies to meat and fish products you've been consuming regularly, which paradoxically may indicate tolerance rather than sensitivity, as one study found higher IgG to meat/fish correlated with insulin resistance but not necessarily food intolerance. 4

• Misleading negative results that could falsely suggest you tolerate foods that might actually trigger symptoms upon reintroduction. 1

Alternative Approaches for Food Reintroduction

If your goal is identifying problematic foods after carnivore elimination, use systematic reintroduction with symptom tracking instead of IgG testing. 1

Structured Reintroduction Protocol

• Reintroduce one food at a time in isolation, consuming it for 3-5 days while monitoring for symptoms (gastrointestinal distress, fatigue, joint pain, skin changes, mood alterations). 1

• Wait 3-5 days between new food introductions to allow delayed reactions to manifest and symptoms to clear before testing the next food. 1

• Track objective measures: stool frequency/consistency, abdominal pain severity (0-10 scale), bloating, energy levels, and any extraintestinal symptoms. 1

• Consider starting with less allergenic foods (well-cooked vegetables, white rice) before progressing to common triggers (dairy, gluten-containing grains, legumes, nightshades). 1

Important Caveats

Do not confuse IgG testing with IgE testing for true food allergies. IgE-mediated allergies (like alpha-gal syndrome causing reactions to mammalian meat) are genuine immunologic conditions requiring different testing and management, including potential epinephrine autoinjector prescription. 1

If you have a history of autoimmune disorders, consider celiac disease testing before gluten reintroduction. This requires specific IgA tissue transglutaminase (tTG) and total IgA testing, not IgG testing, and must be done while consuming gluten. 1, 5, 6

Carnivore diet adherents in one survey (n=2029) reported high satisfaction and few adverse effects, but long-term nutritional adequacy and cardiovascular effects remain uncertain. If reintroducing foods, prioritize nutrient-dense options to address potential deficiencies from prolonged restriction. 2