The Food Inflammation Test: Going Beyond Checking for an Immunoglobulin G (IgG) Response

Written By Dr. Wayne Sodano,
Director of Clinical Support & Education For Evexia Diagnostics


The term ‘food sensitivity’ relates to a purely immune system-mediated response involving various classes of food-specific immunoglobulin molecules that can form food immune complexes.1 “These complexes can stimulate the complement cascade and localized inflammation.”2 “Food is an ideal source of antigens to trigger the enteric immune system as it provides abundant antigens to susceptible location, often presenting the same food proteins on a daily basis.”3 Additionally, undigested food proteins provide ‘feed’ for intestinal dysbiosis that can stimulate hypersensitivity of the mucosal associated lymphoid tissue. IgG (IgE) form against food proteins that cross the enterocyte barrier.4

There are four classes of IgG (IgG1 - IgG4). Their attributes include:

  • The only immunoglobulin able to pass the placental barrier
  • Smallest and most abundant antibody
  • Major antibody providing protection against invading pathogens
  • Neutralization of microbes and toxins
  • Opsonization of antigens for phagocytosis
  • Activation of complement

IgG1 and IgG3 can activate complement. “Complement activation is a multistep cascade which leads to the formation of a membrane attack complex that can kill a target cell or bacteria.”5 The complement system consists of a group of serum proteins that activates inflammation, destroys cells and participates in opsonization. Complement can be activated by a number of different foreign substances. The complement system responds in a sequential manner, producing a cascade of reactions. Most of the proteins are normally inactive, but in response to the recognition of molecular antigens (e.g. bacteria, foods, etc.) they become sequentially activated. The major protein components are C1 through C9. The complement cascade can be activated by the classical pathway, alternative pathway and lectin pathway. “Complement has been considered mainly in the systemic compartment, and serum levels of most components of the complement system, including C3, C4 and MBL (associated serine protease) are produced by the hepatocyte. Other tissues also contain cells capable of complement production: for example, endothelial and epithelial cells are also able to secrete various complement components.”6

The FIT test (Food Inflammation Test) improves sensitivity to testing for a reaction to food by measuring both IgG (1 though 4) plus complement C3d bound to immune complexes, which results in a test that generates two signals; one for the IgG plus one signal for the IC-C3d (immune-complex C3d). This type of testing vastly improves the sensitivity of food testing resulting in improved clinical outcomes.

The important benefits of the FIT test include:

  • Detection of both IgG and immune complexes
  • Increased sensitivity over just measuring IgG
  • Measures 132 foods, colorings and additives
  • Food elimination based on the FIT test reduces symptoms and is an effective tool in patient care.

When to consider ordering the FIT Test:

  • Patient does not feel well/not responding to other treatments
  • Autoimmune disease (esp. thyroiditis)
  • Digestive complaints
  • Fatigue
  • Cognitive issues (brain fog)
  • Infertility or first trimester loss
  • Cancer
  • Hormonal imbalances (uterine fibroids, endometriosis)

1 Lord RS, Brailey JA. Laboratory Evaluations for Integrative and Functional Medicine. Canada; Riverstone Group. 2008. 434.

2 Ibid.

3 Lewis CA. Enteroimmunology. Florida; Psy Press. 2-14. P. 172.

4 Ibid.

5 Ibid. p. 175

6 Lubbers R, van Essen MF, van Kooten C, Trouw LA. Production of complement components by cells of the immune system. Clinical and Experimental Immunology. 2017; 188:183-194.