The gastrointestinal tract is lined by a single layer of epithelial cells connected by tight junctions — protein structures that regulate what passes from the intestinal lumen into the bloodstream. When these junctions become compromised, a condition known as increased intestinal permeability ("leaky gut") allows partially digested food proteins, bacterial endotoxins, and inflammatory molecules to enter systemic circulation, triggering widespread immune activation.
This immune response manifests as food sensitivities that seem to appear out of nowhere. Unlike true food allergies mediated by IgE antibodies (which produce immediate reactions), food sensitivities involve IgG and IgA pathways that create delayed reactions — often 24 to 72 hours after consumption. This delay makes it nearly impossible to identify trigger foods without specialized testing.
The gut microbiome — containing approximately 38 trillion microorganisms — plays a central role in digestive health. Antibiotic use, chronic stress, and processed food diets can reduce microbial diversity by up to 30%, favoring opportunistic organisms that produce inflammatory metabolites and further damage the intestinal barrier.
