Food intolerance (FI) is an adverse reaction to food caused by non-immune mechanisms, mainly related to digestive enzyme deficiencies (e.g. lactase deficiency), metabolic abnormalities (e.g. impaired absorption of fructose) or toxicity of food components (e.g. histamine). Unlike immune-mediated food allergy, FI symptoms are usually delayed (hours to days after ingestion) and mild, but are difficult to diagnose and manage clinically due to the complexity and variety of mechanisms that affect approximately 20% of the world's population.