Chronic complaints can have a variety of causes and these may differ from patient to patient.
Immune-mediated food protein intolerances are not thought to be causative of any disease, however, an increasing number of studies suggest that there could be a correlation between the consumption of certain foods and certain chronic illnesses. Scientific studies have found that identifying foods which appear to be causing an adverse immune response and temporarily eliminating them from the diet has resulted in an improvement or alleviation of symptoms.
It is widely understood that many chronic illnesses are associated with elevated inflammation levels and that symptoms can be exacerbated by inflammatory reactions. It is known that foods can cause elevated levels of inflammation through the build-up of IgG food specific immune complexes which are produced as a result of undigested food proteins moving into the circulation which promote the production of food-specific antibodies, and this might explain why patients report an improvement in their symptoms when they eliminate foods which have tested positive in laboratory analysis from their diet.
A study undertaken by the University of York found that 75% out of 5286 people who were suffering from a specific medical issue reported a significant improvement of their symptoms within 1 month of eliminating those foods which were highlighted positive by a food intolerance test.
When they reintroduced trigger foods back into their diet, 91% reported that their symptoms returned.
Ref: Dietary advice based on food-specific IgG results. Hardmann & Hart (2007)
Scientific research in this area is still ongoing which will improve understanding of this complex pathological process.