Food-Specific IgG Guided Elimination Diet; Role in Irritable Bowel Syndrome?

Abstract

Functional gastrointestinal disorders (FGIDs) are disorders of the digestive system in which symptoms cannot be explained by the presence of structural or tissue abnormality 1. Irritable bowel syndrome (IBS) is one example of a FGID and, with prevalence ranging from 12-30% in the general population, IBS is one of the most common gastrointestinal disorders 2. IBS is typically characterised by abdominal pain, abdominal distension (bloating) and abnormal bowel habits and the diagnosis of IBS is based on symptoms and the exclusion of other organic diseases. Subtypes of IBS are defined by symptoms and a distinction is made between IBS with pain or discomfort and predominant constipation, IBS with diarrhoea, and mixed IBS. There is no cure for IBS and management of IBS can only focus on symptom relief 3. This article reviews the evidence behind a potential role for IgG-guided elimination diet for those with IBS. Pathogenesis The pathogenesis of IBS is very complicated and multifactorial and management remains clinically challenging. IBS affects quality of life and imposes a considerable burden on patients, doctors and the healthcare system and still the overall aetiology of IBS remains elusive. In saying that, there is a growing understanding of potential mechanisms involved in IBS, and it is known that the two main risk factors for development of IBS are gastrointesti-nal inflammation and psychological distress 4 ; IBS is increasingly viewed as a low grade inflammatory disorder 5. Multiple factors contribute to the pathogenesis of IBS including gut hyper-perme-ability ("leaky gut"), intestinal microbiota (the microbiological environment in the gut or gut flora) and food intolerance. These factors in turn are thought to evoke abnormal responses in key regulators of gut function; regulators of gut function including the hypothalamus-pituitary and gut-brain axes, enteric nervous system and the immune system 3,6. Recently, Zhang et al have strongly argued that mast cells (which mediate immune responses) are the "remarkable players" in the pathogenesis and pathophysiology of IBS. Mast cell activation can be triggered by many factors, both immune and non-immune, including gut flora imbalance and factors linked to psychological stress. On activation, mast cells have been linked to the chronic pain, inflammation, disturbed gut motility and the gut permeabil-ity that IBS is associated with 7. There is evidence that mast cells can be activated through IgG-dependent mechanisms 8,9 and this is significant, not only in IBS, but in relation to the inflammatory component of other disorders 10. Studies have shown that people with IBS have higher levels of food-specific IgG antibodies in their blood; much more than in "healthy" subjects 11,12,13. This suggests that the permeability of gut is increased, raising the possibility that undigested food proteins could be responsible for the inflammation and hypersensitivity observed in many patients with IBS. One recent report showed that when those with IBS were challenged with foods to which they reported food intolerance this resulted in epithelial breaks and increased inter-villous spaces, indicative of increased intestinal permeability 14 ; this and other studies have suggested a causative effect of food in increased gut permeability in IBS 3. This may also explain why increases in gut permeability brought about by alcohol, stress, diet, inflammation or changes in the gut flora have not only been implicated in IBS but also in other low grade inflam-matory conditions such as obesity, fatigue, rheumatoid arthritis, and fibromyalgia. Elimination diet In 2004, to date the most rigorous study involving food-specific IgG guided elimination diet and IBS, was reported by Whorwell's team in Manchester, UK, in collaboration with the York Universi