Twenty-five percent of patients diagnosed with irritable bowel syndrome (IBS) are actually hypersensitive to specific foods, according to a study in the November issue of Clinical Gastroenterology and Hepatology.
IBS and food hypersensitivity reactions have many overlapping symptoms, including abdominal pain and discomfort, bloating, and altered bowel habits, making it challenging to distinguish between the disorders. However, symptoms of food hypersensitivity are reduced or disappear when patients are placed on diets that specifically omit certain foods (elimination diets).
Antonio Carroccio et al. investigated the frequency of food hypersensitivity among 160 patients who were diagnosed with IBS based on Rome II criteria. The patients were placed on elimination diets (without cow’s milk and derivatives, wheat, egg, tomato, and chocolate) for 4 weeks, along with 40 patients with other gastrointestinal diseases and 50 healthy individuals (controls).
Symptoms of 70 of the IBS patients (44%) improved on the diet, and 40 (25%) were found to have specific hypersensitivities to cow’s milk or wheat, based on testing. Other causes of IBS-like symptoms were found to include egg (18 cases), tomato (14 cases), soy (5 cases), yeast (6 cases), pork (3 cases), prawn (4 cases), fish (5 cases), celery (3 cases), olive (2 cases), nuts (3 cases), carrot (2 cases), and meat (3 cases).
Carroccio et al. analyzed fecal samples from the patients with sensitivities to wheat or cow’s milk, and found that they had higher levels of trypase and eosinophil cationic protein (ECP)—markers of intestinal inflammation—than the patients with IBS or the healthy controls. In fact, the fecal levels of ECP were 2-fold higher from patients with food hypersensitivity than from IBS patients or the healthy controls.
All the study participants were followed for 2 more years and reassessed at 6-month intervals. The patients found to have food hypersensitivities continued to follow diets that excluded the foods that caused their symptoms, and all reported persistent disappearance of symptoms or consistent improvements. Their symptom scores, which were a mean value of 365 when the study began, fell to 145 after 2 years on their diets.
There are no accurate biomarker assays to identify patients with food hypersensitivity. However, Carroccio et al. report that the ECP test had 65% sensitivity and 91% specificity in identifying patients with food hypersensitivity; ECP seems to be a specific marker of intestinal inflammation from reactions to foods. However, high levels of ECP were also observed in patients with chronic inflammatory bowel disease and intestinal parasitosis, so it would be important to first rule these conditions out.
The authors also concluded that tryptase, a serine proteinase released almost exclusively by mast cells, could be a useful marker of mast-cell activation in patients with food sensitivities.
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Carroccio A, Brusca I, Mansueto P, et al. Fecal assays detect hypersensitivity to cow’s milk protein and gluten in adults with irritable bowel syndrome. Clin Gastroenterol and Hepatol 2011; 9: 965-971.e3.