***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Thirteen out of 49 patients suspected of having specific food intolerance after withdrawal and re introduction of specific foods , were further subjected to double blind placebo controlled food challenges . Only three of these subjects were thus shown to have proven specific food intolerance . Of the remaining 10 , nine were strong ' placebo reactors ' . The study suggests that a small number of patients with gastrointestinal symptoms have verifiable specific food intolerance but that a greater number have symptoms attributable to psychogenic causes BACKGROUND Although previous studies have shown that psychological disturbances are frequently associated with the irritable bowel syndrome ( IBS ) , the relation was not necessarily cause and effect . The development of chronic bowel symptoms after an episode of acute gastroenteritis has allowed us to examine prospect ively the role of psychological factors . METHODS Seventy-five patients with acute gastroenteritis completed a series of psychometric tests  soon after admission to hospital . Of these , 22 had persistent symptoms compatible with IBS after the acute illness , and in 20 of these the symptoms were still present at six months . FINDINGS At the time of their initial illness , patients who subsequently developed IBS had higher scores for anxiety , depression , somatization and neurotic trait than those who returned to normal bowel function . The psychometric scores had not changed when remeasured after the acute illness . Lactose malabsorption was not an important factor . INTERPRETATION These results support the hypothesis that psychological factors are important in IBS Food hypersensitivity as a cause of abdominal symptoms was investigated by means of exclusion diets and double-blind food provocation in patients with irritable bowel syndrome . Twenty-seven patients entered the study ; nineteen complied with dietary manipulation . Food hypersensitivity as a cause of their presenting symptoms was confirmed by double-blind food provocation in only three patients , who also had evidence of associated atopic disease and positive skin tests to common inhalant allergens . Evidence of minor psychiatric disorder was found in twelve of fourteen patients examined by an independent psychiatrist Specific foods were found to provoke symptoms of irritable bowel syndrome ( IBS ) in 14 of 21 patients . In 6 patients who were challenged double blind the food intolerance was confirmed . No difference was detected in changes in plasma glucose , histamine , immune complexes , haematocrit , eosinophil count , or breath hydrogen excretion produced after challenge or control foods . Rectal prostagl and in E2 ( PGE2 ) , however , increased significantly , and in a further 5 patients rectal PGE2 correlated with wet faecal weight . Food intolerance associated with prostagl and in production is an important factor in the pathogenesis of IBS 
    Output:
    
Milk , wheat , and eggs were most frequently identified to cause symptom exacerbation ; of the foods identified the most common trait was a high salicylate content .
Foods high in amines were also identified .
Studies of diarrhea-predominant IBS identified a higher percentage of adverse food reactions .
Conclusion : Whether adverse reactions to foods are a key factor in exacerbating IBS symptoms or whether dietary manipulation is a valid treatment option is unclear .