What is an IgG reaction? 

Most patients with IBS have attempted at least some form of dietary modification, which in some cases can be very extreme. Conflicting results have been reported using exclusion diets and this approach also suffers from the limitation that it has to be empirical. Thus potentially offending foods can only be identified after their elimination and subsequent reintroduction. This time consuming process would be much reduced if the offending foods could be identified beforehand. Attempts to do this using IgE antibodies have been disappointing but the results of this study suggest that measuring IgG antibodies may be much more rewarding. The response to the IgG based diet in our trial did not correlate with atopic status, the prevalence of which was found to be no greater than that occurring in the general population.

It is now well recognised that up to 70% of patients with IBS have evidence of hypersensitivity of the rectum, which probably extends to involve most of the gut in many individuals. It is possible that this hypersensitivity renders patients more reactive to a low grade inflammatory process which would not necessarily cause symptoms in a normal individual. This would explain why excluding foods to which patients have IgG antibodies might be particularly beneficial in IBS despite the fact that these antibodies may also be present in the general population. Indeed, if this mechanism is particularly important in IBS, it might be anticipated that IgG food antibodies would be relatively common in this condition, as was the case in our study.

Many patients with IBS would prefer a dietary solution to their problem rather than having to take medication, and the economic benefits of this approach to health services are obvious. It is well known that patients expend large sums of money on a variety of unsubstantiated tests in a vain attempt to identify dietary intolerances. The results of this study suggest that assay of IgG antibodies to food may have a role in helping patients identify candidate foods for elimination and is an approach that is worthy of further biomedical and clinical research.

Gastroenterol Clin North Am. 2005 Jun;34(2):247-55
Lea R, Whorwell PJ.

Medical Academic Department, Education and Research Centre, Wythenshawe Hospital, Manchester M23 9LT, United Kingdom.

Irritable bowel syndrome patients frequently believe that food intolerances are to blame for many of their symptoms, although not uncommonly this is caused by the nonspecific increase in gut motility that occurs with food ingestion. Nevertheless, dietary manipulation may result in substantial improvement in IBS symptomatology provided it is individualized to the particular patient. By further understanding the mechanisms involved in dietary intolerance, it should be possible to optimize the benefits of this approach to treatment.