Considering the Necessity of a Very Low Carbohydrate Diet on Diarrhea-Predominant Irritable Bowel Syndrome

Dear Editor:

We read with interest the article by Austin et al1 in the June 2009 issue of Clinical Gastroenterology and Hepatology on the impact of a very low-carbohydrate diet (VLCD) on diarrhea-predominant irritable bowel syndrome. We were particularly impressed with the proportion of patients (10 of 13) who experienced adequate relief of diarrhea by following a 20-gram carbohydrate diet over a 4-week period. Reduced-carbohydrate diets have shown improved metabolic parameters and other healthy outcomes in overweight/obese subjects,2 and we agree with the authors that reducing carbohydrate consumption could be beneficial in patients with irritable bowel syndrome.

As we considered the potential of this diet for our own patient population, we thought it important to raise the concern that the feasibility and long-term safety of a 20-gram carbohydrate diet has yet to be established. The typical American diet provides approximately 300 grams of carbohydrates. A 20-gram intervention is particularly restrictive, similar to the 2-week induction phase of the Atkins diet.3 In this study, patients underwent the 20-gram intervention for twice as long as is currently standard. VLCDs carry adherence and safety issues including ketosis, electrolyte abnormalities, and mood disturbance,4 all of which could be problematic for patients already predisposed to gastrointestinal symptoms and visceral sensitivity. Further, obesity itself appears to increase the odds of having diarrhea-predominant symptoms5 and because this study did not indicate whether subjects, who were for the most part overweight or obese, consumed fewer calories from baseline in addition to the VLCD, we wonder whether a more modest reduced-carbohydrate diet would have been sufficient.