Reply

We appreciate Doerfler and Keefer's interest in reading our article regarding the effect of a very low-carbohydrate diet (VLCD) on diarrhea-predominant irritable bowel syndrome (IBS).1 The dietary intervention of limiting carbohydrate intake to 20 grams a day was patterned after the induction phase of the Atkins diet. The short-term safety has been proven in several prospective randomized trials.2, 3, 4 The period of restricting carbohydrate intake to 20 grams a day has ranged from 2 weeks3 to 2 months.2 We chose a 4-week VLCD intervention because we believed it was short enough to maintain participant adherence to the diet but long enough that we would be able to identify changes in our outcomes. In addition, we provided all the meals for the participants during both the control and VLCD diet to maximize adherence.

The issues of long-term adherence and safety of a low-carbohydrate diet are certainly important, and these were not assessed in this study. The first step in understanding whether carbohydrate restriction in any form might be helpful in diarrhea-predominant IBS was to determine whether it is helpful in the most restrictive form. Indeed, participants in our study had specific improvements in bowel habits, abdominal pain, and quality of life. Further research is necessary to identify the following: (1) what is the minimum amount of carbohydrate restriction that is necessary to achieve the same degree of symptom improvement seen in our study; (2) which carbohydrates are the offending agents: simple sugars or complex carbohydrates; and (3) whether there are unintended adverse outcomes specific to individuals with IBS-D with prolonged use of a low-carbohydrate diet. We specifically designed our intervention to maintain energy balance for all 6 weeks. Many individuals were unable to consume all the food administered during the VLCD. However, we did not identify any trends toward improved outcomes based on the amount of weight loss or by the amount of decrease in energy intake.