503555
research-article2013
NCPXXX10.1177/0884533613503555Nutrition in Clinical PracticeBarrett and Gibson
Letter to the Editor
Response to Comment on Low FODMAP Diet
Thank you for the opportunity to respond to the letter following publication of “Extending Our Knowledge of Fermentable, Short-chain Carbohydrates for Managing Gastrointestinal Symptoms” in Nutrition in Clinical Practice. The authors had several concerns that we would like to address. The first concern was related to misreading and misquoting a sentence in the abstract. It was suggested that the statement— “The Monash University low FODMAP diet is now accepted as an effective strategy for managing symptoms of IBS”—was overstating the evidence. The statement did in fact define that this is the case “in Australia,” and further in the article, it was clarified that this is not the case around the world, as yet. We acknowledge that the Monash University low FODMAP diet is an emerging dietary therapy. In Australia however, it has been taken over as the first point of management for irritable bowel syndrome (IBS) by the majority of GPs, gastroenterologists, and dietitians. Second, the authors question the validity of the evidence to date to support the use of this diet for IBS. Dietary studies are easy targets for criticism, as outlined in detail in a recent review article from a Rome Foundation Working Group.1 Application of pharmacological-grade rules to dietary studies is difficult. The authors analyzed the limitations of some of the studies2-5 and concluded that the results should not lead to application of the diet in clinical practice. We quite agree that there are many limitations to the studies and further studies are needed. However, it is unfair to dismiss evidence in the manner of the letter. For example, because different food was given to study participants by Ong et al,2 it cannot be blinded, even if the participants knew nothing of FODMAP content of food (as was the case). If such a criticism is valid, then it is invalid to perform any randomized controlled trials of dietary manipulation and dietary therapies will remain in the “too-hard” basket. The second study by Staudacher et al3 did have an unequal therapeutic relationship, but the study was performed to examine the effect on faecal microbiota, an objective index. To criticize the fact that it did not show benefit for some of the specific symptoms is not surprising as it was not powered to do so. A nonrandomized comparative study by the same group was not addressed.4 The third randomized controlled trial,5 in which blinding was impeccable, was dismissed as it only dealt with responders and was therefore not generalizable, an interesting dismissal of data indeed. To run a dietary trial in a pharmaceutical fashion
Nutrition in Clinical Practice Volume 28 Number 6 December 2013 775–776 © 2013 American Society for Parenteral and Enteral Nutrition DOI: 10.1177/0884533613503555 ncp.sagepub.com hosted at online.sagepub.com
requires blinding of participants and researchers and controlled provision of all food and drinks. The former is not possible unless you use challenge with the component of interest within a blinded drink, rather than modifying the treatment diet, which does not represent “real diet.” There will always be limitations with dietary studies, but this work has endeavored to use the best dietary research practice possible.1 The potential for placebo effect is real, but each of the 4 trials has been placebo controlled to ensure treatment effect is clear. Indeed, all outcomes on the efficacy of the low FODMAP diet in managing gastrointestinal symptoms have been both statistically and clinically relevant. We entirely agree with the authors’ third concern about the long-term safety of the low FODMAP diet for IBS given its effect on lowering bifidobacteria (though only shown in one small randomized controlled study3) due to the concurrent reduction of dietary prebiotics. This was indeed addressed in the article. The idea that prebiotic intake has therapeutic benefit in patients with IBS was championed by the authors and was supported by 3 studies, 1 of which showed no therapeutic benefit at all6 and another was not performed in patients with IBS.7 We also agree with their assertion that the diet should not be followed strictly in the longer term as a rule. We do encourage that IBS patients seek the advice of a dietitian for counseling on the low FODMAP diet, as is recommended for anyone following a special diet. We acknowledge that the diet restricts certain fruits and vegetables, but the list of suitable alternative foods is considerable. That some individuals will follow the diet strictly long term rather than just for the recommended 4 week elimination period is not a reason for discarding such a dietary approach. We can only hope that the treating professionals can guide their patients on the importance of reintroductions and tolerance testing. The nutritional adequacy of the low FODMAP as used in routine practice does require study. Finally, criticism of the application of breath hydrogen testing to individualize dietary planning (in order to reduce restriction needed) on the basis of a consensus statement formed at least 5 years ago by a group not then aware of or at least not discussing dietary approaches like the low FODMAP diet is interesting. We entirely support the notion that more studies are needed to lock in the evidence for efficacy of the low FODMAP diet and that its long-term safety requires assessment, but cannot
Downloaded from ncp.sagepub.com at Bobst Library, New York University on May 31, 2015
776
Nutrition in Clinical Practice 28(6)
accept that the current evidence is insufficient to lead to its application in professionally led clinical dietary practice for a patient group that has very few efficacious options. Jacqueline Barrett, PhD, BSc (Biomed)(Hons), MND Peter Gibson, PhD, BSc
Monash University, Central Clinical School, Melbourne, Victoria Australia References 1. Yao CK, Gibson PR, Shepherd SJ. Design of clinical trials evaluating dietary interventions in patients with functional gastrointestinal disorders. Am J Gastroenterol. 2013;108(5):748-758. 2. Ong DK, Mitchell SB, Barrett JS, et al. Manipulation of dietary short chain carbohydrates alters the pattern of gas production and genesis of symptoms in irritable bowel syndrome. J Gastroenterol Hepatol. 2010;25:1366-1373.
3. Staudacher HM, Lomer MCE, Anderson JL, et al. Fermentable carbohydrate restriction reduces luminal bifidobacteria and gastrointestinal symptoms in patients with irritable bowel syndrome. J Nutr. 2012;142(8):1510-1518. 4. Staudacher HM, Whelan K, Irving PM, Lomer MCE. Comparison of symptom response following advice for a diet low in fermentable carbohydrates (FODMAPs) versus standard dietary advice in patients with irritable bowel syndrome. J Hum Nutr Diet. 2011;24(5):487-495. 5. Shepherd SJ, Parker SC, Muir JG, Gibson PR. Randomised, placebocontrolled evidence of dietary triggers for abdominal symptoms in patients with irritable bowel syndrome. Clin Gastroenterol Hepatol. 2008;6(7):765-771. 6. Olesen M, Gudmand-Hoyer E. Efficacy, safety, and tolerability of fructooligosaccharides in the treatment of irritable bowel syndrome. Am J Clin Nutr. 2000;72(6):1570-1575. 7. Bouhnik Y, Raskine L, Simoneau G, Paineau D, Bornet F. The capacity of short-chain fructo-oligosaccharides to stimulate faecal bifidobacteria: a dose-response relationship study in healthy humans. Nutr J. 2006; 5:8.
Downloaded from ncp.sagepub.com at Bobst Library, New York University on May 31, 2015
research-article2013
NCPXXX10.1177/0884533613503555Nutrition in Clinical PracticeBarrett and Gibson
Letter to the Editor
Response to Comment on Low FODMAP Diet
Thank you for the opportunity to respond to the letter following publication of “Extending Our Knowledge of Fermentable, Short-chain Carbohydrates for Managing Gastrointestinal Symptoms” in Nutrition in Clinical Practice. The authors had several concerns that we would like to address. The first concern was related to misreading and misquoting a sentence in the abstract. It was suggested that the statement— “The Monash University low FODMAP diet is now accepted as an effective strategy for managing symptoms of IBS”—was overstating the evidence. The statement did in fact define that this is the case “in Australia,” and further in the article, it was clarified that this is not the case around the world, as yet. We acknowledge that the Monash University low FODMAP diet is an emerging dietary therapy. In Australia however, it has been taken over as the first point of management for irritable bowel syndrome (IBS) by the majority of GPs, gastroenterologists, and dietitians. Second, the authors question the validity of the evidence to date to support the use of this diet for IBS. Dietary studies are easy targets for criticism, as outlined in detail in a recent review article from a Rome Foundation Working Group.1 Application of pharmacological-grade rules to dietary studies is difficult. The authors analyzed the limitations of some of the studies2-5 and concluded that the results should not lead to application of the diet in clinical practice. We quite agree that there are many limitations to the studies and further studies are needed. However, it is unfair to dismiss evidence in the manner of the letter. For example, because different food was given to study participants by Ong et al,2 it cannot be blinded, even if the participants knew nothing of FODMAP content of food (as was the case). If such a criticism is valid, then it is invalid to perform any randomized controlled trials of dietary manipulation and dietary therapies will remain in the “too-hard” basket. The second study by Staudacher et al3 did have an unequal therapeutic relationship, but the study was performed to examine the effect on faecal microbiota, an objective index. To criticize the fact that it did not show benefit for some of the specific symptoms is not surprising as it was not powered to do so. A nonrandomized comparative study by the same group was not addressed.4 The third randomized controlled trial,5 in which blinding was impeccable, was dismissed as it only dealt with responders and was therefore not generalizable, an interesting dismissal of data indeed. To run a dietary trial in a pharmaceutical fashion
Nutrition in Clinical Practice Volume 28 Number 6 December 2013 775–776 © 2013 American Society for Parenteral and Enteral Nutrition DOI: 10.1177/0884533613503555 ncp.sagepub.com hosted at online.sagepub.com
requires blinding of participants and researchers and controlled provision of all food and drinks. The former is not possible unless you use challenge with the component of interest within a blinded drink, rather than modifying the treatment diet, which does not represent “real diet.” There will always be limitations with dietary studies, but this work has endeavored to use the best dietary research practice possible.1 The potential for placebo effect is real, but each of the 4 trials has been placebo controlled to ensure treatment effect is clear. Indeed, all outcomes on the efficacy of the low FODMAP diet in managing gastrointestinal symptoms have been both statistically and clinically relevant. We entirely agree with the authors’ third concern about the long-term safety of the low FODMAP diet for IBS given its effect on lowering bifidobacteria (though only shown in one small randomized controlled study3) due to the concurrent reduction of dietary prebiotics. This was indeed addressed in the article. The idea that prebiotic intake has therapeutic benefit in patients with IBS was championed by the authors and was supported by 3 studies, 1 of which showed no therapeutic benefit at all6 and another was not performed in patients with IBS.7 We also agree with their assertion that the diet should not be followed strictly in the longer term as a rule. We do encourage that IBS patients seek the advice of a dietitian for counseling on the low FODMAP diet, as is recommended for anyone following a special diet. We acknowledge that the diet restricts certain fruits and vegetables, but the list of suitable alternative foods is considerable. That some individuals will follow the diet strictly long term rather than just for the recommended 4 week elimination period is not a reason for discarding such a dietary approach. We can only hope that the treating professionals can guide their patients on the importance of reintroductions and tolerance testing. The nutritional adequacy of the low FODMAP as used in routine practice does require study. Finally, criticism of the application of breath hydrogen testing to individualize dietary planning (in order to reduce restriction needed) on the basis of a consensus statement formed at least 5 years ago by a group not then aware of or at least not discussing dietary approaches like the low FODMAP diet is interesting. We entirely support the notion that more studies are needed to lock in the evidence for efficacy of the low FODMAP diet and that its long-term safety requires assessment, but cannot
Downloaded from ncp.sagepub.com at Bobst Library, New York University on May 31, 2015
776
Nutrition in Clinical Practice 28(6)
accept that the current evidence is insufficient to lead to its application in professionally led clinical dietary practice for a patient group that has very few efficacious options. Jacqueline Barrett, PhD, BSc (Biomed)(Hons), MND Peter Gibson, PhD, BSc
Monash University, Central Clinical School, Melbourne, Victoria Australia References 1. Yao CK, Gibson PR, Shepherd SJ. Design of clinical trials evaluating dietary interventions in patients with functional gastrointestinal disorders. Am J Gastroenterol. 2013;108(5):748-758. 2. Ong DK, Mitchell SB, Barrett JS, et al. Manipulation of dietary short chain carbohydrates alters the pattern of gas production and genesis of symptoms in irritable bowel syndrome. J Gastroenterol Hepatol. 2010;25:1366-1373.
3. Staudacher HM, Lomer MCE, Anderson JL, et al. Fermentable carbohydrate restriction reduces luminal bifidobacteria and gastrointestinal symptoms in patients with irritable bowel syndrome. J Nutr. 2012;142(8):1510-1518. 4. Staudacher HM, Whelan K, Irving PM, Lomer MCE. Comparison of symptom response following advice for a diet low in fermentable carbohydrates (FODMAPs) versus standard dietary advice in patients with irritable bowel syndrome. J Hum Nutr Diet. 2011;24(5):487-495. 5. Shepherd SJ, Parker SC, Muir JG, Gibson PR. Randomised, placebocontrolled evidence of dietary triggers for abdominal symptoms in patients with irritable bowel syndrome. Clin Gastroenterol Hepatol. 2008;6(7):765-771. 6. Olesen M, Gudmand-Hoyer E. Efficacy, safety, and tolerability of fructooligosaccharides in the treatment of irritable bowel syndrome. Am J Clin Nutr. 2000;72(6):1570-1575. 7. Bouhnik Y, Raskine L, Simoneau G, Paineau D, Bornet F. The capacity of short-chain fructo-oligosaccharides to stimulate faecal bifidobacteria: a dose-response relationship study in healthy humans. Nutr J. 2006; 5:8.
Downloaded from ncp.sagepub.com at Bobst Library, New York University on May 31, 2015
