Dear colleagues and friends,
Dr. Charles Kahi
Thank you for your continued interest and support of the Perspectives debates. In this edition, Dr. Ashwin Ananthakrishnan and Dr. Laura Raffals explore the controversial topic of diet-based therapy in inflammatory bowel disease, highlights of the rationales for and against, and the current state of the evidence. All gastroenterologists frequently face questions pertaining to diet and its purported effects on digestive health. I found the discussion relevant to my own general practice, and I hope you will enjoy reading it as much as I did. As always, I welcome your comments and suggestions for future topics at ginews@gastro.org.
Charles Kahi, MD, MS, AGAF, professor of medicine, Indiana University, Indianapolis. He is also an associate editor for GI & Hepatology News.
IBD can be treated with diet alone
Inflammatory bowel diseases (IBD), comprising Crohn’s disease and ulcerative colitis, have emerged as global diseases. The past 3 decades have seen a rising incidence of these diseases not just in the Western hemisphere, where their prevalence has been well recognized, but also in regions of the world such as Asia and South America where they were previously rare. Whereas several possible factors have been proposed to explain this rising incidence and globalization of disease with varying degrees of supportive evidence, one of the most likely factors is a changing diet. Over the same period that the disease incidence and prevalence have risen, diets worldwide have converged with several common trends observed across countries and continents. These include reductions in dietary fiber, fruits, and vegetables, and increased intake of processed food, animal protein, fats, and sugary drinks, all of which have been linked epidemiologically to Crohn’s disease.
Dr. Ashwin Ananthakrishnan
Treatment of Crohn’s disease and ulcerative colitis over the past 2 decades has focused on the immunologic dysfunction observed in these patients. Successful treatment has relied on suppressing immune responses either broadly or through targeted suppression of specific immunologic pathways. By and large, whereas these approaches have enabled us to make significant progress in reducing disease-related morbidity, success has been moderate at best, with fewer than half of patients in any clinical trial achieving remission at the end of a year. Thus, this approach alone may not be sufficient for most patients with IBD.
Treatment of IBD with diet was long considered out of the mainstream and confined to the realm of anecdotes and message boards. Despite most patients believing that diet played a role in development of IBD and onset of flares and that dietary modification was helpful in relieving symptoms, physicians – who for the most part were not trained in these approaches – were not believers, and probably rightly so in the absence of any supporting data.1 However, the parallel emergence of three bodies of literature has now brought diet back into the mainstream of IBD care (such that not a single IBD conference goes by without at least a session or two on diet). First, large prospective cohorts from Europe and North America provided robust evidence linking long-term adult dietary patterns to disease incidence in adult-onset IBD, which supports many important case-control observations made over the past 2 decades.2 Second, and perhaps most important, we began understanding the role of the microbiome in the development of these diseases and recognizing its centrality to bowel inflammation. One of the key determinants of the microbiome is diet, exerting both short-term and long-term influences on the microbial structure. While microbial changes are by no means the only mechanism through which diet can influence intestinal inflammation, they are among the most important, with broad effects across many dietary components. These findings provided a robust scientific basis for investigating the role of diet. Third, while still far from the high-quality (and expensive) set-up of investigational trials of pharmacologic therapies, dietary therapy studies have also evolved to randomized controlled trial designs and investigation of mechanism-driven dietary combinations. Together, I think these three recent advances, in addition to the wealth of existing literature and anecdotal experience, have been important in moving diet (back) into the IBD mainstream.
So what evidence is there that diet is effective in the treatment of IBD? Randomized controlled trials published more than a decade ago demonstrated that exclusive enteral nutrition, wherein all table foods are eliminated from a diet and the patient relies on an elemental diet alone for nutrition, was effective in not just inducing clinical remission but also improving inflammatory biomarkers.3 With results replicated in several trials, exclusive enteral nutrition is, in many parts of the world, one of the first-line treatments for pediatric Crohn’s disease. That this has not been translated to longer-term maintenance therapy is not necessarily an indicator of lack of durable efficacy, but reflects the challenges of maintaining such a restrictive diet long term while living an active, normal life. However, more recent rigorous studies have demonstrated that the effects of exclusive enteral nutrition can be mimicked either by a selected, less-restrictive diet (such as CD-TREAT4), which is more sustainable, or by combining partial enteral nutrition with an elimination diet that is quite diverse (such as CDED5). The latter two are considerably more promising as longer-term dietary treatments for Crohn’s disease with durable efficacy in open-label studies and randomized trials.
What are my final arguments for diet being used as a treatment for IBD? With the exception of very restrictive ones, diets are generally safe. Of course, patients on restricted diets need monitoring for nutritional deficiencies, but this monitoring is likely less intense than that needed for many of our immunosuppressive therapies. Dietary therapies are not associated with an increase in risk of infections or malignancy (unlike our traditional immunosuppressive therapies), and consequently are much more likely to be accepted by our patients than what we are currently offering. In addition, the existing treatments are expensive and consequently difficult to sustain globally with the increasing burden of these diseases. On the other hand, as eating and dietary choices are a routine part of day-to-day life, dietary therapies are not likely to be associated with any excess costs.
Therefore, treating IBD with diet alone is supported by epidemiologic, mechanistic, and clinical evidence and is a safe, effective, and inexpensive alternative for our patients.
References
1. Zallot C et al. Inflamm Bowel Dis. 2013 Jan;19(1):66-72.
2. Sasson AN et al. Clin Gastroenterol Hepatol. 2019 Dec 5;S1542-3565(19)31394-1.
3. Wall CL et al. World J Gastroenterol. 2013;19:7652-60.
4. Svolos V et al. Gastroenterology. 2019;156:1354-67.e6.
5. Levine A et al. Gastroenterology. 2019;157:440-50.e8.
Dr. Ananthakrishnan is a gastroenterologist in the division of gastroenterology, Crohn’s and Colitis Center, Massachusetts General Hospital and Harvard Medical School, Boston. He is supported by funding from the Crohn’s and Colitis Foundation and the Chleck Family Foundation.
