Specific carbohydrate diet

Specific Carbohydrate Diet (SCD) is a therapeutic eating plan utilized to treat a variety of conditions with primary use in inflammatory bowel disease (IBD), (categorized as Crohn’s disease or ulcerative colitis), irritable bowel syndrome (IBS), diverticulitis and celiac disease (CD) with benefits in other illnesses known to have gut bacterial disturbances such as autism and cystic fibrosis. The diet eliminates all grains (wheat, barley, rye, rice), soy, starchy vegetables like potatoes, sugar, and processed foods.  A complete list of accepted foods can be found on the breaking the viscous cycle website under "legal/illegal".  To achieve the end result, fanatical adherence is considered necessary for a prolonged period at this time, but studies evaluating a broader array of foods and slightly expanded diets with their roots in SCD like the Crohn's Disease Exclusion Diet (CDED), Gut and Psychology Syndrome diet (GAPS) and modified SCD are ongoing. The largest area of research with SCD is in IBD with positive findings in small patient trials with large clinical trials now underway.

The Specific Carbohydrate Diet was developed by Sydney Haas, MD who along with John Howland, MD served as assistants at Vanderbilt Clinic to L. Emmett Holt, Sr, MD, a physician at the turn of the twentieth century taking a lead role in the US studying celiac disease. Holt, together with Christian Herter, MD, a physician and pathologist from Columbia University, reported that the condition is associated with abnormal forms of bacteria and “may confidently be ascribed to the action of putrefactive products”. Howland reports “that of all the elements of food, carbohydrates is the one which must be excluded rigorously”. Howland’s treatment was very successful, but the need for some tolerable carbohydrate remained. Haas discovered a paper on “The value of Banana in the Treatment of Celiac Disease” and began incorporating carefully specific carbohydrates into the diet to determine the tolerability. The SCD, also known at the time in the 1940s’ as the “banana diet”, was met with great success in treating patients with gastrointestinal conditions diagnosed at the time as celiac disease based on symptoms, as no laboratory tests specific to celiac disease existed. ^[1][2][3]

SCD was popularized by Elaine Gotschall with the publication of her book, Food and the Gut Reaction: Intestinal Health through diet first edition published in 1987, with name change and now 15^th edition, Breaking the Vicious Cycle: Intestinal Health through diet. ^[4] Elaine’s daughter, Judy, diagnosed with UC at a very young age, was facing imminent colectomy but was restored to full health following the SCD.  Soon after, Sydney Haas, MD passed away.  Elaine was concerned that the knowledge of this diet was likely to fade with him as this diet was not recognized or utilized by most gastroenterologists. Only after much desperate seeking did she find Dr. Haas. Gotschall pursued her master’s degree in biology, nutritional biochemistry and cellular biology and with lifelong interest in the gastrointestinal system and diet she served as a consultant to hundreds of patients and with her publications she has helped thousands to restore their health. ^[5]

Although old but not forgotten, the SCD is now gaining renewed interest in the community as well as the medical profession with the publication of a number of small patient trials and reports showing benefit in attaining remission for IBD.  The postulated mechanism of benefit from the diet is that the condition of IBS or IBD is due to an overgrowth or imbalance of gut bacteria that can be corrected by the avoidance of specific carbohydrates that feed the overgrowth, hence the name Specific Carbohydrate Diet. The technology at the time of the development of this diet was not able to evaluate this hypothesis.  However, with the current technology of gene sequencing combined with the improvements in data software analysis, the bacterial, viral, and fungal components encompassing the human microbiome are now analyzable and this is among the most active and exciting areas of research for all human diseases and in particular IBD.

It is now commonly accepted that dysbiosis (disruption of gut bacterial balance from normal) is the hallmark of IBD. ^{[6] [7][8]} Overall richness of the bacterial community is decreased with certain species found to be commonly overgrown in particular the phylum of Proteobacteria and members of the family of Enterobacteriaceae, and fungus including candida tropicalis and candida albicans, while other species tend to be either absent or under represented such as faecalibacterium prausnitzii of the Clostridium clade. ^{[9] [10][11][12][13]}The SCD has been shown to alter this balance of bacteria and shift it more toward that found in healthy population without disease. ^[14][15]

The SCD has been shown to induce remission of Crohn’s disease, with reduction or elimination of symptoms, normalization of serum inflammatory markers and evidence of improved mucosal tissue by endoscopy,^[16][17] including remission in seven children with active Crohn’s disease without the use of concomitant medications. ^[18]  These positive findings are considered a result of shifts in the microbiome due to dietary changes.

These small patient trials in combination with patient reports of improvements ^{[19] [20]} have prompted the renewed interest of dietary therapy for IBD.  Two large scale ongoing trials of over 100 patients each are currently underway, PRODUCE (comparing SCD with modified SCD in pediatric patients),^[21] and DINE-CD (comparing SCD with the Mediterranean diet in adult patients).^[22] Additionally, there are over twenty smaller ongoing interventional trials evaluating aspects of diet, microbiome and IBD, many of which are utilizing SCD. ^[23]

As current research documents the role of diet in the pathogenesis and treatment of IBD, there are five ongoing large epidemiologic studies evaluating the relationship to diet and IBD, including the Prognostic Effect of Environmental Factors in Crohn’s and Colitis (PREdiCCT), Inflammation, Microbiome and Alimentation: Gastrointestinal and Neuropsychiatric Effects (IMAGINE), Chronic Inflammatory Disease, Lifestyle and Treatment Response (BELIEVE). ^[23]

Although the data from the small clinical trials described above have not drawn the attention of most gastroenterologists, the interest in dietary therapy for IBD is growing with the increased focus on the microbiome and the implications of it in the pathogenesis of IBD and the potential to manipulate it. Dietary therapy is welcomed by patients because, when utilized either alone or in combination with drug therapy, there is great potential to heal with no potential to harm.

• Kakodkar S, Mutlu EA 2017 "Diet as a Therapeutic Option for Adult Inflammatory Bowel Disease" Gastroenterol Clin N Am 46 (2017) 745-76 http://dx.doi.org/10.1016/j.gtc.2017.08.016
• Lane ER, Lee D, Suskind DL"Dietary Therapies inPediatric Inflammatory Bowel Disease An Evolving Inflammatory Bowel Disease Paradigm" Gastroenterol Clin N Am 46 (2017) 731–744 http://dx.doi.org/10.1016/j.gtc.2017.08.012