The Specific Carbohydrate Diet: Does It Work?
It's been featured in The Wall Street Journal, evokes passionate testimonials from its adherents, and spawned a best-selling book, now in its 11th printing. Yet the Specific Carbohydrate Diet, or SCD, has few published studies behind it, can be very difficult to follow, and has been dismissed by some doctors as scientifically unproven and even potentially risky. All of which leaves the person with Crohn's or colitis caught in the middle, wondering whether the SCD is truly an effective treatment for inflammatory bowel disease (IBD) or a dead end.
This article will review the available facts and offer a variety of perspectives on the diet to help readers navigate its complexities and form their own opinions as to its value for treating IBD.
The Theory Behind the Diet
The Specific Carbohydrate Diet was developed and popularized by biochemist Elaine Gottschall in her 1994 book, Breaking the Vicious Cycle: Intestinal Health Through Diet. Gottschall, who spent time exploring the changes that occur in the intestinal wall in IBD while at the University of Western Ontario, wrote her book after observing the effects of a low-carbohydrate, gluten-free diet on her eight-year-old daughter, who had been diagnosed with colitis at age five.
She and her husband took their daughter to see Drs. Sidney V. and Merrill P. Haas, physicians who had written a book called Management of Celiac Disease, which espoused a low-carbohydrate nutritional approach to celiac and other gastrointestinal diseases. Within two years of starting a radical version of the diet – the precursor of the SCD – Gottschall writes, her daughter was free of symptoms. The girl returned to a normal diet a few years later and has remained in good health for more than 20 years.
The SCD is a grain-free, lactose-free, and sucrose-free meal plan that is several degrees more restrictive than the gluten-free diet. It is built on the premise that carbohydrates are the primary energy source for the intestinal microbes that contribute to the development of IBD. Gottschall believes that undigested carbohydrates in particular spur the formation of acids and toxins that can injure the small intestine, destroying the very enzymes that allow for carbohydrate digestion and absorption in a kind of vicious cycle.
Nuts and Bolts
Specifically, the SCD prohibits:
- Sugar, molasses, sucrose, fructose, high-fructose corn syrup, or any processed sugar
- Canned vegetables
- All grains, including corn, wheat, wheat germ, barley, oats, rye, rice, buckwheat, soy, spelt, amaranth, and others
- Some legumes, including chick peas, bean sprouts, soybeans, mung beans, faba beans, and garbanzo beans
- Starchy tubers, such as potatoes, yams, and parsnips
- Seaweed and seaweed byproducts, such as agar and carrageenan
- Canned and most processed meats, particularly those that contain additives such as corn products, starch, and sugars
- All milk, high-lactose cheeses (generally soft cheeses like ricotta, mozzarella, cottage cheese, cream cheese, feta, and processed cheeses and cheese spreads), as well as commercial yogurt, heavy cream, buttermilk, and sour cream
- Bread, pasta, and other starchy foods
- Canola oil, commercial mayonnaise (because of additives), ice cream, candy, chocolate, carob, whey powder, margarine, commercial ketchup, stevia, baking powder, commercial nut mixes, balsamic vinegar, and products containing FOS (fructooligosaccharides).
So what does that leave? Well, unprocessed meats, poultry, fish, shellfish, eggs, honey for sweetening (if tolerated), most fresh, frozen, raw or cooked vegetables, a variety of legumes, including dried navy beans, lentils, peas, split peas, unroasted cashews, and peanuts in a shell, all-natural peanut butter, lima beans, and string beans, cheeses such as cheddar, Colby, Swiss, havarti, and dry curd cottage cheese, and homemade yogurt fermented for at least 24 hours. Additionally, most fruits and nuts are allowed, as are most oils, tea, coffee, mustard, vinegar, and juices with no additives.
Arthur D. Heller, M.D., a New York City gastroenterologist who is certified by the American Board of Nutrition, points out several inconsistencies in the diet. "Foods are excluded," he says, "because of their purported inability to be digested well. But of the foods allowed, legumes are known to contain certain carbohydrates that are not well digested by humans. And while the diet prohibits regular sugar, it allows most fruits and fruit juices, which are high in fructose, or fruit sugar. Not only is fructose dense in carbohydrates, but fructose malabsorption can cause cramps and diarrhea, intensifying the very symptoms the diet is designed to alleviate."
Stepping Back A Bit
The SCD has its fans and its critics. It's fair to say that, overall, it's getting mixed reviews from both patients and physicians. The reasons why are twofold: the diet is hard to follow, and there's little scientific evidence to show whether it is truly effective or which patient population it helps.
Edward V. Loftus, Jr., M.D., Associate Professor of Medicine and member of the Division of Gastroenterology and Hepatology at the Mayo Clinic in Rochester, MN, hears a lot about the SCD from his patients. Some manage to remain on it successfully, while others try and fail.
"I have one guy on this diet and he swears by it," says Dr. Loftus. "He was diagnosed with Crohn's when he was a kid and had a lot of trouble with colonic problems and fistulas. He went on the diet and did very well; no medications for years. He has intermittent trouble every now and then with fistulas, but overall he's done well."
And that's fine. Dr. Loftus isn't going to dissuade his patients from going on the diet, he says. "We're not ruling out the possibility that it works, but you need more than a few successes to establish proof. In the absence of that, it's hard to recommend this or any diet."
There may be thousands of people whom the diet helped, he adds, but how many other thousands are not being heard from who have had no relief from the diet? "In my experience," says Dr. Loftus, "for every patient I see who tried the diet and it worked, there are three to four others who tried it and it didn't work."
Additionally, doctors are asking whether there is something biologically different about the patients who have responded favorably to the SCD, or to any treatment. After all, some people do well on biologic therapy, while others respond better to immunomodulators such as methotrexate, azathioprine, or 6-MP, and still others experience spontaneous remission without drugs. In other words, is the success of any treatment, pharmacological or non-pharmacological, dependent on an individual's genetically determined disease sub-type?
The Need for Research
One of the few published reports on the diet appeared in Tennessee Medicine in September 2004. It wasn't actually a study, but a case report on two patients who followed the diet: a 51-year-old woman with colitis and a 24-year-old woman with Crohn's disease. Both found significant relief within one month of starting the diet, the authors wrote, and each was able to taper off her medications, remaining in remission on the diet alone.
Most doctors, however, want to see well-designed, randomized controlled trials involving large numbers of people, in which one group follows the diet, one group follows a different diet or no diet, and the results are compared, before recommending a particular treatment. Those studies just don't exist yet.
"Studies are expensive and someone has to pay," Dr. Loftus says. Most clinical studies in this country are funded by pharmaceutical companies, he notes, and since there's no potential drug at stake with this diet, it would be difficult to find the funding. Another challenge is designing such a study. For instance, he asks, how would you determine the comparator diet so that the results of the trial weren't tainted by investigator or patient bias?
The first step, speculates William J. Sandborn, M.D., Professor of Medicine at the Mayo Clinic, would be to conduct a pilot study of a small group of patients on the SCD for a finite period. Patients would be examined via endoscopy at the beginning and end of the study to measure disease-related damage in the GI tract. "There would need to be some compelling pilot data indicating benefit – i.e., a measurable demonstration of healing – before a controlled trial was undertaken," Dr. Sandborn says.
Carefully controlled studies of diet are technically difficult to conduct, he adds. The good news is that there's a growing interest at the national level (among groups such as the National Center for Complementary and Alternative Medicine at the NIH) in looking at the effects of diet on chronic illness. As the ability to conduct such studies improves, the CCFA will, in all likelihood, play an important role in fostering research on nutrition and IBD.
Drs. Loftus and Sandborn note that some aspects of the theory behind the SCD make sense. For instance, current thinking holds that IBD is caused by an abnormality that prevents the immune system in the gut from shutting itself off when it encounters bacterial or viral threats, real or "imagined." So if you starve the bacteria in the gut via this elemental diet, says Dr. Loftus, there may be fewer stimuli, resulting in less inflammation.
Even if the SCD only works for a percentage of the people who try it, doesn't that at least make it worth trying? Maybe, says Dr. Heller. But he's also concerned about the potential for nutritional deficiencies on the diet.
Excluding starchy vegetables and grains eliminates dietary sources of short-chain fatty acids, the preferred fuel source for colon cells, he says. "This is important because without that fuel source, those cells don't function as well." In fact, he notes, in a condition called diversion colitis, which sometimes occurs in any remaining colon after a colectomy, colon cells are depleted of short-chain fatty acids. Restoring those nutrients through an enema cures the diversion colitis. "Thus," he says, "this diet could make the colitis worse. To exclude the dietary source of short-chain fatty acids without a compelling reason just doesn't make sense to me."
The SCD does change the intestinal flora, Dr. Heller adds, but there may be less extreme ways of doing the same thing. Many of his own patients do well on probiotics, antibiotics, and moderate changes in diet – treatments he feels are at least as effective as the SCD and far less intrusive into a person's lifestyle.
Dr. Loftus' concern is that the diet might create additional problems for a patient who is already underweight, something he's seen in the past. However, he notes, like most Americans today, IBD patients are increasingly overweight, so that's probably not going to be a major problem – at least not in adults. But when it comes to kids, a different picture emerges.
Athos Bousvaros, M.D., Associate Director of the IBD Center at Children's Hospital in Boston, thinks the diet, while difficult to follow, is probably safe. However, there is a risk that the SCD may not provide the calories children need to grow and thrive. Calorie issues are more important than vitamin issues, he believes. You can give a child a multivitamin supplement to prevent deficiencies, but it can be challenging for a child to get enough calories on such a restrictive diet.
"If you do decide to put your child on the diet," he says, "do it under the guidance of an experienced nutritionist. Decide on a reasonable time frame – say, three to four months – and don't do anything else new for the duration of that period." That way, if your child's condition improves, you can be reasonably sure that the diet is associated with that improvement.
Dr. Bousvaros warns, however, that imposing such a restrictive diet on a child could be psychologically stressful. "Kids with IBD are already probably taking 15-20 pills a day," he says. "Now you're telling them they can't eat what they like? That takes a toll on a child, and it could also fuel family tensions. To avoid needless stress all around, it's important that parents and child agree before taking on the diet as a family project. And remember to do so only under medical supervision."
"Most doctors will condone the diet as long as the patient continues to be monitored," adds Dr. Heller. In other words, don't start the diet and stop other medical treatment. Unfortunately, he says, that often happens: "Patients start the diet and then stop their medicine without the doctor knowing."
Still, he says, the diet "may be worth a try." After all, he notes, there are much worse diets being touted in cyberspace and elsewhere. "But don't abandon your conventional treatment," he warns, "and keep in touch with your doctor."
Dr. Loftus concurs. "From what I've read, it sounds like it would be awfully difficult to follow. For instance, you couldn't eat any processed foods because they all have carbs in them. But there may be something to it. It's not unreasonable for motivated patients to give it a try."
Where Do We Go From Here?
The SCD has gained popularity among some within the IBD community who seek a complementary approach to the treatment of their Crohn's disease or ulcerative colitis. Unfortunately, though, research studies that prove or disprove the diet's effectiveness are lacking at present. The bottom line: The decision to go on the SCD should be a topic of discussion between the patient, the physician, and the nutritionist on the team. And in the meantime, be sure to keep taking your medicine.
-- Written by Debra Gordon
For further information, call CCFA at our Information Resource Center: 888.MY.GUT.PAIN (888.694.8872).
The Crohn’s & Colitis Foundation of America provides information for educational purposes only. We encourage you to review this educational material with your health care professional. The Foundation does not provide medical or other health care opinions or services. The inclusion of another organization’s resources or referral to another organization does not represent an endorsement of a particular individual, group, company or product.
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Published: June 1, 2012