The Specific Carbohydrate Diet: Does It Work?
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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.
Potential Harm?
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
http://www.ccfa.org/about/news/scd
Stephen Wilson
Autism
What's the evidence for special diets and supplements?
There hasn't been much good research on changing what your child eats or
giving him or her supplements to treat autism.
We found one summary of the research (a systematic review) of diets that cut
out casein and gluten. The review found just two small studies. The studies
showed the diets seemed to help with some symptoms of autism, but not
others. The review's authors said there was not enough good-quality evidence
to say whether or not the diets work.
We found two good-quality studies on vitamin B6 plus magnesium. It didn't
seem to help. But the studies were small. Together, they had only 27
children. So the results aren't reliable.
We didn't find any good-quality studies of fish oil, vitamin A, vitamin C,
probiotics and digestive enzymes as treatments for children with autism.