I think of this diet for patients with IBD (Irritable Bowel Disease) — not to be confused with IBS (Irritable Bowel Syndrome). IBD includes autoimmune conditions Crohn’s and Ulcerative Colitis, both characterized by GI inflammation, and blood and/or mucus in the stool.
The “Vicious Cycle”
The Specific Carbohydrate Diet was, I believe, originally proposed by Elaine Gottschall in her book, “Breaking the Vicious Cycle.” Although the causes of Crohn’s and UC are not completely understood (which is essentially the case with all autoimmune conditions—see here for more explanation), once the process starts, the cycle goes something like this:
For the purposes of this article, think of carbs as sugar (which essentially they are—your body converts them into sugar). Your body can absorb simple (single) sugars directly, but complex sugars have to be broken into simple sugars by enzymes, which are found on your intestinal lining, before absorption becomes possible. Then the newly-minted simple sugars can be absorbed.
If complex carbs don’t get broken down (for whatever reason), then they don’t get absorbed, and they travel on down through your intestines. Then they come in contact with the bacteria in your gut. These bacteria break down the carbs for you, but they produce two major byproducts: gas (so you feel distended) and acid (which causes inflammation in your intestines). Your body responds to the inflammation by producing mucus to protect itself.
The problem is, the mucus blocks the enzymes in your intestines from coming in contact with other complex carbs you eat. So more complex carbs get turned into gas and acid, producing even more mucus.
In a nutshell: inflammation (from autoimmunity or anything else) —> mucus —> inability to break down complex carbs —> gas and acid —> more inflammation —> more mucus… and round and round we go.
The Way to Break It
Gottschall’s answer (and my clinical experience) is this: you have to interfere with the cycle at the only place where you have some control. And the only part you are directly in control of is what you eat.
So if you stop eating carbs that require enzymes to break them down (specifically disaccharides: two sugars hooked up to each other, meaning mostly grains and processed or canned carbs), the nasty bacteria in your gut have nothing to eat. So instead of producing gas and acid, they starve and die. Gas and intestinal inflammation decrease; therefore mucus production decreases.
The rest of the gut-healing protocol is very similar to the approach for food allergies, and there are almost always a bunch of food allergies secondary to IBD-associated inflammation, and these will also need to be addressed. Eventually you should be able to add disaccharides back into your diet, as long as you don’t overdo it and continue to avoid foods you’re allergic to (which may exacerbate or perpetuate the inflammation as well).
As a side note, some (not all) of these patients also tend towards depression or anxiety. My theory is that, because some 80% of the serotonin in the body is produced in the gut, inflammatory gut conditions can sometimes trigger mental/emotional imbalances. If this is the sole or primary source of the problem, your mood may also improve as the gut heals.
For more on this topic, check out “Breaking the Vicious Cycle” by Elaine Gottschall.