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SCD Science

SCD™ Explanation for Kids
SCD™ Explanation for Parents
SCD™ Explanation for Health Care Professionals

SCD™ Explanation for Kids

The mono-saccharides go through the
holes of the small intestine and
there is no food for the gut bugs.

The di-saccharides can not go through
the holes of the small intestine.
The di-saccharides are too big.
The di-saccharides feed the gut bugs.

The poly-saccharides can not go through
the holes of the small intestine.
The poly-saccharides are way too big.
The poly-saccharides feed the gut bugs.

The gut bugs are eating di-saccharides
and poly-saccharides and they muliply.

The villi take up nutrients from the GI tract
and transport them into blood.

The gut bugs emit acids and the villi change.

SCD™ Explanation for Parents

There are different types of food we humans eat. Our meals primarily contain proteins, fats and carbohydrates. Fats and proteins cause no problems. The problem is caused by some carbohydrates. More specifically, the di-saccharides and the poly-saccharides are causing the problems.


Monosaccharides are built out of one sugar molecule. The holes in the lining of the intestines are exactly the size of these sugar molecules. The body can readily use these saccharides when they pass through the holes and enter the bloodstream. They don't even have to be digested, since they can be absorbed directly by the intestines absorptive cells. Monosaccharides are primarily found in (ripe) fruit and honey (in the form of glucose and fructose).

Disaccharides and Polysaccharides

Disaccharides consist of two sugar molecules. Disaccharides are too big to pass the filter in the intestines (only monsaccharides can pass). The body has special enzymes in the first part of the small intestines, the duodenum, where these enzymes are produced. For example, lactose is a disaccharide. The body produces lactase to digest/split the lactose into two monosaccharides. These monosaccharides can then pass the filter. Disaccharides can be found in table sugar, brown sugar and milk (lactose).

Polysaccharides are even bigger molecules. These consist of many sugar molecules. These molecules are even more difficult for the digestive system to handle. First, the pancreas releases a fluid, which contains for an enzyme that can split the polysaccharides (starches) into disaccharides (maltose). Next, the enzymes (maltase), which are produced in the duodenum, must break down the disaccharides (maltose) into monosaccharides, before the body can utilize this kind of carbohydrates. Starches mainly contain polysaccharides.

The problem

In a healthy person all these processes work perfectly. However, in a small group of people, the duodenum can't produce enough enzymes to digest all the carbohydrates (di- and polysaccharides). This is what happens next: Large amounts of undigested carbohydrates remain in the intestines. This would normally be no problem, because whatever the body doesn't utilize will end up in the toilet. However, the intestines also have natural inhabitants: Bacteria. The bacteria have been waiting for a long time for such a feast ! Lots and lots of disaccharides, their favorite meal !

To thank you for the meal, they start to produce large amounts of gas and they start to produce acids. As a result, the gas pressure in the intestines gets higher and higher. The body wants to relieve itself of the overpressure, and the host (you) starts to burp and have gas. Also, the gas is giving the stomach some false signals. The stomach replies by producing more digestive acids. The result for the host: heartburn and throwing up and nausea.

I almost forgot: The bacteria are also producing acids. The acids start to degenerate the intestines lining, its absorptive cells and its enzyme producing cells.

The vicious cycle

This is the introduction of a severe vicious cycle:

The enzyme producing cells in the intestines (duodenum) are dying because of the acids. So, while eating your next meal, there will be an even larger shortage of enzymes. So, more bacteria can eat more undigested disaccharides and they produce even more acids. The acids destroy even more enzyme producting cells. This is where the cycle restarts and restarts and restarts... Until you one day go the physician and complain about heartburn, burping, having gas, throwing up, etc.

The solution

The solution is very simple: Stop eating complex carbohydrates !
Complex carbohydrates are the disaccharides and the polysaccharides.

The list of foods that can be eaten is still very large. It consists mainly of: Fruits, vegetables, oils, honey and nuts. Wheat and every other granes are forbidden. Table sugar, brown sugar are also forbidden. For a complete list of foods, check, a really nice site, made by Mik, from Denmark, who has completely healed himself using the SCDiet. The you can find a large number of recipes. It's even possible to bake your own bread by using almondflour !

I find it not too hard to eat by the diet. Some think it's very hard, but after a couple of weeks on the diet, you start to feel so much better. Next, you even start to like the foods, because they are so much more natural than what you used to eat before. Not much later, you won't even bother when your friends are eating a Big Mac menu and you are not. It's very important to not cheat on the diet.. I learned it the hardway.. After being on the diet for seven weeks I ate some cookies and within 5 days I felt completely misserable. It took another seven weeks to regain my condition !

(from Ned in the Netherlands)

SCD™ Explanation for Health Care Professionals

From Teresa Binstock (10/03):

Four weeks ago I knew nothing about the SCD™. I was sent Elaine Gottschall's book Breaking the Vicious Cycle and was asked to comment regarding its scientific basis. Thus far, aside from perusing the book's first several chapters, I've obtained appx 70 articles (mostly as cited by Elaine) and three books (two cited by Elaine).

The diagnostic category "acquired disaccharidase deficiency" is well established in the med lit (for infants, toddlers, children, adults, and elderly). The syndrome has much interindividual variation, there are several "levels" of disaccharidase deficiency, with lactase deficiency being the most common. These various deficiencies are associated with adverse colonization, and the studies mention many of the gut bugs we read in CDSA/CP fecal-evals from Great Smokies.

We're all fortunate the Elaine Gottschall has created such a foundation via her science chapters and their citations -- which can be augmented via PubMed, etc, and the perusing of whole articles -- even as more parental anecdotes (such important information) keeps accruing.

From Tanya Krievel:

The Specific Carbohydrate Diet™ is predicated on the understanding that Ulcerative Colitis, Crohn's Disease, Irritable Bowel Syndrome, and gluten therapy resistant Celiac are the consequence of an overgrowth and imbalance of intestinal microbial flora. By altering the nutrition we take in, we can effect the constitution of our intestinal flora, and bring it back into balance, healing our digestive tracts and restoring proper absorption.

The intestinal tract forms a rich ecosystem, comprised of over 400 bacterial species. Some are harmless, and others not. In the gut of a healthy person, these various communities of microbes compete with each other for scarce nutritional resources. Consequently, they exist in a state of balance, and the stomach and small intestine harbour only a sparse population of microbial flora. In the large intestine, each type inhibits an overabundance of the others, and this prevents the waste products and toxins of a particular type of microbe from overwhelming the body. The stomach and upper intestine are also protected by high acidity, and the action of peristalsis.

The Vicious Cycle

When the balance in the gut is disturbed, an overgrowth of intestinal flora can result. Microbes migrate to the small intestine and stomach, inhibiting digestion and competing for nutrients. The gut then becomes overloaded with the byproducts of their digestion. This bacterial overgrowth can be triggered by overuse of antacids, reduced stomach acidity due to aging, weakening of the immune system through malnutrition or poor diet, and alteration of the microbial environment through antibiotic therapy.

The components of our diet, particularly carbohydrates, play an enormous role in influencing the type and number of our intestinal flora. When carbohydrates are not fully digested and absorbed, they remain in our gut, and become nutrition for the microbes we host. The microbes themselves must digest these unused carbohydrates, and they do this through the process of fermentation. The waste products of fermentation are gases, such as methane, carbon dioxide & hydrogen, and both lactic & acetic acids, as well as toxins. All serve to irritate and damage the gut.

There is evidence that increased acidity in the gut due to malabsorption and fermentation of carbohydrates, may lead common harmless intestinal bacteria to mutate into more harmful ones. Further, lactic acid produced during the fermentation process has been implicated in the abnormal brain function and behaviour sometimes associated with intestinal disorders.

The overgrowth of bacteria into the small intestine triggers a worsening cycle of gas and acid production, which further inhibits absorption and leads to yet more harmful byproducts of fermentation. The enzymes on the surface of the small intestines are destroyed by the now present bacteria, and this further disrupts the digestion and absorption of carbohydrates, leading to further bacterial overgrowth. As both the microbial flora and their byproducts damage the mucosal layer of the small intestine, it is provoked to produce excessive protective mucus, which further inhibits digestion and absorption.

Damage to the mucosal layer involves injury to the microvilli of our absorptive cells. These microvilli act as the last barrier between the nutrition we take in and our bloodstream. As our absorption is inhibited, folic acid and vitamin B12 deficiency can lead to impaired development of microvilli, while an abnormally thick layer of mucus prevents contact between microvilli enzymes and the carbohydrates we ingest. The small intestine responds to this spiraling irritation by producing more goblet (mucus-making) cells, creating yet more mucus. Finally, as the goblet cells become exhausted, the intestinal surface is laid bare, and is further damaged, and possibly ulcerated.

As more carbohydrates are left in the gut, they cause water and nutrients to be pulled from the body into the colon, resulting in chronic diarrhea. Absorption is further hindered as diarrhea increases the rate with which food travels through the gut.

The Diet

"The Specific Carbohydrate Diet™ is based on the principle that specifically selected carbohydrates, requiring minimal digestive processes, are well absorbed and leave virtually none to be used for furthering microbial overgrowth in the intestine. As the microbial population decreases due to lack of food, its harmful byproducts also decrease, freeing the intestinal surface of injurious substances. No longer needing protection, the mucus-producing cells stop producing excessive mucus, and carbohydrate digestion is improved. Malabsorption is replaced by absorption. As the individual absorbs energy and nutrients, all the cells in the body are properly nourished, including the cells of the immune system, which then can assist in overcoming the microbial invasion."

The simpler the structure of the carbohydrate, the more easily the body digests and absorbs it. Monosaccharides (single molecules of glucose, fructose, or galactose) require no splitting by digestive enzymes in order to be absorbed by the body. These are the sugars we rely on in the diet. They include those found in fruits, honey, some vegetables, and in yogurt.

Double sugar molecules (disaccharides: lactose, sucrose, maltose and isomaltose) and starches (polysaccharides) are primarily avoided on the diet. Some starches have been shown to be tolerated, particularly those in the legume family (dried beans, lentils and split peas only). However, they must be soaked for 10-12 hours prior to cooking, and the water discarded since it will contain other sugars which are indigestible, but which are removed in the soaking process. Small amounts of legumes may only be added to the diet after about three months.

The starches in all grains, corn, and potatoes must be strictly avoided. Corn syrup is also excluded since it contains a mixture of 'short-chain' starches.

Finally, the SCDiet™ relies on properly fermented yogurt, and in some cases, acidophilus supplements, to help repopulate the gut with healthy intestinal flora. By increasing the population of 'good' bacteria in the gut, the overgrowth of harmful bacteria is put in check. As the competition for nutrition between the various strains of bacteria resumes, the variety of intestinal flora is brought back into balance. Yogurt must be properly prepared by fermenting it for 24 hours. This allows enough time for the bacteria in the yogurt culture to break down the lactose (disaccharides) in milk, into galactose (a monosaccharide). All SCDiet yogurt is homemade, as commercially available yogurts are not properly fermented.

For a highly detailed, scientific explanation of the Specific Carbohydrate Diet™, please read Breaking the Vicious Cycle by Elaine Gottschall.

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