In the last decade, inflammatory bowel diseases (IBD) have increased worldwide.
Elimination diets, such as the Specific Carbohydrate Diet (SCD), have gained popularity as potential treatments for IBD and other inflammatory and autoimmune disorders.
While gastroenterologist Sidney Haas introduced SCD in the 1920s, it was expanded and popularized in the 1980s with Elaine Gottschall’s book “Breaking the Vicious Cycle.”
This article explores SCD, the science behind it, and its effectiveness.
What is the Specific Carbohydrate Diet?
SCD is an elimination diet that emphasizes eliminating certain carbohydrate-containing foods based on their chemical structure.
The theory behind SCD is that complex carbohydrates promote an overgrowth of unhealthy bacteria in your small intestine if you have IBD.
As these bacteria grow, they produce byproducts that promote inflammation and eventually reduce the absorption of nutrients in your digestive tract.
The SCD states that it inhibits the growth of these bacteria and restores digestive function by eliminating all carbohydrate food sources that have two or more sugar molecules (di, oligo, and polysaccharides).
Although many carbohydrates are prohibited, SCD allows carbohydrate sources with unique, unbound sugar molecules or monosaccharides, as they are more easily absorbed by your digestive tract.
SCD is an elimination diet that restricts certain carbohydrates to treat various inflammatory and autoimmune bowel diseases.
Foods to Avoid
As its name implies, SCD restricts specific carbohydrates based primarily on their chemical structure.
The diet labels any food or additive “illegal” containing two or more chemically linked sugar molecules. The SCD guide, “Breaking the Vicious Cycle,” collectively refers to these foods like complex carbohydrates.
In scientific terms, any food with disaccharides, oligosaccharides, or polysaccharides will appear as illegal food.
As you can imagine, the list of forbidden foods is extensive. Here are some of the main illegal food groups:
- Grains and pseudographics, including rice, wheat, corn, quinoa, millet, and others.
- Processed meats and meats with additives.
- Dairy products, except some cheese, butter, and homemade yogurt, have been fermented for at least 24 hours.
- Most legumes, although sure dried beans and lentils are allowed after soaking
- More processed sugars, artificial sweeteners, and sugar alcohols.
- Processed foods.
The overall structure of the SCD is very rigid and should be followed exactly as described in the guide, with little or no room for flexibility.
While some people may reintroduce certain illegal foods after symptoms subside, this will vary depending on an individual’s response to the diet.
SCD restricts any food with two or more connected sugar molecules, such as dairy products, starchy vegetables, table sugar, grains, and most legumes. These foods are known as “illegal” and are strictly prohibited.
Food to eat
SCD-approved foods are collectively referred to as “legal.”
Most of the foods on this list are unprocessed whole foods that don’t offer many complex carbohydrates.
The primary approved or “legal” carbohydrate sources in SCD come from the monosaccharides glucose, fructose, and galactose.
Here are some of the SCD legal foods:
- Fruits – Most raw, fresh, or frozen fruits and juices. Canned fruits can be allowed if they do not have added sugar or starch.
- Vegetables: Most vegetables except potatoes, sweet potatoes, bananas, and other high-starch vegetables.
- Meat: most fresh meats, as long as they do not contain any fillers or additives.
- Some dairy: homemade yogurt fermented for at least 24 hours and some natural cheeses.
- Certain legumes: some dried legumes, as long as they are soaked and prepared according to the instructions in the guide.
- Nuts and Butters: Most nuts, as long as they don’t contain added starch or sugar.
- Herbs and Spices: Most dried or fresh herbs and spices. Spice mixes are generally discouraged as they contain “illegal” additives.
Since it can be challenging to determine which foods are legal, the SCD guide recommends eating only explicitly legal foods to avoid accidentally ingesting something illegal.
Most unprocessed fruits, vegetables, nuts, and meats are allowed on the SCD, with a few exceptions. As described in the guide, some legumes and dairy products are permitted as long as they are adequately prepared.
Does it treat digestive disorders?
SCD was initially designed as a therapy for people with IBD, a general term that includes ulcerative colitis, celiac disease, and Crohn’s disease.
These diseases can make it difficult for you to digest and absorb nutrients from food. In this way, the SCD aims to heal the intestinal tissue to restore its functions.
SCD advocates claim that some people are less adept at digesting foods, such as grains, legumes, refined sugar, and starch-rich food additives, resulting from established agricultural practices and the modern food industry.
Supporters claim that continued ingestion of these carbohydrates leads to an overgrowth of unhealthy bacteria in your gut that promotes inflammation, eventually decreasing your ability to digest.
Strict adherence to SCD is supposed to eventually kill these bacteria by depriving them of food, allowing intestinal tissue to heal.
To this day, SCD is used primarily to treat intestinal disorders but with mixed success.
One of the main criticisms of this diet is its lack of concrete scientific evidence.
Most of the available data is weak and limited to microscopic studies or anecdotal evidence, which is not enough to establish whether the SCD works or not definitively.
Ultimately, more research is needed to determine whether SCD is genuinely an effective treatment for IBD.
Although SCD is often promoted for people with IBD, there are very few studies to support its effectiveness.
Other medical conditions
Although primarily used to treat IBD, SCD is also marketed for people with other medical conditions, including autism spectrum disorder (ASD) and cystic fibrosis (CF).
Early research suggests that gut bacteria may be crucial in treating behavioral and autoimmune conditions, such as CF and ASD.
Because the Specific Carbohydrate Diet is designed to balance your digestive tract, its proponents theorize that it may also be an effective therapy for these conditions.
However, the scientific understanding of these disorders is limited. Beyond anecdotal reports, there is no research to suggest that SCD treats diseases outside of IBD, if so.
It is not yet clear whether SCD affects gut bacteria.
More research is needed to understand whether SCD affects autism spectrum disorder and cystic fibrosis.
While SCD advocates claim that it treats autism spectrum disorder and cystic fibrosis, there is no scientific research to support this idea.
A diet as restrictive as SCD carries no risks. When well planned, SCD can be balanced, complete, and healthy.
However, SCD eliminates large nutrient-dense food groups beneficial to most people, including whole grains, some legumes, and most dairy products.
Eliminating these foods without replacing their essential nutrients could result in poor diet quality and subsequent nutritional deficiencies.
Maintaining good nutrition can already be difficult if you have IBD. Adopting an extremely restrictive diet like SCD could increase your risk of malnutrition and associated complications.
Ensuring that SCD is safe and healthy takes effort, but it is not impossible.
If you are considering this diet, check with your dietitian or another qualified healthcare professional to make sure it is meeting your needs.
Because SCD is so restrictive, you could be at risk for malnutrition if your diet is not planned correctly.
Should you try it?
While anecdotal evidence indicates that SCD improved IBD symptoms in some people, there is no guarantee that it will work for everyone. Medical conditions like IBD are complex, and specific interventions may differ for different people.
With current evidence, it is unclear if diet plays any role in IBD treatment beyond the placebo effect.
A well-planned elimination diet can be worth it, especially if you want to avoid the more severe risks associated with certain medications and surgeries in the long term.
Although diet is a personal decision, you should discuss SCD with a qualified healthcare professional before making significant lifestyle changes.
There is very little substantial evidence to support SCD. While it may be less risky than other medical therapies, you should consult your healthcare provider before diving in.
The bottom line
- SCD is an elimination diet designed to treat IBD symptoms and restore digestive function by purging many carbohydrate-containing foods on the idea that they damage the gut.
- While some people may notice improvements in their IBD symptoms, very little research supports its effectiveness beyond the placebo effect.
- Due to the diet’s restrictive nature, it could increase your risk of malnutrition.
- If you consider SCD, speak with your healthcare provider and dietitian first to reduce potential risks and ensure a balanced diet.