What is the Special Carbohydrate Diet (SCD)?

December 26, 2025 •

5 min read

First developed in the 1920s to treat celiac disease, the Special Carbohydrate Diet (SCD) is a restrictive nutritional program that has since been adapted for managing inflammatory bowel diseases and other digestive disorders. It is based on the theory that eliminating specific, hard-to-digest carbohydrates can starve harmful bacteria in the gut, thereby reducing inflammation and allowing the intestinal lining to heal.

Quick Summary

The SCD is a grain-free, sugar-free, and starch-free diet that restricts complex carbohydrates to manage symptoms of inflammatory bowel disease and other gut conditions. It operates on the principle that avoiding hard-to-digest carbs can curb bacterial overgrowth and reduce irritation in the intestines.

Key Points

Origin: The SCD was originally developed in the 1920s to treat celiac disease and was later popularized for inflammatory bowel diseases.
Core Principle: It restricts complex carbohydrates (starches, most sugars, lactose) that are hard to digest, which can feed harmful bacteria in a compromised gut.
Legal vs. Illegal: The diet uses strict lists of allowed ('legal') foods, such as certain fruits, vegetables, meats, and nuts, and forbidden ('illegal') foods like grains, potatoes, and processed sugars.
Evidence: The scientific evidence is largely anecdotal or from small studies, with larger, more robust research still needed to confirm its widespread effectiveness.
Risks: Its highly restrictive nature carries risks of nutritional deficiencies, and it can be difficult and expensive to adhere to long-term.
Medical Guidance: It is crucial to consult a healthcare provider and dietitian before starting the SCD to ensure safety and nutritional adequacy.

The Theory Behind the SCD: "Breaking the Vicious Cycle"

The central concept of the SCD, famously popularized by Elaine Gottschall's book Breaking the Vicious Cycle, is that gut damage can create a self-perpetuating problem. When individuals with compromised intestinal function consume complex carbohydrates, their bodies may struggle to properly digest and absorb them. These undigested starches and sugars linger in the digestive tract, where they ferment and feed an overgrowth of harmful bacteria.

How the "Vicious Cycle" Works

The theory explains the process in a clear, step-by-step manner:

Impaired Digestion: A damaged intestinal lining can lead to a deficiency in the enzymes needed to break down complex carbohydrates.
Bacterial Overgrowth: The undigested carbohydrates become a food source for pathogenic bacteria and yeast in the small intestine.
Increased Inflammation: As these microbes proliferate, they produce toxic waste products that irritate the intestinal lining, leading to increased inflammation and permeability (often called "leaky gut").
Worsening Symptoms: This cycle of inflammation and microbial imbalance causes common digestive symptoms, such as diarrhea, bloating, and abdominal pain.

The SCD aims to break this cycle by eliminating the fuel source for the harmful bacteria, allowing the gut to rest and repair itself.

What to Eat: A Guide to "Legal" Foods

The SCD uses a clear "legal" vs. "illegal" food list. Legal foods are those with simple carbohydrate structures (monosaccharides) that are easily digested and absorbed, without providing a food source for harmful gut microbes.

"Legal" Foods on the Special Carbohydrate Diet

Meat, Poultry, and Fish: Fresh, unprocessed, additive-free versions.
Eggs: All types.
Fruits: Fresh, frozen, or dried (with no added sugar).
Vegetables: Most fresh or frozen non-starchy vegetables, including string beans.
Dairy: Homemade yogurt fermented for at least 24 hours, and aged cheeses like cheddar and Swiss.
Legumes: Dried beans like navy, lentils, and split peas (prepared by soaking), and unroasted cashews and peanuts.
Nuts and Flours: Most nuts, peanuts, and nut flours are allowed.
Sweeteners: Only honey is permitted.

What to Avoid: The "Illegal" Foods

The list of illegal foods includes any food containing complex carbohydrates (disaccharides and polysaccharides), starches, and certain additives that are considered difficult to digest.

"Illegal" Foods to Eliminate

Grains: All grains, including wheat, rice, corn, quinoa, and oats.
Starches: Starchy tubers like potatoes, sweet potatoes, and turnips.
Sugars: Sucrose, molasses, maple syrup, high fructose corn syrup, and most artificial sweeteners.
Most Dairy: Standard milk, store-bought yogurt, ice cream, and mild cheeses due to their high lactose content.
Certain Legumes: Soybeans, chickpeas, and bean sprouts.
Processed Foods: Canned vegetables with additives, processed meats, and most candy and chocolate.

Is the SCD Evidence-Based? What the Research Says

Much of the support for the SCD's effectiveness comes from compelling anecdotal reports and small-scale studies. Several case studies have shown promising results in children and adults with IBD, noting improvements in symptoms and inflammatory markers. However, larger, well-controlled clinical trials are limited, and more robust research is needed to definitively confirm its efficacy.

For example, a 2021 study comparing the SCD to the Mediterranean diet in adults with Crohn's disease found that both diets led to similar rates of symptomatic remission. Notably, the Mediterranean diet is less restrictive, leading researchers to suggest it might be a more sustainable option for some patients. The scientific community remains cautious, and many gastroenterologists recommend working with a dietitian and physician if pursuing this diet to ensure nutritional needs are met.

SCD vs. Other Popular Diets

The SCD is often compared to other diets used for digestive health, such as Paleo and Low-FODMAP. Here's how they differ:


Feature	Special Carbohydrate Diet (SCD)	Paleo Diet	Low-FODMAP Diet
Primary Goal	Heal the gut lining by starving harmful bacteria.	Mimic hunter-gatherer eating patterns for general health.	Reduce symptoms of IBS by identifying carbohydrate triggers.
Carb Restriction	Eliminates all complex carbs (disaccharides & polysaccharides), but allows simple sugars (monosaccharides).	Eliminates grains and legumes, but not as specific about sugar types.	Temporarily restricts specific fermentable carbs (FODMAPs) in a phased approach.
Legume Policy	Restricts most legumes (except specific types like dried navy beans, lentils).	Restricts legumes.	Allows most legumes after reintroduction phase.
Dairy Policy	Restricts most dairy due to lactose, allows homemade 24-hr yogurt and aged cheeses.	Restricts all dairy.	Restricts most dairy (lactose) during elimination phase.
Best For	Chronic digestive conditions like IBD, Celiac, and SIBO.	General health and autoimmune issues.	Irritable Bowel Syndrome (IBS).

How to Start the Special Carbohydrate Diet

Starting the SCD requires preparation and commitment. It is crucial to consult a healthcare provider and a registered dietitian familiar with the SCD before beginning, especially given the restrictive nature of the diet and the potential for nutrient deficiencies.

Introductory Phase: Many protocols begin with a 2-5 day introductory phase consisting of a very limited selection of easily digestible foods, like homemade broth, simple fruits, and cooked vegetables. This helps calm the digestive system before expanding the diet.
Gradual Expansion: After the intro phase, you slowly introduce more foods from the "legal" list, monitoring your body's response.
Food Journaling: Keeping a detailed food diary is essential for tracking symptoms and identifying any potential food triggers. This allows for personalization of the diet.
Long-Term Adherence: For some, the SCD is a long-term commitment. For others, it's a temporary tool for healing, after which they can gradually reintroduce foods.

Challenges and Risks of Following the SCD

While potentially beneficial for some, the SCD presents several challenges and risks that should not be overlooked:

Restrictive and Demanding: The list of forbidden foods is long, which can make dining out and social situations difficult. It often requires significant time and effort for home food preparation.
Nutritional Deficiencies: Eliminating major food groups like grains and most dairy poses a risk of nutrient deficiencies, particularly in vitamins B, D, E, and calcium. This is why medical supervision is critical.
Cost: Relying heavily on whole, unprocessed, and specialty foods can be more expensive than diets that include staple grains and processed items.
Lack of Strong Evidence: The limited large-scale research means the diet is not recommended as a first-line treatment by most medical bodies.
Increased Food Fear: The strict "legal" and "illegal" framework can create anxiety and fear around certain foods, potentially harming one's relationship with food.

Conclusion: Is the SCD Right for You?

The Special Carbohydrate Diet is a powerful, restrictive dietary tool designed for serious digestive healing. While anecdotal evidence and small studies suggest it can be effective for managing inflammatory conditions like Crohn's and ulcerative colitis, it is not without its risks and challenges. Its demanding nature and the potential for nutrient deficiencies underscore the importance of working with a qualified healthcare professional and a dietitian before beginning. For individuals with specific gut issues, the SCD offers a method to break a cycle of inflammation, but it requires significant commitment and careful medical guidance. Ultimately, the decision to pursue this nutritional approach should be made in careful consultation with a trusted medical team. For more information on dietary management of inflammatory bowel diseases, the National Institutes of Health provides research insights related to nutrition.

Frequently Asked Questions

The main purpose of the SCD is to help heal the gut and reduce inflammation in individuals with digestive disorders, such as inflammatory bowel disease (IBD) and celiac disease, by eliminating complex carbohydrates that can feed harmful gut bacteria.

The theory is that a damaged gut lining can lead to improper digestion of complex carbohydrates. These undigested carbs ferment in the intestines, causing an overgrowth of harmful bacteria. By eliminating these carbs, the SCD starves the bad bacteria, reduces inflammation, and allows the gut to heal.

The SCD is most often used for conditions like Crohn's disease, ulcerative colitis, and celiac disease. It is also used for diverticulitis, cystic fibrosis, and chronic diarrhea.

Yes, major risks include potential nutritional deficiencies (especially calcium and certain vitamins) due to its restrictive nature, the challenge of long-term adherence, high cost, and the significant time commitment for food preparation.

The SCD is more specific and restrictive. Unlike a general low-carb diet, it distinguishes between simple and complex carbohydrates. Unlike the Paleo diet, which eliminates grains and most dairy, the SCD is even more specific about which carbohydrates and dairy types are allowed based on their sugar structure.

Yes, given its highly restrictive nature and the potential for nutrient deficiencies, it is crucial to follow the SCD under the supervision of a healthcare provider and a registered dietitian.

While there are many positive anecdotal reports and some small studies showing benefits, most medical professionals agree that more large-scale, robust clinical research is needed before the SCD can be widely recommended as a routine treatment.

The introductory phase is a short, initial period (2-5 days) with a very limited menu of easily digestible foods. This is designed to calm the digestive system before gradually expanding the diet.