What are the rules for the SCD diet?

November 26, 2025 •

4 min read

Developed almost a century ago, the SCD diet gained significant popularity in the late 1980s through the book "Breaking the Vicious Cycle". This therapeutic eating plan eliminates complex carbohydrates to improve gut health and is governed by very specific, detailed rules.

Quick Summary

The SCD diet eliminates complex carbohydrates, starches, and lactose, while emphasizing easily digestible monosaccharides, to starve harmful gut bacteria and promote healing. It involves a restrictive introductory phase followed by a careful reintroduction of allowed foods, focusing on whole, unprocessed options like meats, fruits, and select vegetables.

Key Points

Strict Carb Restriction: The SCD eliminates complex carbohydrates (polysaccharides and disaccharides) that are difficult to digest and ferment in the gut.
Embrace Monosaccharides: Only simple, single-molecule carbohydrates (monosaccharides) found in allowed fruits and honey are permitted, as they are easily absorbed.
Start with the Intro Diet: A restrictive 2-5 day introductory phase is required to calm severe digestive symptoms using only very limited, easy-to-digest foods.
Eat Unprocessed Foods: The diet mandates a focus on whole, unprocessed foods, including fresh meats, fish, eggs, most fruits and vegetables, and homemade fermented dairy.
Avoid All Grains and Starches: All grains and starchy vegetables, including potatoes, rice, corn, and wheat, are strictly forbidden.
Beware of Sugars and Additives: All processed sugars, sweeteners, and food additives must be avoided; honey is the sole allowed sweetener.
Consult a Professional: The diet's highly restrictive nature can lead to nutritional deficiencies, making it crucial to work with a doctor and dietitian.

The Specific Carbohydrate Diet (SCD) is a highly restrictive elimination diet designed to address digestive disorders by altering the balance of gut bacteria. The core principle, championed by biochemist Elaine Gottschall, is that complex carbohydrates are difficult to digest and, if left unabsorbed, can feed harmful bacteria in the intestines, leading to inflammation and damage. By restricting these carbs, the diet aims to "starve out" the bad bacteria and restore a healthier gut microbiome.

The Fundamental Rule: Carbohydrate Classification

The most important rule of the SCD is the clear distinction between legal (allowed) and illegal (forbidden) carbohydrates. Legal carbohydrates are monosaccharides—single-molecule sugars that are easily absorbed by the small intestine and do not require further breakdown. Illegal carbohydrates, such as disaccharides and polysaccharides, are more complex and can pass through the small intestine largely undigested, becoming food for gut bacteria. All grains, including wheat, rice, corn, and oats, are strictly prohibited because of their complex starch content.

Essential Rules for the SCD Introductory Phase

Before starting the full diet, followers must complete a strict introductory phase lasting 2-5 days to help calm severe symptoms. This phase is extremely limited to allow the gut to rest and begin healing.

Rules for the Intro Diet:

Limited Food Selection: Only specific, easy-to-digest foods are permitted, such as homemade chicken soup, broiled meat or fish, gelatin, and SCD-friendly cheesecake.
Cooked and Pureed Vegetables: Vegetables should be well-cooked and potentially pureed, like cooked carrots or squash, to make them easy to digest.
Avoid Raw Foods: All raw fruits and vegetables, which can be harsh on an inflamed gut, are forbidden during this initial period.
No Excess Fat: Fat intake should be kept to a minimum as it is harder to digest.

The Complete Rules: Allowed vs. Forbidden Foods

After the introductory period, individuals can expand their diet by gradually introducing a wider range of 'legal' foods, always monitoring for symptoms. Adherence to the complete 'legal' and 'illegal' lists is the long-term rule.

Allowed (Legal) Foods:

Meats: Unprocessed, fresh meats, poultry, and fish.
Fruits: Most fresh, frozen, or cooked fruits without added sugar.
Vegetables: Most non-starchy, fresh vegetables.
Dairy: Homemade 24-hour fermented yogurt and certain hard, aged cheeses like sharp cheddar and Swiss.
Fats: Oils like olive, coconut, and butter.
Nuts and Legumes: Select legumes (navy beans, lentils, peas) and nuts, often requiring soaking and preparation.
Sweetener: Only honey is permitted.

Forbidden (Illegal) Foods:

Grains: All grains, including wheat, barley, corn, rice, and oats.
Processed Sugars: White sugar, corn syrup, molasses, and most sweeteners.
Lactose-rich Dairy: Milk, cream, ice cream, and most commercial yogurts.
Starchy Vegetables: Potatoes, sweet potatoes, turnips, and parsnips.
Additives: Processed and canned foods with additives, preservatives, or added sugars.
Certain Legumes: Soybeans, bean sprouts, and chickpeas.

Comparison: SCD vs. Mediterranean Diet


Feature	Specific Carbohydrate Diet (SCD)	Mediterranean Diet
Core Philosophy	Restrict complex carbohydrates to starve harmful gut bacteria and heal the digestive tract.	Emphasize whole foods, healthy fats, and plant-based foods for overall health.
Grains	Strictly Prohibited.	Encouraged (e.g., whole grains).
Legumes	Selectively Allowed (after initial phases and specific preparation).	Encouraged.
Dairy	Highly Restricted (only homemade 24hr fermented yogurt and hard cheeses).	Moderate Intake (yogurt and cheese are common).
Processed Foods	Strictly Prohibited.	Discouraged.
Sweeteners	Only honey is allowed.	Very limited intake of sweets.
Level of Restriction	High, with extensive lists of 'legal' and 'illegal' foods.	Flexible, focusing on food groups rather than rigid lists.

Conclusion

The Specific Carbohydrate Diet operates on a clear set of rules centered around the elimination of complex carbohydrates that may feed harmful gut bacteria. The diet begins with a very restrictive introductory phase, followed by a gradual reintroduction of legal foods, including certain meats, fruits, vegetables, and homemade dairy options. While some individuals with digestive conditions like IBD report significant symptom relief, the diet's strict nature can make it challenging to maintain and may risk nutritional deficiencies. Consulting a healthcare provider and a registered dietitian is crucial for anyone considering the SCD to ensure safety and nutritional adequacy. More research is needed to fully understand the diet's effectiveness compared to less restrictive, evidence-based alternatives like the Mediterranean diet. For those considering the SCD, the principles are clear, but the commitment is significant. For further, authoritative information on the diet's protocols, consult the foundational text, Breaking the Vicious Cycle.

Additional Considerations

Beyond the core rules, several additional aspects of the SCD guide successful implementation:

Food Preparation: The diet heavily emphasizes scratch cooking to ensure no illegal additives or ingredients are present.
Reading Labels: Because of the no-additive rule, followers must become meticulous label readers to avoid forbidden sugars or starches hiding in pre-packaged foods.
Hydration: Proper hydration is essential, especially during the initial phase when GI symptoms may be acute.
Patience: The diet is not a quick fix, and healing can take months or even years. Gradual reintroduction of foods based on individual tolerance is key.
Probiotics: Homemade 24-hour fermented yogurt is a key component intended to help repopulate the gut with beneficial bacteria.

Frequently Asked Questions

The primary theory is that by eliminating complex carbohydrates, which are poorly digested and feed harmful gut bacteria, the diet can reduce intestinal inflammation and restore a healthier bacterial balance.

Yes, because the SCD eliminates all grains, including wheat, it is inherently gluten-free. However, it is also free of many non-gluten grains like rice and corn.

No, commercial yogurt is not allowed because it often contains added sugar and higher levels of lactose. The diet only permits homemade yogurt that has been fermented for at least 24 hours to reduce lactose content.

No, potatoes are considered a starchy, complex carbohydrate (a polysaccharide) and are therefore illegal on the SCD diet.

The duration varies depending on the individual and the severity of their condition. Some follow it for several months, while others may follow it for years. Food reintroduction is done gradually after symptom remission.

Accidentally consuming an illegal food may cause a flare-up of symptoms. The best approach is to return to the strict 'legal' foods or even the introductory diet for a few days to let your digestive system recover.

While the SCD was originally developed for celiac disease and popularized for IBD, some practitioners caution that individual responses differ. The diet's efficacy is still being researched, and what works for one person may not work for another.