What is the goal of the SCD diet?

Developed in the 1920s, the Specific Carbohydrate Diet (SCD) was originally used for celiac disease. The central question for many is: what is the goal of the SCD diet, and how does it address digestive issues like Crohn's and colitis?

Quick Summary

The SCD diet aims to repair the intestinal lining by eliminating complex carbs that cause bacterial overgrowth and inflammation. It focuses on easily digestible simple sugars to promote gut healing.

Key Points

• Break the "Vicious Cycle": The diet's core theory is to stop the cycle of bacterial overgrowth and intestinal irritation caused by undigested complex carbohydrates.

• Starve Harmful Bacteria: By removing complex carbs like starches and disaccharides, the SCD deprives harmful gut microbes of their primary food source.

• Heal the Intestinal Lining: The reduction in inflammation and harmful bacteria allows the intestinal tissue to repair and regenerate.

• Improve Nutrient Absorption: By restoring the gut's health, the diet helps the body better absorb essential vitamins and minerals.

• Alleviate Digestive Symptoms: The ultimate aim is to reduce severe symptoms associated with conditions like IBD, such as chronic diarrhea, pain, and bloating.

The Core Principle: Breaking the Vicious Cycle

The Specific Carbohydrate Diet (SCD) is founded on the theory that many digestive disorders arise from an imbalance in intestinal microbial flora, often called dysbiosis. In individuals with compromised digestion, particularly those with conditions like inflammatory bowel disease (IBD), the body struggles to properly digest and absorb complex carbohydrates. When these complex sugars and starches remain in the gut, they become a food source for harmful bacteria and yeast. As these microbes ferment the undigested carbohydrates, they produce toxic byproducts that irritate and damage the intestinal lining. This creates a "vicious cycle" of bacterial overgrowth, inflammation, and further damage, which impairs the gut's ability to absorb nutrients.

How Carbohydrates are Classified in SCD

The SCD classifies carbohydrates based on their chemical structure and how easily they are absorbed. The diet is built on a clear distinction between "legal" and "illegal" foods.

Legal Carbohydrates (Monosaccharides): These are simple, single-molecule sugars that are easily and completely absorbed in the small intestine, leaving no residue for harmful bacteria to feed on.

• Glucose (from ripe fruit)
• Fructose (from ripe fruit)
• Galactose (found in homemade, long-fermented yogurt)

Illegal Carbohydrates (Disaccharides and Polysaccharides): These are complex sugars composed of two or more linked sugar molecules. They require robust digestive enzymes to be broken down, and if digestion is impaired, they contribute to the "vicious cycle".

• Disaccharides: Lactose (milk sugar), sucrose (table sugar).
• Polysaccharides: Starches from grains, starchy vegetables like potatoes, and certain legumes.

How the SCD Diet Aims to Heal the Gut

The overarching goal of the SCD is to stop the destructive cycle of inflammation and microbial imbalance. By exclusively consuming easily digested monosaccharides and eliminating complex carbohydrates, the diet seeks to achieve several therapeutic outcomes:

• Starve Harmful Bacteria: By removing the food source for pathogenic bacteria and yeast, the diet helps to reduce their numbers, allowing beneficial microbes to flourish.
• Promote Intestinal Healing: With the inflammatory load reduced, the intestinal lining is given the opportunity to rest and repair itself. This can help restore the integrity of the gut barrier.
• Improve Nutrient Absorption: A healthier, less inflamed intestinal lining can more effectively absorb essential vitamins and minerals, helping to reverse potential malabsorption and nutrient deficiencies that often accompany digestive disorders.
• Reduce Symptoms: The ultimate clinical goal is to alleviate and manage symptoms such as chronic diarrhea, gas, bloating, and abdominal pain associated with conditions like IBD.

The "Legal" and "Illegal" Food List in Practice

The practical application of the SCD requires strict adherence to a specific food list. This is not a partial or casual approach but a precise elimination protocol.

Legal Foods Allowed on the SCD:

• Most fresh fruits and vegetables (non-starchy)
• Meat, fish, poultry, and eggs without additives
• Certain legumes, like lentils, split peas, and navy beans, after proper soaking
• Homemade yogurt fermented for a minimum of 24 hours
• Most nuts and nut flours
• Honey as a sweetener

Illegal Foods Not Allowed on the SCD:

• All grains (wheat, rice, corn, oats)
• Most dairy products (except for specific aged cheeses and long-fermented yogurt)
• Most added sugars, corn syrup, and molasses
• Starchy vegetables (potatoes, sweet potatoes, yams)
• Canned or processed meats with additives
• Soy products and other select legumes

Comparison of SCD and Low-FODMAP Diets

The SCD and Low-FODMAP diets are both therapeutic elimination diets for digestive issues, but they differ in their approach and which carbohydrates they target.

Feature	Specific Carbohydrate Diet (SCD)	Low-FODMAP Diet
Primary Goal	Heal the gut by starving bacteria and allowing the intestinal lining to repair.	Identify and reduce specific fermentable carbs (FODMAPs) that cause IBS symptoms.
Carb Focus	Excludes disaccharides and polysaccharides, allowing only monosaccharides.	Excludes specific fermentable oligosaccharides, disaccharides, monosaccharides, and polyols.
Foods Eliminated	Grains, starches, most dairy, processed sugars.	A broader range of fruits, vegetables, dairy, grains, and sweeteners high in FODMAPs.
Reintroduction	Often a long-term approach; some may reintroduce foods after prolonged symptom remission.	A defined reintroduction phase to identify specific trigger foods.

Who Might Benefit from the SCD Diet?

While originally developed for Celiac disease, the SCD is most widely known for its use in managing symptoms of inflammatory bowel diseases (IBD), particularly Crohn's disease and ulcerative colitis. It is also explored for a range of other gastrointestinal conditions:

• Small Intestinal Bacterial Overgrowth (SIBO)
• Diverticulitis
• Cystic Fibrosis
• Chronic diarrhea
• Persistent IBS symptoms

Potential Risks and Considerations

The restrictive nature of the SCD is not without risks and challenges. Before starting, it is critical to consult with a healthcare provider, ideally a dietitian experienced with the diet.

Key risks include:

• Nutrient Deficiencies: Eliminating large food groups like grains and dairy can lead to inadequate intake of nutrients such as calcium, vitamin D, and B vitamins.
• Malnutrition and Weight Loss: The diet can be low in calories, potentially leading to unhealthy weight loss, which is a particular concern for individuals already struggling with IBD-related malabsorption.
• Social Challenges: The strict nature of the diet can make socializing and eating out difficult.

Conclusion: A Focused Approach to Digestive Healing

The central goal of the SCD diet is to promote intestinal health and healing by breaking the "vicious cycle" of inflammation caused by bacterial overgrowth. By restricting specific carbohydrates, the diet aims to starve out harmful gut microbes, reduce inflammation, and restore the gut lining. While promising for some individuals with inflammatory and digestive conditions, it is a complex and highly restrictive dietary intervention. Given the significant risks of nutritional deficiencies, anyone considering the SCD must do so under the careful supervision of a qualified medical professional. For more information, you can find a comprehensive overview from the Cleveland Clinic.

Frequently Asked Questions

What types of carbohydrates are eliminated on the SCD diet?

The SCD eliminates complex carbohydrates, specifically disaccharides (like lactose and sucrose) and polysaccharides (like starches from grains and certain vegetables), focusing instead on easily absorbed monosaccharides.

Which health conditions does the SCD diet aim to help?

The diet is primarily used to manage symptoms in conditions such as Inflammatory Bowel Disease (Crohn's, ulcerative colitis), celiac disease, diverticulitis, and chronic diarrhea.

Is the SCD diet a weight-loss plan?

No, the SCD is a therapeutic diet for addressing underlying digestive issues, not a general weight-loss regimen. It can, however, lead to weight changes if not properly managed.

How does the SCD diet differ from a Low-FODMAP diet?

Both are elimination diets, but the SCD is generally more restrictive and based on different carbohydrate classifications (mono-, di-, poly-saccharides) compared to the Low-FODMAP categories (fermentable oligo-, di-, mono-saccharides and polyols).

What is the "vicious cycle" Elaine Gottschall described?

The "vicious cycle" refers to the process where undigested complex carbs ferment in the gut, feeding harmful bacteria. These bacteria produce damaging byproducts that cause intestinal inflammation and further impair digestion.

Is there scientific evidence supporting the SCD diet?

While there is significant anecdotal evidence and some small studies showing positive results for IBD, particularly Crohn's and ulcerative colitis, more large-scale, robust scientific research is needed.

Why is homemade, fermented yogurt a 'legal' food?

Yogurt fermented for at least 24 hours is permitted because the long fermentation process breaks down the lactose (a disaccharide) into more easily digestible monosaccharides.

Are there any risks associated with the SCD diet?

Yes, potential risks include nutrient deficiencies (like calcium and vitamin D), weight loss, and difficulty adhering to the strict protocol, which requires careful planning and medical supervision.