The Specific Carbohydrate Diet (SCD) is a strict elimination diet that removes most complex carbohydrates, all grains, refined sugar, and many dairy products. It allows only carbohydrates made of single sugar molecules (monosaccharides), which are easier to absorb in the small intestine. The diet was developed primarily for people with inflammatory bowel disease (IBD), celiac disease, and other chronic digestive conditions, though it has attracted a wider following over the years.
How the SCD Works
The core theory behind the SCD is that certain complex carbohydrates, particularly those made of two or more sugar molecules linked together, aren’t fully digested in a damaged or inflamed gut. When these carbohydrates pass through unabsorbed, they feed harmful bacteria in the intestines. Those bacteria multiply, produce acids and toxins, and trigger more inflammation, which damages the intestinal lining further and makes absorption even worse. Elaine Gottschall, who popularized the diet in her 1994 book Breaking the Vicious Cycle, called this a self-reinforcing loop of malabsorption and bacterial overgrowth.
By cutting out the carbohydrates that fuel this cycle, the SCD aims to starve out the problematic bacteria, reduce inflammation, and give the intestinal lining a chance to heal. At the same time, the diet emphasizes restoring beneficial gut bacteria through fermented foods, particularly a homemade yogurt that’s central to the protocol.
What You Can and Can’t Eat
The SCD divides all foods into “legal” (allowed) and “illegal” (not allowed) categories. The distinction comes down to carbohydrate structure. Single-sugar carbohydrates like glucose, fructose, and galactose are allowed because they absorb directly through the intestinal wall. Double-sugar and chain carbohydrates like lactose, sucrose, and starches are not.
In practical terms, the allowed list includes:
- Fruits: most fresh and dried fruits, including apricots, berries, bananas, and apples
- Vegetables: most non-starchy vegetables, including squash, spinach, carrots, and tomatoes
- Proteins: unprocessed meat, poultry, fish, and eggs
- Nuts and nut flours: almonds, walnuts, pecans (used as flour substitutes in baking)
- Certain dairy: hard cheeses aged over 30 days, dry-curd cottage cheese, and homemade 24-hour fermented yogurt
- Honey: the only permitted sweetener
The restricted list includes all grains (wheat, rice, oats, corn), potatoes, most commercial dairy products, refined sugar, high-fructose corn syrup, soy, and any processed foods containing thickeners, stabilizers, or added starches. Canned vegetables and most commercial yogurts are also off limits because of added sugars and thickening agents.
For people with active diarrhea, nuts are initially used only as nut flour in cooked recipes rather than eaten whole, and new foods are introduced gradually.
The 24-Hour Fermented Yogurt
One of the most distinctive features of the SCD is its homemade yogurt, which ferments for a full 24 hours rather than the 4 to 8 hours typical of commercial yogurt. The extended fermentation allows bacteria to consume virtually all the lactose in the milk, converting it into a simple sugar (galactose) that the gut can absorb easily. This makes the yogurt tolerable even for many people who are lactose intolerant.
The yogurt must be made with specific bacterial cultures, ideally including acidophilus strains, and kept at a steady temperature between 100 and 108°F throughout the fermentation. Bifidus strains are excluded from the SCD protocol. The yogurt serves as the diet’s primary probiotic source, intended to help repopulate the gut with beneficial bacteria as the intestinal environment improves.
What the Clinical Evidence Shows
The strongest research interest in the SCD has focused on Crohn’s disease and ulcerative colitis. Results are promising but not dramatically different from other therapeutic diets. The largest comparative study to date, known as DINE-CD, tested the SCD against a Mediterranean diet in adults with mild to moderately active Crohn’s disease. At six weeks, 46.5% of SCD participants achieved symptomatic remission, compared to 43.5% on the Mediterranean diet. Clinical remission rates were nearly identical: 48.5% for the SCD and 47.8% for the Mediterranean diet. By week 12, remission rates held steady at around 40 to 47% in both groups, with no statistically significant difference between them.
Both diets improved symptom scores substantially from baseline, but neither was especially effective at lowering objective markers of inflammation. Only about 5 to 11% of participants on either diet saw meaningful drops in C-reactive protein, a blood marker of systemic inflammation. The SCD performed somewhat better on fecal calprotectin, an intestinal inflammation marker, with about 26% of participants responding by week 12 compared to about 8% on the Mediterranean diet, though the difference wasn’t statistically significant given the small sample sizes.
Pediatric studies have been smaller but occasionally more striking. In one study of 10 children with Crohn’s disease using the SCD as their sole treatment, 4 out of 10 achieved complete endoscopic healing (visible resolution of intestinal damage) after 12 weeks, and 6 of 10 reached clinical remission. A separate study of 7 children with Crohn’s who weren’t on any immunosuppressive medications found that all showed clinical improvement by three months.
Nutritional Gaps to Watch For
Because the SCD eliminates grains, most dairy, and many fortified foods, it can leave significant nutritional holes. A study tracking the dietary intake of children on the SCD found that 100% of participants fell below the recommended daily intake for vitamin D, and 75% fell short on calcium. Average intakes of thiamin (B1), folate (B9), and phosphorus were also below recommended levels. Broader concerns have been raised about the diet’s potential to create deficiencies in vitamin B6, potassium, and vitamins A, C, and E as well.
These gaps matter especially for children, who need consistent nutrient intake for growth, and for anyone following the diet long term. Supplementation or careful food planning can help close the gaps, but the restrictions make it genuinely difficult to meet all micronutrient needs through food alone. Periodic blood work to check nutrient levels is a practical safeguard for anyone maintaining the diet over months or years.
What Daily Life on the SCD Looks Like
The SCD is not a casual diet. It requires significant meal planning and home cooking, since almost no packaged or restaurant food qualifies without modification. Baking relies on nut flours instead of wheat or rice flour. Sauces and dressings typically need to be made from scratch to avoid hidden starches and sugars. The 24-hour yogurt requires a yogurt maker or similar setup and regular batch preparation.
Most guides recommend introducing the diet in phases, starting with a limited set of simple, easy-to-digest foods (often called the “intro diet”) for the first few days, then gradually expanding to the full legal list as symptoms improve. Some people notice digestive changes within the first week or two, though the protocol is generally designed around a minimum commitment of several months to assess whether it’s helping.
The diet’s difficulty is one reason the DINE-CD study’s finding is noteworthy: the Mediterranean diet, which is far less restrictive and easier to maintain, produced nearly identical outcomes for Crohn’s disease symptoms. For people considering the SCD, that comparison is worth weighing. The SCD may still be the better fit for individuals who have responded poorly to less restrictive approaches or who have specific conditions like bacterial overgrowth where the carbohydrate restriction has a clearer rationale.
Origins of the Diet
The SCD traces back to Dr. Sidney Haas, a pediatrician who used a banana-based, carbohydrate-restricted diet to treat celiac disease in the early 20th century. Elaine Gottschall, a biochemist and mother of a child with severe ulcerative colitis, refined and expanded Haas’s approach after her daughter improved on the diet. Gottschall spent years researching the science behind carbohydrate malabsorption and published her findings in Breaking the Vicious Cycle in 1994, which became the foundational text for the SCD community and remains the primary reference used in clinical settings today.