[Last updated 13th August, 2018]
The Specific Carbohydrate Diet (SCD) is a diet often used by people suffering from digestive disorders.
But does it really help to improve gut health?
This article explains SCD and looks at the evidence behind it.
What is the Specific Carbohydrate Diet (SCD)?
The Specific Carbohydrate Diet is a diet plan designed to help address inflammatory digestive disorders.
This includes diseases and conditions like ulcerative colitis (UC), Crohn’s disease, diverticulitis, and celiac disease.
The diet became popular from the 1994 book Breaking the Vicious Cycle: Intestinal Health Through Diet, by biochemist Elaine Gottschall. It was based on a few celiac and food intolerance theories from the past century combined with Elaine’s experience treating her daughter’s UC.
It’s called the Specific Carbohydrate Diet because only certain carbohydrates called monosaccharides, or simple sugars, are allowed. Larger carbohydrate molecules like di-, oligo-, and polysaccharides are excluded.
Foods containing fats and proteins are not impacted.
Summary: The Specific Carbohydrate Diet was designed for those suffering from inflammatory digestive disorders. The only carbohydrates allowed on the diet are monosaccharides.
How Does SCD Help?
The purpose of the Specific Carbohydrate Diet is to reduce inflammation in the digestive tract.
It’s also said to improve the balance of bacteria in the gut by providing the body with nutrient-rich and easily digestible foods.
These are the main (theoretical) benefits in more detail:
Addressing bacterial overgrowth
Inflammatory digestive disorders harm the gut lining, which is where digestion and absorption occurs.
The result is that the body doesn’t properly breakdown foods, particularly carbohydrates. Bacteria in the gut then interact (ferment) these poorly digested carbohydrates, producing waste products that irritate and damage the gut.
A vicious cycle forms where bacterial fermentation causes damage, which then worsens digestive and absorptive abilities. The SCD removes poorly digested carbohydrates (i.e. any carbohydrate that is not a monosaccharide) from the diet to improve bacterial overgrowth.
Addressing leaky gut
The lining of a healthy gut is tightly regulated to prevent absorption of harmful substances into the body.
When regulation becomes lax, which is present in inflammatory digestive disorders, larger and potentially harmful substances can pass through (1).
This is known as increased intestinal permeability, or Leaky Gut. The SCD aims to heal the gut lining, thereby improving leaky gut.
Addressing poor absorption
Digestive enzymes are released from cells in the gut lining in the presence of food to help with digestion.
When the gut is damaged, there may be inadequate release of enzymes. Additionally, the gut lining releases more mucus to help protect itself. Excess mucus blocks enzymes from interacting with food.
Because the SCD only allows monosaccharides, digestive enzymes are not required for digestion and absorption since this type of simple sugar cannot break down into smaller parts.
Summary: The SCD may improve digestive disorders by healing the gut lining, reducing bacterial overgrowth, and improving nutrient absorption. It does this by removing carbohydrates that are more difficult to digest.
What Does The Research Say?
Research on SCD is in its infancy, but there have been studies looking at specific health conditions.
Inflammatory Bowel Disease (IBD)
Research on SCD and Inflammatory Bowel Disease (IBD) is emerging.
In a small retrospective study of 7 children with Crohn’s disease, subjects followed the SCD without the use of any medications for 5 to 30 months.
All symptoms and lab markers were significantly improved at their 3-month clinic checkup. Similar study designs showed these same promising results (2, 3, 4, 5).
Following on from that, a prospective 12-week study in 12 pediatric IBD patients following the SCD produced notable symptom and lab improvements. Researchers also found significant changes in the microbiome via stool testing (6).
Additionally, a case study series of 50 IBD patients following the SCD for over 2 years showed it was 91.3% effective in controlling acute flare symptoms and 92.1% effective at maintaining remission (7).
Lastly, adults with IBD have a strong perceived benefit when following the SCD based on results from 417 respondents of an anonymous online survey (8).
Overall, current scientific evidence is promising but in its early stages for IBD. More research is necessary to confirm these findings in both children and adults.
Irritable Bowel Syndrome (IBS)
There are some similarities between SCD and the commonly recommended low FODMAP diet for managing food intolerance.
However, there is no research on using SCD specifically for treating IBS.
There is also a diet that combines SCD with the low FODMAP diet, which was designed for patients with small intestine bacterial overgrowth (SIBO).
While this combination diet could theoretically help improve SIBO, there are no studies supporting its use.
No research indicates SCD would be useful for generally healthy people.
It’s highly restrictive and unnecessary for the vast majority of the population to follow.
Summary: The SCD could be useful for IBD, but there is not enough evidence to recommend it as the first option. There is no research on the SCD for those with IBS or the general healthy public.
SCD Food List
The SCD uses the terms “legal” and “illegal” to help followers understand what to eat.
Legal foods include:
- Fresh and frozen vegetables and fruits: all vegetables (except those listed below), all fruits, dried fruit (no added sugar or preservatives), canned fruit packed in own juice
- Unprocessed meat, eggs and fish: turkey, chicken, beef, pork, lamb, fish, shellfish, canned fish like tuna or salmon (in oil or water)
- Homemade yogurt (fermented 24-hours) and low lactose cheeses: Cheddar, Colby, Havarti, Monterey Jack, Parmesan, Swiss, dry curd cottage cheese, butter
- Oils: olive, canola, sesame, coconut, etc.
- Sweeteners: Honey, small amounts of saccharine
- Nuts: tree nuts, peanuts (no preservatives or added starches)
- Some legumes: dry white beans, lentils, lima beans, split peas
- Spices: all kinds (no starch or anticaking agents), baking soda
- Drinks: 100% fruit juice, tomato juice, very dry wine, weak tea or coffee, occasional gin, Scotch, bourbon or vodka, club soda
Illegal foods include:
- Processed meats and fish: hot dogs, cold cuts, smoked meat/fish, canned meat
- Certain vegetables: potatoes, yams, pickled veggies (if they contain added sugar or preservatives), canned vegetables, Jerusalem artichokes
- Dried and canned fruits: if they contain added sugar or preservatives
- All grains: rice, pasta, cereal, corn, oats, quinoa, barley, wheat, rye, buckwheat, millet, etc.
- High lactose dairy: milk, processed cheeses, fresh cheeses (mozzarella, ricotta), ice cream, margarine, buttermilk
- Food preservatives: cooking sprays, spice mixes, all starches (cornstarch, arrowroot, tapioca, sago, etc.), gums, pectin, baking powder
- Some legumes: soy, bean sprouts, black eyed beans, fava, garbanzo, pinto, canned beans, bean flour (not soaked prior to grinding), shelled peanuts (may have added starch)
- Most sweeteners: corn syrup, cane sugar, molasses, stevia, maple syrup, chocolate, carob
- Drinks: beer, cordials, liqueurs, brandy, V-8 juice, juice boxes, mint tea, soy milk, instant tea or coffee
SCD Introduction Phase
Prior to starting the diet, consider following the introduction phase for about 5 days or until diarrhea subsides.
SCD Introduction Instructions:
- Avoid fruit: Then try adding in ripe, peeled and cooked fruit. Start with ripe, mashed bananas.
- Avoid raw vegetables: Then try adding cooked vegetables one at a time. Start with squash (pumpkin), tomato, string beans, and carrots. Avoid cruciferous vegetables until digestion improves significantly.
- Eliminate eggs: until severe diarrhea subsides
- Avoid excess fat intake
- Reduce and avoid legumes: Then cautiously add them, one at a time, after about 3-months on the diet.
Summary: The SCD allows many healthy, unprocessed foods including proteins, fresh fruits/vegetables, nuts, and some dairy. It avoids most processed foods, especially those that contain starches, sugars and preservatives.
Sample SCD Meal Plan
While changing the diet is not easy, there are many simple and delicious foods when following the SCD.
Here is an example of foods you could choose on an SCD meal plan.
- Baked apples with honey, walnuts and spices.
- Grain free banana bread with almond and coconut flour. Smear nut butter on slice of bread for added protein.
- 2 egg, spinach and cheddar cheese scramble.
- Tuna fish salad, garnished with olives on a bed of lettuce or greens of your choice.
- Italian chopped salad with chicken and oil and vinegar or lemon dressing.
- Grilled chicken wrapped in lettuce topped with homemade guacamole and a side of applesauce.
- Roasted vegetable and chicken soup with butternut squash, onion, spinach and spices.
- Zucchini noodles with meatballs and tomato sauce.
- Broiled ground beef burger with cauliflower mash and roasted asparagus.
- 1/2 cup of dry curd cottage cheese (DCCC) with fruit
- Banana with nut butter
- 1/4 cup mixed nuts
- Homemade kale crisps with sea salt and garlic
Who Should Try the SCD and Is It Safe?
The SCD could be useful for IBD and celiac disease.
However, those who suffer from functional digestive disorders such as irritable bowel syndrome (IBS), chronic constipation, and chronic bloating should not try this as it has not been studied in these populations.
Also note that the SCD is a very restrictive eating plan that can cause more issues if not properly guided. For example, it may cause social isolation, food fear, weight loss, and nutrient deficiencies.
Therefore, it’s important to talk to your doctor or dietitian to find out if this plan is best suited for you.
Summary: The SCD is appropriate to try for those with inflammatory digestive disorders, but should be approached with caution and under professional supervision. It is not appropriate for all digestive conditions.
Summary: Does The Specific Carbohydrate Diet Work?
The Specific Carbohydrate Diet is an approach that may help those with inflammatory digestive disorders, such as IBD.
Research on the SCD and IBD is in its early stages, but results so far are promising.
Just note there is no evidence it’s useful for those with IBS or those who are generally healthy.
Remember to always speak with your healthcare provider before making any serious diet changes