Crohn’s disease is a chronic inflammatory bowel disease (IBD) that primarily affects the gastrointestinal tract. While there is no cure for Crohn’s disease, a chronic digestive disorder that causes inflammation and damage in the digestive tract, certain diets may help reduce symptoms and improve overall health. The Crohn's Disease Exclusion Diet (CDED) is an emerging dietary approach used to induce clinical remission, particularly in children with active Crohn's disease (CD). It combines whole foods and partial enteral nutrition (PEN), a liquid formula, making it a less restrictive alternative to liquid-only diets like exclusive enteral nutrition (EEN).
Understanding CDED
The Crohn’s disease exclusion diet (CDED), a less-restrictive form of the liquid-only diet, combines whole foods and partial enteral nutrition (liquid formula). CDED was originally developed to exclude certain foods from the Western diet, which is thought to alter the gut microbiome - the trillions of bacteria, fungi, parasites, and viruses found in the gut. A disrupted gut microbiome may impair the body’s immune response and may cause increased inflammation, according to an article in the October 2019 issue of Nutrients. “The typical Westernized diet has been suggested to lead to dysbiosis [imbalance of bacteria in the gut] or damage to the protective gut barrier,” says Brittany Roman-Green, a registered dietitian and a member of the Crohn’s & Colitis Foundation’s National Scientific Advisory Committee.
The Rationale Behind CDED
“The reasoning behind the diet format was to combine the benefits of exclusive enteral nutrition with anti-inflammatory foods to help provide an ideal fuel source for beneficial bacteria and optimize the patient’s microbiome,” says Dr. Manning. “When the patient’s microbiome shifts to having more beneficial bacteria, it can lower inflammation in the gut.”
CDED Protocol: A 3-Phase Approach
During CDED, many foods are removed from the diet and slowly reintroduced. The CDED is managed a little differently from the other diets. The CDED is divided into three phases. The diet follows three phases broken into six-week increments, and they each include partial enteral nutrition (liquid formula). The first two 6-week phases are grouped together as the Induction Phase, which is used for inducing remission. The first six-week phase of the Induction Phase limits insoluble fiber to prevent bowel obstructions. By the tenth week, the second phase is 7-12 weeks and reintroduces many vegetables. The Induction Phase is the most important phase of the diet and is required for efficacy. Following remission, the Maintenance Phase is implemented to sustain it. Existing research primarily focuses on the Induction Phase, making it the most substantiated aspect, while investigations into the Maintenance Phase remain ongoing.
Phase 1: Restriction
During phase 1, foods are limited to fish, lean meats, rice, potatoes, tomatoes, onion, garlic, ginger, olive oil, and canola oil. Limited quantities of cucumbers, carrots, spinach, lettuce, bananas, apples, avocados, strawberries, melon, and citrus juices are allowed.
Read also: Improve Your Health with Diet
Phase 2: Reintroduction
In phase 2, participants eat foods from phase 1, and added foods like tuna, limited amounts of whole-grain bread, oatmeal, yams, and red peppers. Certain vegetables, beans, peas, turnips, and parsnips are reintroduced after week 10.
Specific Guidelines for Weeks 1-12
- Weeks 1-6: 1 portion lean fish per week
- After week 6: 1 can tuna per week
- 1 portion of lean steak per week after week 6 (not recommended)
- 1 slice whole grain bread allowed per day after week 6
- 1/2 cup dry oatmeal per week allowed after week 6 (gluten-free oats preferred but not mandatory)
- Unlimited rice and rice flour or noodles are allowed
- 1/2 cup dry beans/legumes allowed per day after week 6
Starchy Vegetables
- Weeks 1-6: Potatoes only allowed
- Weeks 7-9: Potatoes, sweet potatoes, and yams allowed.
- Weeks 10-12: Allowed
Nightshades
- Weeks 1-6: Tomatoes and Potatoes allowed.
- Weeks 7-9: Red Peppers also allowed.
- Weeks 10-12: Allowed
Mandatory Components
- Formula (PEN; eg, Boost®, Ensure®, Pediasure®, Modulen IBD®): 2 per day
- Fresh chicken breast only
Phase 3: Maintenance
Phase 3 begins the maintenance phase of the diet. In addition to foods from phase 2, other foods are introduced, such as more seafood, eggs, cocoa, coffee, grains, some dairy, and alcohol. Foods that trigger symptoms may differ from person to person. If symptoms flare up during the maintenance phase, you can return to phase 1 to regain control over your symptoms. The Maintenance Phase requires five contiguous days following the diet. It allows for a maximum of two contiguous days (generally weekends) of two free meals per day (maximum of four free meals per week), excluding only hot dogs, sausages, soft drinks, luncheon meats, bacon, and frozen dough from those free meals.
Who Can Benefit from CDED?
The CDED can be used for both adults and children with active Crohn’s disease. For children especially, who often can’t take medications like steroids or maintain a liquid-only diet like EEN, CDED can help reduce inflammation in the digestive tract so they can continue to absorb nutrients for normal growth and development.
Research and Clinical Evidence
The effects of the six-week induction phase of CDED were first reported in pediatric Crohn's disease in 2014. The 12-week induction phase in children and adults failing biologics was reported in 2017 with a comparison of CDED + PEN vs EEN in 2019 and data in adults with Crohn's disease in 2021.
Clinical Trial Results
In a study published in June 2019 Gastroenterology that compared the CDED with a liquid-only diet in children with mild to moderate Crohn’s disease, researchers found that while both diets were effective at reducing Crohn’s disease symptoms by week 6, the children were better able to tolerate the CDED with supplemental nutrition and experienced a sustained reduction in symptoms. Clinical remission at Week 6 was achieved in 17/24 (70.8%) patients. Mean PCDAI, CRP, ESR and FC decreased significantly after 6 weeks (p < 0.05). Formula type (cow's milk based, rice based, soy based) did not affect treatment efficacy.
Read also: The Hoxsey Diet
Researchers also found that the composition of gut microbes changed through the study. In particular, they found the protective microbes assembled during the beginning of the study were effective against inflammation, but this protection diminished as more food was introduced into the diet, which changed the environment for the gut bacteria.
In a 24-week study published in the November 2021 issue of the Lancet Gastroenterology & Hepatology, one group of adults (18-55 years old) followed the CDED along with a fortified nutritional drink while the second group followed the CDED only. Researchers found the CDED with or without the addition of the nutrition drink was effective at reducing symptoms.
CDED Compared to Exclusive Enteral Nutrition (EEN)
In patients uninterested or unable to use Exclusive Enteral Nutrition, CDED is an effective alternative for inducing remission and it may provide a more effective option than standard diet plus PEN for maintaining it.
Important Considerations
Because of the restrictive nature of the diet, Roman-Green encourages anyone considering the CDED to work with a registered dietitian and their gastroenterologist. As with all medical treatments, exclusion diets have potential side effects, including disordered eating patterns.
The Role of a Dietitian
Working with a dietitian trained in CDED is strongly advised to be successful. “The CDED diet is highly structured but allows for some flexibility in choices, so you can continue to enjoy eating while being proactive in your care process,” says Manning. “It is important to know that when you do embark on a diet therapy, you give yourself grace occasionally if it is not exact.”
Read also: Walnut Keto Guide
Other Dietary Approaches for Crohn's Disease
While CDED shows promise, other dietary approaches are also used in managing Crohn's disease.
The Anti-Inflammatory Diet (IBD-AID)
Developed by researchers at the University of Massachusetts Medical School in Worcester, the IBD-AID diet aims to restore the bacterial balance in the gut and reduce IBD symptoms. The diet includes probiotic and prebiotic foods while restricting certain carbohydrates.
Probiotic Foods:
- Plain yogurt
- Miso
- Kimchi
- Aged cheeses
- Pickles
Prebiotic Foods:
- Steel-cut oats
- Garlic, onions
- Bananas
- Asparagus
- Beans: kidney, lima, chickpeas, green peas
The diet also requires avoiding pro-inflammatory carbohydrates, anything with lactose, wheat, refined sugar, and corn. Like CDED, the diet is restrictive, and more evidence is needed to determine if it's effective.
The Low-FODMAP Diet
FODMAP, which stands for "fermentable oligosaccharides, disaccharides, monosaccharides, and polyols” refers to the short-chain carbohydrates and polyols that are poorly absorbed in the digestive tract. The low-FODMAP diet eliminates foods that are high in FODMAPs and requires eating foods that are low in FODMAPs. The good news is there is a wide range of foods to choose from, which makes the diet easy to follow.
High-FODMAP Foods:
- Apples
- Dried fruit
- Asparagus
- Wheat
- Honey
- Cow’s milk
- Onions and garlic
Low-FODMAP Foods:
- Lean meats
- Potatoes
- Tomatoes
- Peppers
- Carrots
- Bananas
- Citrus fruits
- Cucumbers
- Oranges
- Hard cheeses
- Eggs
- Oats
- Strawberries
While more research is needed on the effects of the low-FODMAP diet in Crohn’s patients, a study published in October 2019 in Gastroenterology found that when people with IBD, including Crohn’s disease, stuck to a low-FODMAP diet, they experienced a significant reduction in several gut symptoms after just four weeks. The diet had no effect on disease severity, but the research adds to the growing body of evidence that a low-FODMAP diet may provide people with GI symptoms some relief.
The Specific Carbohydrate Diet
Developed in the 1920s by Dr. Sidney Haas, a pediatrician, this diet eliminates refined and processed foods in order to reduce the growth of harmful bacteria in the gut. While there are a few preliminary studies that show a positive effect, experts don’t recommend this diet because it’s more restrictive. In a study published in May 2021 in Gastroenterology, results showed the specific carbohydrate diet wasn’t any better than the Mediterranean diet at achieving remission or improving inflammation in Crohn’s patients with mild to moderate symptoms.
Allowed Foods:
- Fruits and most vegetables
- Fresh meat and fish
- Dairy limited to hard cheeses and homemade yogurt
- Most nuts
- Most oils, teas, coffee, and juices with no additives or sugars
- Honey as a sweetener
- Certain legumes: beans and lentils
Foods to Avoid:
- All grains and starches
- Sugars, maple syrup, sucrose, fructose
- Starchy vegetables: potatoes, yams, parsnips
- Dairy products: cow’s milk, ice cream, sour cream, store-bought yogurt
- Some legumes: chickpeas, bean sprouts
In addition to being highly restrictive, the diet can lead to deficiencies in certain vitamins and minerals, so supplements like vitamin B6, calcium, and vitamin D may be needed.
Mediterranean Diet
Considered more of an eating approach than a diet, the Mediterranean diet is loaded with vegetables and healthy fats like olive oil and omega-3 fatty acids from fish. The diet has been cited as having a number of health benefits, including lowering the risk of heart disease, reducing cancer risk, and improving blood sugar to keep type 2 diabetes in check. A study published in a 2020 issue of Gut found that individuals who adhered to a Mediterranean diet had a 60 percent reduced risk of Crohn’s disease.