At present, there is no cure for ulcerative colitis. However, a person may be able to relieve symptoms and manage flares through diet. Examples include the low FODMAP, paleo, or the specific carbohydrate diet.

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The gut microbiome plays a crucial role in the inflammation of the gut in people with ulcerative colitis (UC). While foods do not cause UC, some may trigger UC flares.

Specific UC diets limit and allow certain foods and food groups to prevent UC flares and improve gut health.

This article explores different diets typically recommended for people with UC, how they can help, and their risks.

UC is a chronic condition of the gastrointestinal tract (GI). It is a form of inflammatory bowel disease (IBD), causing inflammation, irritation, and sores, referred to as ulcers, in the innermost lining of the large intestine and rectum.

While the cause of UC is unknown, experts believe that changes in the gut microbiota and abnormal immune responses in the gut may cause UC. Genes also play a role since having first degree-relatives is the highest risk factor for IBD.

Environmental factors can increase IBD risk at an individual level, such as diet. They may also be factors that modify the risk to entire populations, such as air pollution or UV light exposure.

While diet does not directly cause UC, certain foods can trigger or worsen UC symptoms.

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There is no single best diet for UC. Finding the right diet can help a person with UC lessen the occurrence of flares, improve their quality of life, and ensure proper nutrition.

People with UC, and other autoimmune conditions, widely use the elimination diet. This type of diet involves omitting certain foods or food groups that people believe to be causing the adverse reactions or food intolerance and gradually reintroducing them. About 70% of people use this type of diet when in remission.

A 2018 study showed that random food elimination could cause nutritional deficiencies. However, appropriate supplementation and monitoring from doctors can reduce this risk.

Types of diets

There are different types of specific elimination diets for UC. These commonly share the concept of removing processed foods but vary in which foods they limit or moderate.

Below are diets for people with UC:

It is essential for people with UC to maintain a balanced diet.

General recommendations that can improve a person’s nutrition include:

  • eating 4–6 smaller meals daily
  • staying hydrated
  • drinking slowly and avoid using a straw, which can cause people to ingest air, which may cause gas
  • preparing meals in advance
  • adopting simple cooking techniques — boil, grill, steam, poach
  • using a food journal to keep track of what food and any symptoms

A person with UC can have periods of increased symptoms called flares and periods where symptoms are quiet or absent.

Getting the appropriate nutrition during particular periods can control the symptoms and help achieve remission or delay symptoms from coming back and maintain remission.

What to eat during flares

Aside from taking medications to manage flares and achieve remission, a person should avoid certain foods and look for other food sources to get the nutrients they need. These include:

  • low fiber fruits, cooked fruits, and fruits without hard peels
  • cooked non-cruciferous vegetables, and vegetables without seeds and skin
  • lean protein such as soy, fish, eggs, and lean pork cuts
  • refined grains such as white bread, white rice, and pasta

What to eat in remission

When in remission, a person will not have symptoms. While there is not always a way to avoid them from returning, a person may prolong the state of remission.

A person will benefit the best from a diverse and nutrient-rich food source. Foods to consider include:

Fermentable, oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) are types of carbohydrates or sugars in certain foods. These are poorly absorbed in the small intestine. They also affect gut motility and are rapidly fermented by bacteria, causing gas, stomach pain, and other symptoms.

A low FODMAP diet instructs individuals to limit foods high in FODMAPs.

High FODMAP foods include:

On the other hand, low FODMAP foods include:

Is the diet effective?

A 2021 review of studies found that a low FODMAP diet led to significant improvements in symptoms and quality of life. It is also safe for short-term use.

However, this type of diet can be challenging to sustain and may cause long-term changes in the gut microbiome.

It also has a risk of compromising a person’s nutritional status, so a person should be under the supervision of a dietitian.

Similar to the low FODMAP diet, the SCD restricts certain carbohydrates from a person’s diet to help reduce gastrointestinal symptoms. It is a grain-free, low sugar, and low lactose diet.

It theorizes that people do not fully digest complex carbohydrates and therefore they remain in the gut. These carbohydrates cause an overgrowth of bad bacteria in the small intestine, leading to inflammation.

Studies on the SCD are still in their early stages, but anecdotes support its effectiveness. Research from a 2016 study showed 33% reported remission within 2 months after starting the SCD. Almost half of the people were in remission within 6–12 months of starting the diet.

Foods allowed in the SCD include:

Foods to avoid include:

In addition, a person cannot eat anything processed and canned, including most processed meats. Other prohibited foods include:

  • certain legumes such as chickpeas and bean sprouts
  • seaweeds and their byproducts
  • potatoes, sweet potatoes, and turnips
  • all milk and milk byproducts with high lactose, including sour cream, ice cream, and commercial yogurt
  • candies and chocolates

Is the diet effective?

A 2015 case study discusses a person who followed the SCD after the failure of conventional therapies. They noticed improvements within 3–6 months.

An individual following this diet may find it difficult to maintain a moderate weight and consume enough nutrients, including:

However, a 2018 study found that the nutritional intake of people using the SCD was adequate but was variable compared to the daily recommended intake. Doctors will closely monitor individuals on this diet.

Due to the strict, rigid nature of the SCD, many people may find it challenging. However, with long-term support from dietitians and family and friends, a person can adapt to their new diet and way of life.

Short for the paleolithic diet, the paleo diet includes foods people may have eaten 2.5 million years ago. Individuals may also refer to it as the “stone age” or the “caveman” diet. The diet believes that the human body does not match the modern diet due to the emergence of farming.

Compared to modern Western diets, the paleo diet is rich in nutrients and fiber and low on salt, artificial sugars, and starchy carbohydrates. Here are foods that people can eat:

  • fruits
  • non-starchy vegetables
  • fish such as salmon
  • nuts and seeds
  • oils derived from fruits and nuts
  • saturated fats such as lean meat, preferably wild game or free-range

Foods to avoid include everything that was not accessible to humans in the paleolithic era, such as highly processed food and foods containing dairy, sugar, butter, and yeast. Other foods include:

  • grains such as oats and barley
  • legumes such as beans and peas
  • starchy vegetables such as potatoes
  • processed and cured meats
  • sweets, including refined sugar and honey
  • sugary drinks

Is this diet effective?

There are no formal published studies on the benefits of paleo in the management or prevention of IBD.

Similar to other diets, avoiding certain foods will help reduce inflammation and relieve symptoms of UC.

However, the paleo diet encourages the consumption of high levels of saturated fat in the form of red meat. Saturated fats have a high caloric content, which raises cholesterol levels, and can increase the risk of heart disease.

The IBD-AID is an adaptation of SCD. While it follows the principles of SCD, it is less restrictive, which may make it easier to follow. It includes foods that provide complete and balanced nutrition.

It primarily aims to restore the microbiome in people with IBD. The diet focuses on foods that are easy for the colonic bacteria to degrade dietary fibers and produce short-chain fatty acids (SCFAs). SCFAs are vital in the downregulation of inflammatory markers in the colon.

Foods to eat include:

Foods to avoid include:

  • foods containing lactose, refined sugar, wheat, and corn
  • processed foods
  • fast foods

Is the diet effective?

IBD-AID is relatively new, hence the limited studies. A 2020 study on people with IBD following the IBD-AID diet for 4 weeks showed a reduction in symptoms and use of medications.

An older 2014 small case report showed that 60% of the people who followed the diet had either a good or very good response after reaching compliance.

After following the IBD-AID, all the people involved in the study could discontinue at least one of their IBD medications. They also had symptom reduction, including bowel frequency.

Gluten is a protein family found in grains such as:

Foods that a person following a gluten-free diet can eat include:

  • all gluten-free starches and grains
  • dairy
  • fruits
  • vegetables
  • fresh meat, fish, and poultry
  • juices
  • nuts and seeds

While there is some overlap, such as eliminating certain grains, the gluten-free diet for UC does not include a low FODMAP diet. However, a person may combine the two diets.

Is the diet effective?

Around one-third of those with IBD also report having non-celiac gluten sensitivity, which is why many follow the diet.

A large 2014 study on IBD patients on a gluten-free diet showed that the diet led to GI symptom improvements and fewer or less severe flares.

A downside of this diet is that a person may run low on fiber but high on fats and sugars. These levels may increase a person’s risk of diabetes and metabolic syndrome. An inadequately balanced gluten-free diet may also negatively affect lipid and glucose metabolism and gut health.

The AIP diet is an extension of the paleo diet. It aims to relieve symptoms and reduce inflammation caused by autoimmune diseases such as UC and other conditions, including lupus and rheumatoid arthritis.

The diet encourages the consumption of fresh, nutrient-dense foods, fermented foods, and bone broth. Meanwhile, foods eliminated from the diet include:

Is the diet effective?

Experts from 2017 hypothesize that germs may enter when there are gaps in the gut microbiota, inducing an autoimmune response. The AIP diet aims to target this to reduce inflammation and prevent autoimmune responses.

A small 2017 study on people with active IBD found improvements in UC and Crohn’s disease indexes and simple endoscopic scores that measure the size of ulcers.

Additionally, it can benefit other conditions. The 2019 study showed that females on the AIP diet with Hashimoto’s thyroiditis experienced:

  • improvements in quality of life
  • less symptom burden
  • reduction in inflammation and immune activity

Creating a UC diet can be a trial-and-error process as a person’s food triggers and dietary needs change with their symptoms.

Moreover, foods that trigger symptoms can vary from person to person. It is ideal to use a food journal to help identify food triggers and ensure that a person receives adequate nutrition.

A person should work with a dietitian or another health professional to avoid complications associated with nutritional deficiencies common in people with IBD, especially those who restrict their intake of certain foods.

UC is a chronic condition that currently does not have a cure. A complex interplay of genes, environment, and body function may cause it.

Diet also plays a huge role in the disease process, and dietary changes can improve a person’s symptoms and quality of life.

UC diets have different aims and have similarities in the food they allow and restrict. A person should consult a doctor about the ideal diet and other treatments to help manage their symptoms.