Ulcerative colitis (UC) may cause digestive issues, which can affect the body’s ability to absorb certain nutrients. Vitamins and supplements may help boost nutrient levels when diet alone is not enough.

UC is a form of inflammatory bowel disease (IBD) that causes inflammation and sores in the colon and rectum. People with UC experience a variety of digestive issues, including bloody diarrhea, weight loss, and lack of appetite, which may come and go periodically with disease flares.

Certain foods can trigger symptoms of UC, and many people with the condition find that dietary modifications can help provide relief. Some people also take vitamins and supplements to avoid flares or adjust to dietary changes that help relieve symptoms.

Here, experts share their perspectives on nutritional and gut health in UC, including the effect of UC on nutrition and vice versa. They also discuss the role of vitamins and supplements for people with UC.

People with UC may be prone to certain vitamin deficiencies due to inflammation in the gut and reduced intake caused by reduced appetite and the avoidance of digestive issues.

Iron deficiency, with or without anemia, is a common issue in people with IBDs such as UC, affecting up to three-quarters of people with newly diagnosed IBD.

Low iron levels are often the result of reduced intake and blood loss caused by inflammation and damage to the digestive tract. This is more common during flares.

People with UC may also experience vitamin D deficiency. Jami A Kinnucan, MD, a gastroenterologist and hepatologist at the Mayo Clinic in Jacksonville, FL, explained that the main sources of vitamin D are dairy foods and sunlight.

Some people with UC are sensitive to dairy foods and may limit their intake to avoid digestive issues. This can lead to calcium deficiencies.

Sunlight can help process vitamin D in the body, but this can also be an issue for people with UC.

“People who are medically treated for UC may need to take particular care in the sun because several medicines can cause photosensitivity, which is an exceptionally high sensitivity to the UV waves in sunlight,” explained Danielle Gaffen, MS, RDN, LD, an IBD-registered dietitian nutritionist.

Other potential nutrient deficiencies in UC include:

  • folate deficiency due to reduced intake of dark leafy greens and certain medications, such as methotrexate or sulfasalazine
  • potassium due to chronic vomiting or diarrhea and certain medications such as prednisone

A simple blood test can detect most nutrient deficiencies, though a bone density scan may be necessary to check for calcium deficiency.

“It is important for people with UC to work with a healthcare professional, such as a gastroenterologist and a registered dietitian, to monitor for nutrient deficiencies and ensure adequate intake of key vitamins and minerals through diet and supplementation if necessary,” noted Gaffen.

“It is important that [people] get their main nutrition from the foods they eat,” said Kinnucan. However, understanding that people with UC may have worsening symptoms in response to certain foods, dietary supplements may be more beneficial.

“The use of vitamins and supplements in UC should be individualized and guided by a healthcare professional, such as a gastroenterologist and an IBD-registered dietitian,” added Gaffen.

Vitamin D and calcium

Vitamin D and calcium play important roles in bone health, and vitamin D may provide extra anti-inflammatory benefits for people with UC.

Kinnucan noted that she often recommends a combined vitamin D and calcium supplement for people with UC who may need it.

Gaffen suggested this may be especially important for people taking medications, such as prednisone or other corticosteroids, that increase the likelihood of developing osteoporosis.

“Keep in mind that the recommended dose of vitamin D depends on an individual’s vitamin D blood levels,” added Gaffen. Too much vitamin D can lead to hypercalcemia, an excess of calcium in the blood, which can be harmful.

Kinnucan suggested that people with UC have their vitamin D levels checked every 6–12 months.


“For those with iron deficiency without active inflammation, oral supplementation can improve iron deficiency, especially when paired with a vitamin C supplement, [which] increases iron absorption,” suggested Kinnucan.

Kinnucan and Gaffen noted that some people may have digestive side effects with oral iron supplements, such as nausea, diarrhea, or constipation. They recommend only taking iron supplements under the direction of a healthcare professional.

“If you have been advised to take iron and calcium supplements, it is important to note that iron and calcium do not mix well,” added Gaffen. “Taking them together could potentially hinder their absorption abilities. Therefore, it is ideal to separate the two supplements if possible.”

Other supplements

Depending on a person’s nutritional health, a healthcare professional may recommend certain other supplements, including:

  • folate
  • omega-3 fatty acids
  • magnesium
  • vitamin B12
  • zinc

“However, it is important that these are discussed with a physician to ensure they are right for that person’s unique situation,” explained Desiree Nielsen, a registered dietitian and author of “Good for Your Gut.”

For instance, some people might experience digestive issues, such as cramping or diarrhea, with magnesium supplements. So, these may not be right for everyone.

People with UC may be at risk for nutritional deficiencies due to digestive issues and changes in their diet.

“Chronic diarrhea, as well as the inflammation present in ulcerative colitis, irritates the gastrointestinal tract and can lead to restricted food intake as people try to avoid foods that feel irritating, produce gastrointestinal symptoms, or ‘go right through them’ such as raw vegetables or legumes,” explained Nielsen.

“It is not uncommon for people to inadvertently consume low fiber, low nutrient-density diets as hyper-processed and refined foods tend to be less symptom-producing when there is significant inflammation in the gut,” she said.

Over time, this can lead to weight loss, malnutrition, and vitamin or mineral deficiencies.

“People with UC may [also] have higher nutrient needs due to chronic inflammation and diarrhea,” added Gaffen. “Inadequate intake of certain nutrients can worsen symptoms and increase the risk of complications.”

Does nutrition affect ulcerative colitis?

“A diet high in inflammatory foods — such as processed foods, refined sugars, and unhealthy fats — can increase inflammation, worsening UC symptoms,” explained Gaffen.

“There have been recent studies looking at the impact on diet and developing IBD,” noted Kinnucan. “There seems to be more data that support diet and increased risk for developing Crohn’s disease. However, a few things have been shown to increase the risk for UC within [the] diet, including trans-saturated fats, increased animal protein, [and] high sugar or soft drinks.”

The opposite is also true. “A well-balanced diet, adequate nutrient intake, and weight management can help reduce inflammation, support gut health, and improve the overall quality of life for people with UC,” said Gaffen.

“Because of the nature of immune involvement and the medications required in ulcerative colitis, people should be wary of taking most supplements other than basic vitamins and minerals as they may interact with medical care,” emphasized Nielsen.

Kinnucan echoed these concerns. “In general, IBD patients should not require supplements unless they have deficiencies or are at risk,” she said. “Supplements are not regulated by the [Food and Drug Administration] FDA and don’t have to be studied or even contain reported amounts of active ingredients. They can interact with other medications patients are taking.”

Gaffen suggested avoiding herbal supplements for this reason. “While some may have anti-inflammatory effects, others such as echinacea, ginseng, and licorice root may worsen inflammation or interact with medications.”

While Gaffen and Nielsen indicated that some people might benefit from probiotics, Kinnucan was less convinced.

“Probiotics have limited evidence in IBD, and not all probiotics are created equal,” she said. She noted that there is some evidence that the mixed probiotic VSL#3 (Visbiome) may provide symptom relief in UC, but more data is needed.

“I generally do not recommend probiotics to [people with] IBD due to lack of evidence and cost,” she explained. “Also, probiotics can be found in foods, such as fermented milk (Kefir), sauerkraut, kimchi, miso, and yogurt.”

“If you are advised to take any supplement, a useful tip is to check the label for lactose, artificial colors, sugar alcohols, or preservatives — which can worsen your UC symptoms, particularly during a flare,” added Gaffen. “It can be surprising to discover what some supplements contain, so I suggest taking a look at the label and comparing it with other available options.”

“It has been a longstanding myth that [people with] IBD should avoid fiber-containing foods,” said Kinnucan.

“People with UC often feel that they cannot tolerate any fiber,” echoed Nielsen. “However, by starting slowly with soluble fiber sources, such as oranges, oats, and psyllium, improvements in bowel habits can lead to increased tolerance of nutrient-rich foods.”

“I highly recommend doing this work only with a dietitian experienced in IBD,” she said.

Gaffen added: “Eating smaller, more frequent meals may reduce the workload on the digestive system, alleviate UC symptoms, and provide more opportunities to fit in nutrient-dense foods throughout the day. Instead of three large meals, aim for five to six small meals per day.”

Kinnucan recommended focusing on a plant-forward diet with healthy fats, such as a Mediterranean-style diet, and avoiding food additives such as emulsifiers.

“Emulsifiers are food additives that might make foods taste better or have better consistency but are not helpful to your gut health and have been linked to IBD,” she explained. She noted that these additives are typically present in creamers, milk, some ice creams, chocolate products, margarine, and processed meats.

“Each person is different in their experience with food and their disease and deserves an individualized approach to care,” said Kinnucan. “There is and should not be a one-size-fits-all approach to treatment, diet, or supplements in UC.”

“It is important to note that while vitamins and supplements may be beneficial for some people with UC, they are not a substitute for medical treatment,” echoed Gaffen.

The experts we spoke with agree that working closely with a healthcare professional is crucial to developing a personalized treatment plan that works best for you.