IBD is a term used to describe multiple gastrointestinal diseases characterized by chronic inflammation that damages different parts of the intestinal lining. Crohn’s disease, ulcerative colitis (UC), and microscopic colitis are the most common types of IBD.

Crohn’s disease can cause inflammation anywhere along the digestive tract (from mouth to anus), but usually involves the small intestine and the first part of the large intestine. Microscopic colitis and UC cause inflammation solely in the large intestine. UC also leads to the formation of ulcers (small sores) in the large intestine.^{[1] [2] [3] [4]}

The most common signs of IBD are diarrhea, abdominal pain, and unexplained weight loss. UC may also cause blood, mucus, or pus in the stool, and urgent or persistent feelings of needing to have a bowel movement (tenesmus). Crohn’s disease may cause additional symptoms, including joint or eye pain, nausea, or anemia. Severe cases of UC or Crohn’s may also lead to fever or lasting fatigue.

The symptoms of IBD naturally go through phases of greater severity during flares, and spontaneous resolution during periods of remission.^{[2] [3] [4]}

Multiple tests are required to diagnose IBD and rule out other potential diseases. A physical exam is performed to check for bloating and abdominal tenderness, and blood and stool samples are collected to detect signs of IBD such as anemia and intestinal inflammatory markers.

An endoscopy (e.g., colonoscopy or flexible sigmoidoscopy) allows the doctor to view the intestinal lining with a small camera and collect biopsies (tissue samples) for examination, which can confirm diagnosis. Imaging procedures like CT scans can also be used to observe the gastrointestinal tract.^{[5] [6] [7]}

There is no cure for IBD, but it can be managed with long-term care from a gastroenterologist and anti-inflammatory medications that suppress the immune system or interrupt certain aspects of the immune response that cause damage to the intestinal lining. Symptoms like diarrhea and mild pain can also be treated short-term with anti-diarrheal medications and acetaminophen. Unfortunately, IBD can also lead to infections, which need to be treated with antibiotics.

Exclusive enteral nutrition — which uses specific liquid formulas to meet a patient’s dietary needs — can induce remission, especially in pediatric IBD. Emerging evidence suggests that partial enteral nutrition can prevent flares when a patient is in remission, especially when fed through a nasogastric tube that delivers the formula directly into the stomach through the nose.^[8]

In some cases, surgery is required to remove sections of the intestine that have become severely damaged. If the entire large intestine is removed, the end of the small intestine will be attached to an internal reservoir or external pouch (called an ostomy bag) to collect stool, or can be rerouted via ileoanal anastomosis (a surgery that enables an individual whose large intestine has been removed to defecate normally).^{[9] [10] [11]}

Most evidence indicates that probiotics, prebiotics (including resistant starch), and synbiotics are all equally, modestly effective for inducing remission and reducing some symptoms of IBD, especially in UC.^{[12][13][14][15][16][17]}

Though high-quality evidence is limited to just a few trials, cannabis and cannabinoids may improve quality of life and reduce abdominal pain and IBD symptoms.^[18]

Emerging evidence suggests that resveratrol and curcumin might improve gastrointestinal symptoms and quality of life, while vitamin D supplementation could reduce inflammation and encourage cell turnover for repair of the intestinal lining. In patients under 40, curcumin also improved remission rates.^[19][20][21]

Polyunsaturated fatty acids (PUFAs), such as omega-3 fatty acids and omega-6 fatty acids, have also been studied for IBD. However, when taken in the form of supplements, PUFAs are ineffective for improving IBD remission rates or inflammatory markers.^[22]

A Western dietary pattern — characterized by a high intake of refined grains, animal protein (particularly red or processed meat), and animal fat (from meat or dairy), along with a low intake of fruit and vegetables — may increase the risk of developing IBD.^[23] Higher fruit, vegetable, and fiber consumption are associated with a reduced risk of developing IBD.^[24]

Despite these findings, exclusion diets — like those that remove milk, carrageenan, or animal products — have little to no effect on IBD disease activity or remission rates.^[25] A Low-FODMAP diet improves some GI symptoms without changing markers of disease activity.^[26]

People with IBD tend to consume less fiber than healthy people, and often fail to eat enough calories (which is why they may need enteral nutrition support).^[27][8] They also have lower levels of vitamins A and K in their blood, and over time, low vitamin A status is associated with greater disease activity.^[28]

There’s some evidence that mindfulness can reduce stress in people living with IBD, while cognitive behavioral therapy could improve both quality of life and fatigue.^[29][30][31]

Fecal microbiota transplants are more effective than placebo for inducing remission in ulcerative colitis, but their efficacy in other forms of IBD is still unclear, and most of the available trials for Crohn’s disease lack control groups.^[32][33]

Most of the studies assessing hyperbaric oxygen therapy and acupuncture had serious design flaws (like a lack of randomization or control groups), so although these treatments are associated with remission and clinical improvements, it’s unclear whether those occurred as a result of the treatment or as a normal part of the disease process.^[34][35]

The exact causes of IBD are unknown, but researchers suspect that these diseases result from interactions between the immune system, genes, gut microbiome, and certain lifestyle factors. IBD is thought to be an autoimmune reaction, and genetics likely play a role since it tends to run in families.

Smoking, certain medications, female hormones, infections, and the presence of other autoimmune diseases may slightly increase the chances of developing IBD.^{[2] [3] [4]}