If you find yourself shaking your fists at the sky, demanding to know the truth behind the causes of ulcerative colitis (UC), you’ve probably had your fair share of less-than-pleasant bathroom time.
Ulcerative colitis is a type of inflammatory bowel disease (IBD), and it’s more common than you might think. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) estimates that between 600,000 and 900,000 people in the United States live with this chronic condition, but it’s likely even more than that.
When you have ulcerative colitis, an abnormal immune response leads to an increase in inflammation in the colon, causing ulcers to appear on its inner lining. This ultimately leads to symptoms like bloody diarrhea, abdominal cramping, and the urge to go (like now).
The good news is, with treatment, people diagnosed with ulcerative colitis often have periods of remission, where symptoms go away for a while. Remission can last for weeks or even for several years. If and when ulcerative colitis symptoms return, it’s called an ulcerative colitis flare-up or relapse.
Experts aren’t entirely sure why, exactly, the condition develops in the first place—but there is one thing that’s clear: It’s not your fault. Ulcerative colitis is an autoimmune disease, meaning your body is literally working against you. There are some theories, however, and understanding the various ulcerative colitis risk factors can be helpful when trying to solidify a diagnosis and treatment plan. Here’s what experts know about ulcerative colitis causes so far.
How does ulcerative colitis affect the body?
To understand the possible ulcerative colitis causes, it’s important to first understand a little bit about the structure of your colon, which is your large bowel or large intestine.
Mucus coats the colon’s walls to not only serve as a lubricant for stool moving through your bowels but to also help keep germs and harmful substances away from the cell layer that lines the colon. The scientific name for this layer of cells is the epithelium. The epithelium itself is an important barrier to potentially harmful substances and is fortified by tight connections between each cell. Located below the epithelium is an area called the lamina propria, which is made up of connective tissue and is home to several types of immune cells, according to a 2016 study published in the journal Inflammatory Bowel Diseases.1
In ulcerative colitis, the barriers provided by mucus and the epithelium are dysfunctional. This means that the epithelial cells and nearby immune cells are increasingly exposed to bacteria and potentially other substances, like yeast, that are found in the colon.
Because the immune response is abnormal, this can have several damaging effects in the colon and throughout the body, such as an expanded presence of immune cells that attack the lining of the colon, increased inflammation, and further disruption of the colon’s lining, Nicole Fay, Ph.D., an immunotherapeutics researcher and a director of pharmacology at Nutcracker Therapeutics, tells SELF.
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What do experts know about ulcerative colitis causes?
The one thing experts know for sure about the inherent cause of ulcerative colitis is that “the immune system is in overdrive,” Ariela Holmer, M.D., a gastroenterologist at the Inflammatory Bowel Disease Center of NYU Langone Health, tells SELF.
Doctors and researchers aren’t exactly sure what sets off the immune system to begin with. However, it’s generally accepted that ulcerative colitis is caused by a very complex interaction of several factors. “Evidence has been found for genetic causes, environmental factors, and gut microbiome as drivers to our body’s own immune damage,” Dr. Fay says. Here’s a bit more about each one:
Gut bacteria
Your colon is full of bacteria. These help you digest food and are also important for overall gut health. Normally, your immune system ignores or tolerates these microbes because a majority of them are beneficial to the body.
Your microbiome, which is the makeup of microbes in your gut, is altered in ulcerative colitis. A 2020 systematic review published in the journal Frontiers in Medicine analyzed the microbiomes of five groups of people with IBD. Researchers were able to detect significant differences in the microbiomes between people with IBD and people without IBD. Additionally, they were also able to find differences in the microbiomes of people with different types of IBD, such as ulcerative colitis and Crohn’s disease.2