Food used to be a daily source of joy for Sarah Carter. A self-described “vegetable head” in San Mateo, California, she loved perusing farmers markets, tending her garden, cooking elaborate meals and exploring Bay Area restaurants.

That changed in October 2023, when Carter, 36, had COVID-19 for the first time. Her main symptom, diarrhea, became so relentless that she had to take an ambulance to the emergency room. Her blood pressure and heart rate spiked from severe dehydration, and she needed intravenous fluids to treat it. She was sent home and endured three more days of diarrhea before she finally felt like herself again.

That is, until April 2024, when she felt as if she “inherited a new GI system overnight,” she said. Nearly everything she ate, even bland foods like applesauce and toast, set off diarrhea. She also has had bloating and pain so severe she sometimes feels as if acid is running through her intestines.

In May, a gastroenterologist diagnosed Carter with postinfectious irritable bowel syndrome. It’s a common disorder that results in symptoms of IBS — abdominal pain along with diarrhea, constipation or both — after food poisoning or other gastrointestinal illnesses. Her doctor said her coronavirus infection six months earlier was most likely the cause.

Gastroenterologists say that since the start of the pandemic in 2020, they have noticed an uptick in IBS and other painful and often puzzling gut conditions like Carter’s, with many seeming to have been caused by previous coronavirus infections. We don’t have good estimates for what percentage of people with COVID-19 go on to develop persistent gastrointestinal symptoms, but some limited and small studies suggest they may be between 16% and 40%.

What gut issues can COVID cause?

Gastrointestinal symptoms like nausea, vomiting and diarrhea are common during the initial stages of a coronavirus infection, said Dr. William Chey, a gastroenterologist at Michigan Medicine. But for some people, these and other symptoms, like reflux, constipation, pain and bloating, can stick around for months or even years.

As was the case for Carter, certain gut symptoms may also disappear and then reappear months later, Chey said. And people who had chronic gut issues before they had COVID-19 may notice that the problems worsened after.

For some, gastrointestinal symptoms are their only complaint after COVID-19. But for others, they may be one of a slew of other long COVID symptoms, including fatigue and brain fog, said Dr. Louise King, a physician at the COVID Recovery Clinic at the University of North Carolina School of Medicine.

How might COVID prompt these issues?

The coronavirus infects your body’s cells by latching on to certain proteins that dot their surfaces. Those proteins are present on the cells of many tissues, including those in the lungs, heart, brain and gastrointestinal tract, so it’s not surprising that the virus can cause digestive symptoms, Chey said.

Doctors have also long known that other gastrointestinal infections, like those from norovirus, giardia and salmonella, can lead to IBS as well as functional dyspepsia, a type of chronic indigestion that causes frequent feelings of fullness and stomach pain or burning. It makes sense that COVID might cause the same kinds of issues, said Dr. B. Joseph Elmunzer, a gastroenterologist at the Medical University of South Carolina.

One theory about how COVID might cause these symptoms is that it may ramp up inflammation in the gastrointestinal tract. COVID can also disrupt the gut microbiome, King said, resulting in fewer of the “good” microbes that tamp down inflammation and more of the “bad” ones that cause inflammation.

Over time, inflammation can damage the lining of the intestine, making it more permeable or “leaky,” Chey said. That leakiness may allow molecules from foods to escape from the gut, causing immune cells to mount an allergylike response to foods.

COVID-induced inflammation may also “chew away” at the nerves that control contractions and pain signals in the gut, said Dr. Braden Kuo, a neurogastroenterologist at Massachusetts General Hospital. This might cause the nerves to send pain signals to the brain even when digestion is working normally, he said.

Anxiety and depression often worsen gut symptoms. In a study published in May, Elmunzer and his colleagues surveyed people who were hospitalized with COVID-19 early in the pandemic. Compared with those who didn’t experience post-traumatic stress disorder related to their illnesses, those who did were more likely to develop a condition like IBS 12 to 18 months after their hospitalization.

What treatments are available?

Doctors don’t know how long someone with COVID-related gut symptoms can expect them to last.

But for people who develop IBS after other types of gastrointestinal infections, Chey said that about two-thirds will recover within three to five years. In King’s experience with her long COVID patients, most feel significantly better within a year of their infections.

If your symptoms are affecting your daily life, Chey said, see a primary care doctor. If that doesn’t help, he said, consider an appointment with a gastroenterologist.

It’s especially important to see a doctor if you have blood in your stool or unintended weight loss, or if you have a family history of colorectal cancer, celiac disease or inflammatory bowel disease, so that you can rule these and other conditions out.

Following a low- FODMAP diet, ideally with a dietitian’s guidance, often helps, Chey said, or you could try a Mediterranean-style diet. A psychologist who specializes in gut health can help you learn techniques for managing symptoms, he added.

Over-the-counter medications and supplements may address your symptoms, Chey said. These include loperamide (Imodium) for diarrhea, polyethylene glycol (Miralax) or a magnesium oxide supplement for constipation, and enteric-coated peppermint oil (IBgard) for bloating and abdominal pain. Prescription medications are also available.

For Carter, it has been a long eight months, but with the help of a gastroenterologist, dietitian and gut psychologist, she is gradually improving. She still can’t eat many of her favorite vegetables, but she’s slowly expanding her list of safe foods. It’s like “learning how to eat again,” she said.