Researchers, who published their findings in the American Chemical Society’s Journal of Agricultural and Food Chemistry, found that vinegar suppressed inflammation-inducing proteins while improving the gut’s bacterial makeup in mice.

Ulcerative colitis, an inflammatory bowel disease, is a chronic condition that affects millions of people around the world. Although its cause isn’t completely understood, research suggests that bacteria in the gastrointestinal tract play an important part. People with the condition experience repeated inflammation of the large intestine’s lining, which can cause ulcers, abdominal pain, diarrhea and other symptoms. At least one recent study suggested that vinegar, which has been used in traditional medicine for centuries, might be effective against ulcerative colitis. Lu Yu, Bo Liu and colleagues wanted to further investigate this possibility.

The researchers, from three Chinese research institutions, tested vinegar and its main ingredient, acetic acid, in a mouse model of ulcerative colitis. Giving the mice either substance by adding it in small amounts to their drinking water significantly reduced symptoms of the condition. An analysis of mouse stool samples showed that treated animals had higher levels of bacteria, such as Lactobacillus and Bifidobacteria. Other studies have found these bacteria to be beneficial to mice with colitis-like symptoms. Treatment also lowered the levels of proteins that induce potentially damaging inflammation in the gut.

The researchers say further work would be needed to determine vinegar’s effects on ulcerative colitis in humans.

The illness affects 1.6 million people in the United States, causing abdominal pain, diarrhea, constipation, rectal bleeding and other potentially debilitating symptoms. Crohn’s disease and ulcerative colitis are the most common forms of IBD, an autoimmune condition whose development has been linked to genetic and environmental factors.

The microbes that colonize the gut are likely an important environmental factor. In most cases, these bacteria are beneficial to humans. However, certain bacteria can get through the protective layer of mucus that covers the inner lining of the gut.

Scientists have theorized that under the right conditions, such bacteria burrow their way into the gut lining, inciting immune cells to attack and harm the intestine.

But the Washington University researchers found that these bacteria aren’t the direct fighters in this conflict; instead, they produce small particles that get into the intestinal lining and prompt an aggressive immune-system response.

“You can compare these particles, which are known as vesicles, to fighter jets being released from a bacterial mothership,” said co-author Christina Hickey, MD, a clinical fellow. “Having a more accurate picture of how these jets trigger the onset of an attack should help us devise better ways to help prevent IBD symptoms.”

The findings were published in Cell Host & Microbe.