The study, published in Cancer Prevention Research, is an early step toward finding out whether compounds found in ginger root might prevent colon cancer.
"Many studies in cell culture have shown that ginger is an anti-inflammatory," says study researcher Suzanna M. Zick, ND, a research assistant professor at the University of Michigan Medical School, Ann Arbor.
Other studies in mice and rats have shown that ginger may help prevent the formation of tumors when it's fed to the animals exposed to a chemical that causes colon cancer.
Zick and her team wanted to see whether those findings might translate to humans.
Testing the Effects of Ginger on the Colon
For the study, researchers randomly assigned 30 healthy adults to take capsules containing either 2 grams of powered ginger root or a placebo powder every day for four weeks.
"It's equivalent to about 2 tablespoons of ground-up ginger root," Zick says. "It's probably not what an average American would want to do every day. But certainly in India and China and Japan, they eat that amount on a daily basis," she says, noting that those countries have lower rates of colorectal cancer.
But Asian diets may be protective for other reasons, too. Asian diets tend to include more vegetables and fiber and less red meat, for example.
"It probably all contributes together," she says.
People in the study were asked to take the capsules at mealtimes. They weren't allowed to use any other kind of medications, including aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) immediately before or during the study, because those are known to have anti-inflammatory effects.
The main side effects of taking ginger were minor stomach upset, heartburn, and gas.
Before and after the study, tissue samples were taken from the lining of the colon. Researchers tested these samples for chemicals called eicosanoids that increase inflammation in the gut.
"The ginger was able to decrease the level of inflammatory markers in the gut tissue," compared to the placebo, Zick tells WebMD. "It decreases inflammation. We know that increased inflammation, chronic inflammation in the gut tissue is highly associated with developing precancerous lesions, or cancerous polyps."
The study was funded, in part, by the National Cancer Institute.
Experts said the study was well done and intriguing, but preliminary.
"I think it's a good study. It opens the door for us wanting to have further investigation," says David Bernstein, MD, chief of the division of gastroenterology at North Shore University Hospital in Manhasset, N.Y.
But he notes that even though ginger appears to be relatively safe, it's not time to use large amounts of it to ward off colon cancer. Study volunteers were taking eight 250-milligram capsules a day.
"I don't know that a biochemical response translates into a clinical response," Bernstein says. "For that, you need a larger trial."
"Ginger has been used for a long time for multiple medicinal reasons in the Far East. So I tend to believe that something that's been used for hundreds of thousands of years by a group -- there's probably a reason. Now we have to prove why," he tells WebMD.