Chemicals in curry and onions may help prevent colon cancer

A small but informative clinical trial by Johns Hopkins investigators shows that a pill combining chemicals found in turmeric, a spice used in curries, and onions reduces both the size and number of precancerous lesions in the human intestinal tract.

In the study, published in the August issue of Clinical Gastroenterology and Hepatology, five patients with an inherited form of precancerous polyps in the lower bowel known as familial adenomatous polyposis (FAP) were treated with regular doses of curcumin (the chemical found in turmeric) and quercetin, an antioxidant in onions, over an average of six months. The average number of polyps dropped 60.4 percent, and the average size dropped by 50.9 percent, according to a team led by Francis M. Giardiello, M.D., at the Division of Gastroenterology, The Johns Hopkins University School of Medicine, and Marcia Cruz-Correa, M.D., Ph.D., at Johns Hopkins and the University of Puerto Rico School of Medicine.

"We believe this is the first proof of principle that these substances have significant effects in patients with FAP," says Giardiello.

Familial adenomatous polyposis is a disorder that runs in families and is characterized by the development of hundreds of colorectal adenomas (polyps) and eventual colon cancer. Recently, nonsteroidal anti-inflammatory drugs (NSAIDs) have been used to treat some patients with this condition, but these compounds often produce significant side effects, including gastrointestinal ulcerations and bleeding, according to Giardiello.

Previous observational studies in populations that consume large amounts of curry, as well as laboratory research on rodents have strongly suggested that curcumin - a relatively innocuous yellow pigment extracted from turmeric, the powdered root of the herb curcuma longa and one of the main ingredients in Asian curries - might be effective in preventing and/or treating cancer in the lower intestine, according to Cruz-Correa. She said curcumin has been given to cancer patients, and previous studies have demonstrated that is well tolerated at high doses.

Similarly, quercetin - a member of a group of plant-derived polyphenolic anti-oxidant substances known as flavanoids (found in a variety of foods including onions, green tea and red wine) - has been shown to inhibit growth of colon cancer cell lines in humans and abnormal colorectal cells in rodents.

Although these substances were administered together, due to relative dose levels it is Giardiello's belief that curcumin is the key agent.

"The amount of quercetin we administered was similar to what many people consume daily; however, the amount of curcumin is many times what a person might ingest in a typical diet, since turmeric only contains on average 3 percent to 5 percent curcumin by weight," says Giardiello. Because of this, he cautions that simply consuming curry and onions may not have the same effect as was produced in this study.