WEDNESDAY, Aug. 2 (HealthDay News) -- Chemicals found in onions and curry may help prevent colon cancer, a Johns Hopkins University School of Medicine study suggests.

Published in the August issue of the journal Clinical Gastroenterology and Hepatology, the study included five people with familial adenomatous polyposis (FAP), an inherited form of precancerous polyps in the lower bowel. FAP is characterized by the development of hundreds of colorectal polyps and eventual colon cancer.

For an average of six months, the patients received three daily oral doses of 20 milligrams of quercetin (an antioxidant found in onions) and 480 milligrams of curcumin (found in tumeric, one of the main ingredients of curry).

The average number of polyps in the patients declined by 60.4 percent, and the average size of the polyps decreased by 50.9 percent, the study said.

"We believe this is the first proof of principle that these substances have significant effects in patients with FAP," study leader Dr. Francis M. Giardiello, director of the division of gastroenterology at the university, said in a prepared statement.

He believes 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 tumeric only contains on average three percent to five percent curcumin by weight," Giardiello said.

It's not likely that simply eating onions and curry would provide the same benefits seen in this study, he noted.

The researchers plan to conduct a randomized clinical trial with more patients.

More information

The U.S. National Cancer Institute has more about colon cancer.