According to the results of a small study compounds found in curry and onions may help prevent colon cancer in those at risk.
Patients with pre-cancerous polyps in the colon (familial adenomatous polyposis) FAP, an inherited disorder, commonly get colon cancer.
In the study, patients with FAP were given an experimental combination containing a chemical found in turmeric, the spice that gives curries a yellow colour, and an antioxidant found in onions called quercetin and a marked reduction in both the size and number of polyps was seen.
Dr. Francis M. Giardiello of The Johns Hopkins School of Medicine in Baltimore, who led the study, believes this is the first proof that these substances have significant effects in patients with FAP.
Other studies in animals, and in observational studies of Asian populations that consume a lot of curry, have shown that curcumin has the potential to prevent and treat cancer in the lower intestines.
Studies have also shown that quercetin, one of a group of antioxidants known as flavonoids and found in onions, green tea, and red wine, inhibits the growth of cancer cells in humans and rats.
For the study, Giardiello and colleagues gave five FAP patients who had five or more polyps in their lower intestinal tract 480 milligrams of curcumin and 20 milligrams of quercetin three times daily and over a six month period all five patients had fewer polyps and they were smaller.
The average number of polyps dropped by 60 percent, and the average size dropped by 51 percent.
There were few side effects, one patient experienced nausea and sour taste within a couple of hours of taking the pill, which subsided after three days and did not recur, and another patient reported mild diarrhea.
The researchers believe of the two compounds,curcumin is the key cancer-fighting agent.
Giardiello says the amount of quercetin administered was similar to what many people consume daily but the amount of curcumin was much greater than a person might ingest in a typical diet.
The team says larger trials, comparing curcumin-quercetin capsules with dummy "placebo" pills, are needed to confirm these findings.
The study is published in the journal Clinical Gastroenterology and Hepatology.