In a small study, patients with pre-cancerous polyps in the colon who took a pill containing a combination of curcumin, which is found in the curry spice turmeric, and quercetin, an antioxidant found in onions, experienced a marked reduction in both the size and number of polyps.

The potential of curcumin to prevent and/or treat cancer in the lower intestines surfaced in studies in lab rats fed curry, as well as in observational studies of Asian populations that consume a lot of curry. Quercetin has also been shown to have anti-cancer potential.