The spice contains curcumin, already shown to help prevent tumours from forming in previous lab studies. High consumption of turmeric has also been linked in epidemiological studies to lower rates of breast cancer, prostate cancer, lung cancer and colon cancer.
The new research, by a team at the Department of Experimental Therapeutics at the University of Texas, shows that curcumin may also stop cancer from progressing. In a trial on mice, it helped stop the spread of breast cancer tumour cells to the lungs, they told a meeting on the US Defense Department's 'Era of Hope' Breast Cancer Research Program in Philadelphia this week.
Study leader Bharat Aggarwal said: "What's exciting about this agent is that it seems to have both chemopreventive and therapeutic properties. If we can demonstrate that it is efficacious in humans, it could be of tremendous value, but we're a long way from being able to make any recommendations yet."
Aggarwal and colleagues injected mice with human breast cancer cells and then removed the resulting tumours to simulate a mastectomy. Then the mice were split into four groups, receiving either no additional treatment, curcumin alone, the cancer drug paclitaxel (Taxol), or curcumin in combination with Taxol.
Five weeks later, cancer had spread to the lungs of mice in all four groups. But the two curcumin groups fared best.
Only half the mice in the curcumin-only group and just 22 per cent of those in the curcumin plus Taxol group had evidence of breast cancer that had spread to the lungs.
But 75 per cent of animals that got Taxol alone and 95 per cent of those that got no treatment developed lung tumours.
To confirm their findings, the researchers repeated the test, letting the cancers grow a little bit bigger before removing them.
After five weeks of treatment, half of the mice in the curcumin and curcumin-plus-Taxol groups had cancer in their lungs, they reported.
"Curcumin acts against transcription factors, which are like a master switch," said Aggarwal. "Transcription factors regulate all the genes needed for tumours to form. When we turn them off, we shut down some genes that are involved in the growth and invasion of cancer cells."
Curcumin is also being tested against multiple myeloma and pancreatic cancer in early phase I clinical trials at the University of Texas M.D. Anderson Cancer Center in Houston.
Other groups are conducting a global study of curcumin's ability to prevent oral cancer.