Over half a million men worldwide are diagnosed with prostate cancer every year, with over 200,000 deaths from the disease. The lowest incidence of the cancer is in Asia and the Far East, in particular India and China, and this has been linked to high dietary intake of compounds like turmeric.
The active ingredient in the spice, which is a significant component in curry powders, is the polyphenol curcumin. Epidemiological studies have previously linked high turmeric intake to lower rates of leukaemia, breast, lung and colon cancer.
The research, published in the 15th January issue of the journal Cancer Research (Vol. 66, Issue 2), studied the effects of turmeric and phenethyl isothiocyanate (PEITC), a compound found naturally in cruciferous vegetables like broccoli and cauliflower, on human prostate cancer cells injected into mice.
"The bottom line is that PEITC and curcumin, alone or in combination, demonstrate significant cancer-preventive qualities in laboratory mice," said lead-author Professor Ah-Ng Tony Kong.
The mice were bred specially so that their immune systems would not reject the injection of human prostate cancer cells, which would then continue to grow in the animal models.
Curcumin, PEITC, or a combination of the two, were injected into the mice three times a week over four weeks, starting the day before the introduction of the cancer cells. While injection of turmeric or PEITC significantly retarded prostate cancer cell growth, the combination produced even stronger effects.
The anti-cancer effects of turmeric seem to be applicable to a wide-range of cancers. Dr Gareth Jenkins from the University of Swansea in the UK recently started a new study looking at the effects of curcumin in relation to oesophageal cancer.
Talking to NutraIngredients.com, Dr. Jenkins said: "There are a lot of reports around about the promising effects of curcumin on oesophageal, colorectal and other cancers. Normally, what works on one cancer may not prevent another. However, curcumin appears to have a widespread effect."
"These results are very exciting in that they show a very positive effect of curcumin on prostate cancer development. This adds impetus to carry on our work on oesophageal cancer," he said.
Dr Jenkins stressed that clinical studies are needed before any firm conclusions can be drawn on the prevention of prostate cancer with curcumin.
The Swansea team is studying the effect of curcumin on NF-kappaB, a protein believed to be very important to the development of oesophageal cancer.