New evidence suggests that a combination of soy and the Indian spice turmeric could slow the growth of prostate cancer.
Rates of prostate cancer vary greatly throughout the world and diet may be one reason for the differences. In Japan, where soyfoods are a regular part of traditional menus, prostate cancer risk is remarkably low compared to western countries. And among men in Asia, those who consume the most soy are about 30 percent less likely to develop prostate cancer than those who consume little soy.
In men who have been diagnosed with prostate cancer, consumption of isoflavones, naturally-occurring compounds that are unique to soybeans, can slow the rise of prostate specific antigen (PSA). Levels of this protein, which is produced by the prostate, are proportional to tumor size. As a result, factors that reduce PSA levels may be linked to slower tumor growth.
Other compounds in plant foods, including some herbs and spices, also may help prevent cancer or slow its growth. One is these is the phytochemical cucurmin which gives the Indian spice turmeric its bright yellow color.
Japanese researchers examined the effects of isoflavones in combination with cucurmin on PSA levels in men who did not have prostate cancer. Eighty-five subjects took either a daily supplement of isoflavones—about the amount in 1 ½ servings of soyfoods—and curcumin or a placebo. The isoflavone-cucurmin supplement resulted in a 46% drop in PSA levels among the men whose high levels placed them at greater risk for cancer. The researchers concluded that the combination of isoflavones and curcumin could reduce cancer risk in men with elevated PSA levels.
Prostate tumors are slow-growing and are much more likely to occur in older men. Researchers suggest that anything that slows the growth of the tumors even further could reduce prostate cancer mortality. That is, men with this cancer could die from natural age-related causes before the cancer ever really takes hold and becomes life threatening.
Ide H, Tokiwa S, Sakamaki K, Nishio K, Isotani S, Muto S, Hama T, Masuda H, Horie S. Combined inhibitory effects of soy isoflavones and curcumin on the production of prostate-specific antigen. Prostate 2010;70:1127-33.