Part of the pea family, this plant is commonly found in southeastern Asia. It makes up a large part of the Asian diet (in foods like tofu and tempeh). Because the rate of prostate cancer is very low in Asia, its high consumption is believed to play a role in cancer prevention. But does it?
Soy products and some of its components—which are called isoflavones—have been widely studied for their effects on cancer, including prostate cancer.
Researchers believe that some isoflavones (in particular one called genistein) may have estrogen-like effects. What isn’t yet clear is whether isoflavones have the ability to stimulate or stop the effects of the hormone estrogen.
While we know of one radiation oncologist who advocates it for all men with advanced prostate cancer, a recent study by Bosland et al (JAMA, July 10, 2013) showed that men at high risk of PSA failure who drank a beverage powder supplement that contained a soy protein isolate every day for two years after undergoing radical prostatectomy did not have a reduced biochemical recurrence of prostate cancer compared to men who received placebo. This was the first randomized clinical trial with cancer as the endpoint. Investigators stopped the trial early for lack of treatment effects.
Hwang et al (2009) concluded in their comprehensive meta-analysis of five cohort studies and 8 case-control studies that consumption of soybean milk, miso, or natto did not significantly reduce the risk of prostate cancer.
On the flip side, some earlier studies suggested potential benefits in men with prostate cancer:
Researchers, nutritionists, and prostate cancer specialists have not provided guidelines for what types of foods and/or supplements are ideal for men with prostate cancer and how much men should consume each day. Studies should also be conducted to determine if long-term consumption is safe for men with cancer.
Ahmad IU, Forman JD, Sarkar FH, et al. Nutr Cancer. 2010 Oct;62(7):996-1000.
Bosland MC, Kato I, Zeleniuch-Jacquotte A, et al. JAMA. 2013 Jul 10;310(2):170-8.
Hwang YW, Kim SY, Jee SH, Kim YN, Nam CM. Nutr Cancer. 2009;5(61:598-606.
Pendleton JM, Tan WW, Anai S, Chang M, Hou W, Shiverick KT, Rosser CJ. BMC Cancer.2008;5(8):132.
Yan L, Spitznagel EL. Am J Clin Nutr. 2009;89(4):1155-63.
Always consult a medical professional.