Dr. David Samadi discusses why soy may increase risk of advanced prostate cancer

In Western countries such as the United States, prostate cancer is one of the most common cancers in men.  For the year 2017, there are estimations of 161,360 new cases that will be diagnosed in the U.S. with more than 26,000 men who will die from the disease.  The only established risk factors for this disease that cannot be changed are age, ethnicity, and family history.  Now a new study has revealed that dietary intake of isoflavones appear to be associated with an elevated risk of advanced prostate cancer.

“This finding brings to light what other studies have been showing of how a man’s dietary choices may affect his prostate cancer risk,” stated Dr. David Samadi. “It’s been suggested by other past studies that men who regularly consume a diet rich in processed carbohydrates or a high-fat diet may have a greater likelihood of prostate cancer.  This new study has found a significant positive association of dietary intake of total isoflavones and advanced prostate cancer or cancer which has spread beyond the prostate gland to other areas, which are independent of already established risk factors for this disease.”

Previous experimental studies in rats have shown that phytoestrogen intake influences prostate carcinogenesis, but little is known about whether intake of these bioactive compounds are associated with prostate cancer risk in human populations. The researchers wanted to find out the potential associations between phytoestrogen intake and prostate cancer risk and they did so by analyzing the data of more than 27,000 men who were part of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial.  

“Phytoestrogens are a family of estrogen-like bioactive compounds found in plants,” explained Dr. Samadi.  “These phytoestrogens can be classified into three major categories which are isoflavones, lignans, and coumestans. Three components categorized as isoflavones are genistein, daidzein, and glycitein with each being associated with an increased risk of advanced prostate cancer with genistein having a significant risk.”

Isoflavones are a type of phytoestrogen, compounds found in certain plants that have similar effects on the body as the female sex hormone of estrogen. Dietary sources with the highest concentrations of isoflavones are mainly soy and soy products such as miso, tempeh, tofu, kudzu root, and potato beans. 

“Out of the 27,000 men analyzed, the researchers identified over 2,500 prostate cancer cases over a period of 11 years,” said Dr. Samadi. “Out of these cases, 287 were men with advanced prostate cancer.  To assess each man’s intake of foods rich in isoflavones, they completed food frequency questionnaires.  What the results showed was men who consumed isoflavones in their diet had a greater risk of developing advanced prostate cancer than men who did not.”

Dr. Samadi went on to add, “With any sort of study such as this one, there are always limitations.  One is was the use of food frequency questionnaires rather than biomarkers to assess the intake of isoflavones.  In addition, further prospective cohort and epidemiologic studies are needed to confirm the present study‘s findings.  To get a much clearer picture of what is going on they need to measure both the dietary intake of phytoestrogens and their biomarkers among populations with diverse dietary habits.  Once that is done then we can hope for a better idea of more practical information to offer men for preventing this disease.”

Patients newly diagnosed with prostate cancer can contract world renowned prostate cancer surgeon and urologic oncologist, Dr. David Samadi, for a free phone consultation and to learn more about prostate cancer risk, call 212-365-5000.