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Prostate Cancer, Nutrition, and Dietary Supplements (PDQ®): Complementary and alternative medicine - Health Professional Information [NCI] - Soy

Overview

This section contains the following key information:

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  • Soy foods (e.g., soy milk, miso, tofu, and soy flour) contain phytochemicals that may have health benefits and, among these, soy isoflavones have been the focus of most of the research.
  • Soy isoflavones are phytoestrogens. The major isoflavones in soybeans are genistein (the most abundant), daidzein, and glycitein.
  • Genistein affects components of multiple growth and proliferation -related pathways in prostate cancer cells, including the COX-2 /prostaglandin, epidermal growth factor (EGF), and insulin-like growth factor (IGF) pathways.
  • Some preclinical studies have indicated that the combined effect of multiple isoflavones may be greater than that of a single isoflavone.
  • Some animal studies have demonstrated prostate cancer prevention effects with soy and genistein; however, other animal studies have yielded conflicting results regarding beneficial effects of genistein on prostate cancer metastasis.
  • Epidemiologic studies have generally found high consumption of nonfermented soy foods to be associated with a decreased risk of prostate cancer.
  • Limited human prevention studies have been conducted, and, so far, they have not yielded consistent or definitive findings.
  • Treatment trials of various doses and preparations of soy isoflavones in men with prostate cancer have yielded varying results but have generally failed to demonstrate significant effects on prostate-specific antigen (PSA) levels.
  • A few clinical trials of soy protein or whole soy products have provided preliminary evidence of the ability of these products to lower PSA levels in men with prostate cancer.
  • Soy products are generally well tolerated in patients with prostate cancer. In clinical trials, the most commonly reported side effects were mild gastrointestinal symptoms.

General Information & History

Although records of soy use in China date back to the eleventh century BC, it was not until the 18th century that the plant reached Europe and the United States. The soybean is an incredibly versatile plant: it can be processed into a variety of products including soy milk, miso, tofu, soy flour, and soy oil.[1]

Soy foods contain a number of phytochemicals that may have health benefits but isoflavones have garnered the most attention. Among the isoflavones found in soybeans, genistein is the most abundant and may have the most biological activity.[2] Other isoflavones found in soy include daidzein and glycitein.[3] Isoflavones help soybeans survive in times of stress and have antioxidant, antimicrobial, and antifungal properties.[4]

Isoflavones are quickly taken up by the gut and can be detected in plasma as soon as 30 minutes after the consumption of soy products. Studies suggest that maximum levels of isoflavone plasma concentration may be achieved by 6 hours following soy product consumption.[5] Isoflavones are phytoestrogens (they bind to estrogen receptors) with a greater binding affinity for estrogen receptor beta than for estrogen receptor alpha.[6]

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WebMD Public Information from the National Cancer Institute

Last Updated: February 25, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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