New Study: Soy Improves Prostate Cancer Outlook

A new Australian study suggests that soy products can help decrease the risk of prostate cancer progression. The study, published in the September issue of Urology, included 29 Australian men with prostate cancer who were waiting to undergo a radical prostatectomy. The researchers divided the men into three groups to test how soy affects levels of hormones and prostate-specific antigen (PSA, which is used to screen for and track prostate cancer).

One group was asked to eat specially prepared bread made with soy grits (which contain 50 grams of natural phytoestrogens). A second group also consumed high phytoestrogen bread but it was made with 50 grams of soy grits plus 20 grams of linseed. The third group consumed wheat bread, which is naturally low in phytoestrogens. All three groups were instructed to consume four pieces of bread daily until surgery. The group consuming the soy-only enriched bread had a statistically significant drop in PSA levels (-12.7%) compared to the wheat bread control group whose PSA levels rose 40 percent. The PSA levels of the group consuming the soy-plus-linseed bread increased 21.3 percent, indicating that the addition of linseed may not only have no beneficial effect on PSA levels, but may actually increase prostate cancer progression. Although the study was small, it suggests that isoflavones in soy may be protective against prostate cancer.

China and Japan have some of the lowest rates of prostate cancer in the world, possibly due to the typically soy-rich diets in these countries. Isoflavones and phytoestrogens found in soybeans as well as the phytoestrogens and omega-3 fatty acids found in linseed oil have all been shown to have protective roles in prostate cancer development and progression.

Dalais FS, Meliala A, Wattanapenpaiboon N, Frydenberg M, Suter DA, Thomson WK, Wahlqvist ML. Effects of a diet rich in phytoestrogens on prostate-specific antigen and sex hormones in men diagnosed with prostate cancer. Urology. 2004 Sep;64(3):510-5.

PCRM Online, December 2004

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