Abstract
PurposeWe describe the effects of soy isoflavone consumption on prostate specific antigen (PSA), hormone levels, total cholesterol, and apoptosis in men with localized prostate cancer.Methodology/Principal FindingsWe conducted a double-blinded, randomized, placebo-controlled trial to examine the effect of soy isoflavone capsules (80 mg/d of total isoflavones, 51 mg/d aglucon units) on serum and tissue biomarkers in patients with localized prostate cancer. Eighty-six men were randomized to treatment with isoflavones (n = 42) or placebo (n = 44) for up to six weeks prior to scheduled prostatectomy. We performed microarray analysis using a targeted cell cycle regulation and apoptosis gene chip (GEArrayTM). Changes in serum total testosterone, free testosterone, total estrogen, estradiol, PSA, and total cholesterol were analyzed at baseline, mid-point, and at the time of radical prostatectomy. In this preliminary analysis, 12 genes involved in cell cycle control and 9 genes involved in apoptosis were down-regulated in the treatment tumor tissues versus the placebo control. Changes in serum total testosterone, free testosterone, total estrogen, estradiol, PSA, and total cholesterol in the isoflavone-treated group compared to men receiving placebo were not statistically significant.Conclusions/SignificanceThese data suggest that short-term intake of soy isoflavones did not affect serum hormone levels, total cholesterol, or PSA.Trial RegistrationClinicalTrials.gov NCT00255125
Highlights
Prostate cancer is the most common non-cutaneous cancer in American men [1]
A typical soyrich Japanese diet consists of 25–100 mg soy isoflavones/day, while a typical American diet contains about 2–3 mg soy isoflavones/day [7]
Twenty-three subjects did not complete the third visit because their surgery or radiation therapy treatment date occurred before the last visit was scheduled
Summary
Prostate cancer is the most common non-cutaneous cancer in American men [1]. Epidemiological studies associate soy food consumption in Asian populations with a decrease in prostate cancer risk [2,3], plasma genistein concentration has not been associated with prostate cancer risk at dietary exposures typical of Western populations [2,3,4]. The circulating soy isoflavone concentrations in Japanese men are at least 10-fold higher than American [5,6] and European men [4]. Migration studies of Asian men suggest that their prostate cancer incidence rates increase in direct relation to the length of time spent residing in the United States [8,9].
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