Research: HAMILTON-REEVES and COLLEAGUES,

Listed in Issue 168

Abstract

HAMILTON-REEVES and COLLEAGUES,  Department of Food Science and Nutrition, University of Minnesota, St Paul, MN 55455, USA studied the effects of soy protein, isoflavones and milk protein upon prostate cancer risk in men at high risk of prostate cancer or with log-grade prostate cancer.

Background

Methodology

Fifty-eight men at high risk of prostate cancer or with low-grade prostate cancer were randomly assigned to consume 1 of 3 protein isolates containing 40 g protein: 1) soy protein (SPI+, 107 mg isoflavones/d); 2) alcohol-washed soy protein (SPI-, <6 mg isoflavones/d); or 3) milk protein (MPI). Proliferating cell nuclear antigen (PCNA), epidermal growth factor receptor, B-cell non-Hodgkin lymphoma-2 (Bcl-2), and Bcl-2-associated X protein (Bax) were assessed in baseline and ending prostate biopsy cores. Serum collected at 0, 3, and 6 mo was analyzed for total and free prostate specific antigen (PSA).

Results

Consumption of SPI+ did not alter any of the prostate cancer tumour markers. Bax expression decreased from baseline in the SPI- group, resulting in lower Bax expression than the MPI group. PCNA expression also decreased from baseline in the SPI- group, but this was not different from the other 2 groups. PSA did not differ among the groups at 3 or 6 mo. Interestingly, a lower rate of prostate cancer developed in the soy groups compared to the milk group (P = 0.01).

Conclusion

These data suggest that 6-mo SPI+ consumption does not alter prostate tissue biomarkers, SPI- consumption exerts mixed effects, and less prostate cancer is detected after 6 mo of soy consumption regardless of isoflavone content.

References

Hamilton-Reeves JM, Rebello SA,  Thomas W,  Kurzer MS and Slaton JW. Effects of soy protein isolate consumption on prostate cancer biomarkers in men with HGPIN, ASAP, and low-grade prostate cancer. Nutrition & Cancer. 60 (1) :7-13. Jan-Feb 2008.

Comment

This research demonstrates that there was a lower incidence of prostate cancer in men consuming soy protein. Even more interesting was the finding which presumably was not expected, due to the expression "interestingly" that a lower rate of prostate cancer developed in the soy compared to the milk group.

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