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Serum prostate-specific antigen but not testosterone levels decrease in a randomized soy intervention among men.
Eur J Clin Nutr 2006; 60(12):1423-9EJ

Abstract

BACKGROUND

Low prostate cancer incidence and high soy intake in Asian countries suggest a possible protective effect of soy foods against prostate cancer. The goal of this pilot study was to evaluate the feasibility of a randomized, crossover soy trial among men and to investigate the effects of daily soy intake on serum prostate-specific antigen (PSA) and testosterone levels.

METHODS

We randomized 24 men to a high or a low soy diet for 3 months. After a 1-month washout period, the men crossed over to the other treatment. During the high soy diet, the men consumed two daily soy servings; during the low soy diet, they maintained their usual diet. During the entire study each man donated four blood samples and five overnight urine samples. Dietary compliance was assessed by soy calendars, 24-h dietary recalls, and urinary isoflavone excretion measured by high-pressure liquid chromatography with photodiode array detection. Blood samples were analyzed for serum testosterone and PSA by radioimmunoassay. When necessary, variables were log transformed. Two sample t-tests compared the two groups before each study period. Mixed models incorporating the repeated measurements were used to evaluate the effect of the soy diet on urinary isoflavone excretion and serum analytes.

RESULTS

Twenty-three men aged 58.7+/-7.2 years completed the study. The compliance with the study regimen was high according to self-reported soy food intake and urinary isoflavone excretion. No significant between-group and within-group differences were detected. During the high soy diet, dietary isoflavone intake and urinary isoflavone excretion increased significantly as compared to the low soy diet. A 14% decline in serum PSA levels (P=0.10), but no change in testosterone (P=0.70), was observed during the high soy diet in contrast to the low soy diet.

CONCLUSION

The high adherence as shown by three measures of compliance in this pilot trial demonstrated the feasibility of an intervention based on soy foods among free-living men.

Authors+Show Affiliations

Cancer Research Center of Hawaii, University of Hawaii, Honolulu, HI 96813, USA. gertraud@crch.hawaii.eduNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Randomized Controlled Trial
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

16775579

Citation

Maskarinec, G, et al. "Serum Prostate-specific Antigen but Not Testosterone Levels Decrease in a Randomized Soy Intervention Among Men." European Journal of Clinical Nutrition, vol. 60, no. 12, 2006, pp. 1423-9.
Maskarinec G, Morimoto Y, Hebshi S, et al. Serum prostate-specific antigen but not testosterone levels decrease in a randomized soy intervention among men. Eur J Clin Nutr. 2006;60(12):1423-9.
Maskarinec, G., Morimoto, Y., Hebshi, S., Sharma, S., Franke, A. A., & Stanczyk, F. Z. (2006). Serum prostate-specific antigen but not testosterone levels decrease in a randomized soy intervention among men. European Journal of Clinical Nutrition, 60(12), pp. 1423-9.
Maskarinec G, et al. Serum Prostate-specific Antigen but Not Testosterone Levels Decrease in a Randomized Soy Intervention Among Men. Eur J Clin Nutr. 2006;60(12):1423-9. PubMed PMID: 16775579.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Serum prostate-specific antigen but not testosterone levels decrease in a randomized soy intervention among men. AU - Maskarinec,G, AU - Morimoto,Y, AU - Hebshi,S, AU - Sharma,S, AU - Franke,A A, AU - Stanczyk,F Z, Y1 - 2006/06/14/ PY - 2006/6/16/pubmed PY - 2007/2/16/medline PY - 2006/6/16/entrez SP - 1423 EP - 9 JF - European journal of clinical nutrition JO - Eur J Clin Nutr VL - 60 IS - 12 N2 - BACKGROUND: Low prostate cancer incidence and high soy intake in Asian countries suggest a possible protective effect of soy foods against prostate cancer. The goal of this pilot study was to evaluate the feasibility of a randomized, crossover soy trial among men and to investigate the effects of daily soy intake on serum prostate-specific antigen (PSA) and testosterone levels. METHODS: We randomized 24 men to a high or a low soy diet for 3 months. After a 1-month washout period, the men crossed over to the other treatment. During the high soy diet, the men consumed two daily soy servings; during the low soy diet, they maintained their usual diet. During the entire study each man donated four blood samples and five overnight urine samples. Dietary compliance was assessed by soy calendars, 24-h dietary recalls, and urinary isoflavone excretion measured by high-pressure liquid chromatography with photodiode array detection. Blood samples were analyzed for serum testosterone and PSA by radioimmunoassay. When necessary, variables were log transformed. Two sample t-tests compared the two groups before each study period. Mixed models incorporating the repeated measurements were used to evaluate the effect of the soy diet on urinary isoflavone excretion and serum analytes. RESULTS: Twenty-three men aged 58.7+/-7.2 years completed the study. The compliance with the study regimen was high according to self-reported soy food intake and urinary isoflavone excretion. No significant between-group and within-group differences were detected. During the high soy diet, dietary isoflavone intake and urinary isoflavone excretion increased significantly as compared to the low soy diet. A 14% decline in serum PSA levels (P=0.10), but no change in testosterone (P=0.70), was observed during the high soy diet in contrast to the low soy diet. CONCLUSION: The high adherence as shown by three measures of compliance in this pilot trial demonstrated the feasibility of an intervention based on soy foods among free-living men. SN - 0954-3007 UR - https://www.unboundmedicine.com/medline/citation/16775579/Serum_prostate_specific_antigen_but_not_testosterone_levels_decrease_in_a_randomized_soy_intervention_among_men_ L2 - http://dx.doi.org/10.1038/sj.ejcn.1602473 DB - PRIME DP - Unbound Medicine ER -