• Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, United States.
• Department of Urology, Emory University School of Medicine, Atlanta, GA, United States.
• Department of Population and Quantitative Health Sciences, Case Western Reserve University, Cleveland, OH, United States.
• Department of Public Health Sciences, Pennsylvania State University College of Medicine, Hershey, PA, United States.
• Department of Population and Quantitative Health Sciences, Case Western Reserve University, Cleveland, OH, United States. Electronic address: mxw827@case.edu.

BACKGROUND: Prostate cancer is one of the most common cancers in the United States. Dietary fiber intake may play a role in reducing cancer risk and mortality. However, the relationship of dietary fiber intake with prostate cancer risk and prostate cancer-specific mortality remains uncertain.

OBJECTIVES: This study aims to examine the association between dietary fiber intake and prostate cancer risk, prostate cancer-specific mortality, and all-cause mortality.

DESIGN: Secondary analysis of the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Study, a multicenter randomized trial conducted in the United States that included two arms: one undergoing annual screening and the other receiving usual care.

PARTICIPANTS/SETTING: A total of 49,476 participants (annual screening arm: 25,669 men; usual care arm: 23,807 men) aged between 55-74 years were enrolled from the PLCO between the years 1993 and 2001.

MAIN OUTCOME MEASURES: Prostate cancer risk, prostate cancer-specific mortality, and all-cause mortality were considered as main outcomes.

STATISTICAL ANALYSIS PERFORMED: Cox proportional hazard and competing risk regressions were employed within each arm to examine the associations of dietary fiber intake with prostate cancer risk, all-cause mortality, and prostate cancer-specific mortality.

RESULTS: Compared with the low tertile, high tertile total fiber intake in the annual screening arm was linked to reduced prostate cancer risk (aHR: 0.87, 95% CI: 0.76-0.99), while high soluble fiber intake in the usual care arm showed a similar association (aHR: 0.86, 95% CI: 0.75-0.98) after adjusting for confounders. There were statistically significant inverse associations between dietary fiber intake (total, insoluble and soluble) and all-cause mortality among participants in both arms (P<0.01). Significant associations of dietary fiber intake (total, soluble and insoluble) with advanced prostate cancer risk and prostate cancer-specific mortality in both arms were not observed (P>0.05).

CONCLUSION: High dietary fiber intake (total, soluble and insoluble) was found to be associated with decreased all-cause mortality which may suggest a protective effect of dietary fiber intake. Further prospective studies are needed to build upon these findings.