• Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, DHHS, Bethesda, MD, USA. dkoralek@unc.edu

BACKGROUND: Alpha-linolenic acid (ALA) is the most common omega-3 fatty acid in the Western diet. The relation of dietary intake of ALA to prostate cancer risk remains unresolved.

OBJECTIVE: We prospectively evaluated total ALA and ALA from specific food sources including animal, fish, and plant sources in relation to prostate cancer risk.

DESIGN: A cohort of 29,592 male participants (age 55-74 years) in the screening arm of the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial was followed for an average of 5.1 years.

RESULTS: We ascertained 1,898 cases of total prostate cancer, of which 1,631 were organ-confined cases (stage T1b to T3a and N0M0) and 285 were advanced stage cases (stage>or=T3b, N1, or M1). We found no association between total ALA intake and overall prostate cancer (multivariate RR comparing extreme quintiles=0.94; 95% CI=0.81-1.09; P for trend=0.76). The corresponding RRs for organ-confined and advanced prostate cancer were 0.94 (95% CI=0.80-1.10; P for trend=0.80) and 0.83 (95% CI=0.58-1.19; P for trend=0.34), respectively. In addition, no relations were observed between ALA intake from any specific food source and the risks of total, organ-confined, or advanced prostate cancer. ALA intake also showed no association with low grade (Gleason sum<7; 1,221 cases) tumors (P for trend=0.23) or high grade (Gleason sum>or=7; n=677 cases) tumors (P for trend=0.26).

CONCLUSIONS: In this prospective study of predominantly Caucasian men who were screened annually for newly incident prostate cancer, dietary intake of total ALA and ALA from specific food sources was not associated with risk of total prostate cancer or prostate tumors that were defined by stage and grade.