Flaxseed Supplementation (Not Dietary Fat Restriction) Reduces Prostate Cancer Proliferation Rates In Men Presurgery

A multi-site randomized controlled trial to test the effects of low fat and /or flaxseed-supplemented diets is reported in the December 2008 issue of Cancer Epidemiology, Biomarkers and Prevention. Flaxseed is an oilseed commonly consumed in the Middle Ages, and is not common in the modern era due to its short shelf life. Flaxseed is rich in dietary lignan, which has anti-mitotic, anti-angiogenesis, anti-oxidant and phytoestrogenic effects. It also reduces testosterone and 5-reductase.

A total of 161 men diagnosed with prostate cancer (CaP) and scheduled for radical prostatectomy at least 21 days after accrual were enrolled in the study. They were randomized into 4 groups - control (usual diet), flaxseed-supplemented (30gm/day), low-fat diet (<20% of energy from dietary fat), or flaxseed-supplemented plus low fat. Dietary questionnaires, serum and urine levels of relevant compounds and prostatectomy tissue were assessed. The primary study endpoint was proliferation index (by Ki-67 staining using the antibody MIB-1) in the prostatectomy tissue.

The dropout rate was 7.5%. Most participants had early stage CaP, and dietary logs revealed good to excellent adherence. Both erythrocytes and prostatic tissue had significantly higher levels of longer chained fatty acids. Tumor proliferation was significantly lower in the flaxseed-supplemented arm (proliferation index = 1.66), compared to 3.23 for controls, 2.56 for low-fat diet, and 1.50 for the combined flaxseed with low-fat diet. No differences were noted between groups for apoptosis, Gleason sum, or serum markers although serum PSA, testosterone, IFG-1, and IFGBP-3 decreased in all groups. Men in the low-fat diet group had significant reductions in body mass index and total and low-density lipoprotein cholesterol.

Demark-Wahnefried W, Polascik TJ, George SL, Switzer BR, Madden JF, Ruffin MT 4th, Snyder DC, Owzar K, Hars V, Albala DM, Walther PJ, Robertson CN, Moul JW, Dunn BK, Brenner D, Minasian L, Stella P, Vollmer RT.

Cancer Epidemiol Biomarkers Prev. 2008 Dec;17(12):3577-87.
doi:10.1158/1055-9965.EPI-08-0008 Prev. 2008;17:3577-87