Pilot Study of Dietary Fat Restriction and Flaxseed Supplementation in Men with Prostate Cancer Before Surgery: Exploring the Effects on Hormonal Levels, Prostate-Specific Antigen, and Histopathologic Features
Pilot Study of Dietary Fat Restriction and Flaxseed Supplementation in Men with Prostate Cancer Before Surgery: Exploring the Effects on Hormonal Levels, Prostate-Specific Antigen, and Histopathologic Features
Year: 2001
Authors: W Demark-Wahnefried, D T Price, T J Polascik, C N Robertson, E E Anderson, D F Paulson, P J Walther, M Gannon.
Publication Name: Circulation.
Publication Details: Urology 58; 47 – 52
Abstract:
The leading cancer among American men is prostate carcinoma. Evidence suggests that diet may play a strong role in its etiology and progression, and although several dietary factors are believed to be important, no dietary interventions have shown effective in the prevention of this disease. Previous studies have focused on flaxseed due to its beneficial effects on melanoma and cancers such as breast and colon. Because flaxseed is very complex, it is not clear if its antineoplastic potential is attributed to its fiber or fat portion, or if it is a synergy between the two. Both dietary fat and fiber affect hormonal levels, which may influence cancer progression, and flaxseed is one of the richest sources of both lignans and the omega-3 fatty acid alpha-linolenic acid (ALA). However, the effect of flaxseed on prostate cancer has yielded mixed results in a number of studies. Thus, the purpose of this study is to explore whether a flaxseed supplemented, fat-restricted diet could affect the biomarkers of prostatic neoplasia. A pre-surgical model was chosen to allow for the opportunity to assess changes in serologic markers, as well as to measure the potential effects on target tissue. Twenty-six patients with previously diagnosed clinically localized prostate cancer, who had elected radical prostatectomy, participated in the study. A three-week period between baseline assessment and surgery was also a criterion, as was the abstinence from antibiotic use due to their ability to inhibit the conversion of plant-based lignans to animal lignans. Participants were instructed to consume 30 g/day of ground flaxseed (approximately 3 rounded Tbsp.), which was in the form of a vacuum packed sports drink that also contained small amounts of emulsifiers, stabilizers, and oat flour. Participants were instructed to consume a low fat diet (20% of total kcal or less), where fat grams were calculated individually based on total energy requirements, and fat grams from omega-3 sources such as flaxseed and fish consumption were not to be calculated as part of their daily fat allowance. A baseline phlebotomy was performed prior to dietary instruction, and follow-up assessments were scheduled 1-3 days prior to surgery. At this time, dietary records were reviewed and blood was drawn for analysis of prostate-specific androgen (PSA), testosterone, free androgen index, and total serum cholesterol. In addition, histopathologic studies were performed on the tumors excised during prostatectomy. Tumors of diet treated patients were compared to historic cases matched by age, race, PAS at diagnosis, and biopsy Gleason sum. The average duration on the diet was 34 days. Of the 26 patients, only 25 completed the study. Results demonstrated a significant decrease in total serum cholesterol, total testosterone, and free androgen index. The baseline and follow-up levels of PSA were 8.1 +/- 5.2 ng/ml and 8.5 +/- 7.7 ng/ml respectively for the entire sample. However, among men with Gleason sums of 6 or less (n=19), PSA values were 7.1 +/- 3.9 ng/ml and 6.4 +/- 4.1 ng/ml. The historic controls demonstrated a mean proliferation index of 7.4 +/- 7.8 in comparison to 5.0 +/- 4.9 for the experimental group. Apoptotic indexes also differed significantly with the historic controls showing TUNEL categorical scores of 0 versus 1 for the experimental group. In addition, both apoptosis and proliferation rate were significantly associated with the number of days on the diet. In conclusion, data from this study demonstrate that a fat restricted diet supplemented with flaxseed may affect prostate cancer biology. Researchers believe this effect may be mediated by hormonal mechanisms; however, because this was a pilot study, further studies are necessary to investigate the potential benefit of a fat restricted diet containing flaxseed as a preventative or complementary therapy for prostate cancer.
