Prostate Cancer

Prostate cancer is the second leading cause of cancer death in men in the USA and is increasingly being diagnosed in men in their forties and fifties.  See here for an overview of diet and prostate cancer.

Role of Flaxseed in Preventing Prostate Cancer

Flaxseeds are an exceptionally rich source of dietary lignan, possessing over 800-fold the amount in most other foods (1). Studies have shown that lignan possesses anti-mitotic, anti-angiogenic, antioxidant, and phytoestrogen effects (1) which likely explain it’s potent role in preventing prostate cancer.  Note that lignans are present in ground flaxseed but not in flax oil.

In a randomized clinical trial (1) 161 men with prostate cancer who were scheduled for prostate surgery were randomised to receive one of the following interventions: 1) Control diet (their usual diet), 2) A low fat diet, 3) A diet supplemented with 3 tablespoons (30 g) of GROUND flaxseed per day, 4) A low fat diet plus ground flaxseed.  The researchers saw a statistically significant 48% decrease in cancer cell proliferation in the flaxseed group and a similar 53% decrease in the (flaxseed + low fat diet) group.  In other words, flaxseed had a much greater effect than a low fat diet.

In another study (2) 15 men with atypical (precancerous) cells in their prostate who were scheduled for repeat biopsy in 6 months all received a low fat diet plus supplementation with 3 tablespoons of ground flaxseed.  When they had their 6 month repeat biopsy they were found to have a 32% drop in their prostate specific antigen (P<0.001) as well as a 68% decrease in the rate of proliferation of their prostate cells (P<0.02).

Dr Dean Ornish conducted a randomized controlled study of 93 men with early stage prostate cancer who had chosen not to undergo any conventional treatment.  A control group was told to follow the advice of their physician regarding lifestyle changes.  For one year the intervention group did ALL of the following: a) Following a low fat (10% of calories from fat) vegan diet with soy supplementation, b) Fish oil supplementation (3 g/day), c) Vitamin E (300 units/day) plus selenium (200 mcg/day) plus vitamin C (2 g/day), d) Moderate aerobic exercise (walking 30 minute six days per week), e) Stress management for 60 minutes per day.  At 12 months, these were the results:

1. The prostate specific antigen (PSA) went down by 0.25 in the intervention group while it went up in the control group (statistically significant, P<0.02).
2. While no men in the intervention group dropped out, six men in the control group did so due to progression of their disease.
3. When the serum (blood extract) was placed on a prostate cancer cell line, that of patients in the intervention group resulted in a decrease in cell growth of 69.9 units while in the control group the drop was significantly less at 9.1 units (P<0.001)
4. Men in the intervention group lost 4.5 Kg while there was no change in the weight of those in the control group (P<0.001).

In light of the above studies, I recommend 2-3 tablespoons per day of GROUND flaxseed to decrease the risk of prostate cancer. I find it easiest to add to my breakfast.  Note that ground flaxseed is very sensitive to heat and should be kept in the fridge or freezer (we use a coffee grinder to grind ours every day).

See here for a video on the role of meat, dairy and eggs on the progression of prostate cancer.

Here is a 2014 update from the American Institute for Cancer Research on the prevention of prostate cancer.

References

1. Flaxseed Supplementation (not dietary fat restriction) reduces prostate cancer proliferation rates in men presurgery. W Demark-Wahnefried, TJ Polascik, SL George et al. Cancer Epidemiol Biomarkers Prev 2008:17(12):3577-3587  (Click here for full text)
2. Pilot Study to Explore Effects of Low-fat, flaxseed-supplemented diet on proliferation of benign prostatic epithelium and prostate-specific antigen.  W Demark-Wahnefried, CN Robertson, PJ Walther et al. Urology 2004:63:900-904
3. Intensive Lifestyle Changes May Affect the Progression of Prostate Cancer.  D Ornish, G Weidner, WR Fair et al.  Journal of Urology 2005:174:1065-1070.