Men: Do Not Use Flax Seeds
Disheartening news about flax seeds. Although intake of the essential fatty acid ALA (alpha linolenic acid) contained in flax seeds and nuts helps to prevent heart disease, it also seems to stimulate the growth of prostate cancers. A groundbreaking study from Harvard in 1993 showed that men who consumed the most ALA were 3.4 times more likely to be diagnosed with prostate cancer than men who had the lowest dietary intake. Since then at least five studies have shown an increased risk of prostate cancer from ALA.
A study from Uruguay published in 2000 showed that the two major risk factors associated with prostate cancer are a family history of prostate cancer and intake of ALA. That study showed a 3.9-fold increase in prostate cancer among the men who consumed the most ALA. These studies have shown an increased risk in men who consumed ALA and when ALA levels were measured in the blood. Just to confuse us, in a 1999 study from the Netherlands of over 58,000 men ALA was linked to a decreased risk of prostate cancer.
Some researchers have suggested that the lignans contained in the outer shell of flax seeds are responsible for their cancer preventing effects, and flaxseed oil, which contains more ALA, may promote prostate cancer.
These conflicting studies have convinced me that men should avoid supplementation with flax seeds and flax seed oil until we know much more. ALA is an essential fatty acid that we can get from eating nuts and other plants.
I recommend relying on EPA and DHA derived from fish oil, or DHA derived from algae to get the benefit of Omega-3 fats without the risky effect of ALA on the prostate.
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Andersson, S.O., et al. energy, nutrient intake and prostate cancer risk: a population-based case-control study in Sweden. Int. J. Cancer 68: 716-722, 1996.
Godley, P.A., et al. Biomarkers of essential fatty acid consumption and risk of prostatic carcinoma. Cancer Epidemiol. Biomarkers Prev. 5:889-895, 1996.
Harvei, S. et al. Prediagnostic level of fatty acids in serum phospholipids: omega-3 and omega-6 fatty acids and the risk of prostate cancer. Int. J. Cancer 71: 545-551, 1997.
De Stefani, E., et al. Alpha-linolenic acid and risk of prostate cancer: a case-control study in Uruguay. Cancer Epidemiol. Biomarkers Prev. 9: 335-338, 2000.