Flaxseed oil and prostate cancer

Many people have asked me why I rarely recommend flax oil. Although I consider freshly ground flaxseeds to be a highly nutritious superfood with significant immune-enhancing properties, flax oil presents problems. It is highly vulnerable to rancidity – even if refrigerated – and it is not immediately usable in the body because it depends on an enzymatic conversion that does not always take place.

An interesting new study (Am J Clin Nutr 2004 Jul; 80 (1): 204-16) focused on intakes of different fatty acids in roughly 48,000 men over 14 years in relation to the occurrence of prostate cancer. It found that higher consumption of fats found in meat or butter had no effect on the rate of prostate cancer, while fish oil was protective and those who consumed more of it enjoyed a lower rate of prostate cancer. Intake of ALA (alpha linolenic acid), the primary fat in flaxseed oil, was neutral in terms of overall cancer rates, but those who consumed more of this oil had a higher occurrence of advanced prostate cancer.

Although more research might be needed to confirm this finding it is hard to think it was coincidental, given the large size of the study. It would therefore seem that while ALA does not cause prostate cancer it promotes its growth.

We don’t know exactly what causes prostate cancer, and probably multiple factors are at work, but highly unsaturated oils with a strong tendency to become rancid ‘such as flaxseed oil’ might provide a perfect medium to help this cancer grow.

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