The major health benefits of flaxseeds are derived from their alpha-linolenic acid (ALA) and lignin content. Flaxseed oil contains nearly twice the level of omega-3 fatty acids as fish oil, although it contains the shorter-chain alpha-linolenic acid rather than the longer-chain fats, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Alpha-linolenic acid can be converted to these longer-chain omega-3 fatty acids, but the conversion depends upon the presence and the activity of an enzyme called delta-6-desaturase, which in some individuals, is available in reduced quantities or is less active than in others. In addition, function of delta-6-desaturase is inhibited in people with diabetes and nutrient deficiency, and by the consumption of saturated fat and alcohol.
Although much of the benefit of ALA is via conversion to the longer-chain omega-3 fatty acids, ALA has shown benefits of its own, including reducing the risk of heart disease and cancer. For example, data derived from biopsies of adipose breast tissue at the time of diagnosis from women with breast cancer compared to benign samples indicated that women with breast cancer had a 64 percent lower ALA level than women whose samples were benign. Another study noted that the higher the level of ALA in the breast tissue, the less likely the cancer was to spread into the lymph nodes of the armpit.
In addition, flaxseeds and flaxseed oil are the most abundant sources of plant lignans. These components are fiber compounds that can bind to estrogen receptors and interfere with the cancer-promoting effects of estrogen on breast tissue. Lignans also increase the production of a compound known as sex hormone-binding globulin(SHBG). This protein regulates estrogen levels by escorting excess estrogen from the body. Population studies, as well as experimental studies in humans and animals, have demonstrated that lignans exert significant anti-cancer effects.
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