Flaxseed and Flaxseed Oil

The flax plant yields the fiber from which linen is woven, as well as seeds and oil. Flaxseed oil, also called linseed oil, has many industrial uses. Flaxseed oil also comes in an edible form. Like olive, canola, and most other plant oils, flaxseed is highly unsaturated and heart-healthy. And flaxseeds are rich in yet another very interesting component—lignans—which may have anti-cancer properties. Lignans are a type of fiber, and at the same time a type of phytoestrogen—a chemical similar to the human hormone estrogen. When you eat lignans, bacteria in the digestive tract convert them into estrogen-like substances called enterodiol and enterolactone, which are thought to have anti-tumor effects. Lignans and other flaxseed components may also have antioxidant properties—that is, they may reduce the activity of cell-damaging free radicals. (Flaxseed oil lacks lignans, but some processors add them to their oil.)

Besides lignans, flaxseeds and their oil are also the best food sources of an essential fatty acid, alpha-linolenic acid. "Essential" means we must consume it, because our bodies cannot manufacture it. Essential fatty acids are important for cell membranes, blood pressure regulation, and other functions. Alpha-linolenic acid is an omega-3, similar to some of the fatty acids in fish oil. Omega-3s may reduce blood clotting, thus lessening the chance of a fatal heart attack. Flaxseeds and flaxseed oil may also lower total blood cholesterol, as well as LDL ("bad") cholesterol. But any highly unsaturated oil will do that, particularly if substituted for saturated fats. You can find alpha-linolenic acid in canola oil and walnuts, among other sources.

Claims, purported benefits: Prevents heart disease and cancer.

Bottom line: These claims are overstated. Flaxseed oil is heart-healthy because it contains alpha-linolenic acid. Flaxseed itself (ground or whole) also contains lignans, which may have antioxidant actions and may help protect against certain cancers, though this is far from certain. Add flaxseed and flaxseed oil to your diet if you wish. But don’t take flaxseed supplements. Plant estrogens, like human hormones, are not always benign. At high doses—and no one knows how much is too much—lignans might turn into cancer promoters.