Like olive, canola, and most other plant oils, flax seed oil is highly unsaturated and heart-healthy. Lignans and other flax seed components may also have antioxidant properties, which means they may reduce the activity of cell-damaging free radicals.

Recently small studies of cancer patients who consumed flaxseeds have produced some encouraging results.

In one study men with prostate cancer who ate an ounce of ground flaxseeds (almost three tablespoons) a day as part of a very-low-fat diet were able to slow the progress of their cancers between the time they were diagnosed and the time of surgery. A similar study of women awaiting surgery for breast cancer found that those who ate a flaxseed muffin daily (with about four tablespoons of ground flaxseeds per muffin) had a slower tumor growth rate. Studies of animals, too, suggest some anti-cancer benefit from flaxseed. But it's always difficult to know whether it's the lignans that help, or some other element in the flaxseeds. And not all studies have yielded positive results.

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. Like aspirin, omega-3s may reduce blood clotting, thus lessening the chance of a fatal heart attack.

Flaxseeds and their oil may also lower total blood cholesterol, as well as LDL ("bad") cholesterol.

But that should come as no big surprise, since any highly unsaturated oil will do that, particularly if substituted for saturated fats. The fiber in flaxseeds may also help against cholesterol, since it is soluble (similar to that in oats).