Flax is a blue-flowered plant that has been cultivated for use as food, as a constituent of paint, and as clothing fiber since around 3,000 B.C. More recently, flaxseed has become an "it" food, because it contains lots of alpha-linolenic acid (ALA), an omega-3 fatty acid that studies link to a reduced risk of heart disease. It's also rich in fiber and lignans—plant "hormones" that may help prevent breast and other cancers.
Flaxseed is the whole seed of the flax plant, while flaxseed powder and ground flaxseed is simply the seed after it's been pulverized. Whole flaxseeds tend to pass through your digestive system pretty much intact, so to reap their health benefits, choose ground or powdered versions. You can also crush them yourself in a coffee grinder—just make sure you haven't left a bean behind!
Flaxseed oil is extracted from flaxseeds, and while it's a rich source of ALA, it lacks the fiber and lignans found in the whole seeds. It also goes rancid very quickly, so make sure to refrigerate it after opening, and never use it for cooking. Although they're not as prone to rancidity, you should refrigerate ground and powdered flaxseeds for the same reason.
As far as what to do with ground flaxseeds, I like them sprinkled in cereal, on top of yogurt, and mixed into pancake, waffle and muffin batter. Of course, Jessica provides fantastic ideas in her book! Read more of Jessica's Q&A