The following excerpt from The Living Gluten-Free Answer Book by Suzanne Bowland, Sourcebooks 2008.

Today, along with other nutritious gluten-free grains like quinoa and teff, amaranthis enjoying a renaissance as a whole grain used in cooking, as well as a flour ingluten-free baking. Amaranth is a seed crop native to South America and was the
essential food staple of the ancient Aztecs and Incas. This tiny seed is a nutritionalpowerhouse that contains each of the essential amino acids, in addition to boasting 6grams of protein and 6 grams of dietary fiber in just one ¼ cup serving. Similar to
quinoa, this South American supergrain lends itself well to culinary versatility.Amaranth can be used in a variety of ways, ranging from porridge and pilafs tocasseroles and snacks. Consider taking some of your favorite rice, potato and pasta
dishes and substituting amaranth for a new taste and texture sensation.These tiny seeds remain miniscule even after cooking, but become soft and tenderwhile maintaining a faint, appealing crunch. Amaranth does not fluff up like rice and
quinoa when cooked, but maintains a hearty, dense quality that maintains moisturewell and has a unique, golden shimmer. 
It’s common to see amaranth flour being incorporated into flour blends for glutenfree baking; the high protein content provides a stickiness that is beneficial. But amaranth is also widely used in commercial food products.