Lentils, small disk-shaped legumes about the size of peas, are the oldest cultivated legume, with references dating back to around 2400 B.C. Unlike other dried legumes, lentils require no soaking; they become tender in 30 to 40 minutes of cooking. Lentils are a plant source of incomplete protein, so are best paired with grains such as rice to provide a complete, higher quality protein. A 1/2-cup serving of cooked lentils is an excellent source of fiber and folic acid and a good source of iron as well as lesser amounts of other vitamins and minerals.
Dried lentils are widely available and should be stored tightly covered at room temperature. They will keep up to eight months. Red, brown, yellow or green lentils can be used interchangeably in cooking.