There are many varieties of lettuce but iceberg has large rounder leaves, which makes them perfect as a cup to hold or wrap other foods in. Lettuce is most often used for salads, sandwiches and for wraps (in the place of grain and high carb wraps). Lettuce is a rich source of vitamin K and A, it is a moderate source of folate and iron. Purchase organic where possible, as they are sprayed with herbicides. Wash well as lettuce and be contaminated with bacteria.