 As described around 50 AD , lettuce leaves were often cooked and served by the Romans with an oil @-@ and @-@ vinegar dressing ; however , smaller leaves were sometimes eaten raw . During the 81 – 96 AD reign of Domitian , the tradition of serving a lettuce salad before a meal began . Post @-@ Roman Europe continued the tradition of poaching lettuce , mainly with large romaine types , as well as the method of pouring a hot oil and vinegar mixture over the leaves . Today , the majority of lettuce is grown for its leaves , although one type is grown for its stem and one for its seeds , which are made into an oil . Most lettuce is used in salads , either alone or with other greens , vegetables , meats and cheeses . Romaine lettuce is often used for Caesar salads , with a dressing that includes anchovies and eggs . Lettuce leaves can also be found in soups , sandwiches and wraps , while the stems are eaten both raw and cooked . The consumption of lettuce in China developed differently from in Western countries , due to health risks and cultural aversion to eating raw leaves . In that country , " salads " were created from cooked vegetables and served hot or cold . Lettuce was also used in a larger variety of dishes than in Western countries , contributing to a range of dishes including bean curd and meat dishes , soups and stir @-@ frys plain or with other vegetables . Stem lettuce , widely consumed in China , is eaten either raw or cooked , the latter primarily in soups and stir @-@ frys . Lettuce is also used as a primary ingredient in the preparation of lettuce soup . 
