 In addition to its usual purpose as an edible leafy vegetable , lettuce has had a number of uses in ancient ( and even some more modern ) times as a medicinal herb and religious symbol . For example , ancient Egyptians thought lettuce to be a symbol of sexual prowess and a promoter of love and childbearing in women . The Romans likewise claimed that it increased sexual potency . In contrast , the ancient Greeks connected the plant with male impotency , and served it during funerals ( probably due to its role in the myth of Adonis ' death ) , and British women in the 19th century believed it would cause infertility and sterility . Lettuce has mild narcotic properties ; it was called " <unk> " by the Anglo @-@ Saxons because of this attribute , although the cultivated L. sativa has lower levels of the narcotic than its wild cousins . This narcotic effect is a property of two sesquiterpene lactones which are found in the white liquid ( latex ) in the stems of lettuce , called <unk> or " lettuce opium " . 
