Calories in Lettuce, romaine, green

What makes lettuce so powerful?

Romaine lettuce (Lactuca sativa var. longifolia) is also known as Cos lettuce, named after the Greek island of Kos where it was heavily cultivated before spreading to Rome. The Romans introduced it across their empire, which is why it eventually became known as 'romaine' (French for Roman). Beyond its history, romaine possesses a distinct chemical profile. The milky white fluid found in its stems and ribs contains lactucarium, a complex mixture of compounds including lactucin and lactucopicrin. This sap gives the plant its botanical genus name Lactuca, derived from the Latin word for milk. Historically, lactucarium was recognized for its mild sedative and analgesic properties, leading to the traditional folk remedy of eating lettuce to combat insomnia. While modern commercial romaine contains only trace amounts of these compounds, laboratory studies confirm that lactucin and lactucopicrin still interact with the central nervous system to promote mild relaxation. Furthermore, the deep green outer leaves are packed with chlorophyll and beta-carotene, pigments essential for photosynthesis that also provide significant dietary vitamin A. The satisfying crunch of the central rib comes from specialized, water-filled turgor cells that maintain structural pressure, keeping the leaves rigid until dehydration causes them to wilt.