Nutritional value, bioactive compounds and health benefits of lettuce (Lactuca sativa L.)

Lettuce is one of the most widely consumed vegetables worldwide, but its nutritional value has been underestimated. Lettuce is low in calories, fat and sodium. It is a good source of fiber, iron, folate, and vitamin C. Lettuce is also a good source of various other health-beneficial bioactive compounds. In vitro and in vivo studies have shown anti-inflammatory, cholesterol-lowering, and anti-diabetic activities attributed to the bioactive compounds in lettuce. However, nutrient composition and bioactive compounds vary among lettuce types. Crisphead lettuce, the most popular type of lettuce in the US, is comparatively low in minerals, vitamins, and bioactive compounds. More nutritious lettuces are leaf type lettuce and romaine with folate content comparable to other rich leafy vegetable sources. Red pigmented lettuce contains higher phenolic compounds than green lettuce. Due to increasing popularity, the nutrient contents in baby lettuce were also examined. Baby green romaine was especially high in vitamin C. In this review composition and nutritional value of different lettuce types were summarized, which can help growers and consumers choose lettuce types with higher nutritional benefits.