A green salad is often part of a healthy dinner, and although many vegetables may be used in it, lettuce is by far the most popular ingredient. Lettuce is the second most popular vegetable sold in supermarkets, topped only by potatoes.

Some types of lettuce and other salad greens contain high amounts of beta-carotene, folate, vitamin C, calcium, iron, and potassium, but the amounts vary considerably from one variety to another. In general, those with dark green or other deeply colored leaves have more beta-carotene and vitamin C than the paler varieties. Romaine lettuce, for example, has five times as much vitamin C and more beta-carotene and folate than iceberg lettuce.