Iceberg Lettuce

One cup of shredded iceberg lettuce has 10 calories, 2.1 grams of carbohydrates, 0.7 grams of protein and 0.9 grams of fiber. This variety of lettuce provides a wide range of minerals and vitamins, but one serving of the lettuce isn't a significant source of most of these nutrients. An exception, however, is vitamin K, which contributes to blood clotting. One cup of iceberg lettuce has 17.5 micrograms of this vitamin, accounting for 19 percent of the recommended dietary allowance for adults.

Romaine Lettuce

One cup of shredded romaine lettuce contains 8 calories, 1.6 grams of carbs, 0.6 grams of protein and 1 gram of fiber. This type of lettuce is high in vitamin A, which contributes to skin and eye health. One cup has 205 micrograms, which is 29 percent of the recommended dietary allowance for women and 23 percent for men. Romaine lettuce is also a valuable source of vitamin K. One cup has 48 micrograms, which accounts for 54 percent of the recommended dietary allowance for adults.

Red Leaf Lettuce

Red leaf lettuce, which adds a contrasting color to salads, has 4 calories, 0.6 grams of carbs, 0.4 grams of protein and 0.3 grams of fiber per shredded cup. It's also a valuable source of vitamins A and K. One cup has 105 micrograms of vitamin A, accounting for 15 percent of the recommended dietary allowance for women and 12 percent for men. The same serving has 39 micrograms of vitamin K, which provides 44 percent of the recommended dietary allowance for adults.

Lettuce in Your Diet

Incorporating lettuce into your diet is beneficial, whether you're working on losing a few pounds or just wish to keep your current weight. Because lettuce is about 95 percent water and contains very few calories, you can eat it in significant amounts without overly elevating your calorie intake. Although lettuce isn't as high in fiber as some other vegetables, such as peas or sweet potatoes, its fiber helps fill you up and prevents a rapid blood sugar spike.