8 wonderful Lettuce nutrition facts and health benefits Lettuce leaves are one of the very low-calorie green vegetables. 100 g fresh greens provide just 15 calories. Nonetheless, they are the storehouse of many phytonutrients that possess health-promoting and disease prevenation properties. Vitamins in lettuce are plentiful. Its fresh leaves are an excellent source of several Vitamin-A and β-carotenes.