Complete Protein

Romaine lettuces calories are 20 percent protein. Like all whole foods, much of this protein is complete, but the amount can be increased by combining with balancing proteins. It also contains good amounts of minerals like iron, calcium, magnesium, and potassium, which are very essential for body metabolism. Potassium is an important component of cell and body fluids that helps controlling heart rate and blood pressure. Manganese is used by the body as a cofactor for the antioxidant enzyme, superoxide dismutase. Copper is required in the production of red blood cells. Iron is essential for red blood cell formation.