Many Americans do not get the recommended amounts of this essential mineral. Magnesium helps your immune system, maintains normal muscle and nerve function, keeps your heart rhythm steady and your bones strong. Having an adequate supply of magnesium in the body may also help protect against heart disease. Without this mineral, bones have a hard time absorbing calcium. Magnesium also helps regulate blood sugar levels and promotes normal blood pressure. Some foods that are high in magnesium include pumpkin seeds (pepitas), spinach, almonds, wheat germ, peanuts, Swiss chard, halibut, black beans, sunflower seeds, wheat bran, bananas, avocados, dried apricots and soybeans.