Natural Factors Magnesium Citrate contains 450 mg per serving of this extraordinary mineral. Magnesium is necessary for hundreds of enzyme reactions in the body and for normal heart function. It is necessary for protein synthesis, carbohydrate metabolism, proper muscle function and helps to absorb calcium and potassium. Citrates are extremely well absorbed and well-tolerated by the body making Natural Factors Magnesium Citrate capsules an excellent way to get this important mineral.