Natural Factors Magnesium Citrate 300 mg 250 g Powder Berry FlavourMagnesium is required for the formation of bones and teeth, and for nerve and muscle function. It is involved in numerous enzyme reactions that keep the body working properly. It regulates growth and development, and supports immune function and temperature regulation. Shaky hands, tension headaches, nervousness, and muscle spasms all respond favourably to magnesium.