Magnesium is a mineral that is used in more than 300 enzyme reactions in the body. You need it to build proteins and DNA, regulate blood sugar and blood pressure, manufacture energy, and encourage proper nerve and muscle function. Magnesium deficiency may result in nausea, vomiting, weakness, fatigue, and loss of appetite. Severe deficiency may lead to numbness, tingling, muscle cramps, personality changes, seizures, and even heart palpitations. Good sources of magnesium include nuts like almonds, cashews, and peanuts. Spinach, beans, and avocados supply a good amount of the mineral. Carbohydrates like cereal, bread, potatoes, and rice contain magnesium. People who have diabetes, alcoholism, or gastrointestinal disorders that lead to malabsorption may suffer from inadequate magnesium levels.