A mineral salt important to nerve signaling, healthy bones, and normal muscle contraction. Magnesium is found in unprocessed foods such as nuts, unmilled grains, and legumes. A magnesium deficiency causes problems with the nervous system including hand and foot spasms, twitching, and cramping. The average woman should consume about 320 milligrams per day. Magnesium, as a salt mixed with sulfate, is sometimes used to inhibit premature labor and treat pre-eclampsia.