Magnesium
Why you need it: The body uses magnesium in more than 300 biochemical reactions. These include maintaining muscle and nerve function, keeping heart rhythm steady, and keeping bones strong.
Where to get it: Wheat bran has the highest amount of magnesium per serving (89 mg per quarter-cup, or 22% of your DV), but you have to eat unrefined grains to get the benefit; when the germ and bran are removed from wheat (as is the case with white and refined breads), the magnesium is also lost. Other good sources of the mineral include almonds, cashews, and green vegetables such as spinach.