A key component of red blood cells, this mineral can help prevent fatigue and may improve exercise performance.
How much you need: Ages 19-50: 18 milligrams (mg)/day; ages 51+: 8 mg/day
Where to get it: Beans, fortified cereals, beef, lentils, eggs
Warnings: Consuming more than 45 mg/day can cause tissue damage, especially in the heart, liver and pancreas.