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Potassium

Potassium can lower blood pressure, even out irregular heart rhythms, and counteract the effects of too much sodium. It's found in bananas, raisins, leafy greens, oranges, and milk.

Bottom line: Consider a supplement if you're taking potassium-depleting diuretics for a heart condition, or if you're African American, a group that's at higher risk for hypertension and heart disease. Keep in mind that too much potassium can be harmful to older people and people with kidney disease.

Next: Selenium