26. a (potassium). In large trials, folic acid and vitamins E and C didn't lower the risk of heart disease. And the evidence that calcium can lower blood pressure is iffy. Potassium should cut the risk of heart disease because it lowers blood pressure. (Trials with potassium have looked only at blood pressure, not heart attacks or strokes.) It's best to get potassium from foods rather than supplements. Shoot for 4,700 mg a day from foods like fruits, vegetables, beans, seafood, and low-fat dairy.