There is some evidence that people who eat a diet rich in potassium have lower blood pressure than others, possibly because potassium dilates blood vessels. Now, a recent report from the Harvard School of Public Health and Harvard Medical School indicates that a diet high in potassium may also reduce the risk of stroke, particularly in people with high blood pressure. Potassium is a mineral that is found mainly in fruits and vegetables; good sources include apricots, bananas, cantaloupes, kidney beans, oranges, pears, potatoes, spinach, and tomatoes. 

In 1986, the men reported on questionnaires the types of foods they usually ate and whether they took vitamin and mineral supplements and/or potassium supplements. They then completed follow-up questionnaires every two years until 1994. During the 8-year period, there were 328 strokes. 

The researchers found that the men in the top fifth of potassium intake were 38% less likely to have a stroke than those in the bottom fifth. Men with the lowest risk of stroke ate about 8 servings of fruits and vegetables a day; those with the highest risk consumed about half as much. Because the study is based on reports of what people ate, it can only uncover an association between a high-potassium diet and stroke risk; it cannot prove that the mineral caused the reduction in stroke. Thus it's possible that other chemicals in fruits and vegetables are responsible for some or all of the benefit. 

Another important finding was that men who took diuretics for hypertension and who were taking potassium supplements (about 1 gram per day) had a 64% reduced stroke risk compared to those on diuretics who weren't taking the supplements. Because diuretics often deplete the body of potassium, doctors sometimes prescribe the supplements.

Individuals who are not on diuretics do not need to take potassium supplements; in fact, high levels of the mineral could be toxic. But because the reduction in stroke risk was substantial among those who took both diuretics and potassium for hypertension, people on diuretics should talk to their doctor about the possibility of starting potassium supplements or taking a type of diuretic that protects against potassium loss. 

Finally, the bottom line for people with high or normal blood pressure: eat your vegetables -- and fruits. Not only will they help you stay healthy, they may prolong your life.