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Potassium and the Risk of Stroke

Potassium is a mineral that helps maintain fluid balance in body cells, and is needed to release energy from proteins, carbohydrates and fat during metabolism. The body expends about 20-40% of its resting energy operating pumps that move sodium out of cells in exchange for potassium - an exchange that's critical for sending nerve impulses, muscles to contract, and the heart to function normally. While most of us are familiar with the health benefits of calcium and magnesium, the links between disease prevention and potassium are less widely known.

How much potassium do we need?

The Food and Nutrition Board of the National Academy of Sciences has estimated the minimum adult requirement for potassium to be 2,000 milligrams daily. However, the Board also notes that consuming more fruits and vegetables daily would greatly increase potassium intake and exert a beneficial effect on high blood pressure. Now, a recent study - part of the ongoing Cardiovascular Health Study - suggests that people at risk of stroke need to pay more attention to the amount of potassium they're consuming (1).

Low potassium raises the Risk of Stroke

In examining the records of about 5,600 people over 65 who had been followed for several years, investigators found that among the older participants who did not take diuretics, those with lowest amount of potassium in their diet were 1.5 times as likely to have a stroke than those with the highest intake. Low potassium intake was defined as less than 2,400 milligrams daily; high intake was more than 4,000 milligrams per day.

For people taking diuretics, those with low blood potassium levels had a 2.5 greater chance of stroke compared with to those with the lowest blood levels of this mineral. People who take diuretics for high blood pressure sometimes develop low body stores of potassium since the mineral is lost along with the fluid flushing effects of drugs like Lasix or Diuril.

This is not the first report linking low potassium with stroke. One large-scale study of more than 43,000 men found that participants in the top 20% of potassium intake who averaged 4,300 mg/daily were only 62% as likely to have a stroke than those in the bottom 20%, averaging 2,400 mg daily (2).

Aim for Optimal Potassium Intake

High potency, slow-release potassium tablets are often prescribed for those taking certain diuretics. However federal regulations designed to prevent gastro-intestinal upset from high potassium, limit multivitamin/mineral supplements to containing no more than 99 mg of potassium per serving - an amount that makes a non-significant contribution to the high levels of potassium that evidence suggests are needed. The best way to ensure optimal intake is to eat a produce-rich diet, and choose foods that are high in potassium: bananas, potatoes, prunes, orange and tomato juices, yogurt, beans, spinach and avocados. Since potassium is lost in cooking, the best strategy to retain potassium is to cook foods in a minimal amount of water, for the shortest possible time.

References

1. Green DM et al. Serum potassium level and dietary potassium intake as risk factors for stroke. Neurology 59:314-20, 2002.
2. Asherio A et al. Intake of potassium, magnesium, calcium and fiber and risk of stroke among US men. Circulation 98:1198-1204, 1998.