Potassium

Daily Value: 3,500 milligrams

Good Food Sources: Dried apricots, baked potatoes, dried prunes, cantaloupe, bananas, spinach

If monkeys eat as many bananas in the wild as they do on television, there is no way that any of them will ever suffer from high blood pressure.

That's because potassium--in humans, anyway--is a key factor in keeping blood pressure at the right level for maximum cardiovascular health.

How does potassium regulate blood pressure? Scientists believe it may have something to do with potassium's ability to pump sodium out of the body's cells and reduce body fluid. Potassium may also affect blood vessel tone, or resistance. Or it may be that potassium modifies the way blood vessels react to circulating hormones that affect blood pressure, such as vasopressin and norepinephrine.

In any case, potassium's ability to lower blood pressure is such that some scientists suspect low dietary levels of the mineral may actually trigger high blood pressure in certain people.

Aside from its miraculous effect on blood pressure, potassium is also necessary for good muscle contraction, healthy electrical activity in the heart and rapid transmission of nerve impulses throughout the body. This is why heartbeat irregularities are considered a classic sign of potassium deficiency. Other symptoms of deficiency can include muscle weakness, numbness and tingling in the lower extremities, nausea, vomiting, confusion and irritability.

Using Potassium Safely

Most of us get around 2,650 milligrams of potassium every day, reports the National Center for Health Statistics in Hyattsville, Maryland. That's not enough. And that's why you probably need to add at least three more servings of potassium-rich fruits and vegetables to your diet every day, says David McCarron, M.D., professor of medicine and head of the Division of Nephrology, Hypertension and Clinical Pharmacology at Oregon Health Sciences University in Portland.

Why not simply take a supplement? Dietary sources of potassium are better tolerated than pharmacologic preparations, experts agree, although potassium supplements--available over the counter or, in larger doses, by prescription--may be necessary for those who take diuretic medications. Diuretics help the body lose excess water but also deplete its potassium supply. (Digitalis, a heart medicine, can also cause you to excrete potassium.) If you use over-the-counter supplements, it is usually best, according to Dr. McCarron, to keep your total daily potassium intake from diet and supplements to 3,500 milligrams.

When a potassium supplement is required, talk to your doctor or pharmacist about which kind is best for you. Some doctors feel that potassium chloride is better absorbed than potassium bicarbonate, potassium citrate or potassium gluconate. Supplements containing more than 99 milligrams of potassium are available only by prescription.

Too much potassium (more than 5,000 milligrams a day) can upset the balance of minerals in your body and cause heart and kidney problems. Other potential side effects include muscle weakness, tingling in the hands, feet or tongue and a slow or irregular pulse.

People with diabetes or kidney disease should consult their doctors before taking potassium supplements, as should people on certain medications, including nonsteroidal anti-inflammatory drugs, potassium-sparing diuretics, ACE inhibitors and heart medicines such as heparin.