Potassium is a crucial mineral, the seventh most common element on the planet. For a long time, it was not recognized as a distinct element from sodium. It was first isolated by Sir Humphrey Davy in 1807, who named it after pot ash (plant ash), his source of the mineral. Chemically it is a light, highly reactive alkaline metal, known to scientists by the symbol K (from the Latin word kalium, which means “alkali,” and is derived from the Arabic al qaliy, or "from the ashes").

What does potassium do in the body?

Potassium is critical in maintaining fluid and electrolyte balance in the body, and for enabling cells to send signals to each other. This might not seem so impressive, but these fundamental functions affect everything from breathing and heartbeat to digestion and kidney function.

Potassium doesn't operate alone in the body. The proper balance of sodium and potassium is especially important for your nerves, muscles, heart, and blood pressure. Likewise, the balance of potassium and bicarbonate is important in maintaining strong bones.

According to guidelines set by the Institute of Medicine in 2004, adults should get at least 4,700 mg of potassium each day to lower blood pressure levels, reduce the effects of salt on blood pressure, lower the risk of kidney stones, and possibly decrease bone loss.

If you eat several servings of fruits and vegetables each day, you may be getting plenty of potassium. Beans, leafy greens, bananas, winter squash, and sweet potatoes are all rich in the mineral. Other good sources of potassium include fish, dairy, tomatoes, oranges, dried fruits, nuts, seeds, and chocolate.

(Source for table: United States Department of Agriculture. Dietary Guidelines for Americans, 2005)

Although not common for most healthy people, potassium deficiency -- sometimes caused by a low-potassium diet but usually due to an excessive loss of potassium in the urine or from vomiting or diarrhea -- potentially make a person vulnerable to irregular heartbeat, glucose intolerance, weakened muscles and bones, and kidney stones. Potassium also affects high blood pressure and stroke. When potassium levels are low in some people with salt sensitivity, their blood pressure spikes in response to eating salt, but may remain steady when potassium levels are high.

The importance of potassium becomes apparent during a severe shortfall, also known as hypokalemia. Symptoms include confusion, depression, weakness, fatigue, cramps, and paralysis of the intestines, which can lead to bloating and constipation. Extreme cases can throw the heart out of rhythm, a potentially deadly complication.

Hypokalemia is rarely caused by too little dietary potassium. It can almost always be traced to a specific factor that drains the body of minerals, including alcoholism, the use of certain diuretics, overuse of laxatives, anorexia, bulimia, severe diarrhea or vomiting, or congestive heart failure.

The following medications may increase your risk of hypokalemia (too little potassium):

• Certain diuretics (pills to increase urination) and laxatives

• Steroid drugs

• Theophylline, a stimulant found in tea, used to treat asthma and COPD.

• Low levels of potassium can cause severe problems if taking digoxin (also called digitalis), which helps the heart pump more effectively.

Although uncommon in healthy people, too much potassium -- or hyperkalemia – can also be hazardous. Too much potassium can be as dangerous as too little: like hypokalemia, hyperkalemia can disrupt the heart’s rhythm, possibly causing cardiac arrest. Warning signs for hyperkalemia include muscle weakness, numbness and tingling in the hands and feet, and temporary paralysis.

Hyperkalemia is especially common in people with kidney disease. The kidneys help clear waste products and excess minerals out of the body, so potassium tends to build up when the organs aren’t doing their job well. It’s also possible to develop hyperkalemia by taking large doses (18 grams or more) of potassium supplements. Severe injuries or burns that rupture cells and release their potassium stores can cause hyperkalemia as well.

People at risk for hyperkalemia have to be very careful to limit potassium in their diet. A registered dietitian can steer them towards healthful meal plans that contain relatively small amounts of the mineral.

The following medications may increase your risk of hyperkalemia (too much potassium):

• NSAIDs (nonsteroidal anti-inflammatory drugs) for pain and swelling such as ibuprofen

• Potassium-sparing diuretics (pills to increase urination) like spironolactone, triamterene, and amiloride

• ACE inhibitors (used to treat high blood pressure) such as captopril, enalapril, fosinopril

• Beta blockers, also for high blood pressure, such as labetalol and propranolol (this generally occurs only with an overdose of beta blockers)

• Angiotensin receptor blockers (used to treat high blood pressure, kidney disease, and heart failure), such as losartan and valsartan

• The blood thinner heparin

• Certain antibiotics

The best way to get potassium – and the healthiest -- is to eat potassium-rich foods every day. You can also buy a multivitamin or potassium supplement over the counter, but each serving will give you less than 100 milligrams of potassium -- less than a quarter of the amount you'd get from eating a banana. Also, many salt substitutes are made from potassium chloride. So besides taking a multivitamin/mineral supplement, you might want to use a salt substitute to add potassium to your diet. But be sure to check with your doctor because the amount of potassium in many salt substitutes in very high, and depending on your condition, your doctor may not want you to use them because of safety issues. If you’re at risk for hypokalemia, your doctor may prescribe a potassium supplement that goes far beyond over-the-counter varieties. Prescription supplements are available in tablets, powders, and elixirs. They can even be injected. Because too much potassium can be dangerous, you should only take prescription-strength supplements under close supervision from a doctor. You should also know that prescription-strength potassium supplements can clash with many other medicines, including antihistamines and antidepressants. Make sure you tell your doctor about every other medicine you take.

References

Last updated November 25, 2009
Copyright © 2007 Consumer Health Interactive

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