Potassium is a very important mineral for the proper function of all cells, tissues, and organs in the human body. It is also an electrolyte, a substance that conducts electricity in the body, along with sodium, chloride, calcium, and magnesium. Potassium is crucial to heart function and plays a key role in skeletal and smooth muscle contraction, making it important for normal digestive and muscular function, too. Many foods contain potassium, including all meats, some types of fish (such as salmon, cod, and flounder), and many fruits, vegetables, and legumes. Dairy products are also good sources of potassium.

Potassium in nature occurs only as ionic salt. As such, it is found dissolved in seawater, and as part of many minerals. Potassium ion is necessary for the function of all living cells, and is thus present in all plant and animal tissues. It is found in especially high concentrations in plant cells, and in a mixed diet, it is most highly concentrated in fruits. Potassium and sodium are chemically similar, since both are alkali metals. However, their functions in organisms are quite different, especially in animal cells.

Potassium, assists in muscle contraction and in maintaining fluid and electrolyte balance in body cells. Potassium is also important in sending nerve impulses as well as releasing energy from protein, fat, and carbohydrates during metabolism. Adding more potassium to a high-sodium diet might help decrease calcium excretion, particularly in postmenopausal women. Observational and experimental studies also suggest that individuals who eat a vegetarian diet high in minerals (such as calcium, magnesium, and potassium) and fiber and low in fat tend to have lower blood pressure.

Having too much potassium in the blood is called hyperkalemia; having too little is known as hypokalemia. Keeping the right potassium balance in the body depends on the amount of sodium and magnesium in the blood. Too much sodium -- common in Western diets that use a lot of salt -- may increase the need for potassium. Diarrhea, vomiting, excessive sweating, malnutrition, malabsorption syndromes (such as Crohn's disease) can also cause potassium deficiency, as well as use of a kind of heart medicine called loop diuretics.

Most people get all of the potassium they need from a healthy diet rich in vegetables and fruits. Older people have a greater risk of hyperkalemia because our kidneys are less efficient at eliminating potassium as we age. Older people should be careful when taking medication that may affect potassium levels, such as nonsteroidal anti-inflammatory drugs (NSAIDs) and ACE inhibitors.

A good food source of potassium contains a substantial amount of potassium in relation to its calorie content and contributes at least 200 milligrams of potassium in a selected serving size. The food and Nutrition Board of the National Academy of Sciences has estimated the minimum requirements for potassium for men and women over 18 years of age to be 2,000 milligrams per day.

In 1985 and 1986, one-third of the potassium in the diets of women came from fruits and vegetables. Within this food group, white potatoes provided about one-third of the potassium. Meat, poultry, and fish supplied 20 percent of the potassium. Foods that contain small amounts of potassium but are not considered good sources can contribute significant amounts of potassium to an individual's diet if these foods are eaten often or in large amounts.

Bone Health

At least one study shows a positive link between a diet rich in potassium and bone health. More research is needed to determine whether a diet high in potassium can reduce bone turnover in people.

Hypokalemia

The most important use of potassium is to treat the symptoms of hypokalemia (low potassium), which include weakness, lack of energy, muscle cramps, stomach disturbances, an irregular heartbeat, and an abnormal EKG (electrocardiogram, a test that measures heart function). Hypokalemia is usually caused by the body losing too much potassium in the urine or intestines; it's rarely caused by a lack of potassium in the diet. Hypokalemia can be life-threatening and should always be treated by a doctor.

High Blood Pressure

Some studies have linked low levels of potassium in the diet with high blood pressure. And there is some evidence that potassium supplements might cause a slight drop in blood pressure. But not all studies agree -- two large studies found no effect on blood pressure. It may be that taking potassium only helps lower blood pressure if you're not getting enough of this mineral to start with. Before taking potassium or any supplement for high blood pressure, talk to your doctor.

Stroke

People who get a lot of potassium in their diet have a lower risk of stroke. However, potassium supplements don't seem to have the same benefit.

Inflammatory Bowel Disease (IBD)

People with IBD (ulcerative colitis or Crohn's disease) often have trouble absorbing nutrients from their intestine, and may have low levels of potassium and other important nutrients. If you have IBD, your doctor may check your potassium levels and recommend a supplement.

Precautions:

Because of the potential for side effects and interactions with medications, you should take dietary supplements only under the supervision of a knowledgeable health care provider. Older adults should talk to their doctor before taking potassium supplements.

Side effects can include diarrhea, stomach irritation, and nausea. At higher doses, muscle weakness, slowed heart rate, and abnormal heart rhythm may occur. Contact your health care provider if you develop severe stomach pain, irregular heartbeat, chest pain, or other symptoms.

People with hyperkalemia or kidney disease should not take potassium supplements. People who take ACE inhibitors, potassium-sparing diuretics, or the antibiotic trimethoprim and sulfamethoxazole (Bactrim, Septra) should not take potassium.

If you are being treated with any of the following medications, you should not use potassium without first talking to your health care provider.

The following medications may cause potassium levels to rise:

• Nonsteroidal anti-inflammatory drugs (NSAIDs): People who have poor kidney function and take NSAIDs are at higher risk.
• ACE inhibitors: These drugs treat high blood pressure, heart disease, diabetes, some chronic kidney diseases, migraines, and scleroderma. People who take ACE inhibitors and also take NSAIDs, potassium-sparing diuretics, or salt substitutes may be particularly vulnerable to hyperkalemia (too much potassium). A rise in potassium from ACE inhibitors may also be more likely in people with poor kidney function and diabetes. ACE inhibitors include:
  • Benazepril (Lotensin)
  • Captopril (Capoten)
  • Enlapril (Vasotec)
  • Fosinopril (Monopril)
  • Lisinopril (Zestril)
  • Moexipril (Univasc)
  • Peridopril (Aceon)
  • Ramipril (Altace)
  • Trandolapril (Mavik)
• Heparin (used for blood clots)
• Cyclosporine (used to suppress the immune system)
• Trimethoprimand sulfamethoxazole, called Bactrim or Septra (an antibiotic)
• Beta-blockers: Used to treat high blood pressure, glaucoma, migraines
  • Atenolol (Tenormin)
  • Metoprolol (Lopressor, Toprol-XL)
  • Propranolol (Inderal)

The following medications may cause potassium levels to decrease:

• Thiazide diuretics
  • Hydrochlorothiazide
  • Chlorothiazide (Diuril)
  • Indapamide (Lozol)
  • Metolzaone (Zaroxolyn)
• Loop diuretics
  • Furosemide (Lasix)
  • Bumetanide (Bumex)
  • Torsemide (Demadex)
  • Ethacrynic acid (Edecrin)
• Corticosteroids
• Amphotericin B (Fungizone)
• Antacids
• Insulin
• Fluconazole (Diflucan): Used to treat fungal infections
• Theophylline (TheoDur): Used for asthma
• Laxatives

If you are taking any of these medications, it is important for your doctor to test your potassium levels to see whether or not you need a supplement. Do not start taking a supplement on your own.

Other potential interactions include:

Digoxin -- Low blood levels of potassium increase the likelihood of toxic effects from digoxin, a medication used to treat abnormal heart rhythms and heart failure. Your doctor will test your potassium levels to make sure they stay normal.

Eating a variety of foods that contain potassium is the best way to get an adequate amount. Healthy individuals who eat a balanced diet rarely need supplements. Whatever your age, talk to your doctor before taking potassium supplements.