What Is It?
With the exception of calcium and phosphorus, no other mineral is as abundant in the human body as potassium. Most people don’t need to take supplements of this mineral because it’s so widely available in foods such as bananas, orange juice, and potatoes.
Potassium’s task is a formidable one, primarily because of its role as an electrolyte, a mineral that takes on a positive or negative charge when dissolved in the watery medium of body fluids. (Sodium and chloride are other important electrolytes.) To regulate blood pressure and muscle contraction, and to keep nerves, kidneys, and a host of other body processes working properly, the body needs to maintain these electrolytes in a delicate balance.
In addition, potassium aids in converting blood sugar (glucose, the body’s foremost fuel), into glycogen, a form of energy that can be stored in the muscles and liver and released as needed.
A healthy intake of potassium through foods is valuable for general health and can even help to maintain normal blood pressure. In fact, a diet high in potassium-rich food may help to protect against heart disease and stroke, according to various studies. One study found that people with high blood pressure who had a daily serving of a potassium-rich foods decreased their risk of fatal stroke by 40%. Whether this effect was entirely due to the potassium is not entirely clear, however.
Research also indicates that an adequate level of potassium may have a role to play in regulating heartbeat, staving off heart-rhythm abnormalities, and preventing kidney stones.
Specifically, potassium may help to:
Reduce high blood pressure. Scientists have long known that potassium helps maintain blood pressure. According to the latest studies, people who regularly consume high-potassium foods, such as bananas, avocados, and yogurt, have lower blood pressure than those who don’t. For example, in a recent review of 33 studies that examined the effect of potassium on blood pressure, researchers discovered that participants who started out with normal blood pressure and then added 2,340 mg of potassium daily (from foods, supplements, or both) were able to lower their risk of developing high blood pressure by 25%. The reductions were ultimately greatest for people who already had high blood pressure.
A potassium-rich diet may even enable people with high blood pressure to slash their daily dose of prescription medication. In one study of 54 adults with high blood pressure, the majority (81%) of those who were placed on a high-potassium diet–they ate three to six servings of potassium-rich foods daily–were able to safely and dramatically reduce their dosage of high blood pressure medications within 12 months. In contrast, only 29% of those who continued with their normal diets were able to do so.
Most adults easily get an adequate and safe amount of potassium–about 5.6 g–from foods every day. In fact, there is no RDA for potassium. By law, over-the-counter supplements cannot contain more than 99 mg of potassium per pill, a ruling that applies to multivitamin and mineral preparations as well. Higher doses are available only by prescription and are necessary only in very special situations, such as the use of diuretics that promote potassium loss.
If You Get Too Little
A seriously low level of potassium–a condition called hypokalemia–is an uncommon event but can occur in people who lose large amounts of fluid from severe diarrhea, sweating, or vomiting. Hypokalemia occurs most frequently among people who take diuretics–medications that promote urination and thus lessen the volume of fluid in the body. Although these drugs often help in regulating blood pressure, they also promote the excretion of potassium through the urine, posing the risk for very low potassium levels and related muscle cramps and fatigue.
Some rare endocrine disorders (Liddle’s syndrome, Bartter’s syndrome, Fanconi’s syndrome) are also associated with hypokalemia. In the rare case of a severe potassium deficiency, muscle weakness, muscle twitching, paralysis, and abnormal heart rhythms may develop.
It’s important to remember that in virtually all cases of short-term diarrhea, potassium imbalances are slight and temporary. The body corrects itself without the need for any additional supplementation. It’s only when diarrhea is prolonged, or accompanied by dehydration, that problems with low potassium can cause real complications that may require professionally administered intravenous fluids (possibly including potassium, sodium, and other electrolytes). Such treatment typically corrects the imbalance in a few hours.
If You Get Too Much
Most people can safely absorb up to 18 g of potassium a day. In fact, potassium toxicity–a condition called hyperkalemia–is very unlikely to occur unless you take potassium supplements inappropriately or your kidneys don’t function properly. That’s because the kidneys carefully monitor the balance of potassium in the body and excrete any excess.
However, if your kidneys are malfunctioning for some reason and can’t properly process and eliminate potassium as a result, you may develop toxic levels of potassium in your bloodstream by taking supplements. Signs of too much potassium in your body include muscle fatigue and an irregular heartbeat (cardiac arrhythmia).
General Dosage Information
For high blood pressure: Consume potassium-rich foods daily. Because of the risk of toxicity, however, don’t take potassium in supplement form without professional supervision.
Guidelines for Use
To reduce the risk of stomach upset and nausea with potassium supplements that your doctor has prescribed, always take them with food.
Definitely avoid potassium supplements if you take drugs known as potassium-sparing diuretics (amiloride, spironolactone, triamterene), nonsteroidal anti-inflammatory drugs (NSAIDs), beta-blockers, or an ACE inhibitor for high blood pressure or angina. Always consult a doctor under such circumstances, because combining any of these drugs with potassium can lead to hyperkalemia.
Because of the risk of various complications, consult your doctor before combining a digitalis drug (cardiac glycoside) with supplemental potassium.
Corticosteroids, loop diuretics (such as bumetanide and furosemide), and thiazide diuretics (including hydrochlorothiazide and indapamide) all can lower the level of potassium in the body. Potassium supplementation may be required but should always be undertaken with medical supervision.
If you take a medication to control high blood pressure or heart disease, or if you have a kidney disorder, never take potassium supplements without medical supervision. Consuming potassium-rich foods is fine, however.
David Edelberg, MD