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Potassium

Also known as: Kalium, K

Overview

Potassium is essential for normal bodily function. It is obtained in the diet and found in several foods. Potassium-containing drugs are sometimes used to treat certain conditions. Potassium salts (e.g. potassium chloride) are used in reduced-sodium added-potassium salt substitute interventions and in sodium restriction diets to help treat high blood pressure.

Benefits

The potassium concentration in the blood is primarily regulated by the kidneys, where potassium channels (protein structures that pass potassium ions across cell membranes) in the cells of the distal tubules regulate potassium excretion in the urine. Distribution of potassium within the body’s tissues is regulated by insulin, catecholamines (e.g., noradrenaline and adrenaline), and aldosterone. There is a steep gradient between the potassium concentration in the blood (i.e., the extracellular potassium concentration: 3.5 to 4.5 millimoles per liter, or mmol/L) and the potassium concentration in the cells (the intracellular concentration: 120 to 140 mmol/L). This gradient is critical for maintaining normal function in every cell in the body because it helps potassium ions constantly cross the cell membrane that separates the blood from the cell, generating a membrane potential. This vitally important membrane potential drives electrical impulses in neurons and contractions in muscle cells. This gradient is maintained by the potassium channels found in cell membranes. One of the most important is the sodium-potassium ATPase pump, which is found in every cell in the body and uses energy — adenosine triphosphate (ATP) — to maintain the potassium (and sodium) gradient across the cell membrane.

How it works

Some studies have shown that short-term daily supplementation with a potassium salt (e.g., potassium chloride or potassium citrate) can lower blood pressure in adults without known health conditions and in people with hypertension. While early systematic reviews and meta-analyses found that the evidence was mixed and that there was large variability in effects between studies, it now appears that supplementation with a potassium salt can cause a moderate and meaningful effect to lower blood pressure. However, the blood-pressure-lowering effect of potassium is likely to be greatest in people with lower potassium intake at baseline, higher sodium intake at baseline, or in people who don’t use a blood-pressure-lowering medication. Observational studies find a correlation between higher levels of daily dietary potassium intake and a reduced risk of stroke and cardiovascular disease. However, because these studies estimate dietary potassium intake from food recall questionnaires, the direct protective effect of dietary potassium on cerebrovascular or cardiovascular risk cannot currently be proven. Observational studies also show an association between higher levels of daily dietary potassium intake and better bone health. Furthermore, randomized controlled trials show that supplementation with potassium improves aspects of bone metabolism in postmenopausal women with osteopenia and in older adults with osteoporosis. However, it is currently unclear whether supplementation with potassium prevents bone loss in such people. Potassium-containing drugs — e.g., potassium chloride, potassium gluconate, potassium bicarbonate, potassium acetate, etc. — are used to treat low blood potassium (hypokalemia). Other potassium-containing drugs are also used clinically. For example, potassium citrate is used to treat some kidney defects, and potassium phosphate is used in the treatment and prevention of low blood phosphorus (hypophosphatemia).

Side effects

The adequate intake (AI) for potassium in people without known health conditions — i.e., the daily amount assumed to ensure nutritional adequacy — is as follows: Age Male Female Pregnant Lactating Birth to 6 months 400 mg/day 400 mg/day - - Infants 7–12 months 860 mg/day 860 mg/day - - Children 1–3 years 2000 mg/day 2000 mg/day - - Children 4–8 years 2300 mg/day 2300 mg/day - - Children 9–13 years 2500 mg/day 2300 mg/day - - Teens 14–18 years 3000 mg/day 2300 mg/day 2600 mg/day 2500 mg/day Adult 19–50 years 3400 mg/day 2600 mg/day 2900 mg/day 2800 mg/day Adult 51+ years 3400 mg/day 2600 mg/day - - Some evidence suggests that dietary potassium insufficiency might be common: the global mean potassium intake has been estimated at 2250 mg/day, with only 35% of adults estimated to be achieving adequate intakes. Potassium is found in many foods, including fruits, vegetables, legumes, meat, and animal products. Consult the FoodData Central database to check the amount of potassium in the foods you eat. Potassium supplements are generally safe for consumption and are unlikely to cause adverse effects if used within the recommended dosage.

Dosage

A high blood potassium concentration — hyperkalemia — is associated with an increased risk of heart problems (e.g., heart arrhythmias). Hyperkalemia-related symptoms have been associated with salt substitutes in several case studies, but case studies of individual people only show what is possible rather than what is typical. In people without known health conditions, serum potassium concentrations are between 3.5 and 4.5 millimoles per liter of blood (mmol/L). A meta-analysis of randomized controlled trials found that daily supplementation with potassium chloride in the range of 22 to 140 mmol /day — equivalent to approximately 0.9 to 5.5 grams /day of potassium — caused a statistically significant but clinically meaningless increase in serum potassium. Therefore, generally, supplementation with potassium is unlikely to cause hyperkalemia. Furthermore, in potassium supplementation studies, adverse effects are uncommon and biomarkers of renal function (urinary and serum sodium and creatinine) are typically unaffected. While supplementation with potassium salts (e.g. potassium chloride) can improve (i.e., lower) blood pressure, some evidence shows that very high doses might increase blood pressure. Consequently, if you use a potassium salt to treat high blood pressure, always use the dose recommended by your doctor.

FAQs

What is potassium?

Potassium, an element essential for maintaining normal cellular function in the body, regulates electrolyte balance, blood pressure, and electrical impulses in nerves and muscle cells. The latter is crucial for maintaining contractile function in muscles, including the heart. Potassium is obtained in the diet and is found in many foods, including fruits, vegetables, legumes, meat, and animal products (milk, yogurt, etc.). In the USA, the adequate intake (AI) for potassium — the amount assumed to ensure nutritional adequacy — in adults without known health conditions is 3,400 mg/day in males and 2,600 mg/day in females, but the AI changes with age and during pregnancy.

What are the signs and symptoms of potassium deficiency?

Potassium deficiency can lead to hypokalemia — low blood potassium, less than 3.5 millimoles per liter of blood (mmol/L) — which can cause a variety of signs and symptoms, including tiredness, loss of focus, loss of appetite, vomiting, and muscle weakness. In more serious cases, hypokalemia can also lead to heart arrhythmias, including atrial fibrillation, and is associated with an increased risk of cardiovascular-related mortality.

What are potassium’s main benefits?

What are potassium’s main drawbacks?

Does low blood potassium cause exercise-associated muscle cramps?

Muscle cramps are a complicated phenomenon that are associated with several factors: dehydration, glycogen depletion, overexertion, fatigue, hyperthermia, etc. While electrolyte (potassium and sodium) depletion in the blood can trigger muscle cramps, cramps can also happen with normal levels of electrolytes. Furthermore, because blood concentrations of potassium do not typically differ between people who experience cramps during exercise and people who do not, the current evidence shows that low blood potassium is unlikely to cause exercise-associated muscle cramps.

Are bananas high in potassium?

One ripe uncooked banana (1 serving; 115 grams) contains approximately 375 mg of potassium. However, several foods contain potassium in similar or greater quantities than bananas: meat (pork, beef, and poultry), potatoes, collards, beans, watermelon.