Potassium

Potassium is an essential mineral of the human body and the primary cation found within the intracellular fluid of all cells.

As a major intracellular cation, potassium acts to preserve acid-base balance and maintenance of isotonicity, as well as electrodynamic cellular function.

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It activates many enzymatic reactions within our body, and plays an essential role in the transmission of nerve impulses, contraction of cardiac muscles, as well as skeletal and smooth muscles, tissue synthesis, gastric secretion, and renal function.

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It also reduces mean systolic and diastolic blood pressure, and improves carbohydrate metabolism via upregulation of insulin secretion by the β cells of the pancreas [130].

The gradient of potassium across the cell membrane determines cellular membrane potential, which is largely maintained by the ubiquitous ion channel- the sodium-potassium (Na+/K+) ATPase pump.

Approximately 90% of potassium consumed is lost in the urine, with the other 10% being excreted in the stool, and a very small amount lost in sweat.

Concerning food sources, potassium concentration is higher in fruits and vegetables than in cereals and meat.

Salting foods and discarding their liquids induces sodium (Na+) for potassium (K+) exchange, and further reduces the potassium content of foods.

Western dietary practices with higher consumption of cereals, low nutrient density processed foods, and lower consumption of fruits and vegetables, has led to a diet lower in potassium and higher in sodium in recent decades [2].

Little is known about the bioavailability of potassium, especially from dietary sources, as the only food analyzed is the potato.

The recommended adequate intake for potassium is set at 4700 mg/day [3].

Few Americans meet the recommended intake; the average intake is 2600 mg/day [4].

This large gap between potassium intakes and recommended intakes led to potassium being called a “shortfall nutrient” in the Dietary Guidelines for Americans [5]

Global Potassium Intakes

United States of America

It is estimated that only 3% of adults and 10% of children under the age of five in the United States meet the adequate intake level for potassium [67].

However, it should be noted that the US adequate intake, set at 4700 mg/day for adults, is substantially higher than the World Health Organization’s (WHO) guidelines, which recommend 3150 mg/day for adults [8].

National Health and Nutrition Examination Survey (NHANES) data indicates that 99.2% of potassium in the US diet is naturally occurring, with the remaining 0.8% coming from fortified foods [4].

These naturally occurring sources include milk and other non-alcoholic beverages, as well as potatoes and fruit, which rank highest as sources of potassium intake among US adults [9].

Europe

Welch et al. [10] examined potassium intakes from 10 European countries and found that, for both men and women, Greece had the lowest average intakes at 3536 mg/day and 2730 mg/day, respectively.

The highest potassium intakes were found in Spain, where the average intake for men was 4870 mg/day and for women was 3723 mg/day [10].

Meat and meat products, cereals and cereal products are the main contributors to potassium intake in Europe [10].

However, there is substantial geographical variation in the contribution of other potassium-rich foods.

It is estimated that fruit and vegetables provide 17.5% of total potassium intake in Nordic countries compared to 39% in Greece [10], while in the United Kingdom (UK), vegetables and potatoes are the largest contributors to potassium intake, providing 24.5% [11].

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Asia

Despite an increase of 300 mg/day since 1991, potassium intakes in China remain poor at 1800 mg/day [12].

This does not meet the Chinese dietary reference intake (DRI) for potassium, which is set at 2000 mg/day, and is almost half of the World Health Organization (WHO) recommendation of 3150 mg/day [8].

Intakes are higher in Korea, where the average potassium intake is 2900 mg/day, yet, still do not meet the WHO guidelines [13].

The primary potassium sources in the Korean diet are white rice (30-35 mg per 100 gr. of cooked rice), fruits, and vegetables [13].

Uses

The chief indication for potassium administration is potassium deficiency or hypokalemia, a condition in which the level of serum potassium falls below a critical range.

Hypokalemia can occur due to multiple reasons, mainly inadequate intake of potassium, such as in cases of malnutrition, malabsorption, debilitation, prolonged parenteral nutrition without potassium, or excessive losses of potassium, due to vomiting, diarrhea, excessive drainage of gastrointestinal fluids, dialysis, renal diseases, diabetic ketoacidosis, hyperadrenalism, use of diuretics, corticosteroids and amphotericin B (antifungal medication).

Hyperactivity of the adrenal cortex, known as Cushing syndrome, is another major cause of hypokalemia.

Metabolic alkalosis can also cause hypokalemia by shifting potassium from the extracellular to the intracellular compartment.

Other recommended indications for potassium salt administration include:

  • Hypertension: Adequate intake of potassium is a recommendation to prevent the development of hypertension. Prescribers also give potassium supplements to improve blood pressure control in patients with already known hypertension [1].
  • Arrhythmia: Potassium levels should be restored when cardiac glycoside toxicity occurs as a result of a loss of potassium, or in certain tachyarrhythmias following cardiac surgery.  
  • Thallium toxicity: Used intravenously in a limited fashion [1415].
  • Hyperthyroidism: Potassium iodide is prescribed as an oral adjunctive medication in the immediate pre-operative period for patients with hyperthyroidism undergoing thyroidectomy [16]. It is also useful as an adjunct treatment of patients critically ill with thyrotoxicosis crisis.
  • Radiation protection: Oral potassium iodide can help to protect the thyroid gland by blocking thyroidal uptake of radioactive iodine isotopes, either from environmental hazards, or during treatment with radiopharmaceuticals [17].
  • Sporotrichosis: Sporotrichosis is a type of skin fungal infection. Oral potassium iodide is considered the drug of choice for fixed cutaneous or lymphocutaneous sporotrichosis in resource-constrained countries, due to its low cost [18]. However, there has been no comparison of its efficacy to antifungals, such as itraconazole. Also, prolonged duration of therapy correlates with a high number of side effects.
  • Cough: Historically, clinicians have used potassium iodide to treat symptoms of chronic cough as an expectorant of tenacious mucus. However, its efficacy in this role is not well scientifically supported.
  • Alkalinization: Potassium citrate is useful to alkalinize urine in case of certain kinds of urinary tract calculi and management of conditions associated with chronic metabolic acidosis (chronic renal insufficiency and renal tubular acidosis). In these conditions, potassium citrate is used as an alternative to sodium citrate or sodium bicarbonate, when a high amount of sodium administration is undesirable.
  • Antibiotics: Potassium is also used as a vehicle or compounding chemical for some antibiotic preparations (e.g., potassium benzylpenicillin, potassium penicillin V and amoxicillin-clavulanate potassium).

Benefits

Hypertension

Hypertension is the leading cause of cardiovascular disease (CVD) and a major contributing risk factor for the development of stroke, coronary heart disease (CHD), myocardial infarction, heart failure, and end-stage renal disease, amounting to a US public health financial burden of $50.6 billion [19].

Nearly one in three American adults (~72 million) are estimated to have hypertension, while nearly 70 million are at risk for developing pre-hypertension (blood pressure between 120/80 mmHg and 140/90 mmHg).

Approximately 90% of US adults older than 50 are at risk for developing hypertension, with systolic rises being the most prevalent [20].

Hypertension is a leading cause of morbidity and mortality worldwide and second only to smoking as a preventable cause of death in the United States [21].

Potassium is known to decrease blood pressure.

The antihypertensive effect of increased potassium intake is related to numerous mechanisms.

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Acutely, increased plasma potassium is associated with endothelium-dependent vasodilation via stimulation of Na+/K+ ATPase pumps, as well as the opening of potassium channels in vascular smooth muscle cells and adrenergic nerve receptors [22].

Long-term potassium dosing induces increases in the number of Na+/K+ ATPase pumps in basolateral cell membranes and increases in the transepithelial voltage.

Increased pumping can result from either increased Na+/K+ ATPase turnover (acute K+ loading) or an increase in the number of pumps (long-term K+ loading), or both [22].

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In addition to enhanced vasodilation, other possible mechanisms in which potassium is proposed to lower BP and improve vascular outcomes include increases in sodium excretion, modulation of baroreceptor sensitivity, reduced sensitivity to catecholamine related vasoconstriction, improved insulin sensitivity, and decreases in oxidative stress and inflammation [23].

Insulin Sensitivity

Glucose intolerance can often be the result of severe hypokalemia, due to a deficit in potassium balance, which may occur in primary or secondary aldosteronism (hormonal disorder that leads to high blood pressure), or prolonged treatment with diuretics [24].

The use of thiazide diuretics is widely considered the preferred initial pharmacological treatment for hypertension [25].

The tendency of thiazide diuretics to negatively influence glucose tolerance and increase the incidence of new-onset diabetes has been known [26].

In a recent quantitative review, researchers analyzed 59 clinical trials in which the relationship between the use of thiazide diuretics, hypokalemia, and glucose intolerance was very strong [25].

Thiazide diuretics have a common side effect of lowering serum potassium and evidence shows that diuretic-induced hypokalemia may lead to impaired glucose tolerance via a reduction in insulin secretion in response to glucose loads [27].

In healthy individuals, there is also evidence to support the role of potassium in glucose control.

Studies involving potassium depletion (e.g., low potassium diets) and utilizing a hyperglycemic clamp technique show that low levels of potassium can lead to glucose intolerance via impaired insulin secretion [2829].

Potassium’s role in the control of blood glucose is grounded in its function at a cellular level, where potassium-induced cell depolarization results in insulin secretion from pancreatic β-cells [30].

In addition, when patients with thiazide-induced hypokalemia are given potassium supplements, the defects in insulin release in response to glucose loads are corrected, thus indicating that hypokalemia may be a significant contributing factor to glucose abnormalities [31].

The relationship between potassium and type 2 diabetes mellitus (T2DM) also extends to the kalemic effects of insulin, since insulin activates sodium-potassium ATPases on the cellular membrane, causing a flux of potassium into cells.

Higher plasma insulin levels are associated with increased potassium absorption into cells [32], and without a threshold, as seen in glycemic response, these kalemic effects continue to increase as insulin levels rise [77].

DeFronzo et al. [32] examined this relationship using the insulin clamp technique and graded doses of insulin.

Researchers found that insulin caused a dose-dependent decline in plasma potassium concentration, and that this relationship was independent of glucose uptake [32].

This effect is also seen through the use of intravenous (IV) insulin as a treatment for hyperkalemia, forcing potassium into cells, and thus reducing its concentration in the blood [33].

This effect is likely mediated by an increased sensitivity to intracellular sodium, activation of Na+/K+ ATPase pumps, and inhibition of potassium efflux [32].

Sources

Food 

Many of the foods people eat are naturally high in potassium.

Potassium is primarily a plant-based mineral.

The richest sources of potassium include fruits, vegetables, beans, and legumes, although some fish and dairy products are also excellent sources of the mineral.

Potassium in foods is never found alone, but present with phosphate, sulfate, citrate, and many other organic anions, including proteins.

Some healthy, potassium rich foods include: 

Fruits

  • Avocados (485 mg per 100 gr.)
  • Guavas (417 mg per 100 gr.)
  • Bananas (358 mg per 100 gr.)
  • Kiwis (312 mg per 100 gr.)
  • Persimmons (310 mg per 100 gr.)
  • Cantaloupe (267 mg per 100 gr.)
  • Apricots (259 mg per 100 gr.)
  • Pomegranate (236 mg per 100 gr.)
  • Figs (232 mg per 100 gr.)
  • Honeydew melon (228 mg per 100 gr.)
  • Cherries (222 mg per 100 gr.)
  • Tomatoes (218 mg per 100 gr.)
  • Nectarines (201 mg per 100 gr.)
  • Mulberries (194 mg per 100 gr.)
  • Papaya (182 mg per 100 gr.)
  • Oranges (181 mg per 100 gr.)
  • Mangos (168 mg per 100 gr.)
  • Tangerines (166 mg per 100 gr.)
  • Blackberries (162 mg per 100 gr.)
  • Plums (157 mg per 100 gr.)
  • Strawberries (153 mg per 100 gr.)
  • Cucumbers (147 mg per 100 gr.)
  • Grapefruit (135 mg per 100 gr.)
  • Watermelon (112 mg per 100 gr.)

Dried Fruit 

  • Dried Apricots (1162 mg per 100 gr.)
  • Raisins (749 mg per 100 gr.)
  • Prunes (732 mg per 100 gr.)
  • Dates (656 mg per 100 gr.) 
  • Dried figs (610 mg per 100 gr.)
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Vegetables

  • Beet Greens (raw 762 mg per 100 gr., cooked 909 mg per 100 gr.)
  • Spinach (raw 558 mg per 100 gr., cooked 466 mg per 100 gr.)
  • Fennel (raw 414 mg per 100 gr., cooked with oil or butter 570 mg per 100 gr.)
  • Kale (raw 491 per 100 gr., boiled 228 per 100 gr.)
  • Potatoes (raw 421 mg per 100 gr, boiled with skin 564 mg per 100 gr., boiled without skin 328 mg per 100 gr., baked with skin 535 mg per 100 gr.)
  • Sweet Potatoes (raw 337 mg per 100 gr., boiled 230 mg per 100 gr., baked 475 mg per 100 gr., mashed 210 mg per 100 gr.)
  • Swiss Chard (raw 379 mg per 100 gr., cooked 549 mg per 100 gr.)
  • Brussels Sprouts (raw 389 mg per 100 gr., cooked/boiled 317 mg per 100 gr.)
  • Broccoli (raw 316 mg per 100 gr., cooked/boiled 293 mg per 100 gr.)
  • Artichokes (raw 370 mg per 100 gr., cooked 264 mg per 100 gr.)
  • Acorn Squash (raw 347 mg per 100 gr., boiled 263 mg per 100 gr., baked 437 mg per 100 gr.)
  • Summer Squash (raw 262 per 100 gr., cooked/boiled 192 mg per 100 gr.)
  • Pumpkin (raw 340 mg per 100 gr., boiled 230 mg per 100 gr.)
  • White Button Mushrooms (raw 318 mg per 100 gr., cooked 356 mg per 100 gr.)
  • Rutabagas (raw 305 mg per 100 gr., cooked 216 mg per 100 gr.)
  • Zucchini (raw 261 mg per 100 gr., cooked/boiled 264 mg per 100 gr.)
  • Bok Choy (raw 252 mg per 100 gr., cooked 371 mg per 100 gr.)
  • Peas (raw 244 mg per 100 gr., cooked/boiled 271 mg per 100 gr.) 
  • Asparagus (cooked 224 mg per 100 gr.)
  • Sweet Corn (raw 270 mg per 100 gr., boiled 218 mg per 100 gr.)
  • Collard Greens (raw 213 mg per 100 gr., boiled 117 per 100 gr.)

Fruit and Vegetable Juices

  • Carrot juice (292 mg per 100 gr.)
  • Prune juice (276 mg per 100 gr.)
  • Tomato juice (229 mg per 100 gr.)
  • Pomegranate juice (214 mg per 100 gr.)
  • Orange juice (200 mg per 100 gr.)
  • Tangerine juice (178 mg per 100 gr.)
  • Grapefruit juice (162 mg per 100 gr.)
  • Cucumber juice (147 mg per 100 gr.)
  • Pineapple juice (124 mg per 100 gr.)
  • Apricot juice/nectar (114 mg per 100 gr.)
  • Watermelon juice (112 mg per 100 gr.)
  • Grape Juice (104 mg. per 100 gr)
  • Lemon juice (103 mg per 100 gr.)
  • Apple juice (101 mg per 100 gr.)
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Dairy

  • Milk (150 mg per 100 gr.)
  • Greek Yogurt (full-fat 137 mg per 100 gr., non-fat 141 mg per 100 gr.)
  • Ricotta Cheese (from whole milk 105 mg per 100 gr., from part-skim milk 125 mg per 100 gr.)

Vitamins & Supplements

Fish

  • Wild Atlantic Salmon (raw 490 mg per 100 gr., cooked 628 mg per 100 gr.)
  • Halibut (raw 435 mg per 100 gr., cooked 528 mg per 100 gr.)
  • Rockfish (raw 386 mg per 100 gr., cooked 467 mg per 100 gr.)
  • Trout (raw 377 mg per 100 gr., cooked 448 mg per 100 gr.)
  • Sockeye Salmon (raw 360 mg per 100 gr., cooked 436 mg per 100 gr.)
  • Cod (Atlantic Cod cooked 244 mg per 100 gr., Pacific Cod cooked 372 mg per 100 gr.)
  • White Tuna canned (water-packed 237 mg per 100 gr., oil-packed 333 mg per 100 gr.)

Beans and Legumes

  • Lima Beans (cooked 570 mg per 100 gr.)
  • Large White Beans (cooked 561 mg per 100 gr.)
  • Green Soybeans (cooked 539 mg per 100 gr.) 
  • Edamame (cooked 436 mg per 100 gr.)
  • Pinto Beans (cooked 436 mg per 100 gr.)
  • Kidney Beans (boiled 405 mg per 100 gr.,) 
  • Lentils (sprouted, raw 322 mg per 100 mg, cooked 369 mg per 100 gr.) 

Supplements

Most people who eat a balanced diet should get enough potassium naturally through food.

Low potassium is linked with a higher risk of high blood pressure, heart disease, stroke, arthritis, osteoporosis, kidney disease, cancer, digestive disorders, and infertility [36].

For people with inadequate potassium intake, doctors sometimes recommend adding potassium rich-foods into the diet, or potassium supplements, to prevent or treat some of these conditions.

Potassium deficiencies are most common in individuals who:

  • Use certain medications, such as diuretics, albuterol, pseudoephedrine
  • Have physically demanding jobs
  • Athletes exercising in hot climates and sweating excessively
  • Have health conditions that affect their nutrient absorption ability, such as Celiac disease or Crohn’s disease
  • Have primary aldosteronism
  • Abuse laxatives and enemas
  • Have an eating disorder
  • Smoke
  • Abuse alcohol or drugs

Since potassium is an essential electrolyte usually sourced through our diet, any condition in which a patient is unable to maintain their dietary intake is an indication for exogenous potassium supplementation.

Potassium supplements should be taken with food or just after a meal to reduce the risk of stomach irritation or diarrhea.

They are usually taken in 1 to 4 doses daily.

For patients who cannot tolerate or are non-compliant with multiple daily doses, extended-release potassium chloride supplementation can be useful.

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Despite potassium being considered safe even at high dosages, a person should not take potassium supplements, without first talking to his/her doctor.

Potassium overdose symptoms include feelings of burning or tingling, generalized weakness, paralysis, mental confusion, low blood pressure, irregular heart rhythm (arrhythmias), and in very rare cases death.

Multiple salts of potassium exist and can be useful as a medication for a wide range of indications.

The most commonly used forms include potassium citrate, potassium chloride, potassium gluconate, potassium aspartate, and potassium iodide.

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How Much Potassium Should you Consume?

Recommended adequate intakes for potassium were set by the Food and Nutrition Board of the Institute of Medicine at 4700 mg/day [4].

This was largely based on meta-analyses of randomized, controlled trials investigating the effect of potassium supplementation on reducing blood pressure.

However, actual potassium requirements would vary depending on an individual’s genetics, blood pressure (BP) status, kidney function, and sodium intake.

Blood pressure is currently the primary criterion for determining potassium requirements.

Blacks are more vulnerable to hypertension and more responsive to potassium supplementation than whites, hypertensive individuals are more responsive to increasing potassium intakes than normotensive individuals, and potassium exerts greater health benefit in those consuming a high salt diet [2].

Individual potassium needs also change when someone has kidney disease.

People with kidney disease should often get less potassium than the 4,700 mg guideline.

If the kidneys don’t work well, too much potassium could stay in the body, which can lead to nerve and muscle problems.

Medical doctors should clarify to their kidney disease patients what their potassium limit should be.

Aside from each person’s individual characteristics, recommended potassium intakes also depend on the bioavailability of potassium from foods.

Generally, requirements for any nutrient are based on replacing losses from the body, adding in any demand for growth, and adjusting for absorption from the diet.

However, the official recommendations for potassium intake are based on the absorption from supplements, not from food.

The first study on the potassium bioavailability of foods, in this case, the potato, was only recently completed [34].

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Toxicity

Hyperkalemia is the most common and life-threatening adverse effect of potassium administration, and it can develop rapidly [35].

This condition can manifest as potentially fatal bradycardia (abnormally slow heart rate), asystole (total cessation of the heart’s electrical activity), and ventricular fibrillation (rapid erratic heart rhythm).

Gastrointestinal side effects commonly occur with enteral feeding in hospitals or supplement abuse and include nausea, vomiting, diarrhea, and abdominal pain.

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Hypersensitivity reactions can occur from the use of potassium iodide, as well as chronic iodine poisoning (iodism).

For that reason, potassium iodide is not for use in patients with known sensitivity to iodides.

Conclusion

Potassium is an essential mineral constituent of the human body and is the chief cation found within the intracellular fluid of all cells.

It plays a critical role in cellular metabolism and normal neuromuscular function.

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Tightly regulated homeostatic mechanisms have developed in the process of evolution to provide primary defense against the threats of hyper- and hypokalemia.

The kidney plays a primary role in potassium balance, by increasing or decreasing the rate of potassium excretion.

The distribution of potassium between the intracellular and extracellular fluid compartments is regulated by physiologic factors, such as the hormones insulin and catecholamines (dopamine, epinephrine, and norepinephrine), which stimulate the activity of Na+/K+ ATPase pumps located in the plasma membrane of all cells.

The recommended adequate intake for potassium is set at 4700 mg/day [3], with most of the worldwide population not hitting that target.

Increasing dietary potassium is beneficial for lowering the risk of hypertension, the major risk factor for the development of stroke, coronary heart disease, heart failure, and end-stage renal disease.

Additionally, adequate potassium intake may be extremely influential in glucose control and limiting the risk of diabetes, especially in those on thiazide diuretic treatment, and those already at high risk due to the presence of co-morbidities.

Growing evidence also suggests that increased dietary potassium can have potential health benefits for the skeleton and kidneys.

However, more needs to be understood about the bioavailability of potassium from foods, since only the potato has been studied for its potassium bioavailability, and this food is constituted mostly of easily digested starch.

Potassium is likely a nutrient with forthcoming research, because it is an identified “shortfall nutrient” along with fiber, iron, calcium, and vitamin D, meaning nutrients whose underconsumption has been linked to adverse health outcomes.

Potassium is a well-established modifiable factor for hypertension, the largest risk of some of our most common chronic diseases, and a better understanding of its bioavailability in the diet will help determine how it can be used further to improve overall human health.

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About George Kelly

George Kelly M.Sc is a Sports Nutritionist, Functional Nutritional Therapy Practitioner (FNTP), and Metabolic Type expert. He is the CEO and lead author of Metabolic Body.


References

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