Potassium

What does potassium do?

The NIH defines potassium as the most abundant cation inside cells. It plays a role in maintaining intracellular fluid volume and the electrochemical gradient across the cell membrane; the concentration inside the cell is about 30 times higher than outside, and this difference is maintained by the sodium-potassium ATPase pump. This gradient is required for nerve conduction, muscle contraction and kidney function. An adult body contains about 45 mmol/kg of potassium, most of it inside cells. ^[1]

About 90% of ingested potassium is absorbed mainly in the small intestine; the excess is excreted mainly in urine. The kidneys adjust potassium excretion to intake, but at least about 5 mmol (195 mg) of potassium is excreted in urine per day; because of this and other obligatory losses, balance cannot be achieved with intakes below about 400–800 mg/day. ^[1] EFSA also states that blood potassium and body potassium content are affected very little by changes in intake because of tight homeostatic mechanisms, so there is no status biomarker suitable for deriving a reference value for the general population. ^[2]

The practical consequence: potassium status is not routinely measured and is difficult to measure; the NIH says that because most body potassium is inside cells, blood level may be weakly related to tissue stores. The normal serum range is about 3.6–5.0 mmol/L. ^[1]

How much potassium is needed per day?

Values are given as “adequate intake” (AI) for potassium from food; that is, the amount considered adequate when the evidence is not sufficient to derive an average requirement and RDA.

In 2019 the NASEM committee reported that the data were not sufficient to set an average requirement (EAR) and based the AI values on the highest median intakes in healthy people. The committee also found the evidence insufficient to derive a chronic disease risk reduction intake level (CDRR). The NIH explicitly states that these values do not apply to people whose excretion is impaired by medical conditions such as kidney disease or medicines that impair potassium excretion. ^[1]

EFSA, on the other hand, derived the AI from the relationship with blood pressure and stroke: randomized trials and a cohort conducted in Europe show a beneficial effect on blood pressure in adults from a potassium intake of 3,500 mg (90 mmol) per day, while there is consistent observational evidence that intakes below 3,500 mg are associated with higher stroke risk; the relationship with coronary heart disease is uncertain and inconsistent. Data on diabetes, kidney stones and bone health could not be used to derive a reference value. EFSA also sees no need to increase intake in pregnancy (3,500 mg) and recommends 4,000 mg in lactation. ^[2]

WHO’s 2012 potassium guideline strongly recommends increasing potassium intake from food in adults to reduce blood pressure and the risk of cardiovascular disease, stroke and coronary heart disease; an intake level of at least 90 mmol/day (3,510 mg/day) for adults is a conditional recommendation, because evidence on the exact level providing the highest benefit is limited. The guideline does not apply to people with impaired urinary potassium excretion. ^[3]

Detailed guideWhich foods contain potassium? Serving table and the DASH pattern→

Which foods does potassium come from?

According to the NIH, potassium is found in many plant and animal foods: many fruits and vegetables, legumes (for example soy), potatoes, and also meat, chicken, fish, milk, yogurt and nuts. Whole wheat flour and brown rice contain much more potassium than their refined counterparts (white flour and white rice). About 85–90% of the potassium in food is absorbed. The potassium salts in fruits and vegetables (such as phosphate, sulfate, citrate) are different from the potassium chloride used in salt substitutes and some supplements. ^[1]

In the US, the main sources of potassium in adults were milk, coffee, tea, other non-alcoholic drinks and potatoes; according to the data, potassium intake was below the recommended level in most people, and for this reason the US Dietary Guidelines have identified potassium as a nutrient of public health concern. ^[1] Verified population-level potassium intake data for Türkiye were not used in this guide.

Does potassium lower blood pressure?

The evidence varies by the source and dose of potassium and the group studied.

In the meta-analysis by Aburto and colleagues prepared for WHO, 22 randomized trials (1,606 participants) were pooled: increased potassium intake lowered systolic pressure by a mean of 3.49 mmHg (95% CI 1.82–5.15) and diastolic pressure by 1.96 mmHg (0.86–3.06) in adults; the effect was seen in people with hypertension and not in those without. No significant adverse effect was found on kidney function, blood lipids and catecholamines. ^[4]

The NIH reports that other analyses gave similar results, but that a Cochrane review evaluating the six highest-quality trials found a non-significant reduction in systolic and diastolic pressure. In a NASEM analysis (16 trials), potassium supplements lowered systolic pressure by a mean of 6.87 and diastolic pressure by 3.57 mmHg; the effect was marked in people with hypertension and not significant in those without. The DASH dietary pattern (rich in fruit, vegetables and low-fat dairy products) lowers systolic pressure by a mean of 5.5 and diastolic pressure by 3.0 mmHg; but because this pattern also increases other nutrients related to blood pressure such as magnesium and calcium in addition to potassium, the independent contribution of potassium cannot be determined. ^[1]

For this reason, the sentence “potassium lowers blood pressure” is true for a small effect in people with high blood pressure; it has not been shown in people with normal blood pressure and does not require use of a supplement. The NIH reports that potassium has a strong relationship with sodium and that low potassium intake, particularly combined with high sodium intake, increases the risk of hypertension; for this reason the two are assessed together for blood pressure. ^[1]

What can be said about potassium for stroke and other health outcomes?

In the analysis by Aburto and colleagues, 11 cohort studies (127,038 participants) were pooled: higher potassium intake was associated with lower stroke risk (RR 0.76; 95% CI 0.66–0.89). For total cardiovascular disease (RR 0.88; 0.70–1.11) and coronary heart disease (RR 0.96; 0.78–1.19), the association was not statistically significant. ^[4] This is an observational association; people with higher potassium intake may also differ in other habits.

Other associations cited by the NIH rest on more limited evidence. In observational studies, high dietary potassium was associated with lower kidney stone risk; however, the effect of potassium citrate salts used to prevent stones (2015 Cochrane review: seven trials, 477 participants) is attributed more to citrate than to potassium, and the NIH finds the evidence insufficient to determine the efficacy of potassium supplements. For bone health, while observational studies and some small trials suggest benefit, in a 2-year trial in 276 postmenopausal women bone resorption and bone density did not change. ^[1]

Are potassium salt substitutes safe?

Many salt substitutes contain potassium chloride in place of some or all of the sodium chloride. The NIH reports that potassium in these products varies between about 440–2,800 mg per teaspoon and that people with kidney disease or those using some medicines should consult a physician before use because of the risk of hyperkalemia. ^[1] The T.C. Ministry of Health publication “Salt Consumption and Health” also states that most substances that replace salt contain potassium in place of sodium, that excess potassium consumption can be harmful for some individuals, and that people with kidney disorders in particular should consult a doctor before using these products. ^[8]

A large randomized trial supports the results but conditionally. In SSaSS, 20,995 people (mean age 65.4) in 600 rural villages in China, with a history of stroke or over age 60 with high blood pressure, were assigned in an open-label, cluster-randomized design to a substitute containing 75% sodium chloride + 25% potassium chloride or to regular salt. In a mean of 4.74 years of follow-up, the stroke rate was lower with the substitute (29.14 versus 33.65 per 1,000 person-years; RR 0.86; 95% CI 0.77–0.96); major cardiovascular events (RR 0.87) and death from any cause (RR 0.88) were also fewer. Serious adverse events caused by hyperkalemia did not increase significantly (RR 1.04; 0.80–1.37). ^[5]

The findings of this trial cannot automatically be generalized from the group studied (people with a history of stroke or older hypertensive people, rural China) to other groups, particularly to people with kidney disease or using medicines that reduce potassium excretion. The NIH, based on the 2018 AHRQ review, reports that at least part of the blood-pressure-lowering effect of potassium salt substitutes may stem from the reduction in sodium rather than the increase in potassium. ^[1]

Why is potassium supplementation handled carefully?

Multi-ingredient vitamin-mineral products containing potassium generally provide about 80 mg, and most supplements containing only potassium provide at most 99 mg of potassium; this is about 2% of the US Daily Value (4,700 mg). According to the NIH, many manufacturers limit the amount to 99 mg; the reason is that the FDA has not found some oral drug products containing potassium chloride above 99 mg safe because they are associated with small intestine injuries, and has required a warning label for some potassium salts above 99 mg per tablet. The FDA can limit the amount of a nutrient in dietary supplements only for safety reasons and has not made a decision on whether supplements containing potassium above 99 mg would carry a warning label. This information consists of US regulations. ^[1]

A very high amount of potassium supplement or potassium salt substitute can exceed the amount the kidney can excrete and cause acute hyperkalemia even in a healthy person. The NIH also reports that case reports stating that very high supplement doses caused cardiac abnormalities and death were found insufficient for setting a UL. In healthy people (up to 15,600 mg per day, for 5 days), chronic intake raised plasma level but did not take it outside the normal range. ^[1]

For this reason, choosing a potassium supplement on one’s own is not reliable without knowing blood level, kidney function and the medicines used. When low blood potassium is detected, treatment is a physician’s decision.

How do kidney disease and medicines affect potassium?

In chronic kidney disease or in people using some medicines, urinary potassium excretion decreases and, according to the NIH, hyperkalemia can develop even with food intakes below the AI. ACE inhibitors (such as benazepril) and angiotensin receptor blockers (such as losartan) reduce urinary potassium excretion; potassium-sparing diuretics such as amiloride and spironolactone can also cause hyperkalemia. The NIH recommends monitoring potassium status in people using these medicines, particularly if kidney function is impaired. Conversely, loop diuretics such as furosemide and thiazide-group diuretics increase urinary potassium loss and can cause hypokalemia. ^[1]

According to the KDIGO conference summary by Lindner and colleagues, renin-angiotensin-aldosterone system inhibitors, potassium-sparing diuretics, nonsteroidal anti-inflammatory drugs (NSAIDs), succinylcholine and digitalis (digoxin) are associated with hyperkalemia; moderate or severe kidney disease, heart failure, diabetes and marked tissue damage are also predisposing conditions. ^[7] The NIH also lists type 1 diabetes, adrenal insufficiency and liver disease as risk groups. ^[1]

The KDIGO Controversies Conference results also point to a change in understanding about restricting potassium in kidney disease: as evidence showing the relationship between plant-based diets and better outcomes grows, a shift is proposed from dietary restriction toward supporting dietary patterns associated with better outcomes; however, there are few data on the effect of dietary change in normalizing abnormal serum potassium. Which person will restrict how much is therefore an individual decision. ^[6]

What do low and high potassium mean?

Hypokalemia and hyperkalemia usually arise not from inadequate or excess intake but from losses, excretion disorders, shifts between inside and outside the cell, and medicines. The NIH calls serum potassium below 3.6 mmol/L hypokalemia and above 5.0 mmol/L hyperkalemia; in healthy people with normal kidney function both are uncommon. ^[1] Thresholds vary by source; details are on the relevant pages.

Detailed guideHigh potassium (hyperkalemia): causes, ECG risk and emergency signs→ Detailed guidePotassium deficiency (hypokalemia) symptoms and the magnesium connection→

Evidence table: claim, population and limits

This guide does not recommend personal doses. Before using a potassium supplement, a potassium salt substitute or a medicine containing potassium, blood potassium, kidney function and the medicines used need to be assessed together with a physician.