Benefits
Blood pressure reduction
In the WHO-commissioned pooled analysis of randomized trials (BMJ 2013, PMID 23558164), increasing potassium intake lowered systolic blood pressure by about 3.5 mmHg and diastolic by about 2.0 mmHg compared with control. Reductions were larger in people who already had high blood pressure than in people with normal blood pressure, which is a finding from studies in patients rather than a promise for a healthy reader. The mechanism involves both renal sodium excretion (natriuresis) and direct vascular smooth muscle relaxation. Those pooled numbers come from trials that raised potassium by gram-level amounts, far above the 99 mg allowed in an over-the-counter supplement, so this is an argument for potassium-rich food rather than for a pill. High blood pressure is a diagnosed condition, and no one should change blood pressure medication based on potassium intake.
Salt substitutes and stroke risk in a high-risk trial
An open-label cluster-randomized trial in about 21,000 adults in rural China who were already at high risk (prior stroke, or age 60 and over with high blood pressure) replaced regular cooking salt with a substitute that was 25% potassium chloride. Villages using the substitute had 14% fewer strokes, 13% fewer major cardiovascular events and 12% fewer deaths from any cause. What was tested was a household salt swap in people with existing cardiovascular disease risk, not a potassium supplement in healthy adults. High blood potassium was not raised in that trial. Even so, this is an outcome study in people with existing cardiovascular risk, not evidence that a potassium supplement prevents stroke in a healthy person, and anyone with kidney disease or taking potassium-retaining medicines should not copy the approach without medical advice.
Potassium citrate and urine chemistry (a prescription use)
Prescription potassium citrate makes urine less acidic and lowers urinary calcium, which is why it is FDA-approved as a prescription drug (Urocit-K) for people who repeatedly form kidney stones. That is a prescription medicine given at gram-level doses with monitoring, not a dietary supplement, and none of the studies cited on this page examined kidney stones. Separately, people who eat more potassium-rich fruits and vegetables form fewer stones in observational studies, but an association like that cannot show potassium itself is the reason. Recurrent kidney stones are a medical condition to manage with a doctor.
Potassium and normal muscle function
Potassium is essential for muscle membrane repolarization after each contraction. Low blood potassium (hypokalemia) causes muscle weakness, cramps and fatigue, but it is usually driven by medications such as thiazide or loop diuretics, or by prolonged vomiting or diarrhea, rather than by ordinary eating, because healthy kidneys conserve potassium well. No study cited on this page tested potassium for exercise cramps, and cramping has many causes.
Fluid balance and electrolyte support
As the dominant intracellular cation, potassium pairs with extracellular sodium to maintain the osmotic gradient that regulates cell volume, nerve impulse transmission, and muscle function. Potassium is lost in sweat, though in far smaller amounts than sodium, and very low-carbohydrate diets can increase how much potassium the kidneys pass out in the early weeks. These are physiology points, not trial results: none of the studies cited on this page looked at hydration, exercise or ketogenic diets.
Most adults fall short of the recommended intake
US dietary surveys show most adults come in below the Adequate Intake, which is 2,600 mg a day for women and 3,400 mg for men. Typical intake is around 2,500 mg a day. The older 4,700 mg target was replaced in 2019, so figures based on it overstate the shortfall. Top USDA food sources per typical serving: white potatoes (~926 mg/medium), spinach (~840 mg/cup cooked), beans (~700 mg/cup), yogurt (~625 mg/cup), salmon (~534 mg/3 oz), avocados (~485 mg), bananas (~422 mg). This matters because the landmark DASH trials that produced the largest blood pressure drops tested whole eating patterns rich in fruit, vegetables and low-fat dairy, with less sodium. Those results belong to the diet and cannot be credited to a potassium tablet, especially one capped at 99 mg.
Mechanism of action
Sodium-potassium ATPase pump
Na+/K+-ATPase pumps maintain the steep potassium gradient across cell membranes, which is the foundation of the resting membrane potential in all excitable cells (neurons, cardiac, skeletal muscle). This single pump consumes approximately 20-30% of basal metabolic energy and is the biological basis for both neural transmission and muscle contraction.
Renal natriuresis
High potassium intake stimulates aldosterone-independent renal sodium excretion, directly lowering blood volume and blood pressure. This is the leading explanation for why higher potassium intake lowers blood pressure, and it works differently from cutting sodium. The DASH-Sodium trial (PMID 11136953) found the largest reductions when a potassium-rich eating pattern was combined with lower sodium, again as diets rather than pills.
Vascular smooth muscle relaxation
Potassium activates membrane hyperpolarization in vascular smooth muscle cells via K+ channel opening, causing vasodilation and reduced peripheral resistance. This is thought to work alongside the kidney effect. Laboratory work also points to an effect on nitric oxide release from the blood vessel lining, which has not been shown to matter for blood pressure in people.
Urinary alkalinization and calcium retention
Potassium citrate specifically raises urinary pH, reducing the acid load on bone (which would otherwise leach calcium for buffering) and reducing urinary calcium excretion. This is the rationale behind prescription potassium citrate for people who repeatedly form kidney stones, and behind the idea that fruit- and vegetable-rich diets may spare bone, which remains unproven and is not tested by any study cited here.
Clinical trials
Open-label cluster-randomized trial (whole villages, not individuals, were assigned, and everyone knew which salt they received) comparing a salt substitute that was 75% sodium chloride and 25% potassium chloride against regular salt. The intervention was a cooking-salt swap, not a potassium supplement, and no PubMed citation for this trial appears in this page's reference list. Conducted across 600 rural villages in China. Primary outcomes: stroke, major cardiovascular events, all-cause mortality. Published in NEJM 2021;385:1067-1077.
20,995 high-risk adults (prior stroke or ≥60 years with hypertension). 4.74-year median follow-up.
The potassium-enriched salt substitute reduced stroke by 14%, major cardiovascular events by 13%, and all-cause mortality by 12% vs regular salt. Hyperkalemia (high blood potassium) was not increased in this trial. These results describe what happened when household cooking salt was replaced in adults who already had high cardiovascular risk. They are not evidence that a 99 mg potassium supplement prevents stroke in a healthy person, and people with kidney disease or on potassium-retaining medicines should not copy the approach without medical supervision.
Evidence review and pooled analysis commissioned by the World Health Organization to inform global potassium intake guidelines. Pooled analysis of randomized controlled trials in which potassium intake was increased, with blood pressure as the outcome. Published in BMJ 2013 (Aburto and colleagues, PMID 23558164).
1,606 participants across 22 clinical trials. Various supplementation durations and potassium forms.
Increased potassium intake reduced systolic blood pressure by 3.49 mmHg (95% CI -5.16 to -1.82) and diastolic by 1.96 mmHg vs control. Effects were substantially larger in hypertensive adults compared to normotensives. This review underpins WHO guidance to get more potassium, primarily from food. The same review found no harm to kidney function or blood lipids. Note the gap between what was studied, gram-level intakes, and what a US supplement may legally contain, 99 mg per serving.
Meta-analysis of randomized controlled trials of oral potassium supplementation and blood pressure, published in JAMA 1997 (Whelton and colleagues, PMID 9168293). Of the pooled analyses cited on this page, this is the one that tested actual potassium supplements rather than dietary patterns.
33 randomized trials, 2,609 participants, including both people with normal blood pressure and people with high blood pressure.
Potassium supplementation lowered both systolic and diastolic blood pressure, with larger effects in people who already had high blood pressure and in those eating more sodium. The trial doses were in the gram range, well above the 99 mg cap on over-the-counter potassium supplements in the US.