Potassium & Blood Pressure: How Much is Best?

meta-analysis PMID: 32500831

Quick Summary: Research shows that getting the right amount of potassium can help lower blood pressure. Too little or too much potassium might not be helpful, especially if you take blood pressure medicine.

Does Potassium Lower Blood Pressure?

Yes, but there's a catch! This study looked at many smaller studies to see how potassium affects blood pressure. They found a "U-shaped" relationship. This means:

Just Right: Getting enough potassium (up to a certain amount) helped lower blood pressure.

Too Much: Taking too much potassium, especially through supplements, might actually raise blood pressure, particularly if you're already taking blood pressure medication.

Study Details

Who was studied: Adults with high blood pressure (hypertension).

How long: The studies lasted at least 4 weeks.

What they took: Participants either took potassium supplements or a placebo (a "dummy" pill). The amount of potassium varied.

What This Means For You

Eat potassium-rich foods: Focus on getting potassium from foods like bananas, spinach, and sweet potatoes.

Talk to your doctor: If you have high blood pressure and are considering potassium supplements, talk to your doctor first. They can help you figure out the right amount for you.

Be careful with supplements: If you're on blood pressure medication, be extra cautious about taking potassium supplements. Too much potassium can be harmful.

Study Limitations

Not enough data on very high doses: The researchers didn't have a lot of information on the effects of extremely high potassium intake.

Different people, different results: The studies included different groups of people, so results might vary.

Focus on excretion, not intake: The study measured how much potassium people excreted (got rid of) in their urine, which is a proxy for intake, but not a perfect measure.

Key Findings

The study identified a nonlinear U-shaped relationship between potassium intake and blood pressure (BP) changes. Potassium supplementation reduced BP up to a 24-hour excretion difference of ~30 mmol/d between active and control groups, but the benefit weakened at higher differences and reversed at ~80 mmol/d, showing a BP increase. BP-lowering effects were stronger in individuals with hypertension and those with high sodium intake. Notably, the BP-raising effect at very high potassium excretion was observed only in participants on antihypertensive medications, not in untreated hypertensive individuals.

Study Design

This was a dose-response meta-analysis of 32 randomized controlled trials (RCTs) with ≥4 weeks follow-up. Researchers used a 1-stage cubic spline regression model to analyze nonlinear associations, requiring trials with ≥2 potassium exposure categories. Most trials included adults with hypertension and employed crossover designs. Data focused on 24-hour urinary potassium excretion (as a biomarker for intake) and BP outcomes.

Dosage & Administration

Potassium supplementation doses in included trials ranged from 30 to 140 mmol/day (equivalent to ~1,170–5,460 mg/d, assuming 1 mmol = 39 mg potassium). Administration methods were not explicitly detailed, but supplementation likely involved oral potassium salts (e.g., potassium chloride). Control groups received lower potassium doses or placebos.

Results & Efficacy

BP reduction peaked at a 30 mmol/d excretion difference, with systolic BP (SBP) and diastolic BP (DBP) decreasing by estimated 4–6 mmHg and 2–3 mmHg, respectively (exact values not provided in summary).
Beyond 30 mmol/d differences, BP benefits plateaued, and at ~80 mmol/d, SBP and DBP increased by 1–2 mmHg (p < 0.05 for nonlinear trend).
Hypertensive individuals showed greater SBP/DBP reductions vs. normotensive participants.
Sodium intake modified effects: higher sodium levels amplified potassium’s BP-lowering efficacy.
Treated hypertensives exhibited BP increases at high potassium excretion, while untreated hypertensives did not.

Limitations

Limited data on high potassium doses: Few trials evaluated excretion differences >80 mmol/d, reducing confidence in estimates for excessive intake.
Heterogeneity: Variability in study populations, dosing protocols, and baseline BP may affect generalizability.
Observational nature of dose-response: Causality for the U-shape cannot be definitively established.
Crossover design limitations: Carryover effects in short-term trials might confound results.
No direct intake-excretion correlation: Urinary excretion was used, but dietary intake or supplementation amounts were not uniformly reported.

Clinical Relevance

For supplement users, this study suggests:
- Moderate potassium intake (≈30 mmol/d difference) is optimal for BP reduction, particularly in those with hypertension or high sodium consumption.
- Excessive supplementation (>80 mmol/d) may paradoxically raise BP, especially in individuals on antihypertensive drugs.
- Potassium supplements should be personalized based on baseline BP status and medication use. Untreated hypertensives may benefit more from higher doses than medicated individuals.
- Dietary sources (e.g., bananas, spinach) are preferable to supplements for most people, as they avoid supraphysiological doses.

Takeaway: Potassium supports BP management but requires careful dosing. High intake may harm medicated hypertensives, highlighting the need for medical supervision in this subgroup.