Moderate Sodium plus High Potassium Yields Lowest Mortality

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The risks of cardiovascular events and mortality are lowest with the combination of moderate sodium intake and higher potassium intake, concludes an international prospective cohort study in the British Medical Journal.

The “Prospective Urban Rural Epidemiology” (PURE) study enrolled more than 103,000 adults, aged 35 to 70, from 628 urban and rural communities in low-, middle-, and high-income countries. Twenty-four-hour urinary sodium and potassium excretion were estimated (as surrogates for intake) from morning fasting urine samples.

During a median follow-up of 8 years, 6.1% of patients died or experienced a cardiovascular event. Risks of these outcomes were assessed for participants with low, moderate, and high sodium excretion (less than 3 mg/d, 3 to 5 mg/d, and over 5 mg/d, respectively) and those with high versus low potassium excretion (greater versus equal or less than the median of 2.1 g/d).

Very few individuals—0.002% of the study population—met the World Health Organization target of sodium excretion combined with potassium excretion greater than 3.5 g/d. Risk of the combined outcomes was lowest for individuals with moderate sodium excretion (3 to 5 g/d) plus higher potassium excretion, who comprised 21.9% of the study population. Compared to this group, hazard ratios were 1.23 for the combination of low sodium/low potassium excretion and 1.21 for high sodium and low potassium excretion. These groups accounted for 7.4% and 13.8% of the study cohort, respectively.

Among participants with higher potassium excretion, hazard ratios were 1.19 for those with low sodium excretion (3.3% of the cohort) and 1.18 for those with high sodium excretion (29.6% of the cohort). The increased cardiovascular risk associated with high sodium excretion was attenuated by potassium excretion above the median.

Current dietary recommendations for adults include a very low sodium intake and high potassium intake. Reported associations with mortality vary for sodium, while most studies report a linear reduction in mortality with higher potassium intake.

A very small percentage of the population meets current recommendations for low sodium intake and high potassium intake, this international study suggests. The risk of cardiovascular events and mortality appears lowest with a combination of moderate sodium intake and high potassium intake, found in about 22% of the PURE study cohort. The researchers conclude: “The J-shaped association of sodium intake with mortality and cardiovascular events does not lend support to the current WHO recommendation to consume low sodium diets (<2.0 g/day), and it also argues against use of the sodium:potassium ratio” [O’Donnell M, et al. Joint association of urinary sodium and potassium excretion with cardiovascular events and mortality: prospective cohort study. BMJ 2019; 364:1772].

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