Salt and blood pressure: what really counts?

This is general information, not medical advice. Always discuss your blood values with your doctor.

1. 1

   Blood pressure: less salt lowers it, especially if it is already high

   A dose-response meta-analysis of experimental studies (Filippini et al., Circulation 2021) found a nearly linear relationship between sodium intake and systolic and diastolic blood pressure across the whole range, including in people without high blood pressure. The effect was larger in those who already had higher blood pressure. In the CARDIA-SSBP crossover trial (Gupta et al., JAMA 2023, 213 adults aged 50 to 75), systolic blood pressure after a week on a low-sodium diet was on average 8 mmHg lower than after a week on a high-sodium diet, in about 75% of participants, including those taking blood pressure medication. Each diet lasted only a week, so the study says nothing about the long term.

2. 2

   Heart and vessels: a clear link, but hard trials are missing

   In a pooled analysis of 6 cohorts with 10,709 adults and repeated 24-hour urine collections (Ma et al., NEJM 2022), 1,000 mg more sodium a day went with 18% more cardiovascular risk, and 1,000 mg more potassium with 18% less. The quarter with the highest sodium excretion had 60% more risk than the quarter with the lowest. The authors attribute the J-shaped relationship seen in older studies, where very low sodium also went with more risk, to how sodium was estimated there. A Cochrane review (Adler et al., 2014) concluded that the trials lacked the power to confirm a clinically important effect on mortality and cardiovascular disease. Advice to cut salt lowered systolic blood pressure by 1.2 mmHg on average in people with normal blood pressure and by 4.1 mmHg in people with high blood pressure.

3. 3

   Potassium salt substitute: the strongest trial

   The SSaSS trial (Neal et al., NEJM 2021) assigned, by village, 20,995 adults with a previous stroke or poorly controlled high blood pressure (aged 60 or older) to a salt substitute with less sodium and extra potassium or to regular salt. After 4.7 years on average, there was 14% less stroke (RR 0.86), 13% fewer major cardiovascular events (RR 0.87) and 12% fewer deaths (RR 0.88). It was an open-label trial in rural China. The main safety outcome was hyperkalaemia, too much potassium in the blood. If you have kidney disease or take certain medication, discuss such a substitute with your doctor first.

4. 4

   Athletes: sweating costs sodium, but extra salt is rarely needed

   A 2018 systematic review found minimal evidence that taking sodium during exercise improves endurance performance: only 1 of 5 studies saw a benefit. A 2022 review says replacing sodium is advisable for exercise lasting more than 2 hours, in the heat or with very high sodium losses in sweat (more than 3 to 4 g). The link between sodium and muscle cramps remains uncertain. Outside those cases, the reviews give no reason to take extra sodium.

5. 5

   How much, and where does it come from?

   The WHO guideline is less than 2,000 mg of sodium a day, about 5 g of salt. In the cohorts of the NEJM analysis, median intake was 3,270 mg of sodium, about 8 g of salt. The Harvard researchers name adding less salt, fewer store-bought processed products and eating out less as ways to cut sodium, and fruit, leafy greens, potatoes, beans, dairy and fish to raise potassium.

Updated in October 2026