Researchers said the finding of a 'J-shaped' association with cardiovascular risk pointed to an urgent need to establish safe lower limits for sodium intake, as well as upper thresholds.
Dr Martin O'Donnell and colleagues from Hamilton General Hospital in Ontario examined observation data from two trials involving 28,880 patients.
Patients taking part in the research were followed for four and a half years and during the study period, 4,729 cardiovascular events occurred.
The researchers used urinary excretion measures as a surrogate to assess the link between sodium and potassium intake and cardiovascular events.
They compared patients with sodium excretion levels of 4-6g per day with others in the study. Those with low sodium excretion levels had a 19 per cent increased risk of dying as a result of a cardiovascular event.
Those with high sodium excretion levels also faced an increased risk, which was 53 per cent higher for those excreting 7-8g per day and 66 per cent higher for those excreting more than 8g per day.
Dr O'Donnell and colleagues commented: 'Compared with moderate sodium excretion, we found an association between high sodium excretion and CV events and low sodium excretion and CV death and hospitalisation for congestive heart failure, which emphasises the urgent need to establish a safe range for sodium intake in RCTs.'
A number of mechanisms could account for the increased cardiovascular risk associated with low sodium intake, they said. These include hypotension, a metabolic effect on lipoproteins and insulin activation of the renin-angiotensin and sympathetic nervous system.
The researchers also found higher potassium excretion was associated with lower stroke risk and said raising potassium intake 'merits further evaluation for stroke prevention'.
JAMA 2011; 306: 2229-38