Adding salt to foods and hazard of premature mortality

The relationship between dietary salt intake and health remains a subject of longstanding debate. A recent ecological study has rekindled this controversy by reporting that sodium intake was inversely associated with the risk of all-cause mortality and positively associated with healthy life expectancy in 181 countries worldwide.¹ Notably, previous studies investigating the association between sodium intake and risk of mortality have produced conflicting results, showing positively linear,^2–4 J-shaped,^5,6 or inversely linear associations.

The low accuracy of sodium measurement is an important reason for the inconsistent results related to sodium intake and disease outcomes in previous studies.^10,11 Sodium intake varies widely from day to day. However, the majority of previous studies has largely relied on a single day’s urine collection or dietary survey for estimating the sodium intake, which is inadequate to assess an individual’s usual consumption levels.^10,12 Moreover, it is difficult to separate the contributions of intakes of sodium and potassium to health based on current methods for measuring dietary sodium and dietary potassium,^2,5,13,14 since both the dietary intake and metabolism of sodium in the kidneys are closely related to potassium.^15–17 Notably, such two essential cations have opposite biological effects on the human health,^17–20 thus their collinearity may confound the association between sodium intake and health outcomes.