Sodium, blood pressure, and cardiovascular disease

Persistent recommendations for universal restriction of dietary sodium intake are based on associations of sodium intake with blood pressure. No clinical trial data support an association of sodium intake with mortality and morbidity outcomes, however, while results of observational studies appear heterogeneous. Can these contradictory data be reconciled to inform health policy regarding sodium intake recommendations?

We reported (2006) a statistically significant (P = 0.03) association of sodium intake less than 2.3 g/day with increased cardiovascular disease mortality (hazard ratio 1.37) in a representative sample of the US adult population with an observed baseline mean sodium intake of 2.7 g/day. Others reported (2004) a significant (P < 0.01) higher stroke death among males and borderline significant (P = 0.07) for females, for highest compared with lowest sodium tertile in a community in Japan with mean intake of 5.4 g/day.

These results are consistent with earlier studies suggesting that the association of sodium with morbidity and mortality in industrial societies follows a 'J shape' with a direct association at high levels of average intake (over 4 g), an inverse association at lower levels (less than 2 g) and no measurable effect for the widely prevalent intakes in between.