Salt, blood pressure and cardiovascular diseases

The rise in average blood pressure with age seen in Western populations does not occur in isolated traditional nomadic communities. Several factors contribute to the higher blood pressure in the West. Salt is particularly important, however, because its effect on blood pressure is large, the dietary intake by Western populations is high and a large reduction in its intake is realistic. The size of the relationship between salt and blood pressure depends on age and, in trials, the duration of reduction of intake of salt. Results of many of the randomized trials have suggested that reduction of dietary salt exerts only a small effect on average blood pressure; this is because their subjects have been young (average age 26 years) and trials have been of short duration (average 2 weeks). Analysis of observational data concerning various communities indicated that a reduction in dietary intake of sodium of 100 mmol/24 h (3 g of salt, a realistic reduction) lowers systolic blood pressure in subjects aged 50-65 years by 10 mmHg on average. Much evidence corroborates this estimate, including data from the Intersalt study and a randomized controlled trial of reduction of intake of salt by older persons. This reduction in blood pressure would reduce age-specific stroke mortality by an estimated 22% and mortality from heart disease by 16%. Reducing the amount of salt added to manufactured foods is an important public-health target.