Dr. Torben Jorgensen
Effect of longer term modest salt reduction on blood pressure: Cochrane systematic review and meta-analysis of randomised trialsF. He et al.BMJ 2013;346:f1325
Salt intake has become an emerging public health problem and by some authors claimed to be next in line after tobacco smoking in prevention of cardiovascular diseases. As most of our salt intake comes from industrial processed food (80-85 % of our salt intake) this area is of great interest not only for public health researchers and health authorities, but also for the food giants producing and selling preserved food. For the food industry a reduction in salt means changes in production procedures, which costs money. Is this why we are confronted with somewhat different conclusions from reviews on the effect of salt reduction in the population? Recently the US Institute of Medicine (IOM) published a report speculating whether the evidence for lowering the daily salt intake below 5.75 gram would be beneficial. Other reviews have claimed that lowering of salt intake increases cholesterol and plasma renin activity, which could counteract the beneficial effect of the well documented lowering of blood pressure, and even question whether we should reduce the present intake of salt on 8-12 gram per day at all.In a recent article in BMJ, He and collaborators perform a very comprehensive systematic review of 34 randomized trials (N=3230) aiming at reducing salt intake over more than 4 weeks. The changes in salt intake was of such a magnitude that it was realistic for a free living population (mean change 4.4 g/day) and they omitted short term studies with huge (and from a public health view), unrealistic reductions in salt intake. They analysed the salt reduction in relation to changes in blood pressure, lipids (total cholesterol, HDL- and LDL cholesterol, triglycerides), and hormones (renin, aldosterone, noradrenaline and adrenaline).The authors concluded that a modest reduction of salt intake for four or more weeks had a significant effect on lowering both systolic and diastolic blood pressure in both hypertensive and normotensive individuals, and they confirmed the “rule of thumb” that lowering daily salt intake with one gram reduces the systolic blood pressure with 1 mmHg. The findings were irrespective of sex and ethnic group. They also found a small physiological increase in plasma renin activity, aldosterone, and noradrenaline, but no significant effect in lipid concentrations.This thorough analysis confirm that lowering the population salt intake to the recommended 5-6 gram per day will have beneficial effect on blood pressure and thereby on the incidence of cardiovascular disease.In view of the above mentioned possible conflicts of interest, it is of great importance that the authors declare that they received no specific funds for this work from neither public, commercial, or not-for-profit sectors.
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