Effect of longer term modest salt reduction on blood pressure: Cochrane systematic review and meta-analysis of randomised trials

Abstract

Objective To determine the effects of longer term modest salt reduction on blood pressure, hormones, and lipids.Design Systematic review and meta-analysis. Inclusion criteria Randomised trials with a modest reduction in salt intake and duration of at least four weeks. Data sourcesData extraction and analysis Data were extracted independently by two reviewers. Random effects meta-analyses, subgroup analyses, and meta-regression were performed.Results Thirty four trials (3230 participants) were included. Meta-analysis showed that the mean change in urinary sodium (reduced salt v usual salt) was −75 mmol/24 h (equivalent to a reduction of 4.4 g/day salt), and with this reduction in salt intake, the mean change in blood pressure was −4.18 mm Hg (95% confidence interval −5.18 to −3.18, I 2 =75%) for systolic blood pressure and −2.06 mm Hg (−2.67 to −1.45, I 2 =68%) for diastolic blood pressure. Meta-regression showed that age, ethnic group, blood pressure status (hypertensive or normotensive), and the change in 24 hour urinary sodium were all significantly associated with the fall in systolic blood pressure, explaining 68% of the variance between studies. A 100 mmol reduction in 24 hour urinary sodium (6 g/day salt) was associated with a fall in systolic blood pressure of 5.8 mm Hg (2.5 to 9.2, P=0.001) after adjustment for age, ethnic group, and blood pressure status. For diastolic blood pressure, age, ethnic group, blood pressure status, and the change in 24 hour urinary sodium explained 41% of the variance between studies. Meta-analysis by subgroup showed that in people with hypertension the mean effect was −5.39 mm Hg Conclusions A modest reduction in salt intake for four or more weeks causes significant and, from a population viewpoint, important falls in blood pressure in both hypertensive and normotensive individuals, irrespective of sex and ethnic group. Salt reduction is associated with a small physiological increase in plasma renin activity, aldosterone, and noradrenaline and no significant change in lipid concentrations. These results support a reduction in population salt intake, which will lower population blood pressure and thereby reduce cardiovascular disease. The observed significant association between the reduction in 24 hour urinary sodium and the fall in systolic blood pressure, indicates that larger reductions in salt intake will lead to larger falls in systolic blood pressure. The current recommendations to reduce salt intake from 9-12 to 5-6 g/day will have a major effect on blood pressure, but a further reduction to 3 g/day will have a greater effect and should become the long term target for population salt intake.

Highway proximity and black carbon from cookstoves as a risk factor for higher blood pressure in rural China

“…The effect of BC exposure on DBP was also noticeably larger among women living near the highway (2.6 mmHg; 95% CI, 1.0 to 4.2 vs. 0.3 mmHg; 95% CI, −1.3 to 2.0; interaction P = 0.02). The 3.6-mmHg larger effect of 1-ln(BC) on SBP among women near the highway is similar to the SBP impact of a modest reduction in sodium intake (−4.2 mmHg per 4.4-g daily reduction) (23) and within the range of an SBP decrease with use of antihypertensive medication (−2.5 to 12 mmHg) (24). Highway proximity was also a predictor of the effect of BC on blood pressure at the village level, with the effect strongest among women living in villages near the highway and absent among those living in the two villages farthest away from the highway (Fig.…”

Reducing the Blood Pressure–Related Burden of Cardiovascular Disease: Impact of Achievable Improvements in Blood Pressure Prevention and Control

“…Interventions targeted to populations with blood pressure above goal will therefore become less effective in lowering CVD incidence as blood pressure awareness, treatment, and control continue to improve, limiting the target population 40. Conversely, population‐wide lifestyle approaches to blood pressure reduction, as encouraged by the 2013 AHA/ACC Guideline on Lifestyle Management to Reduce Cardiovascular Risk, have been successful in reducing CVD across a wide range of blood pressures 15, 16, 44. For example, prior population‐wide intervention studies of salt reduction demonstrated decreases in morbidity, mortality, and healthcare costs with as little as 1 g less of salt per day (equivalent to 1/6 of a teaspoon)15 and are feasible, as evidenced by recent dietary salt reduction programs in the United Kingdom focused on manufactured food that decreased mean sodium content in the food supply by 7% 13.…”

Role of the Vascular Wall in Sodium Homeostasis and Salt Sensitivity

“…7 Generally, detrimental effects of excessive sodium intake have been linked to expansion of extracellular volume (ECV) and hypertension, which is evidenced by various observations that low sodium reduces BP in both normotensive individuals and individuals with hypertension. 4,8 The increase in BP after dietary sodium excess is highly variable, with some individuals showing a relatively small increase, whereas large BP increases can be observed in others. 9,10 It is likely that these individual variations in salt sensitivity differentially affect cardiovascular and renal risk and may also explain the inconsistent results from population studies investigating the relation between sodium intake and cardiovascular risk.…”