Wolfson Institute of Preventive Medicine, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London EC1M 6BQ, UK.
BMJ. 2013 Apr 3;346:f1325. doi: 10.1136/bmj.f1325.
To determine the effects of longer term modest salt reduction on blood pressure, hormones, and lipids.
Systematic review and meta-analysis.
Medline, Embase, Cochrane Hypertension Group Specialised Register, Cochrane Central Register of Controlled Trials, and reference list of relevant articles.
Randomised trials with a modest reduction in salt intake and duration of at least four weeks.
Data were extracted independently by two reviewers. Random effects meta-analyses, subgroup analyses, and meta-regression were performed.
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 (-6.62 to -4.15, I(2)=61%) for systolic blood pressure and -2.82 mm Hg (-3.54 to -2.11, I(2)=52%) for diastolic blood pressure. In normotensive people, the figures were -2.42 mm Hg (-3.56 to -1.29, I(2)=66%) and -1.00 mm Hg (-1.85 to -0.15, I(2)=66%), respectively. Further subgroup analysis showed that the decrease in systolic blood pressure was significant in both white and black people and in men and women. Meta-analysis of data on hormones and lipids showed that the mean change was 0.26 ng/mL/h (0.17 to 0.36, I(2)=70%) for plasma renin activity, 73.20 pmol/L (44.92 to 101.48, I(2)=62%) for aldosterone, 187 pmol/L (39 to 336, I(2)=5%) for noradrenaline (norepinephrine), 37 pmol/L (-1 to 74, I(2)=12%) for adrenaline (epinephrine), 0.05 mmol/L (-0.02 to 0.11, I(2)=0%) for total cholesterol, 0.05 mmol/L (-0.01 to 0.12, I(2)=0%) for low density lipoprotein cholesterol, -0.02 mmol/L (-0.06 to 0.01, I(2)=16%) for high density lipoprotein cholesterol, and 0.04 mmol/L (-0.02 to 0.09, I(2)=0%) for triglycerides.
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.
确定长期适度减少盐摄入量对血压、激素和血脂的影响。
系统评价和荟萃分析。
Medline、Embase、Cochrane 高血压组专业注册库、Cochrane 对照试验中心注册库和相关文章的参考文献列表。
盐摄入量适度减少且持续至少四周的随机试验。
两名评审员独立提取数据。进行了随机效应荟萃分析、亚组分析和荟萃回归分析。
共纳入 34 项试验（3230 名参与者）。荟萃分析显示，尿钠平均变化（减少盐摄入量与常规盐摄入量相比）为-75mmol/24h（相当于每天减少 4.4g 盐），随着盐摄入量的减少，收缩压平均变化为-4.18mmHg（95%置信区间-5.18 至-3.18，I²=75%），舒张压平均变化为-2.06mmHg（-2.67 至-1.45，I²=68%）。荟萃回归显示，年龄、种族、血压状况（高血压或正常血压）以及 24 小时尿钠变化均与收缩压下降显著相关，解释了研究间差异的 68%。24 小时尿钠减少 100mmol（每天减少 6g 盐）与收缩压下降 5.8mmHg（2.5 至 9.2，P=0.001）相关，调整年龄、种族和血压状况后。对于舒张压，年龄、种族、血压状况和 24 小时尿钠变化解释了研究间差异的 41%。亚组荟萃分析显示，高血压患者的平均效应为收缩压下降-5.39mmHg（-6.62 至-4.15，I²=61%），舒张压下降-2.82mmHg（-3.54 至-2.11，I²=52%）。在正常血压患者中，数值分别为-2.42mmHg（-3.56 至-1.29，I²=66%）和-1.00mmHg（-1.85 至-0.15，I²=66%）。进一步的亚组分析显示，白人和黑人以及男性和女性的收缩压下降均有统计学意义。对激素和血脂数据的荟萃分析显示，血浆肾素活性平均变化为 0.26ng/mL/h（0.17 至 0.36，I²=70%），醛固酮平均变化为 73.20pmol/L（44.92 至 101.48，I²=62%），去甲肾上腺素平均变化为 187pmol/L（39 至 336，I²=5%），肾上腺素（肾上腺素）平均变化为 37pmol/L（-1 至 74，I²=12%），总胆固醇平均变化为 0.05mmol/L（-0.02 至 0.11，I²=0%），低密度脂蛋白胆固醇平均变化为 0.05mmol/L（-0.01 至 0.12，I²=0%），高密度脂蛋白胆固醇平均变化为-0.02mmol/L（-0.06 至 0.01，I²=16%），甘油三酯平均变化为 0.04mmol/L（-0.02 至 0.09，I²=0%）。
持续四周或更长时间的盐摄入量适度减少会导致高血压和正常血压个体的血压显著下降，且从人群角度来看，这是非常重要的。盐的减少与血浆肾素活性、醛固酮和去甲肾上腺素的生理性轻度增加有关，而血脂浓度无明显变化。这些结果支持减少人群盐摄入量，从而降低人群血压，进而降低心血管疾病的风险。观察到的 24 小时尿钠减少与收缩压下降之间的显著关联表明，盐摄入量的更大减少将导致收缩压更大幅度的下降。目前将盐摄入量从 9-12 克/天减少到 5-6 克/天的建议将对血压产生重大影响，但进一步减少到 3 克/天将会产生更大的影响，并且应该成为人群盐摄入量的长期目标。
