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Effects of Low-Sodium Diet vs. High-Sodium Diet on Blood Pressure, Renin, Aldosterone, Catecholamines, Cholesterol, and Triglyceride (Cochrane Review)
Study Questions:
Does low- versus high-sodium intake affect blood pressure (BP), renin, aldosterone, catecholamines, and lipids?
Methods:
Randomized controlled trials where identified, which randomized participants to either a low- or high-sodium diet, and sodium intake was estimated by the 24-hour urinary sodium excretion. An electronic literature search in PUBMED, EMBASE, and Cochrane Central (1950-through July 2011) was performed using the following combinations of search terms: salt or sodium, restriction or dietary, the outcome measures, and randomized or random. The reference lists of previous meta-analyses were also screened. Studies systematically investigating unhealthy patients with other diseases than elevated BP were excluded. Outcomes examined included systolic BP (SBP), diastolic BP (DBP), mean BP (MBP), renin, aldosterone, adrenaline, noradrenaline, triglyceride, cholesterol, low-density lipoprotein, and high-density lipoprotein. Participants were stratified according to race (Caucasians, Blacks, and Asians) and according to level of BP (hypertension or normotension).
Results:
A total of 167 studies were included. In the studies of participants with elevated BP, the median of the mean ages was 51 years (age range 23-73). The mean 24-hour sodium excretions in the high-salt intake groups was 196 mmol and in the low-salt intake groups was 71 mmol, corresponding to a mean sodium reduction of 125 mmol, and the median of mean sodium reductions was 94 mmol/24 hours. In the studies of persons with normal BP, the median of mean ages was 27 years. The mean 24-hour sodium excretions in the high-salt intake groups was 201 mmol and in the low-salt intake groups was 50 mmol, corresponding to a mean sodium reduction of 150 mmol, and the median of mean sodium reductions was 146 mmol/24 hours (10-90 percentiles: 56-246). The effect of sodium reduction in: normotensive Caucasians was −1.27 mm Hg (p = 0.0001) for SBP, and −0.05 mm Hg (p = 0.85) for DBP. In normotensive Blacks, the effect of sodium reduction was −4.02 mm Hg (p = 0.002) for SBP, and −2.01 mm Hg (p = 0.09) for DBP; and in normotensive Asians the effect was −1.27 mm Hg (p = 0.17) for SBP, and −1.68 mm Hg (p = 0.04) for DBP. Among hypertensive Caucasians, the effect of sodium reduction was −5.48 mm Hg (p < 0.00001) for SBP and −2.75 mm Hg (p < 0.00001) for DBP. Among hypertensive Blacks, the effect of sodium reduction was −6.44 mm Hg (p = 0.00001) for SBP and −2.40 mm Hg (p = 0.04) for DPB. Among hypertensive Asians, the effect of sodium reduction was −10.21 mm Hg (p = 0.003) for SBP, and −2.60 mm Hg (p = 0.0004) for DBP. Sodium reduction also resulted in significant increases in renin, aldosterone, noradrenaline, adrenaline, cholesterol, and triglycerides.
Conclusions:
The investigators concluded that sodium reduction resulted in a significant decrease in BP of 1% among normotensives, and 3.5% among hypertensives. A significant increase in plasma renin, plasma aldosterone, plasma adrenaline, and plasma noradrenaline; a 2.5% increase in cholesterol; and a 7% increase in triglyceride was also observed.
Perspective:
These data support the recommendations to reduce sodium intake, particularly among patients with elevated BP.
Keywords: Cholesterol, Sodium, Epinephrine, Renin, Norepinephrine, Blood Pressure, Triglycerides
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