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Effects of low sodium diet versus high sodium diet on blood pressure, renin, aldosterone, catecholamines, cholesterols, and triglyceride
Editorial Group: Cochrane Hypertension Group
Published Online: 20 NOV 2002
Copyright © 2003 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
How to Cite
Jürgens, G., Graudal, N. 2002. Effects of low sodium diet versus high sodium diet on blood pressure, renin, aldosterone, catecholamines, cholesterols, and triglyceride
- Published Online: 20 NOV 2002
This is not the most recent version of the article. View current version (09 NOV 2011)
One of the controversies in preventive medicine is, whether a general reduction in sodium intake can decrease the blood pressure of a population and thereby reduce cardiovascular mortality and morbidity. In recent years the debate has been extended by studies indicating that reducing sodium intake has effects on the hormone and lipid profile.
To estimate the effects of low sodium versus high sodium intake on systolic and diastolic blood pressure (SBP and DBP), plasma or serum levels of renin, aldosterone, catecholamines, cholesterol and triglycerides.
"MEDLINE" and reference lists of relevant articles were searched from 1966 through December 2001.
Studies randomising persons to low sodium and high sodium diets were included if they evaluated at least one of the above outcome parameters.
Data collection and analysis
Two authors independently extracted the data, which were analysed by means of Review Manager 4.1.
In 57 trials of mainly Caucasians with normal blood pressure, low sodium intake reduced SBP by -1.27 mm Hg (CI: -1.76; -0.77)(p<0.0001) and DBP by -0.54 mm Hg (CI: -0.94; -0.14) (p = 0.009) as compared to high sodium intake. In 58 trials of mainly Caucasians with elevated blood pressure, low sodium intake reduced SBP by -4.18 mm Hg (CI: -5.08; - 3.27) (p < 0.0001) and DBP by -1.98 mm Hg (CI: -2.46; -1.32) (p < 0.0001) as compared to high sodium intake. The median duration of the intervention was 8 days in the normal blood pressure trials (range 4-1100) and 28 days in the elevated blood pressure trials (range 4-365). Multiple regression analyses showed no independent effect of duration on the effect size. In 8 trials of blacks with normal or elevated blood pressure, low sodium intake reduced SBP by -6.44 mm Hg (CI: -9.13; -3.74) (p < 0.0001) and DBP by -1.98 mm Hg (CI: -4.75; 0.78) (p = 0.16) as compared to high sodium intake. The magnitude of blood pressure reduction was also greater in a single trial in Japanese patients. There was also a significant increase in plasma or serum renin, 304% (p < 0.0001), aldosterone, 322%, (p < 0.0001), noradrenaline, 30% (p < 0.0001), cholesterol, 5.4% (p < 0.0001) and LDL cholesterol, 4.6% (p < 0.004), and a borderline increase in adrenaline, 12% (p = 0.04) and triglyceride, 5.9% (p = 0.03) with low sodium intake as compared with high sodium intake.
The magnitude of the effect in Caucasians with normal blood pressure does not warrant a general recommendation to reduce sodium intake. Reduced sodium intake in Caucasians with elevated blood pressure has a useful effect to reduce blood pressure in the short-term. The results suggest that the effect of low versus high sodium intake on blood pressure was greater in Black and Asian patients than in Caucasians. However, the number of studies in black (8) and Asian patients (1) was insufficient for different recommendations. Additional long-term trials of the effect of reduced dietary sodium intake on blood pressure, metabolic variables, morbidity and mortality are required to establish whether this is a useful prophylactic or treatment strategy.
This review of short-term studies shows that in people with elevated blood pressure low salt diets lead to useful drops in blood pressure, but overall harms or benefits are not known.
We are commonly advised to cut down on salt. However, a pair of Cochrane reviews has found that there is little evidence for long-term benefit from reducing salt intake. This review looked at mostly short-term strategies to reduce salt intake. The other review (Hooper 2003) looked at long-term strategies to reduce the amount of salt in foods and drinks.
Advice about reducing salt intake did lower blood pressure but only by a small amount. It was not enough to expect an important health benefit. It is also very hard to keep to a low salt diet. However, the reduction was larger for people with high blood pressure. The studies were not designed to measure long-term health effects so, we don't know if low salt diets improve health outcomes.
The studies in which some people were given low salt diets and compared with others on a normal diet, found that the blood pressure did fall while the people were in the trial. But, it's not known if it stayed down after the trials. This means that the available evidence does not suggest that people with normal blood pressure should reduce the amount of salt they eat or drink. However, for people with high blood pressure low salt diet caused a larger reduction in blood pressure, and would be useful as part of a program to reduce blood pressure.
Most of the people who took part in the studies were Caucasians, but in the small number of non-Caucasians (mostly African) the blood pressure reduction was, if anything, greater. More research on salt intake is required, particularly in non-Caucasian populations.
See also the long-term salt review: Hooper 2003.