HTN: Sodium (2015)


Graudal NA, Hubeck-Gradual T, Jurgens G. Effects of a low-sodium diet vs. high-sodium diet on blood pressure, renin, aldosterone, catecholamines, cholesterol and triglycerides. Am J Hypertension. 2012; 25(1): 1-15.

PubMed ID: 22068710
Study Design:
Meta-analysis or Systematic Review
M - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To estimate the effects of low-sodium vs. high-sodium intake on blood pressure (BP) renin, aldosterone, catecholamines and lipids.

Inclusion Criteria:
Studies randomizing persons to low-sodium and high-sodium diets evaluating at least one of the parameters such as:
  • Blood pressure
  • Renin
  • Aldosterone
  • Catecholamines
  • Lipids.
Exclusion Criteria:
Studies systematically investigating unhealthy patients with diseases other than elevated BP.
Description of Study Protocol:


Randomized controlled trials allocating persons with normal or elevated BP irrespective of race and age to either a low-or a high-sodium diet and in which the sodium intake was estimated by the 24-hour urinary sodium excretion (either measured on the basis of a 24-hour urine collection or estimated from a sample of at least eight hours).


Systematic literature review.

Statistical Analysis

  • Two authors independently recorded the following data from each trial such as the sample size, the mean age of participants, the fraction of females, males, Caucasians, blacks and Asians
  • The duration of interventions, the sodium reduction measured as the difference between 24-hour urinary sodium excretion during low-sodium and high-sodium diets and SD
  • SBP (SD) and DBP (SD) before and after intervention
  • Difference between changes in SBP and DBP obtained during low-sodium and high-sodium diets and the SD of these differences
  • For crossover studies, when possible, the overall effect estimate and SE
  • Levels of hormones and lipids in the blood and their SD during low-sodium and high-sodium diets
  • Concerning lipids, cholesterol units of mmol per L were transformed to mg per dL by means of the factor 38.6; triglyceride units of mmol per L were transformed to mg per dL by means of the factor 88.4
  • If there were discrepancies between reviewers, they looked at the data together and came to an agreement.
Data Collection Summary:

Timing of Measurements

An electronic literature search in PUBMED, EMBASE and Cochrane Central was performed using the following combinations of search terms:
  • Salt or sodium
  • Restriction or dietary
  • Terms of outcome measures
  • Randomized or random.

 Dependent Variables

Outcome measures were effects on:
  • Systolic blood pressure (SBP)
  • Diastolic blood pressure (DBP)
  • Renin
  • Aldosterone
  • Adrenaline
  • Noradrenaline
  • Triglyceride
  • Cholesterol
  • LDL and HDL.  
Description of Actual Data Sample:
  • Initial N: 167 studies
  • Attrition (final N): 167 studies
  • Location: Denmark.


Summary of Results:

Key Findings

  • A total of 167 studies were included
  • The effect of sodium reduction in Normotensives:
    • Caucasians: SBP -1.27mm Hg (95% CI: -1.88, -0.66; P=0.0001); DBP -0.05mm Hg (95% CI: -0.51, 0.42, P=0.85)
    • Blacks: SPS -4.02mm Hg (95% CI: -7.37, -0.68; P=0.002); DBP -2.01mm Hg (95% CI: -4.37, 0.35; P=0.09)
    • Asians: SBP -1.27mm Hg (95% CI: -3.07, 0.54; P=0.17); DBP -1.68mm Hg (95%CI: -3.29, -0.06; P=0.04).
  • Hypertensives:
    • Caucasians: SBP -5.48mm Hg (95% CI: -6.53, -4.43; P<0.00001); DBP -2.75mm Hg (95% CI: -3.34, -2.17; P<0.00001)
    • Blacks: SBP -6.44mm Hg (95% CI: -8.85, -4.03; P=0.00001); DBP -2.40mm Hg (95% CI: -4.68, -0.12;P=0.04)
    • Asians: SBP -10.21mm Hg (95% CI: -16.98, -3.44; P=0.003); DBP -2.60mm Hg (95% CI: -4.03, -1.16; P=0.0004)
  • Sodium reduction resulted in significant increases in:
    • Renin (P<0.00001)
    • Aldosterone (P<0.000001)
    • Noradrenaline (P<0.00001)
    • Adrenaline (P<0.0002)
    • Cholesterol (P<0.001)
    • Triglycerides (P<0.0008).
Author Conclusion:

Sodium reduction resulted in a significantly decrease in BP of 1% (normotensives), 3.5% (hypertensives); and 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.

Funding Source:
AP Moller Foundation
Reviewer Comments:
Quality Criteria Checklist: Review Articles
Relevance Questions
  1. Will the answer if true, have a direct bearing on the health of patients? Yes
  2. Is the outcome or topic something that patients/clients/population groups would care about? Yes
  3. Is the problem addressed in the review one that is relevant to dietetics practice? Yes
  4. Will the information, if true, require a change in practice? No
Validity Questions
  1. Was the question for the review clearly focused and appropriate? Yes
  2. Was the search strategy used to locate relevant studies comprehensive? Were the databases searched and the search termsused described? Yes
  3. Were explicit methods used to select studies to include in the review? Were inclusion/exclusion criteria specified andappropriate? Wereselectionmethods unbiased? Yes
  4. Was there an appraisal of the quality and validity of studies included in the review? Were appraisal methodsspecified,appropriate, andreproducible? Yes
  5. Were specific treatments/interventions/exposures described? Were treatments similar enough to be combined? Yes
  6. Was the outcome of interest clearly indicated? Were other potential harms and benefits considered? Yes
  7. Were processes for data abstraction, synthesis, and analysis described? Were they applied consistently acrossstudies and groups? Was thereappropriate use of qualitative and/or quantitative synthesis? Was variation in findings among studies analyzed? Were heterogeneity issued considered? If data from studies were aggregated for meta-analysis, was the procedure described? Yes
  8. Are the results clearly presented in narrative and/or quantitative terms? If summary statistics are used, are levels ofsignificance and/or confidence intervals included? Yes
  9. Are conclusions supported by results with biases and limitations taken into consideration? Are limitations ofthe review identified anddiscussed? No
  10. Was bias due to the review's funding or sponsorship unlikely? Yes