HTN: Magnesium (2015)


Hatzistavri LK, Sarafidis PA, Georgianos PI, Tziolas JM, Aroditis CP, Zebekakis PE, Pikilidou MI, Lasaridis AN. Oral magnesium supplementaion reduces ambulatory blood pressure in patients with mild hypertension. Am J Hypertens. 2009; 22 (10): 1,070-1,075.

PubMed ID: 19617879
Study Design:
Non-Randomized Controlled Trial
C - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To investigate the effect of oral magnesium supplementation on 24-hour blood pressure and intracellular ion status in patients with uncomplicated mild hypertension and the possible relations between potential changes in these parameters.
Inclusion Criteria:
  • New-onset Stage 1 hypertension, diagnosed in three separate visits with a one-week interval between them
  • Low total cardiovascular risk profile
  • Absence of any anti-hypertensive medication.
Exclusion Criteria:
  • Stage 2 or 3 hypertension (SBP higher than 160mm Hg and DBP higher than 100mm Hg)
  • Secondary hypertension
  • Severe congestive heart failure
  • Coronary artery disease
  • Chronic kidney disease
  • Active liver disease
  • Diabetes mellitus
  • History of malignancy
  • History of drug and alcohol abuse
  • Current use of dietary supplements.
Description of Study Protocol:


  • Patients who were evaluated at Hypertension Department
  • First 26 consecutive patients fulfilling inclusion and exclusion criteria that were willing to receive the magnesium intervention were assigned to the intervention group
  • Those who fulfilled inclusion and exclusion criteria but were not willing to take magnesium supplement formed the control group, age and sex-matched.


Non-randomized controlled trial.


  • Intervention group: A total of 600mg (25mmol) of pidolate Mg2+ orally two times per day for 12 weeks in addition to standard lifestyle recommendations
  • Control group: Standard lifestyle recommendations only.

Statistical Analysis

  • Baseline differences between the two groups: Paired T-tests or chi-square tests
  • Comparisons between baseline and end of study in each study group: Paired T-tests or Wilcoxon's signed rank tests, according to the normality of the distribution
  • Between-group differences: Unpaired T-tests or Mann-Whitney U-tests where appropriate
  • Possible relationships between parameters: Bivariate correlation coefficients using Pearson's product formula.
Data Collection Summary:

Timing of Measurements

Baseline, four weeks, eight weeks and 12 weeks (24-hour BP at baseline and 12 weeks only).

Dependent Variables

  • A 24-hour BP: Spacelabs90207 device at baseline and 12 weeks
  • Daytime ambulatory BP
  • Nighttime ambulatory BP
  • Serum and Intracellular Na, K, Ca, Mg
  • A 24-hour urinary magnesium.

Independent Variables

Magnesium supplementation: 1,200mg per day (50mmol) vs. no supplementation.

Control Variables

Groups were matched for age and sex.
Description of Actual Data Sample:
  • Initial N: N=52
  • Attrition (final N): N=48  (15 males, nine females in each group).
  • Intervention: Ages 45.3±10.1 years
  • Control group: Ages 46.9±8.7 years.



  • Intervention group:
    • BMI: 28.3±2.8kg/m2
    • 24-hour SBP: 146.7±4.1mm Hg
    • 24-hour DBP: 91.5±2.6mm Hg.
  • Control group:
    • BMI: 27.4±4.1kg/m2
    • 24-hour SBP: 144.7±4.6 mmHg
    • 24-hour DBP: 89.6±3.9 mmHg.




Summary of Results:

Key Findings

Changes in SBP and DBP (mm Hg)

  • Overall changes in BP between baseline and 12 weeks (intervention vs. control): 
    •  SBP: -5.6±2.7 vs. -1.3±2.4 (P<0.001)
    •  DBP: -2.8±1.8 vs. -1.0±1.2 (P=0.002).
  • BP changes in intervention group:
    • Baseline SBP: 146.7±4.1
    • 12 week SBP: 141.1±4.1
    • P<0.001
    • Baseline DBP:  91.5±2.6
    • 12 week DBP: 88.7±2.9
    • P<0.00 .
  • BP changes in control group:
    • Baseline SBP: 144.7±4.6
    • 12 week SBP: 143.4±5.4
    • NS
    • Baseline DBP: 89.6±3.9
    • 12 week DBP: 89.5±3.0
    • NS.
Other Findings
  • There was a significant increase in 24-hour urinary magnesium excretion in the intervention group (52.3±50.8mg per dL to 178.4±89.8mg per L, P<0.001), but no changes in the control group
  • There was a significant increase in serum Mg2+ levels in the intervention group (2.3±0.2mg per dL to 2.44±0.2mg per dL, P=0.003)
  • There was a reduction in serum K+ in the intervention group (4.4±0.4 to 4.0±0.3, P<0.001)
  • There were no other significant changes in serum electrolytes in the intervention group
  • Changes in serum electrolytes in the control group were not significant
  • In the intervention group, there were significant decreases in intracellular sodium (P<0.001) and calcium (P<0.001), and significant increases in intracellular magnesium (P<0.001) and potassium (P<0.001)
  • There were no significant changes in the control group.
Author Conclusion:
This study suggests that oral magnesium supplementation is associated with small but consistent ambulatory BP reduction in patients with mild hypertension.
Funding Source:
Other: Not supported by any source
Reviewer Comments:
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? ???
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) No
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? N/A
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes