title: The effect of dietary sodium modification on blood pressure in adults with systolic blood pressure less than 140 mmHg: a systematic review.
abstract: Modifying dietary sodium intake is a cornerstone of diet advice for lowering blood pressure (BP) under the assumption that it is protective against cardiovascular disease. Previous meta-analyses of normotensive participants have not excluded all studies that recruited participants with systolic blood pressure (SBP) > 140 mmHg, which greatly hinders generalization to the wider normotensive population.
  
  
  
  The objective of this review was to identify the effectiveness of reducing or increasing sodium intake on BP in normotensive participants with SBP ≤ 140 mmHg.
  
  
  
  This review considered studies on adult participants (≥18 years) with SBP ≤ 140 mmHg. Studies on pregnant women or patients prescribed antihypertensive or vasoactive medications were excluded.
  
  
  
  Interventions that quantitatively evaluated dietary sodium intake for equal to or greater than four weeks duration were considered. Only studies that included two study arms comprising different levels of sodium intake were included.
  
  
  
  Studies that reported SBP, diastolic blood pressure (DBP), pulse wave velocity (PWV), pulse wave analysis or flow mediated dilatation were considered.
  
  
  
  Experimental study designs including randomized controlled trials and non-randomized controlled trials were considered.
  
  
  
  An initial search strategy was conducted on databases MEDLINE and CINAHL before an extensive search of all relevant published and gray literature databases, and clinical trial registries were searched.
  
  
  
  Potential papers were assessed for methodological validity using the standardized critical appraisal instrument from the Joanna Briggs Institute Meta-Analysis of Statistics Assessment and Review Instrument (JBI-MAStARI).
  
  
  
  Quantitative data were extracted from papers using the standardized data extraction tool from JBI-MAStARI.
  
  
  
  Quantitative data were pooled in statistical meta-analysis. Effect sizes were expressed as weighted mean differences and 95% confidence intervals. Meta-analysis was conducted using a random-effect model, and heterogeneity assessed statistically using the standard Chi-square test and the I index. A priori sub-group analysis was undertaken on studies achieving ≥40 mmol versus <40 mmol in urinary sodium excretion and post hoc on studies with a mean body mass index (BMI) ≥ 30 versus less than 30.
  
  
  
  Five trials were included with a total of 1214 participants. The overall reduction in SBP was -0.71 mmHg (95% CI: -2.62, 1.20, P = 0.47) and DBP -0.57 mmHg (95% CI: -1.26, 0.12, P = 0.10). There was no significant change in PWV following reduction of dietary sodium over a four to six-week period. Sub-group analysis did not find a significant effect of urinary sodium excretion or BMI on outcomes; however, a trend toward a greater reduction in BP was observed in those with a higher BMI (MD -2.41, 95% CI -5.72, +0.91, P = 0.16).
  
  
  
  Blood pressure in normotensive participants was not significantly affected by sodium modification and was controlled to within 1% of baseline values. Reducing dietary sodium in normotensive participants may still be of importance for cardiovascular risk management; however, good quality interventional research is limited.
authors.affiliation: 1School of Allied Health Sciences, Griffith University, Gold Coast 2Faculty of Health Science and Medicine, Bond University, Gold Coast 3Menzies Health Institute Queensland and School of Medicine, Griffith University, Gold Coast, Queensland 4Nutrition and Dietetics, School of Health Sciences, Faculty of Medicine, Nursing and Health Sciences, Flinders University 5Queensland Centre for Evidence Based Nursing and Midwifery: a Collaborating Centre of the Joanna Briggs Institute, Adelaide, South Australia 6Nursing Research Centre, Mater Health Services 7School of Human Movement and Nutritional Sciences 8Mater Research Institute - The University of Queensland 9Menzies Health Institute Queensland, Griffith University, Brisbane, Queensland, Australia.
authors.forename: Jaimon
authors.initials: J
authors.lastname: Kelly
authors.forename: Saman
authors.initials: S
authors.lastname: Khalesi
authors.forename: Kacie
authors.initials: K
authors.lastname: Dickinson
authors.forename: Sonia
authors.initials: S
authors.lastname: Hines
authors.forename: Jeff S
authors.initials: JS
authors.lastname: Coombes
authors.forename: Alwyn S
authors.initials: AS
authors.lastname: Todd
mesh_terms: D000328:Adult; D001794:Blood Pressure; D002318:Cardiovascular Diseases / Q000517:prevention & control*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000517:prevention & control*; D063177:Pulse Wave Analysis; D012307:Risk Factors; D012964:Sodium; D012982:Sodium, Dietary
chemical_list: D012982:Sodium, Dietary; D012964:Sodium