Tools for Practice


#82 Cutting out the sodium: The Bland Supremacy?


CLINICAL QUESTION
Does sodium restriction reduce mortality from cardiovascular disease (CVD)?

BOTTOM LINE
The impact of salt intake on CVD outcomes is controversial. Trials demonstrating beneficial trends enrolled patients with an average sodium intake of 3800 mg/day and reduced their intake by ~600 mg/day. More evidence with clinical outcome is required to better define benefits and harms with different levels of daily sodium intake.


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EVIDENCE
Cochrane review1 of 8 randomized controlled trials (RCTs), 7,198 patients compared reduced dietary sodium to control, and followed them for 6 months to 15 years 
  • Average baseline sodium intake (~3800 mg) was reduced by 600 mg/day. 
  • At longest follow-up, there was no statistically significant difference for outcomes in normotensive and hypertensive patients 
    • All-cause mortality:  
      • Normotensive: Relative risk (RR) 0.90 (0.58-1.40) 
      • Hypertensive: RR 0.99 (0.87-1.14) 
    • CVD events: 
      • Normotensive: RR 0.71 (0.42-1.20) 
      • Hypertensive: RR 0.77 (0.57-1.02) 
    • Trend (non-significant) is for reduced outcomes. 
Observational studies show conflicting associations between sodium intake and outcomes (including opposite conclusions in different analyses of the same cohort2,3): 
  • Systematic review4 of 13 cohort studies (177,000 patients) that assumed a linear association between sodium intake and outcomes found 
    • Non-significant increase in CVD events with higher versus lower intake: RR 1.14 (0.99-1.31) 
    • Increased stroke risk with higher sodium intake: RR 1.23 (1.06-1.43) 
  • Other reviews found a J-curve: 
    • Meta-analysis of 23 cohort studies (274,683 patients)5 found lowest risk of mortality and CVD with sodium intake 2600-5000 mg/day 
    • Pooled analysis of 4 studies (133,118 patients)6 found sodium intake associated risks varied by presence of hypertension. 
      • Normotensive: >3000 mg/day lowest risk.  
        • Lower sodium intake had increased 26% RR of CVD and/or death. 
      • Hypertensive: 4000-7000 mg/day. 
        • Lower or higher sodium intake had 23-34% increased RR of CVD and/or death. 
Context:  
  • Canadian guidelines7 recommend upper limit 2300 mg/day of sodium for persons >14 years-old 
    • Based on best-available evidence this may produce no benefit,1 or cause significant harm.5,6 
  • Estimated sodium intake for Canadian and American adults is ~3600 mg/day.8 
  • Low-sodium diets reduce blood pressure,9,10 a surrogate marker for CVD11  
    • Atenolol12 and aliskiren13 are other interventions that lower blood pressure, but have not been shown to reduce mortality. 
Ricky Turgeon BSc(Pharm) ACPR PharmD updated aug 9 2016
February 4, 2013

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Author(s):

  • Christina Korownyk MD CCFP
  • Ian Taylor MD

1. Adler AJ, Taylor F, Martin N, Gottlieb S, Taylor RS, Ebrahim S. Cochrane Database Syst Rev 2014;12:CD009217.

2. Cohen HW, Hailpern SM, Alderman MH. J Gen Intern Med 2008;23:1297-302.

3. Yang Q, Liu T, Kuklina EV, et al. Arch Intern Med 2011;171:1183-91.

4. Strazzullo P, D'Elia L, Kandala NB, et al. BMJ 2009;339:b4567.

5. Graudal N, Jurgens G, Baslund B, Alderman MH. Am J Hypertens 2014;27:1129-37.

6. Mente A, O’Donnell M, Rangarajan S, et al. Lancet 2016;388:465-75.

7. http://www.hc-sc.gc.ca/fn-an/nutrition/sodium/index-eng.php [Accessed Aug 10 2016]

8. Mozaffarian D, Fahimi S, Singh GM, et al. N Engl J Med 2014;371:624-34.

9. Sacks FM, Svetkey LP, Vollmer WM, et al. N Engl J Med 2001;344:3-10.

10. Graudal NA, Hubeck-Graudal T, Jurgens G. Cochrane Database Syst Rev 2011;11:CD004022.

11. Rutan GH, Kuller LH, Neaton JD, et al. Circulation 1988;77:504-14.

12. Carlberg B, Samuelsson O, Lindholm LH. Lancet 2004;364:1684-9.

13. Parving HH, Brenner BM, McMurray JJ, et al. N Engl J Med 2012;367:2204-13.

Authors do not have any conflicts of interest to declare.