Current Hypertension Reports

, Volume 15, Issue 6, pp 687–693 | Cite as

An Update on the Salt Wars—Genuine Controversy, Poor Science, or Vested Interest?

Prevention of Hypertension: Public Health Challenges (P Muntner, Section Editor)

Abstract

There is unequivocal evidence that increased sodium intake is associated with increased blood pressure, and that increased blood pressure leads to increased risk of vascular diseases. Unfortunately, the published evidence directly linking sodium intake to vascular risk is inconsistent and confusing. This review, emphasising recent developments in national and international settings, considers why this is the case and how vested interests – particularly the food industry – have exploited the vacuum. We argue that legislation is the only tool that is likely to reverse the current situation wherein many millions of lives are put at risk through an unnecessary dietary additive, the reduction of which would be eminently feasible and have no conceivable disadvantage to health.

Keywords

Salt Blood pressure Vascular disease Cohort study Trial Meta-analysis Policy Food industry Regulation Behaviour Hypertension 

Notes

Compliance with Ethics Guidelines

Conflict of Interest

Bruce Neal, Mary-Anne Land, and Mark Woodward declare that they have no conflict of interest.

Human and Animal Rights and Informed Consent

This article does not contain any studies with human or animal subjects performed by any of the authors.

References

Papers of particular interest, published recently, have been highlighted as: • Of importance

  1. 1.
    Drake-Holland J, Noble M. Should we now abandon the low-salt diet? Q J Med. 2011;104:1103–6.CrossRefGoogle Scholar
  2. 2.
    Bayer R, Johns D, Galea S. Salt and public health: contested science and the challenge of evidence-based decision making. Health Aff. 2012;31(12):2738–46.CrossRefGoogle Scholar
  3. 3.
    Kotchen TA, Cowley Jr AW, Frohlich ED. Salt in health and disease–a delicate balance. N Engl J Med. 2013;368(13):1229–37.PubMedCrossRefGoogle Scholar
  4. 4.
    He FJ, MacGregor GA. Salt reduction lowers cardiovascular risk: meta-analysis of outcome trials. Lancet. 2011;378(9789):380–2.PubMedCrossRefGoogle Scholar
  5. 5.
    Yang Q, Liu T, Kuklina E, Flanders D, Hong Y, Gillespie C, et al. Sodium and potassium intake and mortality among US adults - prospective data from the Third National Health and Nutrition Examination Survey. Arch Intern Med. 2011;171(13):1183–91.PubMedCrossRefGoogle Scholar
  6. 6.
    Gardener H, Rundek T, Wright C, Elkind M, Sacco R. Dietary sodium and risk of stroke in the Northern Manhattan study. Stroke. 2012;43:1200–5.PubMedCrossRefGoogle Scholar
  7. 7.
    • Stolarz-Skrzypek K, Kuznetsova T, Thijs L, Tikhonoff V, Seidlerova J, Richart T, et al. Fatal and nonfatal outcomes, incidence of hypertension, and blood pressure changes in relation to urinary sodium excretion. JAMA J Am Med Assoc. 2011;305(17):1777–85. Among the most widely reported of recent studies questioning the association of salt with adverse health outcomes. This cohort study, with a primary result based upon just 84 vascular deaths, is a weak design at very high risk of both systemtic and random errors.CrossRefGoogle Scholar
  8. 8.
    O'Donnell MJ, Yusuf S, Mente A, Gao P, Mann JF, Teo K, et al. Urinary sodium and potassium excretion and risk of cardiovascular events. JAMA J Am Med Assoc. 2011;306(20):2229–38.CrossRefGoogle Scholar
  9. 9.
    Son YJ, Lee Y, Song EK. Adherence to a sodium-restricted diet is associated with lower symptom burden and longer cardiac event-free survival in patients with heart failure. J Clin Nurs. 2011;20(21–22):3029–38.PubMedCrossRefGoogle Scholar
  10. 10.
    Dong J, Li Y, Yang Z, Luo J. Low dietary sodium intake increases the death risk in peritoneal dialysis. Clin J Am Soc Nephrol CJASN. 2010;5(2):240–7.CrossRefGoogle Scholar
  11. 11.
    Thomas MC, Moran J, Forsblom C, Harjutsalo V, Thorn L, Ahola A, et al. The association between dietary sodium intake, ESRD, and all-cause mortality in patients with type 1 diabetes. Diabetes care. 2011;34(4):861–6.PubMedCrossRefGoogle Scholar
  12. 12.
    Campbell NR, Cappuccio FP, Tobe SW. Unnecessary controversy regarding dietary sodium: a lot about a little. Can J Cardiol. 2011;27(4):404–6.PubMedCrossRefGoogle Scholar
  13. 13.
    • Whelton PK, Appel LJ, Sacco RL, Anderson CA, Antman EM, Campbell N, et al. Sodium, blood pressure, and cardiovascular disease: further evidence supporting the American Heart Association sodium reduction recommendations. Circulation. 2012;126(24):2880–9. A careful review focusing on the methodological strengths and weaknesses of recent reports about the effects of salt on disease, with a focus on the implications of the new data for existing dietry recommendations. The review finds no strong rationale for modification to existing American Heart Asssociation guidance on salt intake.Google Scholar
  14. 14.
    Campbell N, Correa-Rotter R, Neal B, Cappuccio FP. New evidence relating to the health impact of reducing salt intake. Nutr Metab Cardiovasc Dis. 2011;21(9):617–9.PubMedCrossRefGoogle Scholar
  15. 15.
    Cruickshank JM, Higgins TJ, Pennert K, Thorp JM, Zacharias FM, Zacharias FJ. The efficacy and tolerability of antihypertensive treatment based on atenolol in the prevention of stroke and the regression of left ventricular hypertrophy. J Hum Hypertens. 1987;1(2):87–93.PubMedGoogle Scholar
  16. 16.
    Paganini-Hill A, Chao A, Ross R, Henderson B. Aspirin use and chronic diseases: a cohort study of the elderly. BMJ. 1989;299:1247–50.PubMedCrossRefGoogle Scholar
  17. 17.
    MacMahon S, Collins R. Reliable assessment of the effects of treatment on mortality and major morbidity, II: observational studies. Lancet. 2001;357:455–62.PubMedCrossRefGoogle Scholar
  18. 18.
    Collins R, MacMahon S. Reliable assessment of the effects of treatment on mortality and major morbidity, I: clinical trials. Lancet. 2001;357:373–80.PubMedCrossRefGoogle Scholar
  19. 19.
    Adler AJ, Taylor F, Ashton KE, Martin N, Gottlieb S, Ebrahim S. WITHDRAWN: Reduced dietary salt for the prevention of cardiovascular disease. Cochrane Database Syst Rev. 2013;12(9):CD009217. doi: 10.1002/14651858.CD009217.pub2.
  20. 20.
    • He FJ, Li J, Macgregor GA. Effect of longer term modest salt reduction on blood pressure: Cochrane systematic review and meta-analysis of randomised trials. BMJ. 2013;346:f1325. Another systematic review of randomised trials addressing the effects of salt reduction on vascular outcomes. With different inclusion citeria, this updated overview reports protection against vascular outcomes, although acknowledges the weakness inherent in the limited data provided by the contributing studies.PubMedCrossRefGoogle Scholar
  21. 21.
    Paterna S, Gaspare P, Fasullo S, Sarullo FM, Di Pasquale P. Normal-sodium diet compared with low-sodium diet in compensated congestive heart failure: is sodium an old enemy or a new friend? Clin Sci (Lond). 2008;114(3):221–30.CrossRefGoogle Scholar
  22. 22.
    • Dinicolantonio JJ, Pasquale PD, Taylor RS, Hackam DG. Retraction. Low sodium versus normal sodium diets in systolic heart failure: systematic review and meta-analysis. Heart. 2013;99(11):820. doi: 10.1136/heartjnl-2011-301156.29ret. A systematic review of randomised trials addressing the effects of salt reduction in heart failure. The meta-analysis was noted after publication to include duplication of data across trials that has not been adequately explained by the investigators. There is an ongoing investigation into the data for the other contributing trials which all derive from the same group of investigators operating from a single investigational site.
  23. 23.
    2011 high level meeting on prevention and control of non-communicable diseases [http://www.un.org/en/ga/ncdmeeting2011/].
  24. 24.
    The World Health Organization. WHO guideline: sodium intake for adults and children. In: Geneva; 2012 Available at: http://www.who.int/nutrition/publications/guidelines/sodium_intake/en/. Accessed March 2013.
  25. 25.
    The World Health Organization. Joint WHO/FAO expert consultation on diet, nutrition and the prevention of chronic diseases. In: 2003 Available at: http://www.who.int/dietphysicalactivity/publications/trs916/en/. Accessed March 2013.
  26. 26.
    Aburto NJ, Ziolkovska A, Hooper L, Elliott P, Cappuccio FP, Meerpohl JJ. Effect of lower sodium intake on health: systematic review and meta-analyses. BMJ. 2013;346:f1326.PubMedCrossRefGoogle Scholar
  27. 27.
    • Institute of Medicine. Sodium intake in populations: assessment of evidence. In: Washington; 2013 Available at: http://www.iom.edu/Reports/2013/Sodium-Intake-in-Populations-Assessment-of-Evidence.aspx. Accessed April 2013. An overview seeking to determine the effects of salt consumption on hard clinical outcomes with particular reference to recently completed studies. Unusually, the overview excluded data about effects of salt on intermediate outcomes like blood pressure, and concluded that salt reduciton to 6 g/day be recommended but questioned advice to lower salt intake to 4 g/day.
  28. 28.
    Webster JL, Dunford EK, Hawkes C, Neal BC. Salt reduction initiatives around the world. J Hypertens. 2011;29(6):1043.PubMedCrossRefGoogle Scholar
  29. 29.
    The World Health Organization. Mapping salt reduction initiatives in the WHO European Region. In: 2013 Available at: http://www.euro.who.int/en/health-topics/disease-prevention/nutrition/publications/2013/mapping-salt-reduction-initiatives-in-thewho-european-region. Accessed April 2013.
  30. 30.
    The World Health Organization. Expert meeting on population sodium reduction strategies for prevention and control of noncommunicable diseases in the South-East Asia Region. In: 2013 Available at: http://www.searo.who.int/entity/noncommunicable_diseases/documents/sea_ncd_86/en/index.html. Accessed March 2013.
  31. 31.
    Sadler K, Nicholson S, Steer T, Gill V, Bates B, Tipping S, et al. National diet and nutrition survey - assessment of dietary sodium in adults (aged 19 to 64 years) in England, 2011 Available at: http://www.wp.dh.gov.uk/transparency/files/2012/06/Sodium-Survey-England-2011_Text_to-DH_FINAL1.pdf. Accessed February 2013.
  32. 32.
    Prevention of cardiovascular disease at the population level. London: NICE [http://guidance.nice.org.uk/PH25].
  33. 33.
    Bibbins-Domingo K, Chertow GM, Coxson PG, Moran A, Lightwood JM, Pletcher MJ, et al. Projected effect of dietary salt reductions on future cardiovascular disease. N Engl J Med. 2010;362(7):590–9.PubMedCrossRefGoogle Scholar
  34. 34.
    Cobiac LJ, Vos T, Veerman JL. Cost-effectiveness of interventions to reduce dietary salt intake. Heart. 2010;96(23):1920–5.PubMedCrossRefGoogle Scholar
  35. 35.
    Rubinstein A, Colantonio L, Bardach A, Caporale J, Marti SG, Kopitowski K, et al. Estimation of the burden of cardiovascular disease attributable to modifiable risk factors and cost-effectiveness analysis of preventative interventions to reduce this burden in Argentina. BMC Public Health. 2010;10(627):1471–2458.Google Scholar
  36. 36.
    Murray CJ, Lauer JA, Hutubessy RC, Niessen L, Tomijima N, Rodgers A, et al. Effectiveness and costs of interventions to lower systolic blood pressure and cholesterol: a global and regional analysis on reduction of cardiovascular-disease risk. Lancet. 2003;361(9359):717–25.PubMedCrossRefGoogle Scholar
  37. 37.
    Selmer RM, Kristiansen IS, Haglerod A, Graff-Iversen S, Larsen HK, Meyer HE, et al. Cost and health consequences of reducing the population intake of salt. J Epidemiol Community Health. 2000;54(9):697–702.PubMedCrossRefGoogle Scholar
  38. 38.
    Joffres MR, Campbell NR, Manns B, Tu K. Estimate of the benefits of a population-based reduction in dietary sodium additives on hypertension and its related health care costs in Canada. Can J Cardiol. 2007;23(6):437–43.PubMedCrossRefGoogle Scholar
  39. 39.
    Palar K, Sturm R. Potential societal savings from reduced sodium consumption in the U.S. adult population. Am J Health Promot AJHP. 2009;24(1):49–57.CrossRefGoogle Scholar
  40. 40.
    Smith-Spangler CM, Juusola JL, Enns EA, Owens DK, Garber AM. Population strategies to decrease sodium intake and the burden of cardiovascular disease: a cost-effectiveness analysis. Ann Intern Med. 2010;152(8):481–7.PubMedCrossRefGoogle Scholar
  41. 41.
    Asaria P, Chisholm D, Mathers C, Ezzati M, Beaglehole R. Chronic disease prevention: health effects and financial costs of strategies to reduce salt intake and control tobacco use. Lancet. 2007;370(9604):2044–53.PubMedCrossRefGoogle Scholar
  42. 42.
    • Lim SS, Vos T, Flaxman AD, Danaei G, Shibuya K, Adair-Rohani H, et al. A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990-2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet. 2012;380(9859):2224–60. A systematic and quantitative assessment of the likely contribution of 67 risks to health on major groups of disease outcomes. The review includes estimates for the effects of excess salt consumption alongside a series of other dietary factors. An excellent data visualization tool is available online at the Institute for Health Metrics and Evaluation.PubMedCrossRefGoogle Scholar
  43. 43.
    Brown IJ, Tzoulaki I, Candeias V, Elliott P. Salt intakes around the world: implications for public health. Int J Epidemiol. 2009;38(3):791–813.PubMedCrossRefGoogle Scholar
  44. 44.
    • Moodie R, Stuckler D, Monteiro C, Sheron N, Neal B, Thamarangsi T, et al. Profits and pandemics: prevention of harmful effects of tobacco, alcohol, and ultra-processed food and drink industries. Lancet. 2013;381(9867):670–9. An overview of the role that the food and beverage industry plays in the causation of the global disease burden caused by poor diet. The paper highlights parallels with the manufacture and retail of tobacco and alcohol and the challenges facing public health in their efforts to combat the health problems caused.PubMedCrossRefGoogle Scholar
  45. 45.
    The World Health Organization. Noncommunicable disease Global Monitoring Framework. Available at: http://www.who.int/nmh/global_monitoring_framework/en/. Accessed April 2013.
  46. 46.
    The World Health Organization. Reducing salt intake in populations. In: Geneva; 2006 Available at: http://www.who.int/dietphysicalactivity/reducingsalt/en/index1.html. Accessed March 2013.
  47. 47.
    The World Health Organization. Global Action Plan for the Prevention and Control of NonCommunicable Diseases: Revised Draft Global Action Plan for the Prevention and Control of Noncommunicable Diseases 2013-2020. In: 2013 Available at: http://www.who.int/nmh/events/2013/consultation_201303015/en/. Accessed March 2013.
  48. 48.
    Cappuccio FP, Capewell S, Lincoln P, McPherson K. Policy options to reduce population salt intake. BMJ. 2011;343:d4995.Google Scholar
  49. 49.
    Brown IJ, Dyer AR, Chan Q, Cogswell ME, Ueshima H, Stamler J, et al. Estimating 24-hour urinary sodium excretion from casual urinary sodium concentrations in Western populations: the INTERSALT study. Am J Epidemiol. 2013;177(11):1180–92.PubMedCrossRefGoogle Scholar
  50. 50.
    Ji C, Sykes L, Paul C, Dary O, Legetic B, Campbell NR, et al. Systematic review of studies comparing 24-hour and spot urine collections for estimating population salt intake. Rev Panam Salud Publica Pan Am J Public Health. 2012;32(4):307–15.CrossRefGoogle Scholar
  51. 51.
    Kearney J. Food consumption trends and drivers. Philos Trans R Soc Lond B Biol Sci. 2010;365(1554):2793–807.PubMedCrossRefGoogle Scholar
  52. 52.
    Lim S, Vos T, Flaxman A, Danaei G, Shibuya K, Adair-Rohani, et al. The burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions 1990-2010: a systematic analysis for the Global Burden of Disease Study. Lancet. 2013;380:2224–6.CrossRefGoogle Scholar
  53. 53.
    Mozaffarian D, Appel LJ, Van Horn L. Components of a cardioprotective diet: new insights. Circulation. 2011;123(24):2870–91.PubMedCrossRefGoogle Scholar
  54. 54.
    World Health Organization. Global status report on noncommunicable diseases 2010: description of the global burden of NCDs, their risk factors and determinants. In: 2011 Available at: http://www.who.int/chp/ncd_global_status_report/en/. Accessed March 2013.
  55. 55.
    Satin M. The salt debate–more salacious than salubrious. Nutrition. 2011;27(7–8):759–60.PubMedCrossRefGoogle Scholar
  56. 56.
    Sharma LL, Teret SP, Brownell KD. The food industry and self-regulation: standards to promote success and to avoid public health failures. Am J Public Health. 2010;100(2):240–6.PubMedCrossRefGoogle Scholar
  57. 57.
    Simon M. Can food companies be trusted to self-regulate? An analysis of corporate lobbying and deception to undermine children's health. Loyola Los Ang Law Rev. 2006;39:169–236.Google Scholar
  58. 58.
  59. 59.
    Puska P. The North Karelia Project: nearly 20 years of successful prevention of CVD in Finland. Hygie. 1992;11:33–5.PubMedGoogle Scholar
  60. 60.
    Dunford E. The importance of branded food composition databases in monitoring the food supply. Sydney: The University of Sydney; 2012.Google Scholar
  61. 61.
    Kraak VI, Harrigan PB, Lawrence M, Harrison PJ, Jackson MA, Swinburn B. Balancing the benefits and risks of public-private partnerships to address the global double burden of malnutrition. Public Health Nutr. 2012;15(3):503–17.PubMedCrossRefGoogle Scholar
  62. 62.
    Norman R, Gaziano T, Laubscher R, Steyn K, Bradshaw D. Estimating the burden of disease attributable to high blood pressure in South Africa in 2000. S Afr Med J. 2007;97(8 Pt 2):692–8.PubMedGoogle Scholar
  63. 63.
    Charlton KE, Steyn K, Levitt NS, Zulu JV, Jonathan D, Veldman FJ, et al. Diet and blood pressure in South Africa: intake of foods containing sodium, potassium, calcium, and magnesium in three ethnic groups. Nutrition. 2005;21(1):39–50.PubMedCrossRefGoogle Scholar
  64. 64.
    Bertram MY, Steyn K, Wentzel-Viljoen E, Tollman S, Hofman KJ. Reducing the sodium content of high-salt foods: effect on cardiovascular disease in South Africa. S Afr Med J. 2012;102(9):743–5.PubMedCrossRefGoogle Scholar
  65. 65.
    Cook NR, Cutler JA, Obarzanek E, Buring JE, Rexrode KM, Kumanyika SK, et al. Long term effects of dietary sodium reduction on cardiovascular disease outcomes: observational follow-up of the trials of hypertension prevention (TOHP). BMJ. 2007;334(7599):885–8.PubMedCrossRefGoogle Scholar
  66. 66.
    Chang HY, Hu YW, Yue CS, Wen YW, Yeh WT, Hsu LS, et al. Effect of potassium-enriched salt on cardiovascular mortality and medical expenses of elderly men. Am J Clin Nutr. 2006;83(6):1289–96.PubMedGoogle Scholar
  67. 67.
    Whelton PK, Appel LJ, Espeland MA, Applegate WB, Ettinger Jr WH, Kostis JB, et al. Sodium reduction and weight loss in the treatment of hypertension in older persons: a randomized controlled trial of nonpharmacologic interventions in the elderly (TONE). TONE Collaborative Research Group. JAMA J Am Med Assoc. 1998;279(11):839–46.CrossRefGoogle Scholar
  68. 68.
    He FJ, MacGregor GA. Effect of longer-term modest salt reduction on blood pressure. Cochrane Database Syst Rev. 2004;3, CD004937.PubMedGoogle Scholar
  69. 69.
    Cutler JA, Follmann D, Allender PS. Randomized trials of sodium reduction: an overview. Am J Clin Nutr. 1997;65(2 Suppl):643S–51S.PubMedGoogle Scholar
  70. 70.
    Dickinson HO, Mason JM, Nicolson DJ, Campbell F, Beyer FR, Cook JV, et al. Lifestyle interventions to reduce raised blood pressure: a systematic review of randomized controlled trials. J Hypertens. 2006;24(2):215–33.PubMedCrossRefGoogle Scholar
  71. 71.
    Hooper L, Bartlett C, Davey SG, Ebrahim S. Advice to reduce dietary salt for prevention of cardiovascular disease. Cochrane Database Syst Rev. 2004;1, CD003656.PubMedGoogle Scholar
  72. 72.
    Strazzullo P. Compelling evidence for salt-dependence of blood pressure from GENSALT. J Hypertens. 2009;27(1):22–3.PubMedCrossRefGoogle Scholar
  73. 73.
    World Economic Forum, The Harvard School of Public Health. The global economic burden of non-communicable diseases. In: 2011 Available at: http://www.weforum.org/reports/global-economic-burden-non-communicablediseases. Accessed March 2013.
  74. 74.
    The World Health Organization. Scaling up action against noncommunicable diseases: how much will it cost? In: Geneva; 2011 Available at: http://www.who.int/nmh/publications/cost_of_inaction/en/. Accessed March 2013.
  75. 75.
    Lozano R, Naghavi M, Foreman K, Lim S, Shibuya K, Aboyans V, et al. Global and regional mortality from 235 causes of death for 20 age groups in 1990 and 2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet. 2012;380(9859):2095–128.PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  1. 1.The George Institute for Global HealthThe University of SydneyNSWAustralia

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