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The health impacts of dietary sodium and a low-salt diet

Rebecca J Suckling and Pauline A Swift
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DOI: https://doi.org/10.7861/clinmedicine.15-6-585
Clin Med December 2015
Rebecca J Suckling
ASouth West Thames Renal and Transplantation Unit, Epsom and St Helier University Hospitals NHS Trust, Carshalton, UK
Roles: consultant nephrologist
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  • For correspondence: rebecca.suckling@esth.nhs.uk
Pauline A Swift
BSouth West Thames Renal and Transplantation Unit, Epsom and St Helier University Hospitals NHS Trust, Carshalton, UK
Roles: consultant nephrologist
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ABSTRACT

High salt intake is now endemic worldwide. It contributes to the generation and maintenance of high blood pressure, which is now the biggest risk factor for global disease. There is now compelling evidence to support salt reduction in hypertensives and a substantial body of evidence to support salt reduction in the general population to reduce risk of death from cardiovascular disease. In specific diseases such as heart failure and chronic kidney disease, guidelines support the World Health Organization target for reduced salt intake at 5 g daily. Achieving a diet that is lower in salt has challenges, but is more likely to be achieved through salt reduction strategies particularly focused on processed food and through educational programs. To be effective, these interventions require collaboration between industry, health agencies and governments.

KEYWORDS
  • Salt intake
  • sodium
  • hypertension
  • cardiovascular disease
  • heart failure
  • chronic kidney disease
Key points
  • Salt intake is an important contributor to the development of high blood pressure.

  • Salt reduction lowers blood pressure effectively in hypertension.

  • Public health strategies to lower salt are key for reduction in cardiovascular disease.

  • High salt intake reduces the effectiveness of key medications, including angiotensin-converting-enzyme inhibitors.

  • The best estimate of salt intake is a 24-h urine collection.

Introduction

For several million years, humans ate very little salt – less than 0.25 g/day. Salt was introduced as a method to preserve food and this was transformational for civilised societies.1 Initially the advent of refrigeration led to a reduction in salt intake; however subsequently the intake of salt has increased and is now estimated to be between 9 and 12 g/day in most countries worldwide, significantly more than our evolutionary ancestors.1,2 This global habituation of salt consumption is of great concern as it is linked to high blood pressure and increased risk of cardiovascular disease, as well as gastric cancer, renal stone disease and osteoporosis.1

In specific diseases, the evidence to reduce salt intake is compelling, at least to levels that are suggested by guidelines, if not lower.1,3,4 However adherence to salt restriction is poor, even in clinical trials with motivated patients. This is at least in part due to the high prevalence of salt in food, in particular baked and processed food, making it difficult for patients to achieve the reduction that they need to gain clinical benefit.1 In this review we have focused on the evidence for lowering salt intake for the general population and in groups with cardiovascular and renal disease.

Salt and high blood pressure

High blood pressure is the leading risk factor for global disease and has the greatest impact of all risk factors on cardiovascular disease, with non-optimal blood pressure accounting for two-thirds of stoke and one-half of ischaemic heart disease.5 Evidence from genetic, epidemiological, migrational and interventional studies contribute to the compelling evidence that salt intake elevates population blood pressure.1 The largest epidemiological study of salt and blood pressure, the INTERSALT study, included 10,079 individuals from diverse populations and found a strong positive relationship between sodium intake and blood pressure that persisted even when four populations with very low salt intake were excluded, with an increase of 6 g/day in salt intake estimated to elevate systolic blood pressure by 9 mmHg over 30 years.6 More recent studies – EPIC-Norfolk and INTERMAP – support these findings.7,8

Lowering salt intake reduces blood pressure. An updated systematic review of studies where salt was reduced by 4.4 g/day for at least 4 weeks found that systolic blood pressure was reduced by 4 mmHg and diastolic blood pressure by 2 mmHg.9 This study found that the effects on blood pressure continued below levels currently suggested by international guidelines. This dose-dependent relationship is supported by 2 independently conducted double blinded randomised controlled studies of different levels of salt intake (12, 6 and 3 g10 and 8, 6 and 4 g11) where the lowest salt reduction reduced blood pressure to the lowest levels.

Salt intake and its relationship to cardiovascular disease

High salt intake is likely to contribute to cardiovascular risk primarily through its effects on blood pressure, as well as through blood pressure independent effects on arterial stiffening and albuminuria.1 The actual effect of lowering population salt intake on cardiovascular outcomes has been more controversial. Available evidence from epidemiological studies is largely supportive. Public health strategy in the UK has successfully achieved a 15% reduction in salt intake from 2003 to 2011. This has been achieved through partnership with industry reducing salt content.12 Several recent cohort studies have found a J-shaped association between urinary sodium excretion and a composite of major cardiovascular events and death.13 While this has led to concern about the effect of lowering population salt intake, a review of available cohort studies found inconsistencies in the relationship between sodium intake, with 13 finding a direct relationship, 8 with an inverse relationship and 2 with a J-shaped relationship. All but 1 had inherent methodological limitations which could change the direction of the relationship, including reverse causality and systematic error, and from this the true relationship remains unclear.14 While there are limited interventional studies of salt reduction and cardiovascular disease, a meta-analysis of available studies found that a modest reduction in salt intake lowered cardiovascular events.15 When individuals who participated in the Trial of Hypertension Prevention I and II were followed up subsequent to the trial completion, those randomised to the low salt arm had a 25% reduction of cardiovascular events, despite receiving no further dietary advice after completing the study.16 It remains appropriate to endorse the current guidelines on salt reduction to prevent cardiovascular events, with the National Institute for Health and Care Excellence endorsing salt reduction as the primary public health strategy for the prevention of cardiovascular disease.3

Salt restriction and heart failure

Haemodynamic changes associated with heart failure lead to increased neurohumoral activity, with a vicious circle of sodium and water retention despite a volume overloaded state. While restricting salt intake is established practice in the management of heart failure, the evidence remains limited to observational studies and small randomised controlled trials of salt restriction, often with additional therapeutic interventions.17–20 Given the lack of robust evidence, it is not surprising that, despite being recommended by all current clinical guidelines, there is no consensus on what level of salt restriction would be appropriate. However, restricting salt intake to 5 g/day, levels recommended by the World Health Organization (WHO) for the general population, is a safe, practical and modest intervention, likely to be of benefit and with no evidence of harm. Individuals on high-dose diuretics will require judicious monitoring of fluid balance when implementing a low salt diet, and adjustment of diuretic therapy may be necessary to ensure that they do not become fluid depleted.21

Salt and the kidney

The kidney is the primary regulator of sodium balance and plays a central role in long-term blood pressure regulation. Chronic kidney disease (CKD) is common, affecting up to 13% of adults.22 The vast majority of patients with CKD do not progress to end-stage kidney disease, and the major risk for individuals with CKD is cardiovascular disease, as it is a potent and independent risk factor for cardiovascular death.23 Progressive CKD leads to increasing prevalence of hypertension, which often requires multiple medical therapies to gain adequate control. Individuals are more susceptible to the effects of high salt intake due to reduced renal sodium excretion. Managing high blood pressure is a cornerstone of CKD management, with the aim of reducing both risk of CKD progression and cardiovascular disease.4,24 Evidence suggests that lowering salt intake will be of benefit in CKD, reducing proteinuria and urinary albumin excretion, as well as enhancing the antiproteinuric and antihypertensive effects of blockers of the renin–angiotensin system.25,26 A recent review of interventional studies in CKD concluded that there was evidence that salt reduction lowered blood pressure in patients with CKD, but acknowledged that there was an overall lack of studies in this patient group.27

Challenges to salt reduction

Dietary behaviour for salt avoidance is influenced by a number of factors, including availability, cost and accessibility of lower salt options, perceived reduction in palatability of low-salt food, as well as educational limitations such as lack of perceived benefit or ability to identify lower salt foods.27 With only 15% of salt consumed added at the table and 80% added by the food industry, it requires motivation to reduce salt effectively. Pressure from an action group formed of specialists (Consensus Action on Salt and Health) has been effective at working with the government and the food industry to agree voluntary reduction in the salt content by levels of 10–15%, levels which are not detectable by consumers.1 It is important to reassure individuals that as salt intake reduces, taste buds become more sensitive to salt within a few months. Once taste buds have adjusted, individuals find they prefer food with lower salt content.28 Monitoring adherence to a low-salt diet also has its challenges with measurement of 24-hour urinary sodium excretion; the most accurate way to determine average daily salt intake (Box 1). A careful dietary history may be helpful in identifying highly salty foods. Useful resources for professionals and patients can be found in Box 2.

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Box 1.

Estimating salt intake and sodium content

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Box 2.

Resources for professionals and patients

Conclusions

High salt intake is endemic worldwide and contributes to the generation and maintenance of high blood pressure, the biggest risk factor for global disease. There is now compelling evidence to support salt reduction to lower blood pressure and a substantial body of evidence to support salt reduction in the general population to reduce risk of death from cardiovascular disease. In specific diseases such as heart failure, diabetes and CKD, guidelines support the WHO target for reduced salt intake at 5 g/day, although the evidence is perhaps only now catching up with the guidance. Further evidence from population studies would be helpful to reinforce the current guidance, but intervention studies at that level are not likely to be supported by either industry or government. Collaborations with the food industry, health agencies and government will be necessary to support salt reduction strategies.

  • © Royal College of Physicians 2015. All rights reserved.

References

  1. 1.↵
    1. He FJ
    , MacGregor GA. A comprehensive review on salt and health and current experience of worldwide salt reduction programmes. J Hum Hypertens 2009;23:363–84.
    OpenUrlCrossRefPubMed
  2. 2.↵
    1. World Health Organization
    . Salt reduction. Fact sheet No 393. Geneva: WHO, September 2014. Available online at www.who.int/mediacentre/factsheets/fs393/en/ [Accessed 5 November 2015].
  3. 3.↵
    1. National Institute for Health and Care Excellence
    . Prevention of cardiovascular disease. Guideline PH25. London: NICE, June 2010.
  4. 4.↵
    1. Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO
    2012 clinical practice guideline for the evaluation and management of chronic kidney disease. Kidney Int 2012;Suppl:1–150.
  5. 5.↵
    1. World Health Organisation
    . The world health report 2002 – reducing risks, promoting healthy life. Geneva: WHO, 2002. Available online at www.who.int/whr/2002/en/index.html [Accessed 5 October 2015].
  6. 6.↵
    1. Elliott P
    , Stamler J, Nichols R, et al. Intersalt revisited: further analyses of 24 hour sodium excretion and blood pressure within and across populations. Intersalt Cooperative Research Group. BMJ 1996;312:1249–53.
    OpenUrlAbstract/FREE Full Text
  7. 7.↵
    1. Zhou BF
    , Stamler J, Dennis B, et al. Nutrient intakes of middle-aged men and women in China, Japan, United Kingdom, and United States in the late 1990s: The INTERMAP Study. J Hum Hypertens 2003;17:623–30.
    OpenUrlCrossRefPubMed
  8. 8.↵
    1. Khaw K
    , Bingham S, Welch A, et al. Blood pressure and urinary sodium in men and women: the Norfolk Cohort of the European Prospective Investigation into Cancer (EPIC-Norfolk). Am J Clin Nutr 2004;80:1397–403.
    OpenUrlAbstract/FREE Full Text
  9. 9.↵
    1. 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;346:1325.
    OpenUrl
  10. 10.
    1. MacGregor GA
    , Markandu ND, Sagnella GA, Singer DRJ, Cappuccio FP. Double-blind study of three sodium intakes and long-term effects of sodium restriction in essential hypertension. Lancet 1989;2:1244–7.
    OpenUrlCrossRefPubMed
  11. 11.
    1. Sacks F
    , Svetkey L, Vollmer W, et al. Effects on blood pressure of reduced dietary sodium and the dietary approaches to stop hypertension. N Engl J Med 2001;344:3–10.
    OpenUrlCrossRefPubMed
  12. 12.↵
    1. MacGregor GA
    , He FJ, Pombo-Rodrigues S. Food and the responsibility deal: how the salt reduction strategy was derailed. BMJ 2015;350:h1936
    OpenUrlFREE Full Text
  13. 13.↵
    1. O'Donnell M
    , Mente A, Rangarajan S, et al. Urinary sodium and potassium excretion, mortality, and cardiovascular events. N Engl J Med 2014;371:612–23.
    OpenUrlCrossRefPubMed
  14. 14.↵
    1. Cobb LK
    , Anderson CAM, Elliott P, et al. Methodological issues in cohort studies that relate sodium intake to cardiovascular disease outcomes: a science advisory from the American Heart Association. Circulation 2014;129:1173–86.
    OpenUrlAbstract/FREE Full Text
  15. 15.↵
    1. He FJ
    , MacGregor GA. Salt reduction lowers cardiovascular risk: meta-analysis of outcome trials. Lancet 2011;378:380–3.
    OpenUrlCrossRefPubMed
  16. 16.↵
    1. Cook N
    , Cutler J, Buring J, 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;334:885–8.
    OpenUrlAbstract/FREE Full Text
  17. 17.↵
    1. Gupta D
    , Georgiopoulou VV, Kalogeropoulos AP, et al. Dietary sodium intake in heart failure. Circulation 2012;126:479–85.
    OpenUrlFREE Full Text
  18. 18.↵
    1. He J
    , Ogden LG, Bazzano LA, et al. Dietary sodium intake and incidence of congestive heart failure in overweight US men and women: first National Health and Nutrition Examination Survey Epidemiologic Follow-up Study. Arch Intern Med 2002;162: 1619–24.
    OpenUrlCrossRefPubMed
  19. 19.↵
    1. Hummel SL DA
    , Skorcz S, Montoye CK, Koelling TM. Recommendation of low-salt diet and short-term outcomes in heart failure with preserved systolic function. Am J Med 2009;122:1029–36.
    OpenUrlCrossRefPubMed
  20. 20.↵
    1. Paterna S GP
    , 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;114:221–30.
    OpenUrlCrossRefPubMed
  21. 21.↵
    1. He FJ
    , Burnier M, MacGregor GA. Nutrition in cardiovascular disease: salt in hypertension and heart failure. Eur Heart J 2011;32:3073–80.
    OpenUrlAbstract/FREE Full Text
  22. 22.↵
    1. NHS Information Centre
    . Health Survey for England 2009: health and lifestyles. London: NHS Information Centre, 2009. Available online at www.hscic.gov.uk/pubs/hse09report [Accessed 5 October 2015].
  23. 23.↵
    1. Hallan S
    , Dahl K, Oien C, et al. Screening strategies for chronic kidney disease in the general population: follow-up of cross sectional health survey. BMJ 2006;333:1047.
    OpenUrlAbstract/FREE Full Text
  24. 24.↵
    1. National Institute for Health and Care Excellence
    . Chronic kidney disease: early identification and management of chronic kidney disease in adults in primary and secondary care. CG182. London: NICE, 2014.
  25. 25.↵
    1. MacGregor GA
    , Markandu ND, Singer DRJ, et al. Moderate sodium restriction with angiotensin converting enzyme inhibitor in essential hypertension: a double blind study. BMJ 1987;294:531–4.
    OpenUrlAbstract/FREE Full Text
  26. 26.↵
    1. Houlihan CA
    , Allen TJ, Baxter AL, et al. A low-sodium diet potentiates the effects of losartan in type 2 diabetes. Diabetes Care 2002;25:663–71.
    OpenUrlAbstract/FREE Full Text
  27. 27.↵
    1. McMahon EJ
    , Campbell KL, Mudge DW, Bauer JD. Achieving salt restriction in chronic kidney disease. Int J Nephrol 2012;2012:10.
    OpenUrl
  28. 28.↵
    1. Cappuccio F
    , Capewell S. Facts, issues and controversies in salt reduction for the prevention of cardiovascular disease. Functional Food Rev 2015; 7:41–61.
    OpenUrl
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The health impacts of dietary sodium and a low-salt diet
Rebecca J Suckling, Pauline A Swift
Clinical Medicine Dec 2015, 15 (6) 585-588; DOI: 10.7861/clinmedicine.15-6-585

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The health impacts of dietary sodium and a low-salt diet
Rebecca J Suckling, Pauline A Swift
Clinical Medicine Dec 2015, 15 (6) 585-588; DOI: 10.7861/clinmedicine.15-6-585
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