ABSTRACT

Objective.

To determine the 24-hour urinary sodium and potassium excretions in the Americas.

Methods.

A systematic review and meta-analysis were performed seeking for studies conducted between 1990 and 2021 in adults living in any sovereign state of the Americas in Medline, Embase, Scopus, SciELO, and Lilacs. The search was first run on October 26^th, 2020 and was updated on December 15^th, 2021. Of 3 941 abstracts reviewed, 74 studies were included from 14 countries, 72 studies reporting urinary sodium (27 387 adults), and 42 studies reporting urinary potassium (19 610 adults) carried out between 1990 and 2020. Data were pooled using a random-effects meta-analysis model.

Results.

Mean excretion was 157.29 mmol/24h (95% CI, 151.42-163.16) for sodium and 57.69 mmol/24h (95% CI, 53.35-62.03) for potassium. When only women were considered, mean excretion was 135.81 mmol/24h (95% CI, 130.37-141.25) for sodium and 51.73 mmol/24h (95% CI, 48.77-54.70) for potassium. In men, mean excretion was 169.39 mmol/24h (95% CI, 162.14-176.64) for sodium and 62.67 mmol/24h (95% CI, 55.41-69.93) for potassium. Mean sodium excretion was 150.09 mmol/24h (95% CI, 137.87-162.30) in the 1990s and 159.79 mmol/24h (95% CI, 151.63-167.95) in the 2010s. Mean potassium excretion was 58.64 mmol/24h (95% CI, 52.73-64.55) in the 1990s and 56.33 mmol/24/h (95% CI, 48.65-64.00) in the 2010s.

Conclusions.

These findings suggest that sodium excretions are almost double the maximum level recommended by the World Health Organization and potassium excretions are 35% lower than the minimum requirement; therefore, major efforts to reduce sodium and to increase potassium intakes should be implemented.

Keywords
Sodium, dietary; potassium, dietary; systematic review; Americas

RESUMEN

Objetivo.

Determinar la excreción urinaria de sodio y potasio en 24 horas en la Región de las Américas.

Métodos.

Se realizaron una revisión sistemática y un metanálisis en busca de estudios realizados entre los años 1990 y 2021 con adultos residentes en cualquier Estado soberano de la Región publicados en Medline, Embase, Scopus, SciELO y Lilacs. La búsqueda se llevó a cabo por primera vez el 26 de octubre del 2020 y se actualizó el 15 de diciembre del 2021. De los 3941 resúmenes revisados, se incluyeron 74 estudios de 14 países, 72 estudios sobre excreción urinaria de sodio (27 387 adultos) y 42 estudios sobre excreción urinaria de potasio (19 610 adultos) realizados entre el 1990 y el 2020. Se agruparon los datos mediante un modelo de metanálisis de efectos aleatorios.

Resultados.

La excreción media de sodio fue de 157,29 mmol/24h (IC de 95%, 151,42-163,16); la de potasio, de 57,69 mmol/24 h (IC de 95%, 53,35-62,03). En los casos en que se consideraron únicamente mujeres, la excreción media de sodio fue de 135,81 mmol/24h (IC de 95%, 130,37-141,25); la de potasio, de 51,73 mmol/24h (IC de 95%, 48,77-54,70). En varones, la excreción media de sodio fue de 169,39 mmol/24h (IC de 95%, 162,14-176,64); la de potasio, de 62,67 mmol/24h (IC de 95%, 55,41-69,93). La excreción media de sodio fue de 150,09 mmol/24h (IC de 95%, 137,87-162,30) en la década de 1990 y de 159,79 mmol/24 h (IC de 95%, 151,63-167,95) en la década del 2010. La excreción media de potasio fue de 58,64 mmol/24h (IC de 95%, 52,73-64,55) en la década de 1990 y de 56,33 mmol/24h (IC de 95%, 48,65-64,00) en la década del 2010.

Conclusiones.

Estos resultados sugieren que la excreción de sodio casi duplica el nivel máximo recomendado por la Organización Mundial de la Salud y las excreción de potasio es 35% más baja que el requisito mínimo, por lo que se deben invertir grandes esfuerzos para reducir el consumo de sodio y aumentar la ingesta de potasio.

Palabras clave
Sodio en la dieta; potasio en la dieta; revisión sistemática; Américas

RESUMO

Objetivo.

Determinar as excreções urinárias de sódio e potássio em 24 horas na Região das Américas.

Métodos.

Revisão sistemática e metanálise de estudos realizados entre 1990 e 2021, em adultos vivendo em qualquer estado soberano da região, indexados nos bancos de dados MEDLINE, Embase, Scopus, SciELO e LILACS. A pesquisa foi realizada pela primeira vez em 26 de outubro de 2020 e foi atualizada em 15 de dezembro de 2021. Dos 3.941 resumos revisados, foram incluídos 74 estudos de 14 países, 72 estudos relatando sódio urinário (27.387 adultos) e 42 estudos relatando potássio urinário (19.610 adultos), realizados entre 1990 e 2020. Os dados foram reunidos utilizando um modelo de metanálise de efeitos aleatórios.

Resultados.

A excreção média foi de 157,29 mmol/24h (IC95% 151,42-163,16) para o sódio e 57,69 mmol/24h (IC95% 53,35-62,03) para o potássio. Quando somente mulheres foram consideradas, a excreção média foi de 135,81 mmol/24h (IC95% 130,37-141,25) para o sódio e 51,73 mmol/24h (IC95% 48,77-54,70) para o potássio. Nos homens, a excreção média foi de 169,39 mmol/24h (IC95% 162,14-176,64) para o sódio e 62,67 mmol/24h (IC95% 55,41-69,93) para o potássio. A excreção média de sódio foi de 150,09 mmol/24h (IC95% 137,87-162,30) na década de 1990 e 159,79 mmol/24h (IC95% 151,63-167,95) na década de 2010. A excreção média de potássio foi de 58,64 mmol/24h (IC95% 52,73-64,55) na década de 1990 e 56,33 mmol/24/h (IC95% 48,65-64,00) na década de 2010.

Conclusões.

Estes achados sugerem que as excreções de sódio são quase o dobro do nível máximo recomendado pela Organização Mundial da Saúde e as excreções de potássio são 35% menores do que o mínimo exigido; portanto, será necessário envidar esforços importantes para reduzir a ingestão de sódio e aumentar a de potássio.

Palavras-chave
Sódio na dieta; potássio na dieta; revisão sistemática; América

Raised blood pressure is the leading risk factor for mortality and morbidity worldwide, accounting for 10.8 million annual deaths (¹1. Roth GA, Mensah GA, Johnson CO, Addolorato G, Ammirati E, Baddour LM, et al. Global Burden of Cardiovascular Diseases and Risk Factors, 1990-2019: Update From the GBD 2019 Study. J Am Coll Cardiol. 2020;76(25):2982-3021.). Excessive sodium and low potassium intakes increase blood pressure (²2. He FJ, MacGregor GA. Potassium Intake and Blood Pressure. Am J Hypertens. 1999;12(8):849-51., ³3. He FJ, Tan M, Ma Y, MacGregor GA. Salt Reduction to Prevent Hypertension and Cardiovascular Disease: JACC State-of-the-Art Review. J Am Coll Cardiol. 2020;75(6):632-47.). Moreover, diets high in sodium are among the leading risk factor for non-communicable diseases in the Americas (⁴4. Qiao J, Lin X, Wu Y, Huang X, Pan X, Xu J, et al. Global burden of non-communicable diseases attributable to dietary risks in 1990-2019. J Hum Nutr Diet. 2021;35(1):202-13.); conversely, diets high in potassium lower blood pressure and thus, have protective effects against cardiovascular diseases (⁵5. He FJ, MacGregor GA. Beneficial effects of potassium on human health. Physiologia Plantarum 2008;133(4):725-35.).

The World Health Organization (WHO) recommends limiting sodium intake to <87 mmol/24h (5 g/d of salt) and a minimum potassium intake of 90 mmol/24h (3.5 g/d) for adults (⁶6. World Health Organization. Guideline: sodium intake for adults and children. Geneva: WHO; 2012., ⁷7. World Health Organization. Guideline: potassium intake for adults and children. Geneva: WHO; 2012.). However, the average salt intake in the Americas ranged from ~148 to 261 mmol/24h (8.5-15 g/d of salt) (⁸8. Trieu K, Neal B, Hawkes C, Dunford E, Campbell N, Rodriguez-Fernandez R, et al. Salt Reduction Initiatives around the World – A Systematic Review of Progress towards the Global Target. PLOS One. 2015;10(7):e0130247.). Likewise, an insufficient intake of potassium in the Americas was reported as only ~5% of the adults met the WHO’s recommendation (⁹9. Cogswell ME, Zhang Z, Carriquiry AL, Gunn JP, Kuklina EV, Saydah SH, et al. Sodium and potassium intakes among US adults: NHANES 2003–2008. Am J Clin Nutr. 2012;96(3):647-57.

10. Vallejo M, Colin-Ramirez E, Rivera Mancia S, Cartas Rosado R, Madero M, Infante Vazquez O, et al. Assessment of Sodium and Potassium Intake by 24 h Urinary Excretion in a Healthy Mexican Cohort. Arch Med Res. 2017;48(2):195-202.

11. Harris RM, Rose AMC, Hambleton IR, Howitt C, Forouhi NG, Hennis AJM, et al. Sodium and potassium excretion in an adult Caribbean population of African descent with a high burden of cardiovascular disease. BMC Public Health. 2018;18(1):998.-¹²12. Rodrigues SL, Souza Junior PR, Pimentel EB, Baldo MP, Malta DC, Mill JG, et al. Relationship between salt consumption measured by 24-h urine collection and blood pressure in the adult population of Vitoria (Brazil). Braz J Med Biol. 2015;48(8):728-35.).

Monitoring sodium and potassium intakes is crucial to evaluate their effects on health and improve intakes (¹³13. Flexner N, L'Abbé M, Legowski B, Toledo RG. Mapping Dietary Sodium Reduction Policies and Initiatives in the Region of the Americas. Curr Dev Nutr. 2020;4(2):1714.). As most of the sodium and potassium intakes are excreted through urine, the most accurate method to determine daily intakes is through measurement of 24-hour urinary excretions (¹⁴14. PAHO/WHO. Protocol for population level sodium determination in 24-hour urine samples. Washington, D.C.: Pan American Health Organization; 2010.). However, as the 24-hour urine collection could be challenging other methods such as dietary surveys or spot urines are widely used. In 2010, international sodium intakes were estimated from urinary and dietary data systematically reviewed, and a study published in 2020 also estimated sodium intakes. However, these studies did not estimate potassium intakes and the latter only comprised Latin America populations (¹⁵15. Powles J, Fahimi S, Micha R, Khatibzadeh S, Shi P, Ezzati M, et al. Global, regional and national sodium intakes in 1990 and 2010: a systematic analysis of 24 h urinary sodium excretion and dietary surveys worldwide. BMJ Open. 2013;3(12):e003733., ¹⁶16. Carrillo-Larco RM, Bernabe-Ortiz A. Sodium and Salt Consumption in Latin America and the Caribbean: A Systematic-Review and Meta-Analysis of Population-Based Studies and Surveys. Nutrients. 2020;12(2):556.).

Due to the lack of reliable potassium intake estimates and pursuing to update sodium intake estimates, the objective of this study was to determine the 24-hour urinary sodium and potassium excretions in the Americas. Moreover, this study assessed the trends of sodium and potassium excretions over the past 30 years.

METHODS

Search strategy and selection criteria

A systematic review and meta-analysis of the published literature were performed seeking for studies conducted in any sovereign state of the Americas (North America, South America, Central America and the Caribbean) between 1990 and 2021 that reported 24-hour urinary sodium or potassium excretions for adult women and men.

Medline, Embase, Scopus, SciELO, and LILACS databases were included. No language or study design restrictions were set. The search was first run on October 26^th, 2020 and was updated on December 15^th, 2021.

Search terms were exploded whenever possible (Supplementary material 1) and were defined in English for Medline, Embase, Scopus and in Spanish for SciELO and LILACS, as more results were obtained. Papers in Portuguese were retrieved; as their full text were available in English, the English-language translations were used for data extraction.

Studies including outpatient participants and people living with non-communicable diseases that do not affect sodium or potassium excretions were included. Studies including only hospitalized participants, pregnant women, participants living with conditions that could affect sodium or potassium excretions (e.g., heart failure, renal diseases) or studies with controlled intakes were excluded.

Following the selection criteria, titles and abstracts were screened by IVM. Selected papers were studied in detail and reference lists were manually searched to identify eligible studies. Full papers previously published as conference/meeting abstracts were searched to assess for eligibility. If several papers reported the same study population, the paper that provided the most completed data was selected in the following order: sodium and potassium reported, data for women and men reported, the most recent data reported; uncertainties were solved by consensus with other authors.

Data extraction and analysis

Data on participants’ characteristics, sample size, mean age, sex, country (geographic location), region (North America, South America, Central America and the Caribbean), study design, date and methods of data collection, 24-hour urinary excretions of sodium, potassium, creatinine, and urine volume (mean, standard deviation [SD], standard error of the mean [SEM]) were extracted.

Study authors were contacted via email when: a) date of data collection was missing (n=25), b) SD was missing (n=5) and c) medians were reported instead of means (n=1). Date of data collection was assumed to be 3 years before publication when authors left unanswered (n=15) (¹⁷17. Sánchez-Castillo CP, Escamilla-Cejudo A, Velázquez-A C, Colmenares-Viladomat DA, Bourges R H. 24 hour urine samples needed to characterize the intake of sodium in healthy mexican volunteers. Acta Bioquim Clin. 1993;27(3):313-23.

18. Dawson-Hughes B, Fowler SE, Dalsky G, Gallagher C. Sodium excretion influences calcium homeostasis in elderly men and women. J Nutr. 1996;126(9):2107-12.

19. Espeland MA, Kumanyika S, Wilson AC, Wilcox S, Chao D, Bahnson J, et al. Lifestyle interventions influence relative errors in self-reported diet intake of sodium and potassium. Ann Epidemiol. 2001;11(2):85-93.

20. Carbone LD, Bush AJ, Barrow KD, Kang AH. The relationship of sodium intake to calcium and sodium excretion and bone mineral density of the hip in postmenopausal African-American and Caucasian women. J Bone Miner Metab. 2003;21(6):415-20.

21. Forrester T, Adeyemo A, Soarres-Wynter S, Sargent L, Bennett F, Wilks R, et al. A randomized trial on sodium reduction in two developing countries. J Hum Hypertens. 2005;19(1):55-60.

22. Dawson-Hughes B, Harris SS, Ceglia L. Alkaline diets favor lean tissue mass in older adults. Am J Clin Nutr. 2008;87(3):662-5.

23. Ferreira-Sae M-CS, Gallani M-CB, Nadruz W, Rodrigues RC, Franchini KG, Cabral PC, et al. Reliability and validity of a semi-quantitative FFQ for sodium intake in low-income and low-literacy Brazilian hypertensive subjects. Public Health Nutr. 2009;12(11):2168-73.

24. Arcand J, Floras V, Ahmed M, Al-Hesayen A, Ivanov J, Allard JP, et al. Nutritional inadequacies in patients with stable heart failure. J Acad Nutr Diet. 2009;109(11):1909-13.

25. Ilich JZ, Brownbill RA, Coster DC. Higher habitual sodium intake is not detrimental for bones in older women with adequate calcium intake. Eur J Appl Physiol. 2010;109(4):745-55.

26. Campagnoli T, Gonzalez L, Cruz FS. Salt intake and blood pressure in the University of Asuncion-Paraguay youths: a preliminary study. J Bras Nefrol. 2012;34(4):361-8.

27. Piovesana PdM, Sampaio KdL, Gallani MCBJ. Association between Taste Sensitivity and Self-Reported and Objective Measures of Salt Intake among Hypertensive and Normotensive Individuals. Int Sch Res Notices. 2013;2013:301213.

28. White LH, Bradley TD, Logan AG. Relationship of circadian pattern of urine sodium excretion to hypertension and obstructive sleep apnoea. J Hypertens. 2014;32(11):2253-60.

29. Baudrand R, Campino C, Carvajal CA, Olivieri O, Guidi G, Faccini G, et al. High sodium intake is associated with increased glucocorticoid production, insulin resistance and metabolic syndrome. Clin Endocrinol. 2014;80(5):677-84.

30. Arantes AC, Sousa ALL, Vitorino PVdO, Jardim PCBV, Jardim TdSV, Rezende JM, et al. Effects of added salt reduction on central and peripheral blood pressure. Arq Bras Cardiol. 2020;114(3):554-61.-³¹31. Gallani MC, Proulx-Belhumeur A, Almeras N, Després JP, Doré M, Giguère JF. Development and validation of a salt food frequency questionnaire (FFQ-NA) and a discretionary salt questionnaire (DSQ) for the evaluation of salt intake among French-Canadian population. Nutrients. 2021;13(1):1-16.). Response was not received from studies with missing SD: three reporting sodium (³²32. Ferrante D, Maria G, Monica C, Claudia E, Claudio D, Konfino J, et al. Less Salt, More life Initiative: Strategy to Reduce Sodium Intake in Argentina. Rev Argent Salud Publica. 2015;6(22):35-39.

33. Robare JF, Milas NC, Bayles CM, Williams K, Newman AB, Lovalekar MT, et al. The key to life nutrition program: results from a community-based dietary sodium reduction trial. Public Health Nutr. 2010;13(5):606-14.-³⁴34. Hisamatsu T, Lloyd-Jones DM, Colangelo LA, Liu K. Urinary sodium and potassium excretions in young adulthood and blood pressure by middle age: the Coronary Artery Risk Development in Young Adults (CARDIA) Study. J Hypertens. 2021;39(8):1586-93.), three reporting potassium (²⁶26. Campagnoli T, Gonzalez L, Cruz FS. Salt intake and blood pressure in the University of Asuncion-Paraguay youths: a preliminary study. J Bras Nefrol. 2012;34(4):361-8., ³⁴34. Hisamatsu T, Lloyd-Jones DM, Colangelo LA, Liu K. Urinary sodium and potassium excretions in young adulthood and blood pressure by middle age: the Coronary Artery Risk Development in Young Adults (CARDIA) Study. J Hypertens. 2021;39(8):1586-93., ³⁵35. Rodrigues FG, Lima TM, Zambrano L, Heilberg IP. Dietary pattern analysis among stone formers: resemblance to a DASH-style diet. J Bras Nefrol. 2020;42(3):338-48.), two reporting creatinine (²⁶26. Campagnoli T, Gonzalez L, Cruz FS. Salt intake and blood pressure in the University of Asuncion-Paraguay youths: a preliminary study. J Bras Nefrol. 2012;34(4):361-8., ³⁵35. Rodrigues FG, Lima TM, Zambrano L, Heilberg IP. Dietary pattern analysis among stone formers: resemblance to a DASH-style diet. J Bras Nefrol. 2020;42(3):338-48.). Therefore, missing data were imputed: estimating the mean SD from studies with full data provided carried out in the same country X=∑i=1nXi/n. No response for the study reporting medians instead of means was received (³⁴34. Hisamatsu T, Lloyd-Jones DM, Colangelo LA, Liu K. Urinary sodium and potassium excretions in young adulthood and blood pressure by middle age: the Coronary Artery Risk Development in Young Adults (CARDIA) Study. J Hypertens. 2021;39(8):1586-93.); thus, the median was considered as the mean since previous urinary sodium data from the country was normally distributed, expecting that mean and median had similar values (³⁶36. Allen NB, Zhao L, Loria CM, Van Horn L, Wang C-Y, Pfeiffer CM, et al. The Validity of Predictive Equations to Estimate 24-Hour Sodium Excretion: The MESA and CARDIA Urinary Sodium Study. Am J Epidemiol. 2017;186(2):149-59.).

All measures were converted into millimoles (1 mmol sodium=1 mEq sodium=23 mg sodium; 1 mmol potassium=1 mEq potassium=39.1 mg potassium). If SEM was not reported, it was calculated from the SD and sample size. If the period of data collection covered more than a year, the midpoint was used. When both baseline and end-of-trial measurements were reported, only the former (n=15) (¹⁹19. Espeland MA, Kumanyika S, Wilson AC, Wilcox S, Chao D, Bahnson J, et al. Lifestyle interventions influence relative errors in self-reported diet intake of sodium and potassium. Ann Epidemiol. 2001;11(2):85-93., ²¹21. Forrester T, Adeyemo A, Soarres-Wynter S, Sargent L, Bennett F, Wilks R, et al. A randomized trial on sodium reduction in two developing countries. J Hum Hypertens. 2005;19(1):55-60., ²²22. Dawson-Hughes B, Harris SS, Ceglia L. Alkaline diets favor lean tissue mass in older adults. Am J Clin Nutr. 2008;87(3):662-5., ²⁴24. Arcand J, Floras V, Ahmed M, Al-Hesayen A, Ivanov J, Allard JP, et al. Nutritional inadequacies in patients with stable heart failure. J Acad Nutr Diet. 2009;109(11):1909-13., ²⁵25. Ilich JZ, Brownbill RA, Coster DC. Higher habitual sodium intake is not detrimental for bones in older women with adequate calcium intake. Eur J Appl Physiol. 2010;109(4):745-55., ³⁰30. Arantes AC, Sousa ALL, Vitorino PVdO, Jardim PCBV, Jardim TdSV, Rezende JM, et al. Effects of added salt reduction on central and peripheral blood pressure. Arq Bras Cardiol. 2020;114(3):554-61., ³³33. Robare JF, Milas NC, Bayles CM, Williams K, Newman AB, Lovalekar MT, et al. The key to life nutrition program: results from a community-based dietary sodium reduction trial. Public Health Nutr. 2010;13(5):606-14., ³⁷37. 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.

38. Ferrante D, Apro N, Ferreira V, Virgolini M, Aguilar V, Sosa M, et al. Feasibility of salt reduction in processed foods in Argentina. Rev Panam Salud Publica. 2011;29(2):69-75.

39. Rodrigues Moreira Lima ST, da Silva Nalin de Souza B, Franca AKT, Salgado Filho N, Sichieri R. Dietary approach to hypertension based on low glycaemic index and principles of DASH (Dietary Approaches to Stop Hypertension): a randomised trial in a primary care service. Br J Nutr. 2013;110(8):1472-9.

40. de Freitas Agondi R, Cornélio ME, Rodrigues RCM, Gallani M-C. Implementation Intentions on the Effect of Salt Intake among Hypertensive Women: A Pilot Study. Nurs Res Pract. 2014;2014:196410.

41. Cornelio ME, Godin G, Rodrigues RC, de Freitas Agondi R, Alexandre NM, Gallani M-CB. Effect of a behavioral intervention of the SALdavel program to reduce salt intake among hypertensive women: A randomized controlled pilot study. Eur J Cardiovasc Nurs. 2015;15(3):e85-94.

42. Appel LJ, Champagne CM, Harsha DW, Cooper LS, Obarzanek E, Elmer PJ, et al. Effects of comprehensive lifestyle modification on blood pressure control: main results of the PREMIER clinical trial. JAMA. 2003;289(16):2083-93.

43. Frassetto LA, Nash E, Morris RC, Jr., Sebastian A. Comparative effects of potassium chloride and bicarbonate on thiazide-induced reduction in urinary calcium excretion. Kidney Int. 2000;58(2):748-52.-⁴⁴44. Calhoun DA, Nishizaka MK, Zaman MA, Thakkar RB, Weissmann P. Hyperaldosteronism among black and white subjects with resistant hypertension. Hypertension. 2002;40(6):892-6.), or the control group were included (n=4) (²⁸28. White LH, Bradley TD, Logan AG. Relationship of circadian pattern of urine sodium excretion to hypertension and obstructive sleep apnoea. J Hypertens. 2014;32(11):2253-60., ³⁵35. Rodrigues FG, Lima TM, Zambrano L, Heilberg IP. Dietary pattern analysis among stone formers: resemblance to a DASH-style diet. J Bras Nefrol. 2020;42(3):338-48., ⁴⁵45. Arcand J, Floras JS, Azevedo E, Mak S, Newton GE, Allard JP. Evaluation of 2 methods for sodium intake assessment in cardiac patients with and without heart failure: the confounding effect of loop diuretics. Am J Clin Nutr. 2011;93(3):535-41., ⁴⁶46. Vitales-Noyola M, Layseca-Espinosa E, Baranda L, Abud-Mendoza C, Niño-Moreno P, Monsiváis-Urenda A, et al. Analysis of sodium chloride intake and Treg/Th17 lymphocytes in healthy individuals and patients with rheumatoid arthritis or systemic lupus erythematosus. J Immunol Res. 2018;2018:9627806.).

Bias of each study was evaluated using a critical appraisal checklist developed for systematic reviews of observational epidemiological studies (⁴⁷47. Munn Z, Moola S, Lisy K, Riitano D, Tufanaru C. Methodological guidance for systematic reviews of observational epidemiological studies reporting prevalence and cumulative incidence data. Int J Evid Based Healthc. 2015;13(3):147-53.) adapted by Tan et al. (⁴⁸48. Tan M, He FJ, Wang C, MacGregor GA. Twenty-Four-Hour Urinary Sodium and Potassium Excretion in China: A Systematic Review and Meta-Analysis. J Am Heart Assoc. 2019;8(14):e012923.) to assess the quality of sampling, reporting, measurement, analysis, rigor of 24-hour urine collection, and response rate through 9 questions (Supplementary material 2). Studies reporting sodium and potassium were assessed separately.

Data were pooled using a random-effects meta-analysis model. Main analyses were carried out with all the studies retrieved. Subgroup analyses were performed to determine sodium and potassium excretions by sex, region, rigor of 24-hour urine collection (24-hour collection was considered rigorous if its completeness was assessed or reported), decade of collection (1990s, 2000s and 2010s), and income level at the year of data collection according to the World Bank (low, lower-middle, upper-middle, high income level (⁴⁹49. Umar S HNWB. New World Bank country classifications by income level: 2020-2021. World Bank; 2021 [Available from: https://blogs.worldbank.org/opendata/new-world-bank-country-classifications-income-level-2020-2021
https://blogs.worldbank.org/opendata/new... ), Supplementary material 3).

Figures to illustrate trends of consumption per decade were made. Tests for subgroup differences were run. One study that collected data in 2020 was considered part of the 2010s. Further analyses to explore excretions per decade segregated by country or income level were not feasible due to the small number of studies available.

Only 5 studies were retrieved from lower-middle income countries; thus, they were grouped with the upper-middle income countries. Studies from low-income countries were not retrieved; main analyses were conducted considering only two income level groups. Due to the limited number of studies from Central America and the Caribbean (n=5) they were included as part of the South America region. There were few studies that provided data stratified by age (n=9) or by hypertension status (n=8); however, it was not feasible to subgrouping (e.g., young vs older adults) since age groups wide-ranging and due to the small number of studies.

Sensitivity analyses were run excluding studies with outpatient participants, studies including participants with hypertension, studies with imputed data, and with the original classifications for region and income level. Moreover, an alternative SD imputation method was employed considering the mean SD of all the included studies with full data provided. This decision was made to assess whether results would be significantly different when other imputation approach is used.

In exploratory analyses, meta-regression analyses were conducted with either 24-hour sodium or potassium as the dependent variable (mmol/24h) and the independent predictors were study characteristics: mean participants’ age, proportion of men, geographic location (each country coded as a unit from north to south), rigor of 24-hour urine collection, data collection year, income level (high-income economies as reference) and proportion of people with hypertension.

Statistical analysis

All analyses were performed using R (version 4.0.3) with the packages “meta” (version 4.15-1) and “metafor” (version 2.4-0). A 2-sided p value of <0.05 was considered significant.

RESULTS

The search yielded 4 204 papers identified via databases and 6 papers via manual searching; 269 duplicates were excluded, and 3 941 titles and abstract were screened. 3 795 papers were excluded as they did not meet inclusion criteria and 6 papers were not retrieved. Finally, 142 papers plus one conference paper published were selected for full-text review. A total of 74 studies (reported in 71 papers) were included: 72 reported sodium and 40 also reported potassium, plus two studies that only reported potassium (Figure 1) (¹⁰10. Vallejo M, Colin-Ramirez E, Rivera Mancia S, Cartas Rosado R, Madero M, Infante Vazquez O, et al. Assessment of Sodium and Potassium Intake by 24 h Urinary Excretion in a Healthy Mexican Cohort. Arch Med Res. 2017;48(2):195-202.

11. Harris RM, Rose AMC, Hambleton IR, Howitt C, Forouhi NG, Hennis AJM, et al. Sodium and potassium excretion in an adult Caribbean population of African descent with a high burden of cardiovascular disease. BMC Public Health. 2018;18(1):998.-¹²12. Rodrigues SL, Souza Junior PR, Pimentel EB, Baldo MP, Malta DC, Mill JG, et al. Relationship between salt consumption measured by 24-h urine collection and blood pressure in the adult population of Vitoria (Brazil). Braz J Med Biol. 2015;48(8):728-35., ¹⁷17. Sánchez-Castillo CP, Escamilla-Cejudo A, Velázquez-A C, Colmenares-Viladomat DA, Bourges R H. 24 hour urine samples needed to characterize the intake of sodium in healthy mexican volunteers. Acta Bioquim Clin. 1993;27(3):313-23.

18. Dawson-Hughes B, Fowler SE, Dalsky G, Gallagher C. Sodium excretion influences calcium homeostasis in elderly men and women. J Nutr. 1996;126(9):2107-12.

19. Espeland MA, Kumanyika S, Wilson AC, Wilcox S, Chao D, Bahnson J, et al. Lifestyle interventions influence relative errors in self-reported diet intake of sodium and potassium. Ann Epidemiol. 2001;11(2):85-93.

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51. Melse-Boonstra A, Rozendaal M, Rexwinkel H, Gerichhausen MJ, van den Briel T, Bulux J, et al. Determination of discretionary salt intake in rural Guatemala and Benin to determine the iodine fortification of salt required to control iodine deficiency disorders: studies using lithium-labeled salt. Am J Clin Nutr. 1998;68(3):636-41.

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59. Bedford JL, Barr SI. Higher urinary sodium, a proxy for intake, is associated with increased calcium excretion and lower hip bone density in healthy young women with lower calcium intakes. Nutrients. 2011;3(11):951-61.

60. Luzardo L, Sottolano M, Lujambio I, Boggia J, Barindelli A, Noboa O. Aproximación clínica al consumo de sodio. Rev Med Urug. 2011;27(4):228-37.

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62. Mill JG, Silva ABTd, Baldo MP, Molina MCB, Rodrigues SL. Correlation between sodium and potassium excretion in 24- and 12-h urine samples. Braz J Med Biol. 2012;45(9):799-805.

63. Tayo BO, Luke A, McKenzie CA, Kramer H, Cao G, Durazo-Arvizu R, et al. Patterns of sodium and potassium excretion and blood pressure in the African Diaspora. J Hum Hypertens. 2012;26(5):315-24.

64. Gerber LM, Mann SJ. Inaccuracy of self-reported low sodium diet. Am J Hum Bio. 2012;24(2):189-91.

65. Cohall DH, Scantlebury-Manning T, Nakhleh C, Toure D, James S, Hall K. Predicting 24-hour urinary sodium excretion in Afro-Caribbean Barbadians by comparing urine sodium excretion over different durations versus spot collection. West Indian Med J. 2013;62(3):181-5.

66. Cohall DH, Scantlebury-Manning T, Rafie C, James S, Hall K. Dietary potassium intake and renal handling, and their impact on the cardiovascular health of normotensive afro-caribbeans. West Indian Med J. 2014;63(1):13-9.

67. Cornejo K, Pizarro F, Atalah E, Galgani JE. Assessment of dietary intake and urinary excretion of sodium and potassium in adults. Rev Med Chil. 2014;142(6):687-95.

68. Wang C-Y, Carriquiry AL, Chen T-C, Loria CM, Pfeiffer CM, Liu K, et al. Estimating the population distribution of usual 24-hour sodium excretion from timed urine void specimens using a statistical approach accounting for correlated measurement errors. J Nutr. 2015;145(5):1017-24.

69. Wielgosz A, Robinson C, Mao Y, Jiang Y, Campbell NRC, Muthuri S, et al. The Impact of Using Different Methods to Assess Completeness of 24-Hour Urine Collection on Estimating Dietary Sodium. J Clin Hypertens. 2016;18(6):581-4.

70. Mente A, Dagenais G, Wielgosz A, Lear SA, McQueen MJ, Zeidler J, et al. Assessment of Dietary Sodium and Potassium in Canadians Using 24-Hour Urinary Collection. Can J Cardiol. 2016;32(3):319-26.

71. Campino C, Hill C, Baudrand R, Martinez-Aguayo A, Aglony M, Carrasco CA, et al. Usefulness and Pitfalls in Sodium Intake Estimation: Comparison of Dietary Assessment and Urinary Excretion in Chilean Children and Adults. Am J Hypertens. 2016;29(10):1212-7.

72. Fernández V, Sobrero MS, Brissón C, Marsili N, Belzarena RB, Bartolomé J, et al. Reference values for urinary oxalate, calcium, citrate, uric acid, phosphate, magnesium, sulphate and sodium in biochemistry students at universidad nacional del litoral, Argentina. Rev Nefrol Dialisis Transp. 2017;37(3):146-56.

73. Elfassy T, Yi SS, Llabre MM, Schneiderman N, Gellman M, Florez H, et al. Neighbourhood socioeconomic status and cross-sectional associations with obesity and urinary biomarkers of diet among New York City adults: the heart follow-up study. BMJ Open. 2017;7(12):e018566.

74. Mossavar-Rahmani Y, Sotres-Alvarez D, Wong WW, Loria CM, Gellman MD, Van Horn L, et al. Applying recovery biomarkers to calibrate self-report measures of sodium and potassium in the Hispanic Community Health Study/Study of Latinos. J Hum Hypertens. 2017;31(7):462-73.

75. Padilha BM, Ferreira RC, Bueno NB, Tassitano RM, Holanda LdS, Vasconcelos SML, et al. Association between blood cholesterol and sodium intake in hypertensive women with excess weight. Medicine. 2018;97(15):e0371.

76. Perin MS, Cornélio ME, Oliveira HC, São-João TM, Rhéaume C, Gallani M-CBJ. Dietary sources of salt intake in adults and older people: a population-based study in a Brazilian town. Public Health Nutr. 2019;22(8):1388-97. Epub 2018 Nov 26. PMID: 30472972.

77. Sisa I, Herrera-Fontana Ma, Bovera Ma, Palomeque Ma, Teran E. Urinary sodium excretion in a young to middle-aged adults urban population: a pilot study in Ecuador. Rev Salud Publica. 2018;20(5):568-73.

78. Vega-Vega O, Fonseca-Correa J, Mendoza-De la Garza A, Rincón-Pedrero R, Espinosa-Cuevas A, Baeza-Arias Y, et al. Contemporary Dietary Intake: Too Much Sodium, Not Enough Potassium, yet Sufficient Iodine: The SALMEX Cohort Results. Nutrients. 2018;10(7):816.

79. Carrillo-Larco RM, Saavedra-Garcia L, Miranda JJ, Sacksteder KA, Diez-Canseco F, Gilman RH, et al. Sodium and Potassium Consumption in a Semi-Urban Area in Peru: Evaluation of a Population-Based 24-Hour Urine Collection. Nutrients. 2018;10(2):245.

80. Moliterno P, Alvarez-Vaz R, Pecora M, Luzardo L, Borgarello L, Olascoaga A, et al. Blood Pressure in relation to 24-Hour Urinary Sodium and Potassium Excretion in a Uruguayan Population Sample. Int J Hypertens. 2018;2018:6956078.

81. Cogswell ME, Loria CM, Terry AL, Zhao L, Wang C-Y, Chen T-C, et al. Estimated 24-Hour Urinary Sodium and Potassium Excretion in US Adults. JAMA. 2018;319(12):1209-20.

82. Mann SJ, Gerber LM. Addressing the problem of inaccuracy of measured 24-hour urine collections due to incomplete collection. J Clin Hypertens. 2019;21(11):1626-34.

83. Oliveira LS, Schade-Coelho J, Herzog-Siqueira JT-SN-M, Silva-Pereira T-S, Bisi-Molina M-d-C. Sodium/potassium urinary ratio and consumption of processed condiments and ultraprocessed foods. Nutr Hosp. 2019;36(1):125-132.

84. Cunha MR, Cunha AR, Marques BCAA, Mattos SS, D’El-Rei J, França NM, et al. Association of urinary sodium/potassium ratio with structural and functional vascular changes in non-diabetic hypertensive patients. J Clin Hypertens. 2019;21(9):1360-9.

85. Al-Shaar L, Yuan C, Rosner B, Dean SB, Ivey KL, Clowry CM, et al. Reproducibility and Validity of a Semiquantitative Food Frequency Questionnaire in Men Assessed by Multiple Methods. Am J Epidemiol. 2021;190(6):1122-32. Published online 2020 Dec 22.

86. Sepúlveda RA, Huidobro E JP, Jara A, Tagle R. A new equation to estimate daily natriuresis from parameters in plasma and spot urine sample in the Chilean population. Rev Med Chil. 2021;149(2):178-86.-⁸⁷87. Heeney ND, Lee RH, Hockin BCD, Clarke DC, Sanatani S, Armstrong K, et al. At-home determination of 24-h urine sodium excretion: Validation of chloride test strips and multiple spot samples. Auton Neurosci. 2021;233:102797.).

One multisite study reported separate estimates for two countries (⁶³63. Tayo BO, Luke A, McKenzie CA, Kramer H, Cao G, Durazo-Arvizu R, et al. Patterns of sodium and potassium excretion and blood pressure in the African Diaspora. J Hum Hypertens. 2012;26(5):315-24.); each site was considered as an individual study. One paper reported two different studies; however, one was carried before 1990 and was excluded (³⁷37. 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.). One paper reported individual data for three different studies, and each was treated as an individual study (⁸⁸88. Curhan GC, Willett WC, Speizer FE, Stampfer MJ. Twenty-four-hour urine chemistries and the risk of kidney stones among women and men. Kidney Int. 2001;59(6):2290-8.).

The 72 studies reporting 24-hour urinary sodium data were drawn from 27 387 adults: 44.6% men, mean age 47.5 years. The 42 studies reporting 24-hour urinary potassium data were drawn from 19 610 adults: 44.5% men, mean age 46.1 years.

The data spanned from 1990 to 2020 and covered 14 of the 35 sovereign states of the Americas, (Argentina, n=3 [1 study with missing sodium SD]); Barbados, n=3; Brazil, n=16 (1 study with missing creatinine SD); Canada, n=8; Chile, n=4; Ecuador, n=1; Guatemala, n=1; Jamaica, n=2; Mexico, n=5; Paraguay, n=1 (1 study with missing potassium and creatinine SD); Peru, n=1; Uruguay, n=2; United States, n=26 (2 studies with missing sodium SD and 1 with missing potassium SD); Venezuela, n=1]. One 24-hour urine sample was collected per participant in 79.1% (n=57) of the studies reporting sodium and 71.4% (n=30) of the studies reporting potassium. More than half of the studies were carried out in high income countries.

24-hour urine collection was considered rigorous in 62.5% (n=45) of studies reporting sodium and 71.4% (n=30) of studies reporting potassium. The characteristics of the studies and participants are provided in Supplementary material 4. The risk of bias of each study varied substantially across criteria (Supplementary material 5).

Mean sodium excretion was 157.29 mmol/24h (95% CI, 151.42-163.16) (Figure 2) with an I²=98.5% (95% CI, 98.3-98.6) and mean potassium excretion was 57.69 mmol/24h (95% CI, 53.35-62.03) (Figure 3) with an I²=99.5% (95% CI, 99.5-99.6). Mean creatinine excretion was 11.70 mmol/24h (95% CI, 10.81-12.59). Mean urine volume was 1.73 l/24h (95% CI, 1.60-1.85).

The analyses by sex showed higher excretion of both electrolytes in men with a mean sodium excretion of 169.39 mmol/24h (95% CI, 162.14-176.64), and mean potassium excretion of 62.67 mmol/24h (95% CI, 55.41-69.93). In women, mean sodium excretion was 135.81 mmol/24h (95% CI, 130.37-141.25) and mean potassium excretion was 51.73 mmol/24h (95% CI, 48.77-54.70). In meta-regression analyses, a significantly higher excretion of both electrolytes was found among men, that remained significant after adjusting for age, geographic location, rigor of 24-hour urine collection, year of data collection, income level and percentage of people living with hypertension (p<0.01; table 1).

A higher sodium excretion in Central America, South America and the Caribbean was found, 163.88 mmol/24h (95% CI, 152.83-174.92), in comparison with North America, 151.48 mmol/24h (95% CI, 144.20-158.75). Potassium excretion was higher in North America, 62.16 mmol/24h (95% CI, 57.36-66.95), in comparison with Central America, South America and the Caribbean, 52.02 mmol/24h (95% CI, 47.06-56.97) (Supplementary materials 6-7). In meta-regression analyses, geographic location was associated positively with an increased sodium excretion in the south (p<0.01) that remained significant after adjusting for other potential modifiers. A lower excretion of potassium appeared in univariate analyses (p=0.01) which was no longer significant after adjusting for other covariables (Table 1).

Subgroup analyses by income level showed that high-income countries had a lower sodium excretion, 154.19 mmol/24h (95% CI, 146.83-161.54), in comparison with lower-middle and upper-middle income countries, 160.91 mmol/24h (95% CI, 150.28-171.55). For potassium, it was found that the lower the income level, the lower the potassium excretion: lower-middle and upper-middle income countries presented an excretion of 50.07 mmol/24h (95% CI, 45.46-54.68), vs. high-income countries, 63.24 mmol/24h (95% CI, 58.20-68.27). Meta-regression analyses did not show significant association between income level and sodium excretion; for potassium, high income countries showed a higher excretion (p<0.01), but after adjustment for multiple covariates was no longer statistically significant (Table 1).

Among studies in which the 24-hour urine was assessed for completeness, mean excretions were 156.42 mmol/24h (95% CI, 149.84-163.00) for sodium and 57.35 mmol/24h (95% CI, 52.54-62.16) for potassium. Mean excretions were 158.62 mmol/24h (95% CI, 145.83-171.41) for sodium, and 58.56 mmol/24h (95% CI, 47.28-69.84) for potassium (Supplementary materials 6-7) among studies with 24-hour urine completeness assessment not performed or not reported. Meta-regression analyses did not show significant association between rigor of 24-hour urine collection and urinary excretions.

The analyses per decade of data collection showed a slightly increasing trends in sodium excretion, from an excretion of 150.09 mmol/24h (95% CI, 137.87-162.30) in the 1990s, to 158.99 mmol/24h (95% CI, 143.99-173.99) in the 2000s, to 159.79 mmol/24h (95% CI, 151.63-167.95) in the 2010s (Figure 4a). For potassium, there were relatively stable trends, with an excretion of 58.64 mmol/24h (95% CI, 52.73-64.55) in the 1990s, 59.95 mmol/24h (95% CI, 53.02-66.88) in the 2000s, and 56.33 mmol/24h (95% CI, 48.65-64.00) in the 2010s (Figure 4b). However, these trends were not statistically significant, neither significant association between year of data collection and sodium or potassium excretions appeared in the meta-regression analyses (Table 1).

Sensitivity analyses findings for sodium remained unchanged apart from differences when alternative groupings were used for region and income level. In the base analyses, sodium excretions were higher in Central America, the Caribbean and South America; however, in the analyses with Central America and the Caribbean as an independent region, lower sodium excretions appeared in Central America and the Caribbean in comparison with North America and South America. The latter still presented the highest sodium excretions. Likewise, lower-middle and upper-middle income countries presented higher sodium excretions in the base analyses, but when the lower- and upper-middle income countries were split into two groups, lower sodium excretions were shown among the lower-middle income countries, without affecting the higher sodium excretions pattern among upper-middle income countries (Supplementary material 6). For potassium, all findings remained unchanged (Supplementary material 7).

DISCUSSION

This work summarizes the increasing trends of urinary sodium and relatively stable trends of urinary potassium excretions from the 1990s to the 2020s in the Americas, reported through the most accurate method of assessment, i.e., 24-hour urine collection. The most recent means (2010s) of 24-hour sodium and potassium excretions were 159.79 mmol (equivalent to 9.2 g of salt), and 56.33 mmol (equivalent to 2.2 g of potassium). Moreover, these results denote the high sodium and low potassium excretions that could be linked to the high rates of hypertension and cardiovascular disease in the Americas (⁸⁹89. World Health Organization. Global Status Report on noncommunicable diseases. Geneva: WHO; 2014., ⁹⁰90. Nugent R, Bertram MY, Jan S, Niessen LW, Sassi F, Jamison DT, et al. Investing in non-communicable disease prevention and management to advance the Sustainable Development Goals. Lancet. 2018;391(10134):2029-35.).

Subgroup analyses showed different patterns of excretion per region, with a sodium excretion of 151.48 mmol/24h in North America, lower in comparison with Central America, the Caribbean, and South America of 163.88 mmol/24h.

Carrillo-Larco and Bernabé-Ortiz quantified a daily sodium excretion of 4.13 g (~179 mmol/24h) in Latin America and the Caribbean (¹⁶16. Carrillo-Larco RM, Bernabe-Ortiz A. Sodium and Salt Consumption in Latin America and the Caribbean: A Systematic-Review and Meta-Analysis of Population-Based Studies and Surveys. Nutrients. 2020;12(2):556.), while Powles et al. stated a daily sodium excretion in North America (United States and Canada) of 3.62 g (~157.3 mmol/24h), 2.61 g (~113.4 mmol/24h) in the Caribbean and 3.19 g (~138.6mmol/24h) in Central America (¹⁵15. Powles J, Fahimi S, Micha R, Khatibzadeh S, Shi P, Ezzati M, et al. Global, regional and national sodium intakes in 1990 and 2010: a systematic analysis of 24 h urinary sodium excretion and dietary surveys worldwide. BMJ Open. 2013;3(12):e003733.); both estimations were constructed with dietary and urinary data including spot and 24-hour urine samples.

Unfortunately, these data cannot be directly compared with the mentioned estimates since each analysis employed different methods (e.g., dietary records or models to estimate excretions) but the results pointed out sodium excretions higher than the maximum level recommended by the WHO. A few studies included in this review reported sodium excretions slightly below the WHO’s recommendation; these studies were based in small sample sizes (⁵¹51. Melse-Boonstra A, Rozendaal M, Rexwinkel H, Gerichhausen MJ, van den Briel T, Bulux J, et al. Determination of discretionary salt intake in rural Guatemala and Benin to determine the iodine fortification of salt required to control iodine deficiency disorders: studies using lithium-labeled salt. Am J Clin Nutr. 1998;68(3):636-41.), convenience samples (⁷⁷77. Sisa I, Herrera-Fontana Ma, Bovera Ma, Palomeque Ma, Teran E. Urinary sodium excretion in a young to middle-aged adults urban population: a pilot study in Ecuador. Rev Salud Publica. 2018;20(5):568-73.), or control samples for diseases related to uncommon genetic alterations (⁴⁶46. Vitales-Noyola M, Layseca-Espinosa E, Baranda L, Abud-Mendoza C, Niño-Moreno P, Monsiváis-Urenda A, et al. Analysis of sodium chloride intake and Treg/Th17 lymphocytes in healthy individuals and patients with rheumatoid arthritis or systemic lupus erythematosus. J Immunol Res. 2018;2018:9627806.).

Higher sodium excretions and lower potassium excretions were found among lower-middle and upper-middle income countries in comparison to high-income countries. Also, more studies were carried out in high income countries as previous reviews reported (⁹¹91. Thout SR, Santos JA, McKenzie B, Trieu K, Johnson C, McLean R, et al. The Science of Salt: Updating the evidence on global estimates of salt intake. J Clin Hypertens. 2019;21(6):710-21., ⁹²92. Hawkes C, Webster J. National approaches to monitoring population salt intake: a trade-off between accuracy and practicality? PloS One. 2012;7(10):e46727.). Thus, there is a need to conduct further research to determine sodium and potassium excretions in low-income and lower-middle income countries.

In the analyses per decade, slightly increases in 24-hour urinary sodium excretions were observed increasing from 150.09 in 1990s to 159.79 mmol/d in 2010s. Moreover, countries located in the south showed significantly higher sodium excretions. This can be partially explained by the fact that in the Americas, especially in Latin America, the availability, and sales of processed food with high amounts of sodium had been increasing in the last decades (⁹³93. Pan American Health Organization. Ultra-processed food and drink products in Latin America: Sales, sources, nutrient profiles, and policy implications. Washington, D.C.: Pan American Health Organization; 2019.). Since 2009, the Pan American Health Organization (PAHO) has been supporting the development and implementation of country level and cost effectiveness strategies to reduce sodium intake (¹³13. Flexner N, L'Abbé M, Legowski B, Toledo RG. Mapping Dietary Sodium Reduction Policies and Initiatives in the Region of the Americas. Curr Dev Nutr. 2020;4(2):1714.); these findings, however, call for more interventions and policies. Recently, new nutrition policies have been adopted in upper-middle and high income countries that are recognized by their potential to reduce sodium intake such as the front-of-pack labelling (⁹⁴94. Kanter R, Reyes M, Vandevijvere S, Swinburn B, Corvalán C. Anticipatory effects of the implementation of the Chilean Law of Food Labeling and Advertising on food and beverage product reformulation. Obes Rev. 2019(20):129-40.). Future research will be needed to determine their effectiveness in reducing sodium intakes.

Additionally, other policies have been adopted. For example, Argentina was the first country in the region to introduce mandatory sodium targets for specific food groups (³²32. Ferrante D, Maria G, Monica C, Claudia E, Claudio D, Konfino J, et al. Less Salt, More life Initiative: Strategy to Reduce Sodium Intake in Argentina. Rev Argent Salud Publica. 2015;6(22):35-39.). Also, most of the countries have established public awareness programs and educational materials to reduce sodium consumption with the participation of governments, academia and civil society, e.g., salt awareness week (¹³13. Flexner N, L'Abbé M, Legowski B, Toledo RG. Mapping Dietary Sodium Reduction Policies and Initiatives in the Region of the Americas. Curr Dev Nutr. 2020;4(2):1714.). However, fiscal policies such as sodium taxes have not yet been established by any country included in this analysis and more efforts to establish supportive environments to reduce sodium consumption should be made (¹³13. Flexner N, L'Abbé M, Legowski B, Toledo RG. Mapping Dietary Sodium Reduction Policies and Initiatives in the Region of the Americas. Curr Dev Nutr. 2020;4(2):1714.).

Salt is used as a vehicle to prevent iodine deficiency disorders; thus, cutting its consumption could potentially lead to an insufficient iodine intake if fortification levels are not adjusted accordingly. In order to prevent iodine deficiency disorders, several technical groups led by the WHO and the PAHO recommend monitoring iodine intakes and adjusting the level of iodine fortification in table salt or other food products when iodine deficiency disorders appeared (⁹⁵95. PAHO/WHO. PAHO/WHO Regional expert group for cardiovascular disease prevention through population-wide dietary salt reduction. PAHO/WHO; 2011.).

Furthermore, there are different methods available to estimate sodium and potassium intakes. It is recommended that countries should determine baseline intakes and monitor them ideally through 24-hour urine collection (¹⁴14. PAHO/WHO. Protocol for population level sodium determination in 24-hour urine samples. Washington, D.C.: Pan American Health Organization; 2010.). However, it is a costly and burdensome data collection method, and missed or lost samples or under/over collection due to incorrect timing are commonly reported. Thus, other methods such as spot urinary sodium concentration could potentially be used to monitor the percentage change in sodium intake in the population (⁹⁶96. Terry AL, Cogswell ME, Wang C-Y, Chen T-C, Loria CM, Wright JD, et al. Feasibility of collecting 24-h urine to monitor sodium intake in the National Health and Nutrition Examination Survey. Am J Clin Nutr. 2016;104(2):480-8.).

Incomplete urine samples were excluded in more than half of the studies included in this review. Incomplete urine samples were defined as, e.g., samples that do not meet minimum creatinine levels or volume. Thus, these findings could be used to inform which countries or regions had accurately estimated sodium and potassium excretions in the past three decades.

For potassium, insufficient excretions were drawn from all included countries. This data did not differ from the United States national dietary survey (NHANES) carried out in 2003-2008, that reported a median potassium excretion of ~67.28 mmol/24h. Moreover, they reported 98% of the population did not meet WHO’s potassium intake recommendations (⁹9. Cogswell ME, Zhang Z, Carriquiry AL, Gunn JP, Kuklina EV, Saydah SH, et al. Sodium and potassium intakes among US adults: NHANES 2003–2008. Am J Clin Nutr. 2012;96(3):647-57.). More recent data from the NHANES 2014 reported a median potassium excretion of ~51.15 mmol/24h, denoting a decrease of potassium intakes at populational level (⁸¹81. Cogswell ME, Loria CM, Terry AL, Zhao L, Wang C-Y, Chen T-C, et al. Estimated 24-Hour Urinary Sodium and Potassium Excretion in US Adults. JAMA. 2018;319(12):1209-20.). These findings highlight the urgent need to adopt strategies to increase potassium intake, mainly through the promotion of fruit and vegetable consumption. Also, since potassium helps to maintain blood pressure levels in normal ranges, promoting its intake could help to mitigate health effects due to high sodium intakes (⁵5. He FJ, MacGregor GA. Beneficial effects of potassium on human health. Physiologia Plantarum 2008;133(4):725-35.).

Strengths and limitations

To the authors’ knowledge, this is the first study to systematically search for 24-hour sodium and potassium excretions in the Americas with data collected through the most accurate method to measure both sodium and potassium excretions (⁹⁷97. 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. 2012;32(4):307-15.). Furthermore, a comprehensive search strategy was performed, including broad search terms, no language restrictions, and ultimately retrieved almost four times the studies included in previous similar reviews.

The main limitation was the high heterogeneity and the small samples in the studies. However, the results are more accurate and robust than previous estimates for the Americas, since only studies reporting 24-hour urinary sodium or potassium were included. Also, despite of the different participants’ characteristics of the studies it was possible to grouping them by regions or income level, and the excretion trends did not differ from base analyses when alternative groups where set or imputed data were excluded. Other sodium/potassium losses were not considered; thus, the figures could underestimate the true excretions. Finally, further analysis including dietary methods or spot urine samples may be considered, particularly if low- and middle-income countries are included.

Conclusion

These findings synthesized the sodium and potassium excretions in the Americas retrieving data from the published papers in the last three decades suggesting that sodium excretions are almost double the maximum level recommended by the WHO and potassium excretions are 35% lower than the minimum requirement in the Americas. Therefore, major efforts to reduce sodium and to increase potassium intakes at population level should be implemented, including a focus on food reformulation and fruits and vegetables promotion, along with health education campaigns.

Perspective

Our study provides a comprehensive overview of the sodium and potassium intakes in the Americas assessed with 24-hour urine samples, the most accurate method. We found that over the past three decades, mean potassium intakes have been consistently low across the Americas. In contrast, mean sodium intakes have been high and also slightly increasing. Importantly, our analyses also revealed a higher sodium and lower potassium intakes in lower-middle and upper-middle income countries of the Americas and a lack of data in low-income countries.

Our findings call for robust action to reduce sodium and increase potassium intakes and to undertake further efforts to monitor their consumption through 24-hour urine samples especially among lower income countries to obtain comparable data.

Disclaimer.

Authors hold sole responsibility for the views expressed in the manuscript, which may not necessarily reflect the opinion or policy of the Revista Panamericana de Salud Pública / Pan American Journal of Public Health and/or those of the Pan American Health Organization.

Acknowledgments.

We would like to thank the authors of the original studies, especially those who provided relevant data after we requested via email.

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