Abstract

This paper aims to identify the factors associated with high salt intake in the Brazilian adult population. This is a cross-sectional study with 8,083 adults participating in the National Health Survey (PNS, 2014/15). Salt intake was based on the estimation of 24-hour urinary sodium calculated from the sodium/creatinine ratio in spot urine samples. The highest quartile of the distribution was considered high salt intake. The relationship between high salt consumption and sociodemographic factors, lifestyles, morbidity, and self-rated health status was analyzed by calculating the crude prevalence ratios and the prevalence ratios adjusted for age and gender. Approximately 28.1% had an estimated salt intake higher than 10.56 g/day. Overweight (Adjusted Prevalence Ratio; 95%CI - PRadj 1.23; 1.09-1.39), obesity (PRadj 1.61; 1.43-1.83), and diabetes (PRadj 1.36; 1.17-1.58) were positively associated with high salt intake. Female gender (PRadj 0.73; 0.66-0.80), high schooling level (PRadj 0.88; 0.79-0.99), living in the North and chronic kidney disease (PRadj 0.71; 0.56-0.90) were protective factors. Salt consumption is elevated nationwide and in all population subgroups, requiring coordinated actions.

Key words:
Dietary Sodium; Feeding Behavior; Health Surveys; Urine

Introduction

Despite the current, almost omnipresence of salt in food, its introduction into the diet is relatively recent in human history. It probably started with the discovery of its food preservation properties. Since their ancestors, humans evolved for millions of years with a diet of less than 0.1 g/day of sodium (0.25 g/day of NaCl), an amount naturally present in food¹1 Eaton SB, Konner M. Paleolithic Nutrition - A consideration of its Nature and current implications. N Engl J Med 1985; 312(5):283-289.. Salt addition only became part of the diet in the last 5,000 to 10,000 years²2 He FJ, MacGregor GA. Dietary salt, high blood pressure and other harmful effects on health. In: Kilcast D, Angus F, editores. Reducing salt in foods: Practical strategies. Boca Raton: Woodhead Publishing Limited, CRC Press; 2007. p. 18-54.. Thus, excessive salt intake and, consequently, sodium are significant challenges to physiological systems, given the continuous need to eliminate diet sodium ingested through the kidneys³3 Henney JE, Taylor CL, Boon CS, editores. Strategies to reduce sodium intake in the United States/Committee on Strategies to Reduce Sodium Intake, Food and Nutrition Board. Washington: National Academy of Sciences; 2010..

Excessive salt consumption is the main dietary risk factor for NCDs, mainly because of its relationship with cardiovascular outcomes mediated by arterial hypertension (AH), such as stroke, myocardial infarction, hypertensive cardiomyopathy, and chronic kidney disease²2 He FJ, MacGregor GA. Dietary salt, high blood pressure and other harmful effects on health. In: Kilcast D, Angus F, editores. Reducing salt in foods: Practical strategies. Boca Raton: Woodhead Publishing Limited, CRC Press; 2007. p. 18-54.^,44 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):632-647.. Moreover, other outcomes, such as stomach cancer, osteoporosis, and obesity, are also associated with excessive sodium intake⁴4 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):632-647.. Overall, it is estimated that excessive sodium consumption is associated with about 3 million deaths and the loss of 70 million DALYs (Disability-Adjusted Life Years)⁵5 GBD 2017 Diet Collaborators. Health effects of dietary risks in 195 countries, 1990-2017: a systematic analysis for the Global Burden of Disease Study 2017. Lancet 2019; 393(19):1958-1972..

In global terms, it is estimated that more than 95% of the population consume excess sodium (on average 3.9 g/day, ranging from 2.2 g to 5.5 g/day), while the recommended level of the WHO is up to 2 g/day, equivalent to 5 g of table salt⁶6 Powles J, Fahimi S, Micha R, Khatibzadeh S, Shi P, Ezzati M, Engell RE, Lim SS, Danaei G, Mozaffarian D, Global Burden of Diseases Nutrition and Chronic Diseases Expert Group (NutriCoDE). 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..

The first salt/sodium intake estimates of the Brazilian population were obtained in 2002-2003, through indirect methods, based on home food purchase⁷7 Sarno F, Claro RM, Levy RB, Bandoni DH, Ferreira SRG, Monteiro CA. Estimativa de consumo de sódio pela população brasileira, 2002-2003. Rev Saúde Pública 2009; 43(2):219-225., and in 2008-2009, through 24-hour food records⁸8 Araújo MC, Bezerra IN, Barbosa FS, Junger WL, Yokoo EM, Pereira RA, Sichieri R. Consumo de macronutrientes e ingestão inadequada de micronutrientes em adultos. Rev Saúde Pública 2013; 47(Supl. 1):177s-189s.. Home purchase-based estimates tend to overestimate intake, while recalls may underestimate it. However, they are essential for identifying dietary sodium sources⁹9 Pan American Health Organization (PAHO/WHO). Salt-Smart Americas: A Guide for Country-Level Action. Washington: PAHO; 2013.. In this sense, sodium’s primary dietary source for Brazilians is added salt, including salt used in food preparation (74%) and sodium in processed foods (19%)¹⁰10 Sarno F, Claro RM, Levy RB, Bandoni DH, Monteiro CA. Estimated sodium intake for the Brazilian population, 2008-2009. Rev Saúde Pública 2013; 47(3):571-578..

In 2013, the first direct assessment of salt consumption in the population was carried out in the National Health Survey (PNS). Therefore, the sodium/creatinine ratio was obtained in a spot urine sample. Mean daily consumption of 9.34 g of salt was estimated. More than 95% of the adult population had excessive salt intake (>5 g/day), regardless of gender, age group, schooling, skin color, and geographic region¹¹11 Mill JG, Malta DC, Machado IE, Pate A, Pereira CA, Jaime PC, Szwarcwald CL, Rosenfeld LG. Estimativa do consumo de sal pela população brasileira: resultado da Pesquisa Nacional de Saúde 2013. Rev Bras Epidemiol 2019; 22(Supl. 2):E190009.SUPL.2.. The study also showed significant inter-individual variability, with daily consumption estimates from 1 to around 25 g/day.

The factors that affect individual salt intake are still little known in the Brazilian population. Despite the widespread recognition of the harmful effects of excessive salt intake, especially regarding its effects on blood pressure, little is known about adequate intake levels in Brazil and other Latin American countries¹²12 Claro RM, Linders H, Ricardo CZ, Legetic B, Campbell NRC. Consumer attitudes, knowledge, and behavior related to salt consumption in sentinel countries of the Americas. Rev Panam Salud Publica 2012; 32(4):265-273.. Also, in Brazil, self-perceived salt consumption is very distorted, and, in the PNS, only 14.2% highly rated their intake¹³13 Oliveira MM, Malta DC, Santos MAS, Oliveira TP, Nilson EAF, Claro RM. Consumo elevado de sal autorreferido em adultos: dados da Pesquisa Nacional de Saúde, 2013. Epidemiol Serv Saúde 2015; 24(2):249-256..

Reducing salt consumption is one of the goals of the Strategic Action Plan for Coping with NCDs in Brazil (2011-2022)¹⁴14 Brasil. Ministério da Saúde (MS). Plano de Ações Estratégicas para o Enfrentamento das Doenças Crônicas Não Transmissíveis (DCNT) no Brasil 2011-2022. Brasília: MS; 2011. and, globally, the WHO has set a goal of 30% reduction in salt intake by 2025 in all the countries. Thus, this study aimed to identify the factors associated with salt consumption in the adult Brazilian population, which can contribute to the planning of actions to achieve these goals.

Methods

This is an analytical cross-sectional study based on data from the PNS laboratory tests collected in 2014/15. PNS is a nationwide, home-based survey conducted by the Brazilian Institute of Geography and Statistics, in partnership with the Ministry of Health. The survey used a three-stage probabilistic sample. Interviews were conducted with adult residents (>18 years) of 64,348 residential homes. Additional methodological details have been previously described¹⁵15 Szwarcwald CL, Malta DC, Souza JPRB, Almeida WS, Damacena GN, Pereira CA, Rosenfeld LG. Exames laboratoriais da Pesquisa Nacional de Saúde: metodologia de amostragem, coleta e análise dos dados. Rev Bras Epidemiol 2019; 22(Supl. 2):E190004.SUPL.2.^,1616 Malta DC, Szwarcwald CL, Silva JJB. Primeiros resultados da análise do laboratório da Pesquisa Nacional de Saúde. Rev Bras Epidemiol 2019; 22(Supl. 2):E190001.SUPL.2..

A random subsample of 8,952 individuals with blood and urine collection was separated from the PNS sample, and 869 samples with insufficient material, losses, and others were excluded from this analysis¹⁵15 Szwarcwald CL, Malta DC, Souza JPRB, Almeida WS, Damacena GN, Pereira CA, Rosenfeld LG. Exames laboratoriais da Pesquisa Nacional de Saúde: metodologia de amostragem, coleta e análise dos dados. Rev Bras Epidemiol 2019; 22(Supl. 2):E190004.SUPL.2.. Thus, the current analysis refers to 8,083 participants. The study adopted post-stratification weights according to gender, age, education, and region, to establish estimates for the Brazilian adult population¹⁵15 Szwarcwald CL, Malta DC, Souza JPRB, Almeida WS, Damacena GN, Pereira CA, Rosenfeld LG. Exames laboratoriais da Pesquisa Nacional de Saúde: metodologia de amostragem, coleta e análise dos dados. Rev Bras Epidemiol 2019; 22(Supl. 2):E190004.SUPL.2..

Urine samples were collected at home at different times of the day. A 5 mL aliquot was transferred to a sterile flask in a thermal bag and stored in a refrigerator until it was sent to the central laboratory in São Paulo. The urinary sodium was measured with a selective electrode, and creatinine was gauged by the Jaffe’s kinetic method without deproteinization¹⁵15 Szwarcwald CL, Malta DC, Souza JPRB, Almeida WS, Damacena GN, Pereira CA, Rosenfeld LG. Exames laboratoriais da Pesquisa Nacional de Saúde: metodologia de amostragem, coleta e análise dos dados. Rev Bras Epidemiol 2019; 22(Supl. 2):E190004.SUPL.2..

The 24-hour urinary sodium excretion was estimated using Tanaka et al.¹⁷17 Tanaka T, Okamura T, Miura K, Kadowaki T, Ueshima H, Nakagawa H, Hashimoto T. A simple method to estimate populational 24-h urinary sodium and potassium excretion using a casual urine specimen. J Hum Hypertens 2002; 16(2):97-103., which was validated for the Brazilian population in a pilot study of the PNS¹⁸18 Mill JG, Rodrigues SL, Baldo MP, Malta DC, Szwarcwald CL. Estudo de validação das equações de Tanaka e de Kawasaki para estimar a excreção diária de sódio através da coleta da urina casual. Rev Bras Epidemiol 2015; 18(Supl. 2):224-237.. Using this equation requires estimating the urinary excretion (Ur) of creatinine (Cr) expected for 24 hours (CrPr24h, in mg), from age (years), weight (kg), and height (cm) of the individual, obtained in the home visit, as follows:

Given CrPr24h, the sodium/creatinine ratio in urine in 24 hours (Na Ur 24h, mEq) is estimated by the following equation:

The estimated sodium excretion in 24 h (mEq) is given by the equation:

Salt consumption was estimated by considering all sodium excreted in the urine as being ingested as NaCl:

For the current study, the estimated mean salt intake in the Brazilian population was 9.34 g/day (95% confidence interval - 95%CI: 9.27-9.41)¹¹11 Mill JG, Malta DC, Machado IE, Pate A, Pereira CA, Jaime PC, Szwarcwald CL, Rosenfeld LG. Estimativa do consumo de sal pela população brasileira: resultado da Pesquisa Nacional de Saúde 2013. Rev Bras Epidemiol 2019; 22(Supl. 2):E190009.SUPL.2.. Urinary excretion was distributed in quartiles, and, in this analysis, we chose to consider “high consumption” individuals located in the highest quartile, equivalent to the 75^th percentile or above (≥P75); that is, those with daily salt intake ≥10.56 g, which corresponds to the daily urinary excretion of 4.15 g of sodium. The following blocks of variables of interest were included in the analysis: a) sociodemographic variables gender (male and female), age group (18-29, 30-44, 45-59, and 60 or more years), education (illiterate to incomplete elementary school, complete elementary school to incomplete high school, complete high school and over), skin color (white, black, brown, and other) and the country’s macro-region (North, Northeast, Southeast, South, and Midwest); b) variables lifestyle, fatty red meat consumption (yes or no), soft drinks consumption 5 or more days a week (yes or no), alcohol beverages consumption 1 or more times a month (yes or no), and tobacco use (yes or no); c) variables related to morbidities, adiposity according to the Body Mass Index - BMI (underweight or normal, overweight, obesity¹⁹19 World Health Organization (WHO). Obesity: preventing and managing the global epidemic. Geneva: WHO; 2000.), diabetes (glycated hemoglobin - HbA1c ≥6.5% or use of a hypoglycemic agent²⁰20 The International Expert Committee. International expert committee report on the role of the A1c assay in the diagnosis of diabetes. Diabetes Care 2009; 32(7):1327-1334.^,2121 World Health Organization (WHO). Use of glycated haemoglobin (HbA1c) in the diagnosis of diabetes mellitus. Geneva: WHO; 2011., yes or no), high blood pressure (>140-90mm Hg²²22 Malta DC, Santos NB, Perillo RD, Szwarcwald CL. Prevalence of high blood pressure measured in the Brazilian population, National Health Survey, 2013. São Paulo Med J 2016; 134(2):163-170., yes or no), high total cholesterol (total cholesterol ≥200 mg/dL²³23 Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults. Executive summary of the third report of the National Cholesterol Education Program (NCEP) expert panel on detection, evaluation, and treatment of high blood cholesterol in adults (Adult Treatment Panel III). JAMA 2001; 285(19):2486-2497., yes or no), Chronic Kidney Disease - CKD (Glomerular Filtration Rate - GFR <60 mL/min/1.73 m²²⁴24 Kidney Disease Improving Global Outcomes. KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int Suppl 2013; 3(1):1-150., yes or no, without adjustment factor for black race), anemia (hemoglobin - Hb <12 g/dL²⁵25 World Health Organization (WHO). Haemoglobin concentrations for the diagnosis of anaemia and assessment of severity. Vitamin and Mineral Nutrition Information System. Genebra: WHO; 2011., yes or no); d) self-assessed health status (very good and good, fair, poor and very poor). Prevalence and 95% confidence intervals (95%CI) were calculated, and bivariate analyses were performed using the chi-square test. Crude (PR) and adjusted (PRadj) prevalence ratios were also calculated according to age and gender using the Poisson regression method with robust variance and respective 95%CI.

The analyses were performed with statistical program Data Analysis and Statistical Software (Stata), version 14, using the survey command to analyze data from surveys with a complex sample.

The National Research Ethics Commission (CONEP) of the National Health Council, Ministry of Health, approved the 2013 PNS. Research participants signed an informed consent form (ICF) before data collection.

Results

Figure 1 shows that the consumption curve follows an approximately normal distribution (Figure 1A), with a higher intake in males (Figure 1B). As shown in Table 1, 28.14% (95%CI: 26.79-29.52%) of the participants were in the highest consumption quartile (≥10.56 g of salt/day). Prevalence data with the respective 95%CI showed that this highest consumption was found in the male population (32.84%; 95%CI: 30.68-35.07), in overweight patients (28.89%; 95%CI: 26.67-31.21) and obesity (35.84%; 95%CI: 32.92-38.87), in those who reported fatty red meat consumption (30.41%; 95%CI: 27.84-33.12), patients with diabetes (34.30%; 95%CI: 29.88-39.01) and who consumed alcoholic beverages once or more times per month (31.00%; 95%CI: 28.11-34.04). High salt consumption was lower in older adults (24.8%; 95%CI: 22.21-27.6), in the population of the North region (20.64%; 95%CI: 18.85-22.56), in CKD patients (18.96%; 95%CI: 15.04-23.61). There was no association between the distribution of quartiles and salt intake for different levels of education, skin color, consumption of soft drinks, tobacco use, high blood pressure measured during the home visit where urine was collected, high cholesterol, anemia, and self-assessment of health status.

Table 2 presents the crude and adjusted PR of the relationship between high salt intake and the factors studied. The PRadj by gender and age (PRadj; 95% CI) showed that the highest salt consumption (≥P75) was associated with male, overweight (PRadj 1.23; 95%CI: 1.09-1.39), obesity (PRadj 1.61; 95%CI: 1.43-1.83) and diabetes (PRadj 1.36; 95%CI: 1.17-1.58). Female (PRadj 0.73; 95%CI: 0.66-0.80), higher schooling (0.88; 95%CI: 0.79-0.99), living in the North, and CKD (GFR <60 ml/min/1.73 m²) (PRadj 0.71; 95%CI: 0.56-0.90) were identified as protective factors, that is, lower salt intake.

Discussion

The study analyzed PNS data and identified the demographic, behavioral, and clinical factors associated with high salt consumption (≥10.56 g/day), corresponding to the P75 of this parameter’s distribution in the adult Brazilian population. Higher intake was associated with male or overweight, obesity, or diabetes, while lower consumption was associated with higher education, living in the North, and CKD.

For the first time, PNS allowed estimating salt consumption in the Brazilian population through urine analysis¹¹11 Mill JG, Malta DC, Machado IE, Pate A, Pereira CA, Jaime PC, Szwarcwald CL, Rosenfeld LG. Estimativa do consumo de sal pela população brasileira: resultado da Pesquisa Nacional de Saúde 2013. Rev Bras Epidemiol 2019; 22(Supl. 2):E190009.SUPL.2.. Data point to widespread high intake in the population since only 3.4% of them showed consumption recommended by the WHO (<5 g daily), which converges with results from other studies in Brazil and other countries¹¹11 Mill JG, Malta DC, Machado IE, Pate A, Pereira CA, Jaime PC, Szwarcwald CL, Rosenfeld LG. Estimativa do consumo de sal pela população brasileira: resultado da Pesquisa Nacional de Saúde 2013. Rev Bras Epidemiol 2019; 22(Supl. 2):E190009.SUPL.2.^,2626 Brown IJ, Dyer AR, Chan Q, Cogswell ME, Ueshima H, Stamler J, Elliott P. Estimating 24-h urinary sodium excretion from casual urinary sodium concentrations in western populations: The Intersalt Study. Am J Epidemiol 2013; 177(11):1180-1192.

27 Elliott P, Marmot M, Dyer A, Joossens J, Kesteloot H, Stamler R, Stamler J, Rose G. The INTERSALT study: main results, conclusions and some implications. Clin Exp Hypertens A 1989; 11(5-6):1025-1034.

28 Lim SS, Vos T, Flaxman AD, Danaei G, Shibuya K, Adair-Rohani H, Amann M, Anderson HR, Andrews KG, Aryee M, Atkinson C, Bacchus LJ, Bahalim AN, Balakrishnan K, Balmes J, Barker-Collo S, Baxter A, Bell ML, Blore JD, Blyth F, Bonner C, Borges G, Bourne R, Boussinesq M, Brauer M, Brooks P, Bruce NG, Brunekreef B, Bryan-Hancock C, Bucello C, Buchbinder R, Bull F, Burnett RT, Byers TE, Calabria B, Carapetis J, Carnahan E, Chafe Z, Charlson F, Chen H, Chen JS, Cheng AT-A, Child JC, Cohen A, Colson KE, Cowie BC, Darby S, Darling S, Davis A, Degenhardt L, Dentener F, Des Jarlais DC, Devries K, Dherani M, Ding EL, Dorsey ER, Driscoll T, Edmond K, Ali SE, Engell RE, Erwin PJ, Fahimi S, Falder G, Farzadfar F, Ferrari A, Finucane MM, Flaxman S, Fowkes FGR, Freedman G, Freeman MK, Gakidou E, Ghosh S, Giovannucci E, Gmel G, Graham K, Grainger R, Grant B, Gunnell D, Gutierrez HR, Hall W, Hoek HW, Hogan A, Hosgood 3rd HD, Hoy D, Hu H, Hubbell BJ, Hutchings SJ, Ibeanusi SE, Jacklyn GL, Jasrasaria R, Jonas JB, Kan H, Kanis JA, Kassebaum N, Kawakami N, Khang Y-H, Khatibzadeh S, Khoo J-P, Kok C, Laden F, Lalloo R, Lan Q, Lathlean T, Leasher JL, Leigh J, Li Y, Lin JK, Lipshultz SE, London S, Lozano R, Lu Y, Mak J, Malekzadeh R, Mallinger L, Marcenes W, March L, Marks R, Martin R, McGale P, McGrath J, Mehta S, Mensah GA, Merriman TR, Micha R, Michaud C, Mishra V, Hanafiah KM, Mokdad AA, Morawska L, Mozaffarian D, Murphy T, Naghavi M, Neal B, Nelson PK, Nolla JM, Norman R, Olives C, Omer SB, Orchard J, Osborne R, Ostro B, Page A, Pandey KD, Parry CDH, Passmore E, Patra J, Pearce N, Pelizzari PM, Petzold M, Phillips MR, Pope D, Pope 3rd CA, Powles J, Rao M, Razavi H, Rehfuess EA, Rehm JT, Ritz B, Rivara FP, Roberts T, Robinson C, Rodriguez-Portales JA, Romieu I, Room R, Rosenfeld LC, Roy A, Rushton L, Salomon JA, Sampson U, Sanchez-Riera L, Sanman E, Sapkota A, Seedat S, Shi P, Shield K, Shivakoti R, Singh GM, Sleet DA, Smith E, Smith KR, Stapelberg NJC, Steenland K, Stöckl H, Stovner LJ, K Straif, Straney L, Thurston GD, Tran JH, Van Dingenen R, van Donkelaar A, Veerman JL, Vijayakumar L, Weintraub R, Weissman MM, White RA, Whiteford H, Wiersma ST, Wilkinson JD, Williams HC, Williams W, Wilson N, Woolf AD, Yip P, Zielinski JM, Lopez AD, Murray CJL, Ezzati M, AlMazroa MA, Memish ZA. A comparative risk assessment of burden disease and injury attributable to 67 risk factor clusters in 21 regions, 1990-2010: a systematic review for the Global Burden of Disease Study 2010. Lancet 2012; 380(9859):2224-2260.^-2929 He FJ, Li J, MacGregor GA. Effect of longer term modest salt reduction on blood pressure: Cochrane systematic review and meta-analysis of randomized trials. BMJ 2013; 346:f1325..

The gold standard for estimating salt consumption is 24-hour urine collection. However, this method is challenging to perform in population studies due to the great possibility of collection errors, which significantly reduces the measurement’s precision and, consequently, the method’s reliability. Thus, there is a trend in the literature to adopt spot collection to obtain the sodium/creatinine ratio and estimate the mean population intake³⁰30 McLean RM. Measuring population sodium intake: A review of methods. Nutrients 2014; 6(11):4651-4662.^,3131 Campbell NRC, He FJ, Tan M, Cappuccio FP, Neal B, Woodward M, Cogswell ME, McLean R, Arcand J, MacGregor G. The international consortium for quality research on dietary sodium/salt (TRUE) position statement on the use of 24-hour, spot, and short duration (&lt;24 hours) timed urine collections to assess dietary sodium intake. J Clin Hypertens (Greenwich) 2019; 21(6):700-709. using formulas. This strategy was adopted in the PNS and other countries³²32 Xu J, Zhang J, Liu M, Bai Y, Guo X, Dong J, Xu A, Wu J. Estimating 24-hour sodium excretion from spot urine samples in Chinese adults: Can spot urine substitute 24-hour urine samples? Nutrients 2020; 12(3):798., enabling greater adherence and speed in obtaining the data. Applying the Tanaka equation was because it showed better performance in a validation study¹⁸18 Mill JG, Rodrigues SL, Baldo MP, Malta DC, Szwarcwald CL. Estudo de validação das equações de Tanaka e de Kawasaki para estimar a excreção diária de sódio através da coleta da urina casual. Rev Bras Epidemiol 2015; 18(Supl. 2):224-237., which was also found in other populations³²32 Xu J, Zhang J, Liu M, Bai Y, Guo X, Dong J, Xu A, Wu J. Estimating 24-hour sodium excretion from spot urine samples in Chinese adults: Can spot urine substitute 24-hour urine samples? Nutrients 2020; 12(3):798.. A validation study¹⁸18 Mill JG, Rodrigues SL, Baldo MP, Malta DC, Szwarcwald CL. Estudo de validação das equações de Tanaka e de Kawasaki para estimar a excreção diária de sódio através da coleta da urina casual. Rev Bras Epidemiol 2015; 18(Supl. 2):224-237. showed that the Tanaka formula estimates salt consumption with an accuracy of 1 g/day, with good performance to estimate large groups’ mean intake. However, accuracy is low at the extremes. Therefore, in clinical practice, the recommendation remains to measure salt intake by 24-hour urine collection or 12-hour nighttime collections, when collection errors tend to be smaller³¹31 Campbell NRC, He FJ, Tan M, Cappuccio FP, Neal B, Woodward M, Cogswell ME, McLean R, Arcand J, MacGregor G. The international consortium for quality research on dietary sodium/salt (TRUE) position statement on the use of 24-hour, spot, and short duration (&lt;24 hours) timed urine collections to assess dietary sodium intake. J Clin Hypertens (Greenwich) 2019; 21(6):700-709.^,3333 Mill JG, Silva AB, Baldo MP, Molina MC, Rodrigues SL. Correlation between sodium and potassium excretion in 24- and 12-h urine samples. Braz J Med Biol Res 2012; 45(9):799-805..

Studies point to an association between high salt consumption and arterial hypertension³⁴34 Henry JP. Stress, salt and hypertension. Soc Sci Med 1988; 26(3):293-302. and cardiovascular diseases³⁵35 Oparil S. Low sodium intake - Cardiovascular health benefit or risk? N Engl J Med 2014; 371:677-679.. However, in the current study, arterial hypertension was not associated with high salt intake. This may have occurred due to the study’s cross-sectional design or because blood pressure was not considered a continuous variable in the analysis but regarding the proportion of individuals in quartiles. Also, high overall consumption in the Brazilian population can hinder the detection of an existing association. However, the evidence for the association of sodium consumption and hypertension is well established in the literature, and guidelines regarding the application of preventive actions remain, aiming at reducing consumption and events related to NCDs³⁶36 GBD 2017 Risk Factor Collaborators. Global, regional, and national comparative risk assessment of 84 behavioural, environmental and occupational, and metabolic risks or clusters of risks for 195 countries and territories, 1990-2017: a systematic analysis for the Global Burden of Disease Study 2017. Lancet 2018; 392(10159):1923-1994.

37 Mente A, O'Donnell MJ, Rangarajan S, McQueen MJ, Poirier P, Wielgosz A, Morrison H, Li W, Wang X, Di C, Mony P, Devanath A, Rosengren A, Oguz A, Zatonska K, Yusufali AH, Lopez-Jaramillo P, Avezum A, Ismail N, Lanas F, Puoane T, Diaz R, Kelishadi R, Iqbal R, Yusuf R, Chifamba J, Khatib R, Teo K, Yusuf S, PURE Investigators. Association of urinary sodium and potassium excretion with blood pressure. New Engl J Med 2014; 371(7):601-611.^-3838 Malta DC, Bernal RTI, Andrade SSCA, Silva MMA, Velasquez-Melendez G. Prevalência e fatores associados com hipertensão arterial autorreferida em adultos brasileiros. Rev Saúde Pública 2017; 51(Supl. 1):11s..

This study pointed to an association with lower salt consumption in individuals with CKD (GFR ≤60 ml/min/1.73 m²), calculated using the CKD-EPI formula (Chronic Kidney Disease Epidemiology Collaboration)²⁴24 Kidney Disease Improving Global Outcomes. KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int Suppl 2013; 3(1):1-150.. It is noteworthy that in this condition, it is already established that the reduction of salt intake is necessary to avoid the appearance of edema and to reduce renal overload³⁹39 Nerbass FB, Pecoits-Filho R, McIntyre NJ, McIntyre CW, Taal MW. High sodium intake is associated with important risk factors in a large cohort of chronic kidney disease patients. Eur J Clin Nutr 2015; 69(7):786-790.. Thus, this data suggests adherence, at least in part of the individuals, to the recommendation to reduce salt intake in these conditions. On the contrary, there was no difference in salt consumption in individuals with high blood pressure at home. One of the essential recommendations in hypertensive patients is the reduction of salt in the diet to reduce the pressure and increase the pharmacological response to antihypertensive drugs. This finding can be explained because, in cross-sectional studies, hypertensive individuals have higher urinary sodium excretion than normotensive individuals⁴⁰40 Rodrigues SL Souza Júnior, PR, Pimentel EB, Baldo MP, Malta DC, Mill JG, Szwarcwald CL. Relationship between salt consumption measured by 24-h urine collection and blood pressure in the adult population of Vitória (Brazil). Braz J Med Biol Res 2015; 48(8):728-735.. This data indicates low adherence to this dietary recommendation among people with high blood pressure.

The high salt consumption detected in this study had already been observed in the 2002-2003 POF⁷7 Sarno F, Claro RM, Levy RB, Bandoni DH, Ferreira SRG, Monteiro CA. Estimativa de consumo de sódio pela população brasileira, 2002-2003. Rev Saúde Pública 2009; 43(2):219-225.. POF analyses showed that the primary source of sodium comes from the salt added in food preparation⁷7 Sarno F, Claro RM, Levy RB, Bandoni DH, Ferreira SRG, Monteiro CA. Estimativa de consumo de sódio pela população brasileira, 2002-2003. Rev Saúde Pública 2009; 43(2):219-225.^,88 Araújo MC, Bezerra IN, Barbosa FS, Junger WL, Yokoo EM, Pereira RA, Sichieri R. Consumo de macronutrientes e ingestão inadequada de micronutrientes em adultos. Rev Saúde Pública 2013; 47(Supl. 1):177s-189s.. A progressive reduction in the annual household purchase of salt (refined or coarse) was observed in Brazil, from 2.98 to 2.47 kg per capita⁷7 Sarno F, Claro RM, Levy RB, Bandoni DH, Ferreira SRG, Monteiro CA. Estimativa de consumo de sódio pela população brasileira, 2002-2003. Rev Saúde Pública 2009; 43(2):219-225.. However, this fact may not have affected individual consumption due to the increased intake of processed and ultra-processed foods⁴¹41 Instituto Brasileiro de Geografia e Estatística (IBGE). Aquisição alimentar domiciliar per capita. Rio de Janeiro: IBGE; 2010., which contain high salt levels, besides the increased participation of food outside the home in the population’s dietary behavior⁴¹41 Instituto Brasileiro de Geografia e Estatística (IBGE). Aquisição alimentar domiciliar per capita. Rio de Janeiro: IBGE; 2010.^,4242 Nilson EAF, Spaniol AM, Gonçalves VSS, Moura I, Silva SA, L'Abbé M, Jaime PC. Sodium reduction in processed foods in Brazil: Analysis of food categories and voluntary targets from 2011 to 2017. Nutrients 2017; 9(7):742.. Thus, it can be considered that there has been no substantial reduction in salt consumption in the Brazilian population since the 2002-2003 POF. However, the variation in consumption can only be determined in serial studies and using the same methods to measure the consumption of this nutrient³¹31 Campbell NRC, He FJ, Tan M, Cappuccio FP, Neal B, Woodward M, Cogswell ME, McLean R, Arcand J, MacGregor G. The international consortium for quality research on dietary sodium/salt (TRUE) position statement on the use of 24-hour, spot, and short duration (&lt;24 hours) timed urine collections to assess dietary sodium intake. J Clin Hypertens (Greenwich) 2019; 21(6):700-709..

Self-reported research, such as “Surveillance of Risk and Protection Factors for Chronic Diseases by Telephone Survey” (VIGITEL), showed that men have unhealthier dietary indicators than women and lower perception of high salt consumption¹³13 Oliveira MM, Malta DC, Santos MAS, Oliveira TP, Nilson EAF, Claro RM. Consumo elevado de sal autorreferido em adultos: dados da Pesquisa Nacional de Saúde, 2013. Epidemiol Serv Saúde 2015; 24(2):249-256.. Also, higher salt intake among younger people has been described in the previous analyses¹¹11 Mill JG, Malta DC, Machado IE, Pate A, Pereira CA, Jaime PC, Szwarcwald CL, Rosenfeld LG. Estimativa do consumo de sal pela população brasileira: resultado da Pesquisa Nacional de Saúde 2013. Rev Bras Epidemiol 2019; 22(Supl. 2):E190009.SUPL.2.. However, when adjusting for schooling, these differences disappeared, showing that the exceptionally high salt consumption is distributed in all age groups in the general Brazilian population.

The literature points out worse diet quality indicators in individuals with lower education¹¹11 Mill JG, Malta DC, Machado IE, Pate A, Pereira CA, Jaime PC, Szwarcwald CL, Rosenfeld LG. Estimativa do consumo de sal pela população brasileira: resultado da Pesquisa Nacional de Saúde 2013. Rev Bras Epidemiol 2019; 22(Supl. 2):E190009.SUPL.2.^,4343 Simões BDS, Barreto SM, Molina MDCB, Luft VC, Duncan BB, Schmidt MI, Benseñor IJM, Cardoso LO, Levy RB, Giatti L. Consumption of ultra-processed foods and socioeconomic position: a cross-sectional analysis of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil). Cad Saúde Pública 2018; 34(3):e00019717., and schooling is a proxy for socioeconomic status. Higher education results in greater access to information, preventive exams, and earlier medical diagnoses, which would result in better health indicators, corroborating other data found in the PNS³⁸38 Malta DC, Bernal RTI, Andrade SSCA, Silva MMA, Velasquez-Melendez G. Prevalência e fatores associados com hipertensão arterial autorreferida em adultos brasileiros. Rev Saúde Pública 2017; 51(Supl. 1):11s..

The lower salt intake in the North region must be analyzed and compared with POF data, but it can be explained by the lower consumption of ultra-processed foods in this region (11.4% of calories, while the national average is 18.4%), with a high proportion of rural and riverside population sustaining a more traditional food style⁴⁴44 Instituto Brasileiro de Geografia e Estatística (IBGE). Pesquisa de orçamentos familiares 2017-2018: avaliação nutricional da disponibilidade domiciliar de alimentos no Brasil. Rio de Janeiro: IBGE; 2020..

This study revealed a direct association between body fat accumulation and higher salt consumption. In this sense, studies show the association between high sodium intake and obesity by increasing consumption of sugar-added drinks, which also contain sodium in their composition⁴⁵45 Grimes CA, Wright JD, Liu K, Nowson CA, Loria CM. Dietary sodium intake is associated with total fluid and sugar-sweetened beverage consumption in US children and adolescents aged 2-18 y: NHANES 2005-2008. The Am J Clin Nutrition 2013; 98(1):189-196.. However, there may also be a relationship between sodium intake and obesity regardless of the energy consumed, due to still little known physiological and metabolic mechanisms²2 He FJ, MacGregor GA. Dietary salt, high blood pressure and other harmful effects on health. In: Kilcast D, Angus F, editores. Reducing salt in foods: Practical strategies. Boca Raton: Woodhead Publishing Limited, CRC Press; 2007. p. 18-54.^,4646 Ma Y, He FJ, MacGregor GA. High salt intake: Independent risk factor for obesity? Hypertension 2015; 66(4):843-849..

Another finding of the study was the association between diabetes and high salt consumption. Studies show that reducing sodium intake can attenuate insulin resistance (IR) and induce changes in serum lipoproteins and inflammation markers similar to those found in the metabolic syndrome (MS)⁴⁷47 Nakandakare ER, Charf AM, Santos FC, Nunes VS, Ortega K, Lottenberg AMP, Mion Jr D, Nakano T, Nakajima K, D'Amico EA, Catanozi S, Passarelli M, Quintão ECR. Dietary salt restriction increases plasma lipoprotein and inflammatory marker concentrations in hypertensive patients. Atherosclerosis 2008; 200(2):410-416.. Meta-analysis indicates beneficial effects of moderate sodium restriction in the diet in diabetes control⁴⁸48 Sarno F, Jaime PC, Ferreira SRG, Monteiro CA. Consumo de sódio e síndrome metabólica: uma revisão sistemática. Arq Bras Endocrinol Metab 2009; 53(5):608-616.. Therefore, the opposite of what was found in the current study was expected, which requires further investigation. It is necessary to question the industry’s call for patients with diabetes to prefer foods with diet or light labels, which have a higher amount of sodium in their composition, and guide the reformulation of ultra-processed foods⁴⁹49 Zanini RV, Araújo CL, Martínez-Mesa J. Utilização de adoçantes dietéticos entre adultos em Pelotas, Rio Grande do Sul, Brasil: um estudo de base populacional. Cad. Saúde Pública 2011; 27(5):924-934.^,5050 Oliveira ALM. Comparação do teor de sódio em produtos industrializados diet e light e seus análogos convencionais. Nutrição Brasil 2017; 16(1):29-36.. Thus, soft drinks, sweeteners, and others widely consumed by people with diabetes could contribute to these patients’ high sodium consumption and explain the data found here. Recent evidence indicates a possible higher sodium intake in diabetic individuals in some countries, particularly when they are also hypertensive⁵¹51 Kim MK. Dietary sodium intake in patients with type 2 diabetes mellitus. Diabetes Metab J 2016; 40(4):280-282.. Still, studies point to people’s growing consumption of non-caloric sweeteners worldwide and that people with diabetes are the largest consumers of artificial sweeteners⁵²52 Martyn D, Darch M, Roberts A, Lee H Y, Tian TY, Kaburagi N, Belmar P. Low-/no-calorie sweeteners: A review of global intakes. Nutrients 2018; 10(3):357.. They also evidence that the high intake of sugar-added drinks, which also contribute to sodium intake through sweeteners based on this mineral, is associated with a higher risk of stroke⁵³53 Pase MP, Himali JJ, Beiser AS, Aparicio HJ, Satizabal CL, Vasan RS, Seshadri S, Jacques PF. Sugar- and artificially sweetened beverages and the risks of incident stroke and dementia: A prospective cohort study. Stroke 2017; 48(5):1139-1146..

This study points to high salt consumption in general in the Brazilian population and indicates that intake reduction programs should be aimed at the entire population. Among the initiatives, noteworthy are the 2011 National Plan for Coping with NCDs¹⁴14 Brasil. Ministério da Saúde (MS). Plano de Ações Estratégicas para o Enfrentamento das Doenças Crônicas Não Transmissíveis (DCNT) no Brasil 2011-2022. Brasília: MS; 2011.^,5454 Malta DC, Morais Neto OL, Silva Junior JB. Apresentação do plano de ações estratégicas para o enfrentamento das doenças crônicas não transmissíveis no Brasil, 2011 a 2022. Epidemiol Serv Saúde 2011; 20(4):425-438., the WHO Global NCD Action Plan⁵⁵55 World Health Organization (WHO). Global Action Plan for the Prevention and Control of NCDs 2013-2020. Genebra: WHO; 2013., which contains sodium content reduction targets, and the “Brazilian Population Food Guide”, which contains information and guidance on the choice, preparation, and consumption of food (including the use of small amounts of culinary ingredients, such as salt, sugar, oils, and fats) and strengthens the narrative of valuing the consumption of fresh food of regional origin, alerting for the risks associated with the consumption of ultra-processed foods, resulting from high levels of sodium, fats, and sugars⁵⁶56 Brasil. Ministério da Saúde (MS). Secretaria de Atenção à Saúde. Secretaria de Atenção à Saúde. Departamento de Atenção Básica. Guia alimentar para a população brasileira. 2ª ed. Brasília: MS; 2014.. From this perspective, the implementation of voluntary agreements (terms of commitment) with segments of the productive sector in the industrial food chain reduced the sodium content in most processed foods evaluated⁴¹41 Instituto Brasileiro de Geografia e Estatística (IBGE). Aquisição alimentar domiciliar per capita. Rio de Janeiro: IBGE; 2010.. However, the data analyzed here indicate that we are far from reaching the voluntary goals of reducing sodium intake. Thus, it seems necessary to move forward in food regulation and control measures, such as frontal nutritional labeling with a warning, regulation of the sale and advertising of ultra-processed foods, and taxation of unhealthy foods and drinks⁴³43 Simões BDS, Barreto SM, Molina MDCB, Luft VC, Duncan BB, Schmidt MI, Benseñor IJM, Cardoso LO, Levy RB, Giatti L. Consumption of ultra-processed foods and socioeconomic position: a cross-sectional analysis of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil). Cad Saúde Pública 2018; 34(3):e00019717..

Among the main limitations of this study is that the standard gold method was not used to estimate sodium consumption. However, a lower-cost and easier-to-use method was adopted in population surveys, already validated for the Brazilian population in a previous study¹⁸18 Mill JG, Rodrigues SL, Baldo MP, Malta DC, Szwarcwald CL. Estudo de validação das equações de Tanaka e de Kawasaki para estimar a excreção diária de sódio através da coleta da urina casual. Rev Bras Epidemiol 2015; 18(Supl. 2):224-237.. We underscore that due to the Brazilian population’s excessive salt intake, the reference category for consumption used also contains individuals who consume over the daily 5 g recommended by the WHO⁶6 Powles J, Fahimi S, Micha R, Khatibzadeh S, Shi P, Ezzati M, Engell RE, Lim SS, Danaei G, Mozaffarian D, Global Burden of Diseases Nutrition and Chronic Diseases Expert Group (NutriCoDE). 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.. This fact may have influenced the results presented here, reducing the strength of the association between high sodium consumption and the factors studied. However, it is noteworthy that, even so, statistically significant results were observed, which reinforces the value of the findings.

This study points out that salt intake is high nationwide and in all subgroups of the population, requiring coordinated coping actions, such as improving access to healthy food, implementing health education actions, and regulating and monitoring agreements signed with the food industry.

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