ABC | Volume 114, Nº3, March 2020

Original Article Arantes et al. Added salt and blood pressure Arq Bras Cardiol. 2020; 114(3):554-561 Table 03 – Within-group comparison (Visits 1B and V4) of ambulatory blood pressure monitoring, casual blood pressure, serum creatinine and urinary sodium (n = 55) Variables Normotensive group n = 18 Prehypertensive group n = 15 Hypertensive group n = 22 Mean SD p Mean SD p Mean SD p ASBPM V1b 115.7 9.7 0.87* 125.0 8.2 0.88* 128.6 10.3 0.63* ASBPM SBP V4 115.1 11.8 125.5 11.8 127.0 11.6 ADBPM V1b 69.3 6.6 0.86* 76.1 7.7 0.72* 80.0 7.3 0.81* ADBPM V4 69.7 7.2 77.3 10.8 79.5 8.0 casual SBP V1B 116.3 10.6 0.44* 125.9 8.4 0.94* 128.5 11.1 0.18* casual SBP V4 113.8 9.3 126.1 7.5 124.2 10.1 Casual DBP V1B 71.1 7.4 0.58* 79.3 8.8 0.87* 81.4 8.5 0.10* Casual DBP V 4 69.8 7.2 0.44* 78.8 7.3 77.3 73.8 Sodium V1B 163.2 71.7 0.20* 158.4 68.7 0.60* 156.8 52.7 0.63* Sodium V4 135.2 58.1 0.20** 172.7 80.8 0.60** 147.3 75.9 0.63** SD: standard deviation; *paired Student’s t-test; **Wilcoxon test; ASBPM: ambulatory systolic blood pressure monitoring (mmHg); ADBPM: ambulatory diastolic blood pressure monitoring (mmHg); SBP: systolic blood pressure (mmHg); DBP: diastolic blood pressure (mmHg); V1b: visit 1b; V2: visit 2; V3: visit 3; V4: visit 4. Table 4 – Correlation of blood pressure parameters with 24-hour urinary sodium excretion, n = 55 Variables Normotensive group n = 18 Prehypertensive group n = 15 Hypertensive group n = 22 r p r p* r p cSBP x sodium V4 0,208 0,40 0,282 0,30 0,276 0,21 cDBP x sodium V4 0,397 0,10 0,328 0,23 0,458 0,03* PPc x sodium V4 -0,024 0,92 0,023 0,93 -0,174 0,43 AIx 75% x sodium V4 0,201 0,42 0,014 0,95 0,116 0,60 ASBPM x sodium V4 0,241 0,33 0,216 0,43 0,298 0,17 ADBPM x sodium V4 0,188 0,45 0,205 0,46 0,369 0,09 casual SBP x sodium V4 0,010 0,96 0,294 0,28 0,157 0,48 Casual DBP x sodium V4 0,156 0,53 0,413 0,12 0,480 0,02* Spearman test; r: rho value; * ≤ 0.005; ASBPM: ambulatory systolic blood pressure monitoring (mmHg); ADBPM: ambulatory diastolic blood pressure monitoring (mmHg); SBP: systolic blood pressure (mmHg); DBP: diastolic blood pressure (mmHg); V4: visit 4. A meta-analysis evaluating the effect of salt intake reduction on intermediate outcomes, including BP, detected mean BP reductions of 3.39 mmHg in SBP and 1.54 mmHg in DBP. Such effect was greater in hypertensive (4.06 mmHg in SBP and 2.26 mmHg in DBP) than normotensive individuals (1.38 mmHg in SBP and 0.58 mmHg in DBP). In addition, greater reductions in BP was observed in individuals with sodium intake < 2 g/day versus ≥ 2 g/day, and in those with a reduction in daily salt intake ≥ 1/3 versus < 1/3. 22 A controlled dietary intervention consisting of 7.6 g/day sodium supplementation versus placebo (no supplementation) caused a significant increase in CBP measurements – 8.5 mmHg in SBP, 3.6 mmHg in cDBP and 4.8 mmHg in PPa. 23 It is therefore clear that strategies towards reductions in salt intake (salt in packaged foods or total salt consumption) are an effective nonpharmacological approach for the prevention and treatment of hypertension. Since reducing the amount of added salt in the diet is commonly recommended by healthcare professionals, we decided to investigate whether such strategy, adopted for a short period of time, would be effective in reducing BP levels. It is worth pointing out that theWorldHealthOrganization recommends the reduction in salt intake to less than 5 grams per day to reduce BP. 15 It is possible that an intervention towards lowering added salt intake in more meals and for a longer period would lead to more effective results than those obtained in this study. A meta-analysis of studies on interventions of salt intake reduction showed that reductions in salt intake for up to five weeks in hypertensive individuals and for up to four weeks in normotensive individuals are ineffective to cause significant falls in BP. 18 In our study, intervals between the different levels of salt reduction were of four weeks, aiming to achieve good adherence to the intervention proposed. Based on scientific evidence, European countries have established population-wide recommendations to lower salt intake to less than 5 grams per day. In the United Kingdom and Finland, there are government policies focusing on reducing salt intake to less than 3 grams per day by the year of 2025. 24 558