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Can Double Fortification of Salt with Iron and Iodine Reduce Anemia, Iron Deficiency Anemia, Iron Deficiency, Iodine Deficiency, and Functional Outcomes? Evidence of Efficacy, Effectiveness, and Safety.
Larson, LM, Cyriac, S, Djimeu, EW, Mbuya, MNN, Neufeld, LM
The Journal of nutrition. 2021;(Suppl 1):15S-28S
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Abstract
BACKGROUND Anemia, iron deficiency, and iodine deficiency are problems of important public health concern in many parts of the world, with consequences for the health, development, and work capacity of populations. Several countries are beginning to implement double fortified salt (DFS) programs to simultaneously address iodine and iron deficiencies. OBJECTIVE Our objective was to summarize the evidence for efficacy and effectiveness of DFS on the full range of status and functional outcomes and across different implementation and evaluation designs essential to successful interventions. METHODS We conducted a systematic review and meta-analysis of published and gray literature examining the effects of DFS on nutritional status, cognition, work productivity, development, and morbidity of all population groups. We searched for articles in Medline, Embase, CINAHL, Cochrane Central Register, and ProQuest for randomized trials, quasi-randomized trials, and program effectiveness evaluations. RESULTS A total of 22 studies (N individuals = 52,758) were included. Efficacy studies indicated a significant overall positive effect on hemoglobin concentration [standardized mean difference (95% CI): 0.33 (0.18, 0.48)], ferritin [0.42 (0.08, 0.76)], anemia [risk ratio (95% CI): 0.80 (0.70, 0.92)], and iron deficiency anemia [0.36 (0.24, 0.55)]. Effects on urinary iodine concentration were not significantly different between DFS and iodized salt. The impact on functional outcomes was mixed. Only 2 effectiveness studies were identified. They reported programmatic challenges including low coverage, suboptimal DFS quality, and storage constraints. CONCLUSIONS Given the biological benefits of DFS across several populations in efficacy research, additional evaluations of robust DFS programs delivered at scale, which consider effective implementation and measure appropriate biomarkers, are needed.
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Effect of salt reduction interventions in lowering blood pressure in Chinese populations: a systematic review and meta-analysis of randomised controlled trials.
Jin, A, Xie, W, Wu, Y
BMJ open. 2020;(2):e032941
Abstract
RATIONALE AND OBJECTIVE Salt reduction remains a global challenge and different salt reduction strategies have been studied in China. This study is to systematically evaluate evidence from randomised controlled trials (RCT) in China and inform the effective salt reduction strategies. DESIGN Systematic review and meta-analysis. DATA SOURCES MEDLINE, Embase, Cochrane Central Register of Controlled Trials, Wanfang Data and the China National Knowledge Infrastructure databases through October 2019. ELIGIBILITY CRITERIA RCTs conducted in China with at least 4 weeks' duration of study and blood pressure (BP) reported. DATA EXTRACTION AND SYNTHESIS Data were screened, extracted and appraised by two independent reviewers. The quality of study was assessed using a modified Cochrane Collaboration's risk of bias tool. The primary outcome was the difference in BP change from baseline to the end of study between interventions and control. The effects were pooled using a random effects model and associated factors were explored by a meta-regression. RESULTS We identified 24 studies involving 10 448 participants, including 8 studies on health education (4583 participants), 2 studies on salt restriction diet (162 participants), 1 study on salt restriction spoon (50 participants) and 13 studies on salt substitute (5653 participants). Six studies on salt substitute and three studies on health education were identified with high quality. Pooled results from the six studies showed that salt substitutes significantly reduced systolic BP (-5.7 mm Hg; 95% CI -8.5 to -2.8) and diastolic BP (-2.0 mm Hg; 95% CI -3.5 to -0.4). The School-EduSalt study showed that the school-based health education significantly reduced systolic BP among parents (-2.3 mm Hg; 95% CI -4.5 to -0.04). CONCLUSIONS Among four salt reduction strategies studied in China with RCT design, only salt substitute was proved effective in lowering BP by the pooled effect from multiple studies with high quality. More well-designed studies are warranted for other strategies.
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Associations of dietary carbohydrate and salt consumption with esophageal cancer risk: a systematic review and meta-analysis of observational studies.
Banda, KJ, Chiu, HY, Hu, SH, Yeh, HC, Lin, KC, Huang, HC
Nutrition reviews. 2020;(8):688-698
Abstract
CONTEXT Evidence has shown that essential nutrients are highly correlated with the occurrence of esophageal cancer (EC). However, findings from observational studies on the associations between dietary carbohydrate, salt consumption, and the risk of EC remain controversial. OBJECTIVE The aim of this study was to conduct a systematic review and meta-analysis to confirm the associations of dietary carbohydrate and salt consumption with EC risk. DATA SOURCE Various electronic databases (PubMed, MEDLINE, Embase, Google Scholar, Cochrane Library, Chinese Electronic Periodical Services, and China Knowledge Resource Integrated) were searched up until January 31, 2019. DATA EXTRACTION Data related to patient characteristics and study characteristics were extracted by 2 independent reviewers. The risk ratio reported as relative risk (RR) or odds ratio (OR) was extracted, and random-effects models were performed to estimate the summary risk ratio. RESULTS In total, 26 studies were included in this analysis, of which 12 studies, including 11 case-control studies and 1 cohort study, examined dietary carbohydrates, and 18 studies, including 16 case-control studies and 2 cohort studies, examined dietary salt. The pooled OR showed that dietary carbohydrate intake was inversely related to EC risk (OR = 0.62; 95% confidence interval [CI], 0.50-0.77), but positive correlations between dietary salt intake and the risk of EC were supported by the recruited case-control studies (OR = 1.97; 95% CI, 1.50-2.61) and cohort studies (RR = 1.04; 95% CI, 1.00-1.08). CONCLUSIONS Salt is an essential nutrient for body functions and biochemical processes. Providing health education and management regarding proper use of salt in daily foods and labeling the amount of sodium in manufactured products to reduce the risk of developing EC should be more appropriately performed in the general population.
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The hypotensive effect of salt substitutes in stage 2 hypertension: a systematic review and meta-analysis.
Jafarnejad, S, Mirzaei, H, Clark, CCT, Taghizadeh, M, Ebrahimzadeh, A
BMC cardiovascular disorders. 2020;(1):98
Abstract
BACKGROUND Hypertension (HTN) is a ubiquitous risk factor for numerous non-communicable diseases, including cardiovascular disease and stroke. There are currently no wholly effective pharmacological therapies for subjects with HTN. However, salt substitutes have emerged as a potential therapy for the treatment of HTN. The aim of the present study was to assess the effect of salt substitutes on reducing systolic blood pressure (SBP) and diastolic BP (DBP), following a meta-analysis of randomized controlled trials. METHODS Studies were found via systematic searches of the Pubmed/Medline, Scopus, Ovid, Google Scholar and Cochrane library. Ten studies, comprised of 11 trials and 1119 participants, were included in the meta-analysis. RESULTS Pooled weighted mean differences showed significant reductions of SBP (WMD - 8.87 mmHg; 95% CI - 11.19, - 6.55, p < 0.001) and DBP (WMD - 4.04 mmHg; 95% CI - 5.70, - 2.39) with no statistically significant heterogeneity between the 11 included comparisons of SBPs and DBPs. The stratified analysis of trials based on the mean age of participants showed a significant reduction in the mean difference of SBP in both adults (< 65 years old) and elderly (≥65 years old). However, the DBP-lowering effect of salt substitutes was only observed in adult patients (WMD - 4.22 mmHg; 95% CI - 7.85, - 0.58), but not in the elderly subjects. CONCLUSIONS These findings suggest that salt-substitution strategies could be used for lowering SBP and DBP in patients with stage 2 HTN; providing a nutritional platform for the treatment, amelioration, and prevention of HTN.
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Effects of low sodium diet versus high sodium diet on blood pressure, renin, aldosterone, catecholamines, cholesterol, and triglyceride.
Graudal, NA, Hubeck-Graudal, T, Jurgens, G
The Cochrane database of systematic reviews. 2020;(12):CD004022
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Abstract
BACKGROUND Recent cohort studies show that salt intake below 6 g is associated with increased mortality. These findings have not changed public recommendations to lower salt intake below 6 g, which are based on assumed blood pressure (BP) effects and no side-effects. OBJECTIVES To assess the effects of sodium reduction on BP, and on potential side-effects (hormones and lipids) SEARCH METHODS The Cochrane Hypertension Information Specialist searched the following databases for randomized controlled trials up to April 2018 and a top-up search in March 2020: the Cochrane Hypertension Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (from 1946), Embase (from 1974), the World Health Organization International Clinical Trials Registry Platform, and ClinicalTrials.gov. We also contacted authors of relevant papers regarding further published and unpublished work. The searches had no language restrictions. The top-up search articles are recorded under "awaiting assessment." SELECTION CRITERIA Studies randomizing persons to low-sodium and high-sodium diets were included if they evaluated at least one of the outcome parameters (BP, renin, aldosterone, noradrenalin, adrenalin, cholesterol, high-density lipoprotein, low-density lipoprotein and triglyceride,. DATA COLLECTION AND ANALYSIS Two review authors independently collected data, which were analysed with Review Manager 5.3. Certainty of evidence was assessed using GRADE. MAIN RESULTS Since the first review in 2003 the number of included references has increased from 96 to 195 (174 were in white participants). As a previous study found different BP outcomes in black and white study populations, we stratified the BP outcomes by race. The effect of sodium reduction (from 203 to 65 mmol/day) on BP in white participants was as follows: Normal blood pressure: SBP: mean difference (MD) -1.14 mmHg (95% confidence interval (CI): -1.65 to -0.63), 5982 participants, 95 trials; DBP: MD + 0.01 mmHg (95% CI: -0.37 to 0.39), 6276 participants, 96 trials. Hypertension: SBP: MD -5.71 mmHg (95% CI: -6.67 to -4.74), 3998 participants,88 trials; DBP: MD -2.87 mmHg (95% CI: -3.41 to -2.32), 4032 participants, 89 trials (all high-quality evidence). The largest bias contrast across studies was recorded for the detection bias element. A comparison of detection bias low-risk studies versus high/unclear risk studies showed no differences. The effect of sodium reduction (from 195 to 66 mmol/day) on BP in black participants was as follows: Normal blood pressure: SBP: mean difference (MD) -4.02 mmHg (95% CI:-7.37 to -0.68); DBP: MD -2.01 mmHg (95% CI:-4.37, 0.35), 253 participants, 7 trials. Hypertension: SBP: MD -6.64 mmHg (95% CI:-9.00, -4.27); DBP: MD -2.91 mmHg (95% CI:-4.52, -1.30), 398 participants, 8 trials (low-quality evidence). The effect of sodium reduction (from 217 to 103 mmol/day) on BP in Asian participants was as follows: Normal blood pressure: SBP: mean difference (MD) -1.50 mmHg (95% CI: -3.09, 0.10); DBP: MD -1.06 mmHg (95% CI:-2.53 to 0.41), 950 participants, 5 trials. Hypertension: SBP: MD -7.75 mmHg (95% CI:-11.44, -4.07); DBP: MD -2.68 mmHg (95% CI: -4.21 to -1.15), 254 participants, 8 trials (moderate-low-quality evidence). During sodium reduction renin increased 1.56 ng/mL/hour (95%CI:1.39, 1.73) in 2904 participants (82 trials); aldosterone increased 104 pg/mL (95%CI:88.4,119.7) in 2506 participants (66 trials); noradrenalin increased 62.3 pg/mL: (95%CI: 41.9, 82.8) in 878 participants (35 trials); adrenalin increased 7.55 pg/mL (95%CI: 0.85, 14.26) in 331 participants (15 trials); cholesterol increased 5.19 mg/dL (95%CI:2.1, 8.3) in 917 participants (27 trials); triglyceride increased 7.10 mg/dL (95%CI: 3.1,11.1) in 712 participants (20 trials); LDL tended to increase 2.46 mg/dl (95%CI: -1, 5.9) in 696 participants (18 trials); HDL was unchanged -0.3 mg/dl (95%CI: -1.66,1.05) in 738 participants (20 trials) (All high-quality evidence except the evidence for adrenalin). AUTHORS' CONCLUSIONS In white participants, sodium reduction in accordance with the public recommendations resulted in mean arterial pressure (MAP) decrease of about 0.4 mmHg in participants with normal blood pressure and a MAP decrease of about 4 mmHg in participants with hypertension. Weak evidence indicated that these effects may be a little greater in black and Asian participants. The effects of sodium reduction on potential side effects (hormones and lipids) were more consistent than the effect on BP, especially in people with normal BP.
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The effect of dietary salt on blood pressure in individuals receiving chronic dialysis: a systematic review and meta-analysis of randomised controlled trials.
Cole, NI, Swift, PA, He, FJ, MacGregor, GA, Suckling, RJ
Journal of human hypertension. 2019;(4):319-326
Abstract
Dietary salt reduction in the general population lowers blood pressure and cardiovascular risk. Despite being widely recommended, there is limited evidence as to whether this is applicable to individuals with end-stage renal disease (ESRD) receiving dialysis. Therefore, we carried out a systematic review and meta-analysis of randomised controlled trials (RCTs) investigating dietary salt reduction in individuals receiving dialysis. Studies were identified through search strategies for CENTRAL, MEDLINE, and EMBASE. Two authors independently assessed studies for eligibility with the inclusion criteria as follows: participants aged 18 years and over; a reduction in salt intake of at least 1 g/day over one week; no concomitant interventions during the study. The primary outcome was change in systolic and diastolic blood pressure. 848 reports were screened, from which 12 studies were selected for the systematic review. Four were RCTs (91 participants) that met the study inclusion criteria: three were conducted in haemodialysis patients and one in peritoneal dialysis patients; three were crossover trials and one was a parallel study. Dietary salt reduction was associated with an 8.4 mmHg reduction in systolic blood pressure (95% CI 4.8-12.0, Ι2 = 0%), and a 4.4 mmHg reduction in diastolic blood pressure (95% CI 2.2-6.6, Ι2 = 0%). In conclusion, few studies have investigated the role of dietary salt reduction in individuals with ESRD receiving dialysis, but these results suggest the importance of this intervention for lowering blood pressure in this group.
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Dose-response relation between dietary sodium and blood pressure: a meta-regression analysis of 133 randomized controlled trials.
Graudal, N, Hubeck-Graudal, T, Jürgens, G, Taylor, RS
The American journal of clinical nutrition. 2019;(5):1273-1278
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BACKGROUND The projected reduced mortality effect of reduced sodium intake in model-based studies conflicts with the observed increased mortality associated with low sodium intake in population studies. This may reflect an overestimation of the dose-response relation between sodium reduction (SR) and blood pressure (BP) used in mortality modeling studies. OBJECTIVES The present meta-regression analysis sought to estimate the dose-response relations between SR and BP in study groups with mean BP above or below the 75th percentile of the general population. METHODS Based on a literature search from 1 January 1946 to 11 April 2018, we identified 133 randomized controlled trials allocating healthy or hypertensive individuals to SR or usual sodium intake. Multivariable regression analyses of the mean SR versus the mean blood pressure effect adjusted for effect modifiers were performed. RESULTS In study groups with mean BP above the 75th percentile [131/78 mm Hg systolic BP (SBP)/diastolic BP (DBP)], there was strong evidence of a linear dose-response relation between SR and BP. For SBP, the dose-response relation was -7.7 mm Hg/100 mmol SR (95% CI: -10.4, -5.0), and for DBP it was -3.0 mm Hg/100 mmol SR (95% CI: -4.6, -1.4). In study groups with mean BP ≤ 131/78 mm Hg, the relation between SR and BP was weak. For SBP it was -1.46 mm Hg/100 mmol SR (95% CI: -2.7, -0.20) and for DBP it was: -0.07 mm Hg/100 mmol SR (95% CI: -1.5, 1.4). CONCLUSIONS Only study groups with a BP in the highest 25th percentile of the population showed a clinically significant drop in BP with SR. The policy of lowering dietary sodium intake in the general population may need to be reframed to target patients with hypertension. This study was registered at PROSPERO 2015 as CRD42015017773.
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Dietary Salt Restriction in Chronic Kidney Disease: A Meta-Analysis of Randomized Clinical Trials.
Garofalo, C, Borrelli, S, Provenzano, M, De Stefano, T, Vita, C, Chiodini, P, Minutolo, R, De Nicola, L, Conte, G
Nutrients. 2018;(6)
Abstract
BACKGROUND A clear evidence on the benefits of reducing salt in people with chronic kidney disease (CKD) is still lacking. Salt restriction in CKD may allow better control of blood pressure (BP) as shown in a previous systematic review while the effect on proteinuria reduction remains poorly investigated. METHODS We performed a meta-analysis of randomized controlled trials (RCTs) evaluating the effects of low versus high salt intake in adult patients with non-dialysis CKD on change in BP, proteinuria and albuminuria. RESULTS Eleven RCTs were selected and included information about 738 CKD patients (Stage 1⁻4); urinary sodium excretion was 104 mEq/day (95%CI, 76⁻131) and 179 mEq/day (95%CI, 165⁻193) in low- and high-sodium intake subgroups, respectively, with a mean difference of −80 mEq/day (95%CI from −107 to −53; p <0.001). Overall, mean differences in clinic and ambulatory systolic BP were −4.9 mmHg (95%CI from −6.8 to −3.1, p <0.001) and −5.9 mmHg (95%CI from −9.5 to −2.3, p <0.001), respectively, while clinic and ambulatory diastolic BP were −2.3 mmHg (95%CI from −3.5 to −1.2, p <0.001) and −3.0 mmHg (95%CI from −4.3 to −1.7; p <0.001), respectively. Mean differences in proteinuria and albuminuria were −0.39 g/day (95%CI from −0.55 to −0.22, p <0.001) and −0.05 g/day (95%CI from −0.09 to −0.01, p = 0.013). CONCLUSION Moderate salt restriction significantly reduces BP and proteinuria/albuminuria in patients with CKD (Stage 1⁻4).
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Comparative Efficacy of Antihypertensive Agents in Salt-Sensitive Hypertensive Patients: A Network Meta-Analysis.
Qi, H, Liu, Z, Cao, H, Sun, WP, Peng, WJ, Liu, B, Dong, SJ, Xiang, YT, Zhang, L
American journal of hypertension. 2018;(7):835-846
Abstract
BACKGROUND Salt-sensitive hypertension (SSH) is an intermediate inherited phenotype of essential hypertension as well as being an independent risk factor for cardiovascular disease. However, effective medications for the treatment of SSH have not been clarified. This study was to compare the efficacious of different classes of antihypertensive agents combined with salt intake on the reduction of blood pressure (BP) in patients with SSH. METHODS We used sources as PubMed, EMBASE, Cochrane Library, Cochrane Central Register of Controlled Trials (CENTRAL), ClinicalTrials.gov, International Clinical Trials Registry Platform (ICTRP), CNKI, and WANFANG database from inception to November 2016. Studies that compared the efficacy of 2 or more antihypertensive agents or placebos in adult salt-sensitive hypertensive patients were included. The outcomes included variations in mean arterial blood pressure, systolic and diastolic blood pressure. RESULTS Twenty-five studies were involved in this meta-analysis. A calcium channel blocker (CCB) with hydrochlorothiazide and moderate salt intake was significantly the most efficacious in comparison with placebo (standardized mean differences (SMD), 95% credibility intervals (CI): 26.66, 12.60 to 40.16), angiotensin receptor blockers (ARBs) (SMD, 95% CI: 22.94, 5.26 to 40.51), and the other interventions for patients with SSH and no concomitant diseases. For SSH patients who were obese, CCB with metformin and moderate salt intake would decrease blood pressure with 17.90 mm Hg. CONCLUSIONS For SSH patients with no concomitant diseases, CCB combined with hydrochlorothiazide and moderate salt intake was optimal in reducing BP, while CCB combined with metformin and moderate salt intake was the most efficacious at reducing BP in SSH patients with coexisting obesity.
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Sodium intake and blood pressure in children and adolescents: a systematic review and meta-analysis of experimental and observational studies.
Leyvraz, M, Chatelan, A, da Costa, BR, Taffé, P, Paradis, G, Bovet, P, Bochud, M, Chiolero, A
International journal of epidemiology. 2018;(6):1796-1810
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Abstract
BACKGROUND High sodium intake is a cause of elevated blood pressure in adults. In children and adolescents, less evidence is available and findings are equivocal. We systematically reviewed the evidence from experimental and observational studies on the association between sodium intake and blood pressure in children and adolescents. METHODS A systematic search of the Medline, Embase, CINAHL and CENTRAL databases up to March 2017 was conducted and supplemented by a manual search of bibliographies and unpublished studies. Experimental and observational studies involving children or adolescents between 0 and 18 years of age were included. Random-effects meta-analyses were performed by pooling data across all studies, separately for experimental and observational studies, and restricting to studies with sodium intake and blood pressure measurement methods of high quality. Subgroup meta-analyses, sensitivity analyses and meta-regressions were conducted to investigate sources of heterogeneity and confounding. The dose-response relationship was also investigated. RESULTS Of the 6572 publications identified, 85 studies (14 experimental; 71 observational, including 60 cross-sectional, 6 cohort and 5 case-control studies) with 58 531 participants were included. In experimental studies, sodium reduction interventions decreased systolic blood pressure by 0.6 mm Hg [95% confidence interval (CI): 0.5, 0.8] and diastolic blood pressure by 1.2 mm Hg (95% CI: 0.4, 1.9). The meta-analysis of 18 experimental and observational studies (including 3406 participants) with sodium intake and blood pressure measurement methods of high quality showed that, for every additional gram of sodium intake per day, systolic blood pressure increased by 0.8 mm Hg (95% CI: 0.4, 1.3) and diastolic blood pressure by 0.7 mm Hg (95% CI: 0.0, 1.4). The association was stronger among children with overweight and with low potassium intake. A quasi-linear relationship was found between sodium intake and blood pressure. CONCLUSIONS Sodium intake is positively associated with blood pressure in children and adolescents, with consistent findings in experimental and observational studies. Since blood pressure tracks across the life course, our findings support the reduction of sodium intake during childhood and adolescence to lower blood pressure and prevent the development of hypertension.