Low urinary sodium is associated with greater risk of myocardial infarction among treated hypertensive men

Sodium Intake and Incident Atrial Fibrillation in Individuals With Vascular Disease

Importance

Numerous prospective cohort studies have reported a J-shaped association of urinary sodium excretion with cardiovascular events and mortality.

Objective

To study the association between sodium intake and incident atrial fibrillation (AF).

Design, Setting, and Participants

This cohort study included participants in the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET) and Telmisartan Randomised Assessment Study in ACE Intolerant Subjects With Cardiovascular Disease (TRANSCEND) multicenter, randomized clinical trials comparing the effect of ramipril 10 mg daily with telmisartan 80 mg daily, or their combination (ONTARGET) or 80 mg telmisartan daily with placebo (TRANSCEND) for the outcome of death from cardiovascular causes, myocardial infarction, stroke, or hospitalization for heart failure. ONTARGET and TRANSCEND included 31 546 participants with vascular disease or high-risk diabetes, and this study excluded participants without a urine sample for sodium measurement, missing data for key covariates, a history of AF, or AF detected in the first year after enrollment. Analyses were performed in July 2023 to May 2024.

Exposure

Estimated sodium intake from a morning fasting urine sample (Kawasaki formula).

Main Outcomes and Measures

The main outcome was incident AF. The association between estimated sodium intake and incident AF was modeled using multivariable adjusted Cox regression and cubic splines.

Results

A total of 27 391 participants (mean [SD] age, 66.3 [7.2] years; 19 310 [70.5%] male) were included. Mean (SD) estimated sodium intake was 4.8 (1.6) g/d. During a mean (SD) follow-up of 4.6 (1.0) years, 1562 participants (5.7%) had incident AF. After multivariable adjustment, a J-shaped association between sodium intake and AF risk was observed (P for nonlinearity = .03). Sodium intake of 8 g/d or greater (3% of participants) was associated with incident AF (hazard ratio, 1.32; 95% CI, 1.01-1.74) compared with sodium intake of 4 to 5.99 g/d. Cubic splines showed that sodium intake greater than 6 g/d (19% of participants) was associated with a 10% increased AF risk per additional 1-g/d sodium intake (hazard ratio, 1.10; 95% CI, 1.03-1.18), but with no further lowering of AF risk at lower levels of sodium intake.

Conclusions and Relevance

In this cohort study of sodium intake and AF risk, there was a J-shaped association between sodium intakes and AF risk in patients with cardiovascular disease or diabetes. Lowering sodium intake for AF prevention is best targeted at individuals who consume high sodium diets.

Sodium - a systematic review for Nordic Nutrition Recommendations 2023

Blood pressure (BP) rises along with increasing sodium intake from early childhood to late adulthood, and leads to hypertension among most men and women living in Nordic and Baltic countries. Elevated BP is the leading global risk factor for premature deaths and disability-adjusted life-years. A reduction in sodium intake is essential in the prevention of hypertension in individuals, in the lowering of BP levels, in the treatment of hypertensive individuals, and in decreasing risks associated with elevated BP. There is a progressive linear dose-response relationship between sodium intake and BP beginning from a sodium intake of less than 0.8 g/day. Sodium reduction decreases BP linearly by a dose-response manner down to a sodium intake level of less than 2 g/day. Randomised intervention studies with a duration of at least 4 weeks confirm the efficiency and safety of reducing blood sodium intake to a level of less than 2 g/day. Results from prospective cohort studies show that higher sodium intake is positively associated with an increased risk of stroke and cardiovascular events and mortality among the general adult population, and the associations are linear in studies using proper sodium assessment methods. Analyses assessing sodium intake using at least two 24-h urine samples have shown a linear positive relationship between sodium intake and the risk of a cardiovascular event or death. Based on an overall evaluation of the available data, a limitation of the sodium intake to 2.0 g/day is suggested for adults. The optimal sodium intake level would be probably about 1.5 g/day. Sodium intake recommended for children can be extrapolated from the recommended sodium intake for adults. According to national dietary surveys, the average sodium intakes in Nordic countries range in adult men from 3.6 to 4.4 g/day and in adult women from 2.6. to 3.2 g/day, and in Baltic countries in men from 2.6 to 5.1 g/day and in women from 1.8 to 3.6 g/day.

Sodium restriction and insulin resistance: A review of 23 clinical trials

Background: Many clinicians recommend low-salt diets for lowering blood pressure but there may be unintended consequences such as worsening insulin resistance.Aim: This paper aimed to find human clinical studies looking at low-salt diets on markers of glucose and insulin.Methods: We reviewed PubMed using the search terms ‘sodium’, ‘insulin’ and ‘insulin resistance’ and found 23 human clinical studies testing low-salt diets showing negative harms on insulin or glucose.Results: Twenty-three human clinical trials have shown that low-salt diets lead to systemic or vascular insulin resistance, glucose intolerance, elevated fasting insulin and/or elevations in glucose and/or insulin levels after an oral glucose tolerance test.Conclusion: We discovered 23 human clinical studies showing that low-salt diets worsen markers of insulin and glucose. Caution is advised when recommending salt restriction for blood pressure control as this may lead to worsening insulin resistance.Contribution: This review has revealed that low salt diets can induce insulin resistance.

Monitoring population salt intake using casual urinary sodium: Tehran Lipid and Glucose Study

BACKGROUND

We aimed to estimate salt intake among an Iranian population using spot urine-based equations and a dietary-based method.

METHODS

Adult men and women (n = 2069) were recruited from the Tehran Lipid and Glucose Study (2014-2017). Urinary sodium (Na), potassium (K), and creatinine (Cr) concentrations were measured in the morning spot urine samples. The 24-h urinary Na excretion and predicted salt intake was estimated using five equations, i.e., Kawasaki, Tanaka, Intersalt, Toft, and Whitton. A validated food frequency questionnaire (FFQ) was used to obtain dietary intake of salt. The agreement of each urinary- and FFQ-based salt estimation with the overall mean of the methods, considered as the gold standard, was assessed using the Bland-Altman method.

RESULTS

Mean age of the participants was 45.6 ± 14.8 y, and 45.4% were men. Mean (SD) estimated salt intake, derived from the overall mean of the methods, was 9.0 ± 2.2 g/d (10.2 ± 2.1 and 7.9 ± 1.7 g/d in men and women, respectively). Mean bias of the estimations from the overall mean ranged from - 0.2.42 to 2.75 g/d, with the Tanaka equation having the least bias (mean bias = 0.13 ± 1.10, 95% CI - 2.37, 2.30 g/d). Tanaka estimated a mean salt intake of 8.9 g/d (range 2.1 to 18.7 g/d); accordingly, only 5.1% of participants adhered to the recommendation (< 5 g/d salt intake), whereas 26.8% and 2.4% exceeded the recommendation by 2- and threefold.

CONCLUSION

The Tanaka equation could provide a more accurate mean-population estimated salt intake from casual urinary Na concentration in our population. About 95% of the Iranian population exceeded the current recommendations of salt intake.

Salt and cardiovascular disease: insufficient evidence to recommend low sodium intake

Several blood pressure guidelines recommend low sodium intake (<2.3 g/day, 100 mmol, 5.8 g/day of salt) for the entire population, on the premise that reductions in sodium intake, irrespective of the levels, will lower blood pressure, and, in turn, reduce cardiovascular disease occurrence. These guidelines have been developed without effective interventions to achieve sustained low sodium intake in free-living individuals, without a feasible method to estimate sodium intake reliably in individuals, and without high-quality evidence that low sodium intake reduces cardiovascular events (compared with moderate intake). In this review, we examine whether the recommendation for low sodium intake, reached by current guideline panels, is supported by robust evidence. Our review provides a counterpoint to the current recommendation for low sodium intake and suggests that a specific low sodium intake target (e.g. <2.3 g/day) for individuals may be unfeasible, of uncertain effect on other dietary factors and of unproven effectiveness in reducing cardiovascular disease. We contend that current evidence, despite methodological limitations, suggests that most of the world's population consume a moderate range of dietary sodium (2.3-4.6g/day; 1-2 teaspoons of salt) that is not associated with increased cardiovascular risk, and that the risk of cardiovascular disease increases when sodium intakes exceed 5 g/day. While current evidence has limitations, and there are differences of opinion in interpretation of existing evidence, it is reasonable, based upon observational studies, to suggest a population-level mean target of <5 g/day in populations with mean sodium intake of >5 g/day, while awaiting the results of large randomized controlled trials of sodium reduction on incidence of cardiovascular events and mortality.

24-h urinary sodium excretion and the risk of adverse outcomes

AIMS

The objective was to evaluate whether sodium intake, assessed with the gold standard 24-h urinary collections, was related to long-term incidence of death, cardiovascular disease (CVD) and diabetes mellitus (DM).

METHODS

A cohort of 4630 individuals aged 25-64 years collected 24-h urine samples in 1979-2002 and were followed up to 14 years for the incidence of any CVD, coronary heart disease (CHD), stroke, heart failure (HF) and DM event, and death. Cox proportional hazards models were used to estimate the association between the baseline salt intake and incident events and adjusted for baseline age, body mass index, serum cholesterol, prevalent DM, and stratified by sex and cohort baseline year.

RESULTS

During the follow-up, we observed 423 deaths, 424 CVD events (288 CHD events, 142 strokes, 139 HF events) and 161 DM events. Compared with the highest quartile of salt intake, persons in the lowest quartile had a lower incidence of CVD (hazard ratio [HR] 0.70; 95% confidence interval [CI], 0.51-0.95, p = .02), CHD (HR 0.63 [95% CI 0.42-0.94], p = .02) and DM (HR 0.52 [95% CI 0.31-0.87], p = .01). The results were non-significant for mortality, HF, and stroke.

CONCLUSION

High sodium intake is associated with an increased incidence of CVD and DM.

Effectiveness and Feasibility of Taxing Salt and Foods High in Sodium: A Systematic Review of the Evidence

Diets high in salt are a leading risk for death and disability globally. Taxing unhealthy food is an effective means of influencing what people eat and improving population health. Although there is a growing body of evidence on taxing products high in sugar, and unhealthy foods more broadly, there is limited knowledge or experience of using fiscal measures to reduce salt consumption. We searched peer-reviewed databases [MEDLINE, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), and the Cochrane Database of Systematic Reviews] and gray literature for studies published between January 2000 and October 2019. Studies were included if they provided information on the impact on salt consumption of: taxes on salt; taxes on foods high in salt, and taxes on unhealthy foods defined to include foods high in salt. Studies were excluded if their definition of unhealthy foods did not specify high salt or sodium. We found 18 relevant studies, including 15 studies reporting the effects of salt taxes through modeling (8), real-world evaluation (4), experimental design (2), or review of cost-effectiveness (1); 6 studies providing information relevant to country implementation of salt taxes; and 2 studies reporting stakeholder perceptions toward salt taxation. Although there is some evidence on the potential effectiveness and cost-effectiveness of salt taxation, especially from modeling studies, uptake of salt taxation is limited in practice. Some modeling studies suggested that food taxes can have unintended outcomes such as reduced consumption of healthy foods, or increased consumption of unhealthy, untaxed substitutes. In contrast, modeling studies that combined taxes for unhealthy foods with subsidies found that the benefits were increased. Modeling suggests that taxing all foods based on their salt content is likely to have more impact than taxing specific products high in salt given that salt is pervasive in the food chain. However, the limited experience we found suggests that policy-makers favor taxing specific products.

Sodium Intake, Circulating Microvesicles and Cardiovascular Outcomes in Type 2 Diabetes

There is ongoing debate surrounding the complex relationship between dietary sodium intake and cardiovascular morbidity and mortality. The existing literature consists largely of observational studies that have demonstrated positive, negative, U-/J-shaped or unclear associations between sodium intake and cardiovascular outcomes. Our group and others have previously demonstrated an inverse relationship between dietary sodium intake and cardiovascular outcomes in people with type 2 diabetes. Increased activity of the renin-angiotensin-aldosterone system and sympathetic nervous system is postulated to contribute to these paradoxical findings through endothelial dysfunction, a precursor to the development of cardiovascular disease. Microvesicles are submicron (0.1 - 1.0μm) vesicles that form during cellular activation, injury or death with endothelial microvesicles being recognized markers of endothelial dysfunction. They are pathologically elevated in a variety of vascular-related conditions including type 2 diabetes. Lower habitual sodium intake in type 2 diabetes has been associated with higher pro-coagulant platelet microvesicles levels but not with endothelial microvesicles. Research utilizing endothelial microvesicles to evaluate the mechanistic relationship between dietary sodium intake and adverse cardiovascular outcomes in type 2 diabetes remains scarce.

Association of sodium intake and major cardiovascular outcomes: a dose-response meta-analysis of prospective cohort studies

Background

The association of sodium intake with the risk of cardiovascular morbidity and mortality is inconsistent. Thus, the present meta-analysis was conducted to summarize the strength of association between sodium intake and cardiovascular morbidity and mortality.

Methods

PubMed, Embase, and the Cochrane Library were searched systematically to identify the relevant studies up to October 2017. The effect estimates for 100 mmol/day increase in sodium intake were calculated using 95% confidence intervals (CIs) of cardiac death, total mortality, stroke, or stroke mortality for low (< 3 g/d), moderate (3–5 g/d), or heavy (> 5 g/d) sodium intake, and minimal sodium intake comparison.

Results

A total of 16 prospective cohort studies reported data on 205,575 individuals. The results suggested that an increase in sodium intake by 100 mmol/d demonstrated little or no effect on the risk of cardiac death (P = 0.718) and total mortality (P = 0.720). However, the risk of stroke incidence (P = 0.029) and stroke mortality (P = 0.007) was increased significantly by 100 mmol/day increment of sodium intake. Furthermore, low sodium intake was associated with an increased risk of cardiac death (P = 0.003), while moderate (P < 0.001) or heavy (P = 0.001) sodium intake was associated with an increased risk of stroke mortality.

Conclusions

These findings suggested that sodium intake by 100 mmol/d increment was associated with an increased risk of stroke incidence and stroke mortality. Furthermore, low sodium intake was related to an increased cardiac death risk, while moderate or heavy sodium intake was related to an increased risk of stroke mortality.

Simple dietary advice reduces 24-hour urinary sodium excretion, blood pressure, and drug consumption in hypertensive patients

Sodium intake should be restricted to 100 mEq, that is, about 2.3 grams per day. Strict diets, however, are often cumbersome and seldom matched by rigorous compliance. We studied 291 patients on antihypertensive treatment, 240 of whom were instructed to avoid salty foods, such as cheese and cured meats, and to switch from regular bread to salt-free bread. The remaining 51 matched patients constituted a control group and received only generic dietary advice. Na[U]/24h, K[U]/24h, and office BP (automated repeated measurements) were recorded before dieting started and after 9 ± 1 weeks of dieting. Our intervention group showed a significant decrease in body weight (71.75 ± 14.0 to 70.54 ± 13.33 kg, P < .0001), sodium excretion (153.1 ± 44.61 to 133.5 ± 37.1 mEq/24h, P < .05), systolic and diastolic BP (134.16 ± 16.0 to 126.5 ± 10.53 mm Hg, P = .014 and 80.59 ± 11.47 to 75.9 ± 8.72 mm Hg, P = .026, respectively), and drug consumption (1.71 ± 0.91 to 1.49 ± 0.84 DDD, P < .05). The rate of responders to antihypertensive therapy increased (51.4% to 79.5%). In the control group neither significant nor substantial changes were seen. Our data suggest that even a minimal reduction in the apparent sodium intake (∼0.5 grams per day) can improve both BP values and responder rates in treated hypertensive patients, while reducing the consumption of antihypertensive drugs.

Addictive salt may not be solely responsible for causing hypertension: A sweet and fatty hypothesis

In literature, since many decades, it is often believed and condoned that excessive common salt (Nacl) ingestion can lead to hypertension. Hence, every health organisation, agencies and physicians have been advising salt restriction to hypertensive patients. However, there is no concrete evidence suggesting that salt restriction can reduce the risk of hypertension (HTN). The present article is based on the current literature search which was performed using MEDLINE, EMBASE, Google Scholar and PubMed. The meta-analysis, randomised control trials, clinical trials and review articles were chosen. The present review article suggests that consumption of high salt diet does not lead to hypertension and there are other factors which can lead to hypertension, sugar and fats being the main reasons. Salt can however lead to addiction and generally, these salty food items have a larger proportion of sugar and fats, which if over-consumed has a potential to cause obesity, hyperlipidaemia and subsequently, hypertension and other cardiovascular disorders. Hence, through the present review, I would like to suggest all the physicians to ask the hypertensive patients to cut down the intake of sugar and fat containing food items and keep a check on addiction of salty food items.

Rationale, design, and baseline characteristics of the Salt Substitute and Stroke Study (SSaSS)-A large-scale cluster randomized controlled trial

Lowering sodium intake with a reduced-sodium, added potassium salt substitute has been proved to lower blood pressure levels. Whether the same strategy will also reduce the risks of vascular outcomes is uncertain and controversial. The SSaSS has been designed to test whether sodium reduction achieved with a salt substitute can reduce the risk of vascular disease. The study is a large-scale, open, cluster-randomized controlled trial done in 600 villages across 5 provinces in China. Participants have either a history of stroke or an elevated risk of stroke based on age and blood pressure level at entry. Villages were randomized in a 1:1 ratio to intervention or continued usual care. Salt substitute is provided free of charge to participants in villages assigned to the intervention group. Follow-up is scheduled every 6months for 5years, and all potential endpoints are reviewed by a masked adjudication committee. The primary end point is fatal and nonfatal stroke, and the 2 secondary endpoints are total major cardiovascular events and total mortality. The study has been designed to provide 90% statistical power (with 2-sided α = .05) to detect a 13% or greater relative risk reduction for stroke. The power estimate assumes a primary outcome event rate of 3.5% per year and a systolic blood pressure difference of 3.0mm Hg between randomized groups. Recruitment is complete and there are 20,996 participants (about 35 per village) that have been enrolled. Mean age is 65years and 49% are female. There were 73% enrolled on the basis of a history of stroke. The trial is well placed to describe the effects of salt substitution on the risks of vascular disease and death and will provide important policy-relevant data.

Assessing Sex Differences in the Risk of Cardiovascular Disease and Mortality per Increment in Systolic Blood Pressure: A Systematic Review and Meta-Analysis of Follow-Up Studies in the United States

In the United States (US), cardiovascular (CV) disease accounts for nearly 20% of national health care expenses. Since costs are expected to increase with the aging population, informative research is necessary to address the growing burden of CV disease and sex-related differences in diagnosis, treatment, and outcomes. Hypertension is a major risk factor for CV disease and mortality. To evaluate whether there are sex-related differences in the effect of systolic blood pressure (SBP) on the risk of CV disease and mortality, we performed a systematic review and meta-analysis. We conducted a comprehensive search using PubMed and Google Scholar to identify US-based studies published prior to 31 December, 2015. We identified eight publications for CV disease risk, which provided 9 female and 8 male effect size (ES) observations. We also identified twelve publications for CV mortality, which provided 10 female and 18 male ES estimates. Our meta-analysis estimated that the pooled ES for increased risk of CV disease per 10 mmHg increment in SBP was 25% for women (95% Confidence Interval (CI): 1.18, 1.32) and 15% for men (95% CI: 1.11, 1.19). The pooled increase in CV mortality per 10 mm Hg SBP increment was similar for both women and men (Women: 1.16; 95% CI: 1.10, 1.23; Men: 1.17; 95% CI: 1.12, 1.22). After adjusting for age and baseline SBP, the results demonstrated that the risk of CV disease per 10 mm Hg SBP increment for women was 1.1-fold higher than men (P<0.01; 95% CI: 1.04, 1.17). Heterogeneity was moderate but significant. There was no significant sex difference in CV mortality.

Sodium Excretion and the Risk of Cardiovascular Disease in Patients With Chronic Kidney Disease

IMPORTANCE

Patients with chronic kidney disease (CKD) are at an increased risk of cardiovascular disease (CVD) compared with the general population. Prior studies have produced contradictory results on the association of dietary sodium intake with risk of CVD, and this relationship has not been investigated in patients with CKD.

OBJECTIVE

To evaluate the association between urinary sodium excretion and clinical CVD events among patients with CKD.

DESIGN, SETTING, AND PARTICIPANTS

A prospective cohort study of patients with CKD from 7 locations in the United States enrolled in the Chronic Renal Insufficiency Cohort Study and followed up from May 2003 to March 2013.

EXPOSURES

The cumulative mean of urinary sodium excretion from three 24-hour urinary measurements and calibrated to sex-specific mean 24-hour urinary creatinine excretion.

MAIN OUTCOMES AND MEASURES

A composite of CVD events defined as congestive heart failure, stroke, or myocardial infarction. Events were reported every 6 months and confirmed by medical record adjudication.

RESULTS

Among 3757 participants (mean age, 58 years; 45% women), 804 composite CVD events (575 heart failure, 305 myocardial infarction, and 148 stroke) occurred during a median 6.8 years of follow-up. From lowest (<2894 mg/24 hours) to highest (≥4548 mg/24 hours) quartile of calibrated sodium excretion, 174, 159, 198, and 273 composite CVD events occurred, and the cumulative incidence was 18.4%, 16.5%, 20.6%, and 29.8% at median follow-up. In addition, the cumulative incidence of CVD events in the highest quartile of calibrated sodium excretion compared with the lowest was 23.2% vs 13.3% for heart failure, 10.9% vs 7.8% for myocardial infarction, and 6.4% vs 2.7% for stroke at median follow-up. Hazard ratios of the highest quartile compared with the lowest quartile were 1.36 (95% CI, 1.09-1.70; P = .007) for composite CVD events, 1.34 (95% CI, 1.03-1.74; P = .03) for heart failure, and 1.81 (95% CI, 1.08-3.02; P = .02) for stroke after multivariable adjustment. Restricted cubic spline analyses of the association between sodium excretion and composite CVD provided no evidence of a nonlinear association (P = .11) and indicated a significant linear association (P < .001).

CONCLUSIONS AND RELEVANCE

Among patients with CKD, higher urinary sodium excretion was associated with increased risk of CVD.

Effect of sodium intake on renin level: Analysis of general population and meta-analysis of randomized controlled trials

BACKGROUND

We evaluated the association between sodium intake and plasma renin levels in the cross sectional study and meta-analysis of randomized controlled trials, whether there is a persistent elevation of plasma renin by longer-term sodium intake restriction.

METHODS

Plasma renin activity (PRA) and 24-h urine sodium (24HUNa) excretion were measured from individuals randomly selected from a community. Simple and multiple linear regression analyses adjusted for age, 24-h systolic blood pressure, 24-h average heart rate, fasting blood glucose and gender were performed. For meta-analysis, 74 studies published from 1975 to mid-2014 were identified in a systematic literature search using EMBASE, CINAHL, and MEDLINE. Random effects meta-analyses and a meta-regression analysis were performed.

RESULTS

Among the 496 participants recruited, 210 normotensive and 87 untreated hypertensive subjects were included in the analysis. There was no significant association between PRA and 24HUNa in the total population, or hypertensive and normotensive individuals. In the meta-analysis, the standard mean difference (SMD) of renin level by sodium intake reduction was 1.26 (95% CI: 1.08 to 1.44, Z=12.80, P<0.001, I(2)=87%). In the meta-regression analysis, an increase in a day of intervention was associated with a fall in SMD by -0.04 (95% CI: -0.05 to -0.02, Z=-5.27, P<0.001, I(2)=86%), indicating that longer duration of reduced sodium intake would lead to lesser SMD of renin level.

CONCLUSIONS

The present population based cross-sectional study and meta-analysis suggests that prolonged reduction in sodium intake is very unlikely associated with elevation of plasma renin levels.

Dietary sodium modulation of aldosterone activation and renal function during the progression of experimental heart failure

AIMS

Aldosterone activation is central to the sodium–fluid retention that marks the progression of heart failure (HF). The actions of dietary sodium restriction, a mainstay in HF management, on cardiorenal and neuroendocrine adaptations during the progression of HF are poorly understood. The study aim was to assess the role of dietary sodium during the progression of experimental HF.

METHODS AND RESULTS

Experimental HF was produced in a canine model by rapid right ventricular pacing which evolves from early mild HF to overt, severe HF. Dogs were fed one of three diets: (i) high sodium [250 mEq (5.8 g) per day, n =6]; (ii) standard sodium [58 mEq (1.3 g) per day, n =6]; and (iii) sodium restriction [11 mEq (0.25 g) per day, n =6]. During the 38-day study, haemodynamics, renal function, plasma renin activity (PRA), and aldosterone were measured. Changes in haemodynamics at 38 days were similar in all three groups, as were changes in renal function. Aldosterone activation was demonstrated in all three groups; however, dietary sodium restriction, in contrast to high sodium, resulted in early (10 days) activation of PRA and aldosterone. High sodium demonstrated significant suppression of aldosterone activation over the course of HF progression.

CONCLUSIONS

Excessive dietary sodium restriction particularly in early stage HF results in early aldosterone activation, while normal and excess sodium intake are associated with delayed or suppressed activation. These findings warrant evaluation in humans to determine if dietary sodium manipulation, particularly during early stage HF, may have a significant impact on neuroendocrine disease progression.

Salt, Angiotensin II, Superoxide, and Endothelial Function

Proper function of the vascular endothelium is essential for cardiovascular health, in large part due to its antiproliferative, antihypertrophic, and anti-inflammatory properties. Crucial to the protective role of the endothelium is the production and liberation of nitric oxide (NO), which not only acts as a potent vasodilator, but also reduces levels of reactive oxygen species, including superoxide anion (O2•-). Superoxide anion is highly injurious to the vasculature because it not only scavenges NO molecules, but has other damaging effects, including direct oxidative disruption of normal signaling mechanisms in the endothelium and vascular smooth muscle cells. The renin-angiotensin system plays a crucial role in the maintenance of normal blood pressure. This function is mediated via the peptide hormone angiotensin II (ANG II), which maintains normal blood volume by regulating Na+ excretion. However, elevation of ANG II above normal levels increases O2•- production, promotes oxidative stress and endothelial dysfunction, and plays a major role in multiple disease conditions. Elevated dietary salt intake also leads to oxidant stress and endothelial dysfunction, but these occur in the face of salt-induced ANG II suppression and reduced levels of circulating ANG II. While the effects of abnormally high levels of ANG II have been extensively studied, far less is known regarding the mechanisms of oxidant stress and endothelial dysfunction occurring in response to chronic exposure to abnormally low levels of ANG II. The current article focuses on the mechanisms and consequences of this less well understood relationship among salt, superoxide, and endothelial function.

Lanosterol Synthase Gene Polymorphisms and Changes in Endogenous Ouabain in the Response to Low Sodium Intake

Circulating levels of endogenous ouabain (EO), a vasopressor hormone of adrenocortical origin, are increased by sodium depletion. Furthermore, lanosterol synthase, an enzyme involved in cholesterol biosynthesis, has a missense polymorphism (rs2254524 V642L) that affects EO biosynthesis in adrenocortical cells. Here, we investigated the hypothesis that lanosterol synthase rs2254524 alleles in vivo impact the blood pressure (BP) and EO responses evoked by a low dietary Na intake (<100 mEq/d, 2 weeks) among patients with mild essential hypertension. During the low salt diet, the declines in both systolic BP (SBP: -8.7±1.7 versus -3.0±1.5; P=0.013) and diastolic BP (DBP: -5.1±0.98 versus -1.4±0.94 mm Hg; P<0.05), and the slope of the long-term pressure-natriuresis relationship affected significantly the presence of the lanosterol synthase rs2254524 A variant (AA: 0.71±0.22, AC 0.09±0.13, and CC 0.04±0.11 mEq/mm Hg/24 h; P=0.028). In addition, BP rose in ≈25% of the patients in response to the low salt diet and this was associated with increased circulating EO. Lanosterol synthase gene polymorphisms influence both the salt sensitivity of BP and changes in circulating EO in response to a low salt diet. The response of BP and EO to the low salt diet is markedly heterogeneous. Approximately 25% of patients experienced adverse effects, that is, increased BP and EO when salt intake was reduced and may be at increased long-term risk. The augmented response of EO to the low salt diet further supports the view that adrenocortical function is abnormal in some essential hypertensives.

High sodium intake: review of recent issues on its association with cardiovascular events and measurement methods

There has been a long-known association between high dietary sodium intake and hypertension, as well as the increased risk of cardiovascular disease. Reduction of sodium intake is a major challenge for public health. Recently, there have been several controversial large population-based studies regarding the current recommendation for dietary sodium intake. Although these studies were performed in a large population, they aroused controversies because they had a flaw in the study design and methods. In addition, knowledge of the advantages and disadvantages of the methods is essential in order to obtain an accurate estimation of sodium intake. I have reviewed the current literatures on the association between sodium intake and cardiovascular events, as well as the methods for the estimation of sodium intake.

Reducing salt intake for prevention of cardiovascular disease--times are changing

The evidence relating blood pressure to salt intake in humans originates from population studies and randomized clinical trials of interventions on dietary salt intake. Estimates from meta-analyses of trials in normotensive subjects generally are similar to estimates derived from prospective population studies (+1.7 mm Hg increase in systolic blood pressure per 100-mmol increment in 24-hour urinary sodium). This estimate, however, does not translate into an increased risk of incident hypertension in subjects consuming a high salt diet. Prospective studies relating health outcomes to 24-hour urinary sodium excretion produced inconsistent results. Taken together, available evidence does not support the current recommendations of a generalized and indiscriminate reduction of salt intake at the population level, although the blood pressure-lowering effect of dietary sodium restriction might be of value in hypertensive patients.

Assessing the associations of sodium intake with long-term all-cause and cardiovascular mortality in a hypertensive cohort

BACKGROUND

Although higher sodium intake is known to increase blood pressure, its association with cardiovascular mortality is less established. We examined the association of baseline sodium intake in a hypertensive cohort with all-cause and cardiovascular mortality over a mean follow-up of 18.6 years.

METHODS

Three thousand five hundred five subjects were participants in a worksite hypertension program. Sodium intake was estimated by 24-hour urine excretion. Mortality data were obtained from the U.S. National Death Index. Unadjusted and multivariable-adjusted associations between sodium quartiles (quartile I (QI) to quartile IV (QIV)) and mortality were assessed using Cox models.

RESULTS

Estimated mean ± SD sodium intake was 130±69 mmol overall (55±20 mmol in QI; 220±56 mmol in QIV). Baseline systolic blood pressure did not vary significantly between groups. Last available mean systolic blood pressure was highest in QI and lowest in QIV (137±16 vs. 134±14 mm Hg; P = 0.009). Overall there were 1,013 deaths (399 cardiovascular). Unadjusted models exhibited significant inverse relationships between sodium and mortality outcomes. In adjusted models, sodium intake was not significantly associated with cardiovascular mortality (QI vs. QIV: hazard ratio (HR) = 1.00; 95% confidence interval (CI) = 0.71-1.42; P = 0.99). A borderline significant direct association with all-cause mortality was observed (QI vs. QIV: HR = 0.81; 95% CI = 0.66-1.00; P = 0.05) driven partly by noncardiovascular deaths.

CONCLUSIONS

Our study found no significant association between sodium intake and cardiovascular outcomes, although a significant association with all-cause mortality was observed. Although these findings suggest that sodium may not have a strong relationship with cardiovascular mortality, the inconsistent results cast doubt on whether a single measurement can reliably predict mortality over a prolonged follow-up period.

Making Sense of the Science of Sodium

Despite the Institute of Medicine's commitment to base its nutrient intake recommendations in evidence, the 2004/2005 Dietary Reference Intakes for sodium were not supported by evidence, as the subsequent 2013 Institute of Medicine review admitted. In this review, I suggest an approach to setting nutrient intake requirements based in physiology. Briefly, the requirement of a given nutrient can best be said to be the intake that calls for the least adaptation or compensation by the intact organism. For sodium, evidence indicates that such an intake is typically between 3000 and 5000 mg/d.

The science upon which to base dietary sodium policy

Few nutrient intake recommendations become subjects of heated scientific debate, but sodium is 1 of them. In the absence of sufficient clinical trials focused on sodium intake and health outcomes, studies that used the surrogate marker of blood pressure have been used to support extreme sodium reduction. Under tightly controlled conditions, maximum achievable sodium reduction leads to a 1-6 mm Hg reduction in systolic blood pressure, which presumably leads to reduced cardiovascular disease morbidity and mortality. However, in observational cohort studies that used not blood pressure but actual health conditions as outcomes, the presumed relation between sodium intakes <2500 mg/d was not observed. Thus, the blood pressure effect of sodium restriction can no longer be accepted as a surrogate for health outcomes associated with sodium intake. Evidence that reducing sodium intakes to <2500 mg/d will improve health is needed to justify continuing efforts to modify diet.

Estimated daily salt intake in relation to blood pressure and blood lipids: the role of obesity

BACKGROUND

Excessive salt intake causes increased blood pressure which is considered the leading risk for premature death. One major challenge when evaluating associations between daily salt intake and markers of non-communicable diseases is that a high daily salt intake correlates with obesity, which is also a well described risk factor for poor cardiometabolic outcome. The aim of this study was to evaluate the relationship of estimated daily salt intake with blood pressure and blood lipids and to investigate the effect of taking different measures of obesity into account.

METHODS

We included 3294 men and women aged 18-69 years from a general population based study in Copenhagen, Denmark. Estimated 24-hour sodium excretion was calculated by measurements of creatinine and sodium concentration in spot urine in combination with information of sex, age, height and weight. The relations of estimated 24-hour sodium excretion with blood pressure and blood lipids were evaluated by linear regression models.

RESULTS

The daily mean estimated intake of salt was 10.80 g and 7.52 g among men and women, respectively. Daily salt intake was significantly associated with blood pressure (β-estimates 1.18 mm Hg/g salt (systolic) and 0.74 mm Hg/g salt (diastolic), p < 0.0001) - however this association was markedly affected by adjustment for obesity (β-estimates around 0.60 mm Hg/g salt (systolic) and around 0.25 mm Hg/g salt (diastolic), p < 0.05). Also associations between daily salt intake and blood lipids were highly affected by adjustment for obesity.

CONCLUSIONS

Associations of estimated daily salt intake with blood pressure and blood lipids were highly affected by adjustment for obesity.

Compared with usual sodium intake, low- and excessive-sodium diets are associated with increased mortality: a meta-analysis

BACKGROUND

The effect of sodium intake on population health remains controversial. The objective was to investigate the incidence of all-cause mortality (ACM) and cardiovascular disease events (CVDEs) in populations exposed to dietary intakes of low sodium (<115 mmol), usual sodium (low usual sodium: 115-165 mmol; high usual sodium: 166-215 mmol), and high sodium (>215 mmol).

METHODS

The relationship between individual measures of dietary sodium intake vs. outcome in cohort studies and randomized controlled trials (RCTs) measured as hazard ratios (HRs) were integrated in meta-analyses.

RESULTS

No RCTs in healthy population samples were identified. Data from 23 cohort studies and 2 follow-up studies of RCTs (n = 274,683) showed that the risks of ACM and CVDEs were decreased in usual sodium vs. low sodium intake (ACM: HR = 0.91, 95% confidence interval (CI) = 0.82-0.99; CVDEs: HR = 0.90, 95% CI = 0.82-0.99) and increased in high sodium vs. usual sodium intake (ACM: HR = 1.16, 95% CI = 1.03-1.30; CVDEs: HR = 1.12, 95% CI = 1.02-1.24). In population representative samples adjusted for multiple confounders, the HR for ACM was consistently decreased in usual sodium vs. low sodium intake (HR = 0.86; 95% CI = 0.81-0.92), but not increased in high sodium vs. usual sodium intake (HR = 1.04; 95% CI = 0.91-1.18). Within the usual sodium intake range, the number of events was stable (high usual sodium vs. low usual sodium: HR = 0.98; 95% CI = 0.92-1.03).

CONCLUSIONS

Both low sodium intakes and high sodium intakes are associated with increased mortality, consistent with a U-shaped association between sodium intake and health outcomes.

Dietary salt intake and hypertension

Over the past century, salt has been the subject of intense scientific research related to blood pressure elevation and cardiovascular mortalities. Moderate reduction of dietary salt intake is generally an effective measure to reduce blood pressure. However, recently some in the academic society and lay media dispute the benefits of salt restriction, pointing to inconsistent outcomes noted in some observational studies. A reduction in dietary salt from the current intake of 9-12 g/day to the recommended level of less than 5-6 g/day will have major beneficial effects on cardiovascular health along with major healthcare cost savings around the world. The World Health Organization (WHO) strongly recommended to reduce dietary salt intake as one of the top priority actions to tackle the global non-communicable disease crisis and has urged member nations to take action to reduce population wide dietary salt intake to decrease the number of deaths from hypertension, cardiovascular disease and stroke. However, some scientists still advocate the possibility of increased risk of CVD morbidity and mortality at extremes of low salt intake. Future research may inform the optimal sodium reduction strategies and intake targets for general populations. Until then, we have to continue to build consensus around the greatest benefits of salt reduction for CVD prevention, and dietary salt intake reduction strategies must remain at the top of the public health agenda.

Dietary sodium and potassium intake is not associated with elevated blood pressure in US adults with no prior history of hypertension

The relationship between dietary sodium and potassium intake with elevated blood pressure (BP) levels is unclear. The authors examined the association between dietary sodium and potassium intake and BP levels in 6985 adults aged 18 years and older with no prior history of hypertension who participated in the National Health and Nutrition Examination Survey (2001-2006). After adjustment for age, sex, race, body mass index, diabetes, and estimated glomerular filtration rate, there was no association between higher quartiles of sodium or potassium intake with the risk of a BP >140/90 mm Hg or >130/80 mm Hg. There was also no relationship between dietary sodium and potassium intake with BP when systolic and diastolic BP were measured as continuous outcomes (P=.68 and P=.74, respectively). Furthermore, no association was found between combinations of sodium and potassium intake with elevated BP. In the US adult population without hypertension, increased dietary sodium or low potassium intake was not associated with elevated BP levels.

Daily sodium consumption and CVD mortality in the general population: systematic review and meta-analysis of prospective studies

OBJECTIVE

The purpose of the present study was to determine whether elevated dietary Na intake could be associated with CVD mortality.

DESIGN

We performed a systematic review and meta-analysis of prospective studies representing the general population. The adjusted relative risks and their 95 % confidence intervals were pooled by the inverse variance method using random-effects models. Heterogeneity, publication bias, subgroup and meta-regression analyses were performed. Settings MEDLINE (since 1973), Embase (since 1975), the Cochrane Library (since 1976), ISI Web of Science, Google Scholar (until September 2013) and secondary referencing were searched for inclusion in the study. Subject Eleven prospective studies with 229 785 participants and average follow-up period of 13.37 years (range 5.5-19 years).

RESULTS

Higher Na intake was significantly associated with higher CVD mortality (relative risk=1.12; 95 % CI 1.06, 1.19). In the sensitivity analysis, the exclusion of studies with important relative weights did not significantly affect the results (relative risk=1.08; 95 % CI 1.01, 1.15). The meta-regression analysis showed that for every increase of 10 mmol/d in Na intake, CVD mortality increased significantly by 1 % (P=0.016). Age, hypertensive status and length of follow-up were also associated with increased CVD mortality.

CONCLUSIONS

Higher Na intake was associated with higher CVD mortality in the general population; this result suggests a reduction in Na intake to prevent CVD mortality from any cause.

Hyperosmolarity drives hypertension and CKD--water and salt revisited

An epidemic of chronic kidney disease (CKD) in Mesoamerica is providing new insights into the mechanisms by which salt and water might drive hypertension and CKD. Increasingly, evidence suggests that recurrent dehydration and salt loss might be a mechanism that causes CKD, and experimental studies suggest a key role for increased plasma osmolarity in activating both intrarenal (polyol-fructokinase) and extrarenal (vasopressin) pathways that drive renal injury. Thus, we propose that water and salt might influence blood pressure and kidney disease through the timing and combination of their intake, which affect plasma osmolarity as well as intrarenal and extrarenal mechanisms of renal injury. The type of fluid intake might also be important, as fluids containing fructose can trigger activation of these pathways. Future studies should investigate the effects of salt, sugar and fluid intake on plasma osmolarity as a potential pathogenetic mechanism in renal injury and high blood pressure.

A reduction of 3 g/day from a usual 9 g/day salt diet improves endothelial function and decreases endothelin-1 in a randomised cross_over study in normotensive overweight and obese subjects

BACKGROUND AND AIM

It is unclear if a modest reduction in dietary salt intake has beneficial effects on vascular function. The aim was to compare the effects of 9 g salt/day with 6 g salt/day intake on measures of vascular function and explore mechanisms of effect in overweight and obese adults.

METHODS

Twenty-five overweight/obese subjects (BMI 27-40 kg/m(2)) completed a randomised cross-over study of 6 weeks each on a reduced salt (RS) (6 g/day) and usual salt diet (US) (9 g/day). Flow-mediated-dilatation (FMD), 24 h blood pressure (BP), augmentation index (AIx), pulse wave velocity (PWV), plasma and urinary nitrate/nitrite, asymmetric dimethylarginine (ADMA), renin, aldosterone and endothelin-1 and vascular adhesion molecules were measured after 2 days and 6 weeks. Adherence to the diets was determined from two 24 h urine collections.

RESULTS

Urinary sodium excretion was 155 ± 58 mmol/24 h US vs 113 ± 45 mmol/24 h RS (p = 0.002). Following the RS diet there was a significant improvement in FMD from 3.5 ± 2.8% to 5.6 ± 2.8% (P < 0.001) and decrease in serum endothelin-1 from 1.45 ± 0.38 pg/ml to 1.25 ± 0.39 pg/ml (P < 0.05). Endothelium-independent vasodilatation was also significantly different between treatments (P < 0.05). AIx, PWV, serum ADMA and plasma and urinary nitrate/nitrite concentrations were not different between treatments. Change in FMD was related to the urinary sodium: creatinine ratio (r = -0.47, P < 0.05) and was independent of blood pressure. Aldosterone and renin were unchanged.

CONCLUSIONS

A small reduction in dietary salt intake of 3 g/day improves endothelial function in normotensive overweight and obese subjects. This response may be mediated by serum endothelin-1. This small reduction in salt had no effect on aldosterone and renin concentrations. This trial was registered with the Australian and New Zealand Clinical Trials Registry Unique Identifier: ACTRN12609000321246 http://www.anzctr.org.au/ACTRN12609000321246.aspx.

Relationship between urinary sodium excretion and serum aldosterone in patients with diabetes in the presence and absence of modifiers of the renin-angiotensin-aldosterone system

Although low dietary salt intake has beneficial effects on BP (blood pressure), low 24hUNa (24 h urinary sodium excretion), the most accurate estimate of dietary salt intake, is associated with increased mortality in people with diabetes. In the non-diabetic population, low salt intake is associated with increased RAAS (renin-angiotensin-aldosterone system) activity. In this cross-sectional study, we examined the relationship between 24hUNa, PRA (plasma renin activity), serum aldosterone and BNP (brain natriuretic peptide) in patients with diabetes. Clinical characteristics, 24hUNa, PRA, serum aldosterone and BNP were recorded in 222 consecutive patients (77% with Type 2 diabetes) attending a diabetes clinic at a tertiary hospital. The relationship between 24hUNa, serum aldosterone, PRA, BNP, urinary potassium excretion, serum potassium, serum sodium, eGFR (estimated glomerular filtration rate), urinary albumin excretion and HbA1c (glycated haemoglobin) was examined by a multivariable regression model. Levels of 24hUNa significantly predicted serum aldosterone in a linear fashion (R²=0.20, P=0.002). In the subgroup of patients (n=46) not taking RAAS-modifying agents, this relationship was also observed (R²=0.10, P=0.03), and the effect of 24hUNa on serum aldosterone was found to be more pronounced than in the whole cohort (coefficient=-0.0014, compared with -0.0008). There was no demonstrable relationship between 24hUNa and PRA or BNP. Low 24hUNa is associated with increased serum aldosterone in people with diabetes, in the presence and absence of RAAS-modifying agents. This raises the possibility that stimulation of the RAAS may be a mechanism that contributes to adverse outcomes observed in patients with low 24hUNa.

Dietary sodium, potassium, and alcohol: key players in the pathophysiology, prevention, and treatment of human hypertension

Western industrialized societies are currently experiencing an epidemic expansion of hypertension (HTN), which extends alarmingly even to children and adolescents. HTN constitutes an independent risk factor for cardiorenal disease and represents an extremely common comorbidity of diabetes and obesity. Numerous randomized clinical trials and meta-analyses have provided robust scientific evidence that reduced dietary salt intake, increased dietary potassium intake, moderation of alcohol consumption, optimal weight maintenance, and the adoption of "heart-friendly" dietary patterns such as the Dietary Approaches to Stop Hypertension or the Mediterranean diet can effectively lower blood pressure. Interestingly, the susceptibility of blood pressure to nutritional interventions is greatly variable among individuals, depending on age, race, genetic background, and comorbidities. The purpose of this review is to provide a comprehensive overview of currently available scientific evidence in the constantly evolving field of diet and HTN, placing particular emphasis on the key role of dietary sodium, dietary potassium, and alcohol intake in the pathophysiology, prevention, and treatment of human hypertension.

A review of nutritional factors in hypertension management

Hypertension is a major health problem worldwide. Its attendant morbidity and mortality complications have a great impact on patient's quality of life and survival. Optimizing blood pressure control has been shown to improve overall health outcomes. In addition to pharmacological therapies, nonpharmacological approach such as dietary modification plays an important role in controlling blood pressure. Many dietary components such as sodium, potassium, calcium, and magnesium have been studied substantially in the past decades. While some of these nutrients have clear evidence for their recommendation, some remain controversial and are still of ongoing study. Dietary modification is often discussed with patients and can provide a great benefit in blood pressure regulation. As such, reviewing the current evidence will be very useful in guiding patients and their physician and/or dietician in decision making. In this review article of nutritional factors in hypertension management, we aim to examine the role of nutritional factors individually and as components of whole dietary patterns.

Effect of lower sodium intake on health: systematic review and meta-analyses

OBJECTIVE

To assess the effect of decreased sodium intake on blood pressure, related cardiovascular diseases, and potential adverse effects such as changes in blood lipids, catecholamine levels, and renal function.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Cochrane Central Register of Controlled Trials, Medline, Embase, WHO International Clinical Trials Registry Platform, the Latin American and Caribbean health science literature database, and the reference lists of previous reviews.

STUDY SELECTION

Randomised controlled trials and prospective cohort studies in non-acutely ill adults and children assessing the relations between sodium intake and blood pressure, renal function, blood lipids, and catecholamine levels, and in non-acutely ill adults all cause mortality, cardiovascular disease, stroke, and coronary heart disease.

STUDY APPRAISAL AND SYNTHESIS

Potential studies were screened independently and in duplicate and study characteristics and outcomes extracted. When possible we conducted a meta-analysis to estimate the effect of lower sodium intake using the inverse variance method and a random effects model. We present results as mean differences or risk ratios, with 95% confidence intervals.

RESULTS

We included 14 cohort studies and five randomised controlled trials reporting all cause mortality, cardiovascular disease, stroke, or coronary heart disease; and 37 randomised controlled trials measuring blood pressure, renal function, blood lipids, and catecholamine levels in adults. Nine controlled trials and one cohort study in children reporting on blood pressure were also included. In adults a reduction in sodium intake significantly reduced resting systolic blood pressure by 3.39 mm Hg (95% confidence interval 2.46 to 4.31) and resting diastolic blood pressure by 1.54 mm Hg (0.98 to 2.11). When sodium intake was <2 g/day versus ≥ 2 g/day, systolic blood pressure was reduced by 3.47 mm Hg (0.76 to 6.18) and diastolic blood pressure by 1.81 mm Hg (0.54 to 3.08). Decreased sodium intake had no significant adverse effect on blood lipids, catecholamine levels, or renal function in adults (P>0.05). There were insufficient randomised controlled trials to assess the effects of reduced sodium intake on mortality and morbidity. The associations in cohort studies between sodium intake and all cause mortality, incident fatal and non-fatal cardiovascular disease, and coronary heart disease were non-significant (P>0.05). Increased sodium intake was associated with an increased risk of stroke (risk ratio 1.24, 95% confidence interval 1.08 to 1.43), stroke mortality (1.63, 1.27 to 2.10), and coronary heart disease mortality (1.32, 1.13 to 1.53). In children, a reduction in sodium intake significantly reduced systolic blood pressure by 0.84 mm Hg (0.25 to 1.43) and diastolic blood pressure by 0.87 mm Hg (0.14 to 1.60).

CONCLUSIONS

High quality evidence in non-acutely ill adults shows that reduced sodium intake reduces blood pressure and has no adverse effect on blood lipids, catecholamine levels, or renal function, and moderate quality evidence in children shows that a reduction in sodium intake reduces blood pressure. Lower sodium intake is also associated with a reduced risk of stroke and fatal coronary heart disease in adults. The totality of evidence suggests that most people will likely benefit from reducing sodium intake.

High salt intake and stroke: meta-analysis of the epidemiologic evidence

Research on the potential impact of high salt intake on health has grown rapidly over the last decades. Recent studies have suggested that high salt intake could also be associated with adverse effects on cardiovascular system. The review evaluated the current level of epidemiologic evidence on the association between the level of habitual salt intake and stroke outcome. We also suggest further research direction. There were 21 independent samples from 12 studies, with 225,693 participants (follow-up, 3-19 years) and 8135 stroke events. High salt intake was associated with risk of stroke event (pooled odd ratio [OR], 1.34; 95% confidence interval [CI], 1.19-1.51), stroke death (1.40; 1.21-1.63) and stroke onset (1.11; 1.00-1.24), ischemic stroke death (2.15; 1.57-2.95), not associated with risk of ischemic stroke onset (1.07, 0.95-1.2), with no significant evidence of publication bias. High salt intake is associated with significantly increased risk of stroke event. Further research should be directed toward clarifying and quantifying these possible effects and generating testable hypotheses on plausible biologic mechanisms.

Low daily salt intake is correlated with albuminuria in patients with type 2 diabetes

Both high and low salt intakes have been reported to be associated with an increased risk of cardiovascular events. The aim of this study was to investigate the relationship between daily salt intake and albuminuria, a marker of diabetic nephropathy and cardiovascular disease, in patients with type 2 diabetes. We classified 270 patients with type 2 diabetes, who were not receiving antihypertensive medication into four groups according to their daily salt intake (<8, 8-10, 10-12 and >12 g per day). We investigated the relationship between daily salt intake and the logarithm of urinary albumin excretion (UAE). A multivariate linear regression analysis was used to evaluate whether daily salt intake independently correlated with the logarithm of UAE. In addition, we assessed the contribution of the variables, including age, sex, duration of diabetes, body mass index, systolic blood pressure, hemoglobin A(1C), low-density lipoprotein cholesterol, triglycerides, serum creatinine, alcohol intake, smoking status and square of (daily salt intake-10) on albuminuria, defined as a UAE>30 mg g(-1) of creatinine, using a multiple logistic regression analysis. The logarithm of the UAE was lowest in the third quartile of daily salt intake. The multivariate linear regression analysis demonstrated that the logarithm of the UAE was significantly correlated with the quadratic term of daily salt intake centered at 10 g per day (β=0.170, P=0.008). The multivariate logistic regression analysis demonstrated that the odds ratio (95% confidence interval) of albuminuria was 3.996 (1.295-12.327; P=0.016) in patients whose daily salt intake was less than 8 g per day compared with patients whose daily salt intake was 10-12 g per day. In conclusion, low daily salt intake was correlated with albuminuria in patients with type 2 diabetes, who were not receiving antihypertensive medication.