Salt and the metabolic syndrome

The high salt intake in adults with metabolic syndrome is related to increased waist circumference and blood pressure: the Brazilian Longitudinal Study of Adult Health study (ELSA-Brasil)

OBJECTIVES

The association between metabolic syndrome (MetS), a cluster of cardiometabolic risk factors, and salt consumption has fed intense debate in recent years, although it is yet to be fully elucidated. We aimed to evaluate whether individuals with MetS have a high salt consumption and to identify which components of the MetS diagnosis could be independently related to high salt consumption.

METHODS

We analyzed data from 11 982 adults, ages 35 to 74 y, from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) cohort study, from which clinical and anthropometric data were assessed, and a validated 12-h overnight urine collection was used to estimate salt intake. MetS was defined according to the Adult Treatment Panel III criteria.

RESULTS

Salt intake was increased in individuals with MetS compared with individuals without MetS, regardless of sex (men: 14.3 ± 6.4 g/d versus 12.2 ± 5.5 g/d, P < 0.001; women: 10.6 ± 4.9 g/d versus 8.9 ± 4.0 g/d, P < 0.001) and increased progressively as the MetS criteria accumulated. The high salt intake in MetS participants, however, was observed only in the presence of elevated waist circumference and/or blood pressure and not with the other MetS criteria (reduced high-density lipoprotein, increased triglycerides, and impaired fasting blood glucose), regardless of the presence of MetS. When diabetes was incorporated as a MetS criterion, increased salt intake was observed in men but not in women.

CONCLUSIONS

Salt intake should be reduced worldwide, but strategies must be more intense in people with elevated blood pressure and waist circumference, regardless of MetS diagnosis, to avoid the associated morbidity and mortality.

Epigenetics of the blood pressure reactivity to salt: Is the salt sensitive phenotype correctable?

Salt sensitivity defines a state characterized by a highly reactive blood pressure to changes in salt intake. The salt-sensitive phenotype is strongly associated with hypertension, visceral adiposity/metabolic syndrome, and ageing. Obesity accounts for around 70% of hypertension in young adults, and 30% to 50% of adult hypertensives carry the salt-sensitive phenotype. It is estimated that the salt-sensitive phenotype is responsible for high blood pressure in over 600 million adults. But is the salt-sensitive phenotype correctable? Interventional, controlled, clinical trials in obese adolescents and young obese adults, demonstrated that weight-reducing lifestyle modifications revert the salt-sensitive to the salt-resistant phenotype, and restored the faulty production of nitric oxide. Correction of the salt-sensitive phenotype lowers the blood pressure by reducing its reactivity to dietary salt. In a random sample of obese adults subjected to lifestyle modifications, those who were salt-resistant at baseline, were also normotensive and failed to further lower their blood pressure despite a 12% drop in body weight. The salt-resistant phenotype protects the metabolically healthy obese from hypertension, even if their salt consumption is comparable to that of salt-sensitive obese. In summary, at early stages, the elevated blood pressure of obesity, is determined by epigenetic changes leading to a state of salt-sensitivity.

Small intestinal microbiota composition altered in obesity-T2DM mice with high salt fed

Obesity has become a global concern because of increasing the risk of many diseases. Alterations in human gut microbiota have been proven to be associated with obesity, yet the mechanism of how the microbiota are altered by high salt diet (HSD) remains obscure. In this study, the changes of Small Intestinal Microbiota (SIM) in obesity-T2DM mice were investigated. High-throughput sequencing was applied for the jejunum microbiota analysis. Results revealed that high salt intake (HS) could suppress the body weight (B.W.) in some extent. In addition, significant T2DM pathological features were revealed in high salt-high food diet (HS-HFD) group, despite of relatively lower food intake. High-throughput sequencing analysis indicated that the F/B ratio in HS intake groups increased significantly (P < 0.001), whereas beneficial bacteria, such as lactic acid or short chain fatty acid producing bacteria, were significantly decreased in HS-HFD group (P < 0.01 or P < 0.05). Furthermore, Halorubrum luteum were observed in small intestine for the first time. Above results preliminary suggested that in obesity-T2DM mice, high dietary salt could aggravate the imbalance of composition of SIM to unhealthy direction.

The role of dietary salt in metabolism and energy balance: Insights beyond cardiovascular disease

Dietary salt (NaCl) is essential to an organism's survival. However, today's diets are dominated by excessive salt intake, which significantly impacts individual and population health. High salt intake is closely linked to cardiovascular disease (CVD), especially hypertension, through a number of well-studied mechanisms. Emerging evidence indicates that salt overconsumption may also be associated with metabolic disorders. In this review, we first summarize recent updates on the mechanisms of salt-induced CVD, the effects of salt reduction and the use of salt substitution as a therapy. Next, we focus on how high salt intake can impact metabolism and energy balance, describing the mechanisms through which this occurs, including leptin resistance, the overproduction of fructose and ghrelin, insulin resistance and altered hormonal factors. A further influence on metabolism worth noting is the reported role of salt in inducing thermogenesis and increasing body temperature, leading to an increase in energy expenditure. While this result could be viewed as a positive metabolic effect because it promotes a negative energy balance to combat obesity, caution must be taken with this frame of thinking given the deleterious consequences of chronic high salt intake on cardiovascular health. Nevertheless, this review highlights the importance of salt as a noncaloric nutrient in regulating whole-body energy homeostasis. Through this review, we hope to provide a scientific framework for future studies to systematically address the metabolic impacts of dietary salt and salt replacement treatments. In addition, we hope to form a foundation for future clinical trials to explore how these salt-induced metabolic changes impact obesity development and progression, and to elucidate the regulatory mechanisms that drive these changes, with the aim of developing novel therapeutics for obesity and CVD.

Impact of urinary sodium excretion on the prevalence and incidence of metabolic syndrome: a population-based study

OBJECTIVE

To evaluate the association of metabolic syndrome (MetS) risk with 24-hour urinary sodium excretion (24hUNaE) estimated from spot urine samples.

DESIGN

Serial cross-sectional studies were conducted, and those with multiple repeated examinations were used to assess the MetS incidence risk.

SETTING AND PARTICIPANTS

A health check-up programme was conducted between 2018 and 2021 and enrolled 59 292 participants to evaluate the relationship between MetS risk and 24hUNaE in the Third Xiangya Hospital, Changsha, China. Among these participants, 9550 had at least two physical examinations during this period, which were used to evaluate the association of a new occurrence of MetS with 24hUNaE.

OUTCOMES

Guidelines for the prevention and treatment of dyslipidaemia in Chinese adults (revised in 2016) were used to define prevalent and incident MetS.

RESULTS

The prevalence of MetS was 19.3% at the first check-up; among individuals aged ≤55 years, the risk was higher in men than women, while among older individuals, a similar prevalence was observed in both sexes. A significant increase in MetS prevalence was observed per unit increase in 24hUNaE (adjusted OR (AOR) 1.11; 95% CI 1.09 to 1.13), especially for the prevalence of central obesity and elevated blood pressure. Additionally, 27.4% of the participants among the 7842 participants without MetS at the first check-up (male vs female: 37.3% vs 12.9%) were found to have a new occurrence of MetS at the second, third and/or fourth check-ups. A 25% increase in MetS incidence was observed per unit increase in 24hUNaE (95% CI 1.19 to 1.32), which was more prominent in the participants with a new occurrence of central obesity and elevated fasting blood glucose.

CONCLUSIONS

Although the prevalence of MetS seemed stable, new occurrences of MetS remained high, which might result in MetS recurrence. The influence of sodium intake on MetS development is probably attributed to the increase in blood pressure and central obesity, but a new occurrence of MetS may develop through elevated blood glucose and central obesity.

The association between dietary sodium intake and obesity in adults by sodium intake assessment methods: a review of systematic reviews and re-meta-analysis

BACKGROUND/OBJECTIVES

The scientific evidence of a sodium-obesity association is limited by sodium intake assessments. Our specific aim is to synthesize the association between dietary sodium intake and obesity across the sodium intake assessments as evidenced by systematic reviews in adults.

SUBJECTS/METHODS

A systematic search identified systematic reviews comparing the association of dietary sodium intakes with obesity-related outcomes such as body mass index (BMI), body weight, waist circumference, and risk of (abdominal) obesity. We searched PubMed on October 24, 2022. To assess the Risk of Bias in Systematic Reviews (ROBIS), we employed the ROBIS tool.

RESULTS

This review included 3 systematic reviews, consisting of 39 unique observational studies (35 cross-sectional studies and 4 longitudinal studies) and 15 randomized controlled trials (RCTs). We found consistently positive associations between dietary sodium intake and obesity-related outcomes in cross-sectional studies. Studies that used 24-h urine collection indicated a greater BMI for those with higher sodium intake (mean difference = 2.27 kg/m2; 95% confidence interval [CI], 1.59-2.51; P < 0.001; I2 = 77%) compared to studies that used spot urine (mean difference = 1.34 kg/m2; 95% CI, 1.13-1.55; P < 0.001; I2 = 95%) and dietary methods (mean difference = 0.85 kg/m2; 95% CI, 0.1-1.51; P < 0.05; I2 = 95%).

CONCLUSIONS

Quantitative synthesis of the systematic reviews has shown that cross-sectional associations between dietary sodium intake and obesity outcomes were substantially different across the sodium intake assessments. We need more high-quality prospective cohort studies and RCTs using 24-h urine collection to examine the causal effects of sodium intake on obesity.

Urinary Sodium Excretion and Obesity Markers among Bangladeshi Adult Population: Pooled Data from Three Cohort Studies

We evaluated the relationship of urinary sodium excretion with a conditional mean, 10th and 90th percentiles of body mass index (BMI), and waist circumference among 10,034 person-visits of Bangladeshi population. We fitted linear mixed models with participant-level random intercept and restricted maximum likelihood estimation for conditional mean models; and quantile mixed-effect models with participant-level random intercept and Laplace estimation for 10th and 90th percentiles models. For each 100 mmol/24 h increase in urinary sodium excretion, participants had a 0.10 kg/m2 (95% CI: 0.00, 0.10) increase in the mean; a 0.39 kg/m2 (95% CI: 0.23, 0.54) increase in the 10th percentile; and a 0.59 kg/m2 (95% CI: 0.39, 0.78) increase in the 90th percentile of BMI. For each 100 mmol/24 h increase in urinary sodium excretion, participants had a 0.20 cm (95% CI: 0.10, 0.30) increase in mean; a 0.18 cm (95% CI: -0.03, 0.40) change in the 10th percentile; and a 0.23 cm (95% CI: 0.03, 0.43) increase in the 90th percentile of waist circumference. We found a modest association between urine sodium and conditional mean of BMI and waist circumference. The magnitude of associations between urine sodium and the 10th and 90th percentile BMI distributions were higher compared to the conditional mean models, suggesting high sodium intake could be more detrimental to underweight and obese participants.

Urinary sodium, iodine, and volume in relation to metabolic syndrome in Mesoamerican children and their parents

BACKGROUND AND AIMS

The roles of sodium or iodine intake on the metabolic syndrome (MetS) etiology remain controversial. We evaluated the associations of 24 h urinary sodium and iodine with MetS among Mesoamerican children and their adult parents.

METHODS AND RESULTS

We conducted a cross-sectional study among 217 school-age children and 478 parents from 9 Mesoamerican cities. Exposures were high 24 h urinary sodium excretion and concentration (>2000 mg/d or mg/L, respectively) and high 24 h urinary iodine excretion and concentration (≥300 μg/d or μg/L, respectively). In children, the outcome was a standardized metabolic score from five criteria analogous to the Adult Treatment Panel (ATP) III criteria. In adults, MetS was defined according to the ATP III criteria. We estimated adjusted mean differences in the metabolic risk score and adjusted prevalence ratios of MetS between exposure categories using multivariable regression. In children, high sodium concentration was associated with a 0.10 units (43% of a SD) higher score (P = 0.001) and high iodine concentration was related to a 0.09 units (39% of a SD) higher score (P = 0.009). Unexpectedly, high 24 h urinary volume was associated with a lower metabolic score. In adults, high 24 h sodium excretion was related to hypertension and high iodine concentration was related to increased MetS prevalence.

CONCLUSION

High sodium and iodine concentrations, but not 24 h iodine excretion, are significantly associated with MetS in children, whereas high 24 h urinary volume is related to a decreased metabolic score. In adults, high iodine concentration tends to be related to increased MetS prevalence, but not 24 h iodine excretion.

24-hour sodium and potassium excretion in the Americas: a systematic review and meta-analysis

Objective

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

Methods

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

Results

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

Conclusions

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

High-fat and high-sodium diet induces metabolic dysfunction in the absence of obesity

OBJECTIVE

Excess dietary fat and sodium (NaCl) are both associated with obesity and metabolic dysfunction. In mice, high NaCl has been shown to block high-fat (HF) diet-induced weight gain. Here, the impact of an HF/NaCl diet on metabolic function in the absence of obesity was investigated.

METHODS

Wild-type mice were administered chow, NaCl (4%), HF, and HF/NaCl diets. Metabolic analysis was performed by measuring fasted blood glucose and insulin levels and by glucose tolerance test and insulin tolerance test.

RESULTS

After 10 weeks on diets, male and female mice on the HF diet gained weight, and HF/NaCl mice had significantly reduced weight gain similar to chow-fed mice. In the absence of obesity, HF/NaCl mice had significantly elevated fasting blood glucose and impaired glucose control during glucose tolerance tests. Both NaCl and HF/NaCl mice had decreased pancreas and β-cell mass. Administration of NaCl in drinking water did not protect mice from HF-diet-induced weight gain and obesity. Further analysis revealed that longer administration of HF/NaCl diets for 20 weeks resulted in significant weight gain and insulin resistance.

CONCLUSIONS

The data demonstrate that despite early inhibitory effects on fat deposition and weight gain, an HF/NaCl diet does not prevent the metabolic consequences of HF diet consumption.

Impact of Dietary Sodium Reduction on the Development of Obesity and Type 2 Diabetes in db/db Mice

The impact of dietary sodium reduction on mouse models of type 2 diabetes is not well understood. Therefore, we analyzed the effect of a low-salt diet on obesity and parameters of type 2 diabetes in db/db mice. Five-week-old male db/db and lean db/m mice were fed a normal salt (0.19% Na⁺, NS) or a low-salt diet (<0.03% Na⁺, LS) for 5 weeks. Body and organ weight and parameters of glucose and insulin tolerance were analyzed. Plasma levels of steroids were determined by liquid chromatography tandem mass spectrometry. Body weight, glucose, and insulin tolerance were not affected by LS. The amount of gonadal adipose tissue showed a trend to be increased by LS whereas liver, pancreas, kidney, heart, and adrenal weight remained unaffected. LS reduced urinary sodium-to-creatinine ratio but did not affect plasma Na⁺ levels in both genotypes. Plasma and urinary potassium-to-creatinine ratio did not differ in all groups of mice. Aldosterone as a major determinant of changes in dietary sodium remained unaffected by LS in db/db mice as well as further investigated steroid hormones. The present study showed reduced sodium-to-creatinine ratio, but no additional effects of dietary sodium reduction on major metabolic parameters and steroid levels in obese and hyper-glycemic db/db mice.

The role of caloric intake in the association of high salt intake with high blood pressure

Since current recommendations call for a substantial reduction in overall sodium consumption, we tested whether or not these recommendations are implemented in common large subpopulations such as those with abnormal weight or hypertension in the current high sodium, high-calorie nutritional environment. In a national representative cross-sectional survey of the community-dwelling subjects aged 25-65 years conducted in Israel between 2015 and 2017, 582 randomly selected subjects completed health and dietary questionnaires, underwent blood pressure and anthropometric measurements and collected 24-h urine specimens, to assess dietary sodium intake. Overall mean 24-h sodium excretion was 3834 mg, more than double the recommended upper intake for adults < 1500 mg/day. Sodium excretion was directly related to caloric intake and blood pressure and linked to the presence of hypertension and overweight/obesity. The highest sodium excretion was seen in overweight/obese hypertensive subjects. This recent national survey shows a high consumption of sodium in the Israeli population and a dose-response association between caloric intake and urinary sodium excretion, independent of BMI and hypertension. Nevertheless, overweight/obese subjects with hypertension consume (excrete) more sodium than other BMI/ blood pressure-related phenotypes and may thus comprise a target subpopulation for future efforts to reduce sodium intake.

Molecular biochemical aspects of salt (sodium chloride) in inflammation and immune response with reference to hypertension and type 2 diabetes mellitus

Obesity, insulin resistance, type 2 diabetes mellitus (T2DM) and hypertension (HTN) are common that are associated with low-grade systemic inflammation. Diet, genetic factors, inflammation, and immunocytes and their cytokines play a role in their pathobiology. But the exact role of sodium, potassium, magnesium and other minerals, trace elements and vitamins in the pathogenesis of HTN and T2DM is not known. Recent studies showed that sodium and potassium can modulate oxidative stress, inflammation, alter the autonomic nervous system and induce dysfunction of the innate and adaptive immune responses in addition to their action on renin-angiotensin-aldosterone system. These actions of sodium, potassium and magnesium and other minerals, trace elements and vitamins are likely to be secondary to their action on pro-inflammatory cytokines IL-6, TNF-α and IL-17 and metabolism of essential fatty acids that may account for their involvement in the pathobiology of insulin resistance, T2DM, HTN and autoimmune diseases.

Salt intake was higher among males and those with high BMI and waist circumference: introduction to the Malaysian Community Salt Survey (MyCoSS), a population-based salt intake survey in Malaysia

BACKGROUND

Recognising that excessive dietary salt intake is associated with high blood pressure and adverse cardiovascular health, the Ministry of Health Malaysia conducted the Malaysian Community Salt Survey (MyCoSS) among Malaysian adults. This paper introduced MyCoSS projects and presented findings on the salt intake of the Malaysian adult population.

METHODS

MyCoSS was a nationally representative survey, designed to provide valuable data on dietary salt intake, sources of salt in the diet, and knowledge, perception, and practice about salt among Malaysian adults. It was a cross-sectional household survey, covering Malaysian citizens of 18 years old and above. Multi-stage-stratified sampling was used to warrant national representativeness. Sample size was calculated on all objectives studied, and the biggest sample size was derived from the knowledge on the effect of high salt on health (1300 participants). Salt intake was estimated using a single 24-h urine collection and its sources from a food frequency questionnaire. Knowledge, attitude, and practice were determined from a pre-tested questionnaire. All questionnaires were fully administered by trained interviewers using mobile devices. Anthropometric indices (weight, height, and waist circumference) and blood pressure were measured using a standardised protocol. Ethical approvals were obtained from the Medical Research Ethics Committee, Ministry of Health Malaysia, and Queen Mary University of London prior to conducting the survey.

RESULTS

Findings showed that the average sodium intake of Malaysian adults (3167 mg/day) was higher than the WHO recommendation of 2000 mg/day. Daily intake was significantly higher among males and individuals with higher BMI and higher waist circumference.

CONCLUSION

Salt intake in the Malaysian population was higher than the WHO recommendation. MyCoSS's findings will be used for the development and implementation of national salt reduction policy. A successful implementation of a national salt reduction programme in Malaysia will benefit the whole population.

Sodium status is associated with type 2 diabetes mellitus: a systematic review and meta-analysis of observational studies

PURPOSE

The relationship between sodium intake and the risk of developing type 2 diabetes mellitus (T2DM) is inconsistent. We, therefore, aimed to summarize the current evidence by conducting a systematic review and meta-analysis of observational studies.

METHODS

We retrieved studies which compared any marker of sodium status between individuals with T2DM and those without diabetes published in any language by searching online databases from inception up to June 2019. Summary effects were derived using random-effects model.

RESULTS

A total of 44 studies with 503,830 participants from 25 countries were included in this study. Sodium status was significantly different between individuals with and without T2DM (Hedges' g = 0.21; 95% CI 0.02, 0.40; P = 0.029). Individuals with T2DM had higher sodium intake compared to non-diabetic controls (WMD = 621.79 mg/day; 95% CI 321.53, 922.06; P < 0.001) and 24-h urinary excretion was associated with likelihood of developing T2DM (OR = 1.27, 95% CI 1.15, 1.41; P < 0.001). Furthermore, salivary, hair, and platelet sodium were higher in patients with T2DM compared to controls (P < 0.05).

CONCLUSION

The findings of the current meta-analysis suggest that sodium levels are higher in patients with T2DM compared to non-diabetic controls; however, given that these studies are observational, it is not possible to infer causality.

Relationship of Sodium Intake with Overweight/Obesity among Chinese Children and Adolescents: Data from the CNNHS 2010-2012

This study aims to examine association between sodium intake and overweight/obesity among Chinese children and adolescents. Data were obtained from China National Nutrition and Health Surveillance (CNNHS), 2010–2012. All participants recruited in this study aged 7–18 years old and provided complete dietary data on three-day consecutive 24 h dietary recalls combining with the household weighing method. Body Mass Index (BMI) was used to define overweight/obesity, and waist-to-height ratio (WHtR) was used to define abdominal obesity. Sodium intake showed association with risk of overweight/obesity assessed by BMI in the highest tertile group with OR of 1.48 (95%CI 1.13–1.94) and 1.89 (95%CI 1.33–2.67) for WHtR. After adjusted for gender, age, household income, area, energy, carbohydrates, protein, fat, saturated fatty acids, and fiber intake, the relationship between sodium intake and overweight/obesity and abdominal obesity are not changed. The same results were founded in subjects aged 10–18 years old. Our results reveal a positive association between sodium intake and overweight/obesity in Chinese children and adolescents, independent of energy consumption.

Causal associations between urinary sodium with body mass, shape and composition: a Mendelian randomization study

Observational studies have found associations between urinary sodium (UNa) with obesity, body shape and composition; but the findings may be biased by residual confounding. The objective of this two-sample Mendelian randomization (MR) study was to analyze their causal associations in both sex-combined and sex-specific models. Genome-wide association studies of UNa, body mass index (BMI), BMI-adjusted waist-to-hip ratio (WHR), body fat (BF) percentage and estimated glomerular filtration rate (eGFR) were identified. We initially extracted fifty SNPs associated with UNa at significance level of 5 × 10^–8, but further removed those SNPs with potential horizontal pleiotropy. Univariable and multivariable MR with adjustment for eGFR were performed. Inverse-variance weighted MR was performed as the primary analysis, with MR-Egger methods as sensitivity analysis. The potential bidirectional association between BMI and UNa was investigated. All exposure and outcomes were continuous, and the effect measure was regression coefficients (beta) and their 95% confidence intervals (95% CI). The total sample size was up to 322 154. UNa was causally associated with increased BMI in both men [eGFR-adjusted beta 0.443 (0.163–0.724)] and women [0.594 (0.333–0.855)]. UNa caused BF percentage increase in men [0.622 (0.268–0.976)] and women [0.334 (0.007–0.662)]. UNa significantly elevated BMI-adjusted WHR in men [0.321 (0.094–0.548)], but not in women [0.170 (− 0.052 to 0.391)]. Additionally, we found that BMI causally increased UNa [0.043 (0.023–0.063)]. UNa increased BMI and BF percentage. Salt intake affects male body shape by increasing BMI-adjusted WHR, but showed no effects on female body shape. The bidirectional association between BMI and UNa suggested that salt reduction measures and weight reduction measures should be implemented simultaneously to break the vicious cycle and gain more health benefits.

The association between dietary sodium intake, adiposity and sugar-sweetened beverages in children and adults: a systematic review and meta-analysis

Higher intakes of Na may contribute to weight gain. The primary aim of this systematic review and meta-analysis was to examine the relationship between dietary Na intake and measures of adiposity in children and adults. Given the previous link between Na intake and the consumption of sugar-sweetened beverages (SSB), which are a known risk factor for obesity, a secondary aim examining the relationship between Na intake and SSB consumption was assessed. A systematic literature search identified cross-sectional and longitudinal studies and randomised controlled trials (RCT) which reduced dietary Na (≥3 months). Meta-analysis was performed for outcomes with ≥3 studies. Cross-sectionally higher Na intakes were associated with overweight/obesity in adults (five studies; n 11 067; OR 1·74; 95 % CI 1·43, 2·13) and in children (three studies; n 3625, OR 3·29; 95 % CI 2·25, 4·80), and abdominal obesity (five studies; n 19 744; OR 2·04; 95 % CI 1·72, 2·42) in adults. Overall, associations remained in sensitivity analyses which adjusted for energy. Findings from longitudinal studies were inconsistent. RCT in adults indicated a trend for lower body weight on reduced-Na compared with control diets (fifteen studies; n 5274; -0·29 kg; 95 % CI -0·59, 0·01; P = 0·06); however, it is unclear if energy intakes were also altered on reduced-Na diets. Among children higher Na intakes were associated with higher intake of SSB (four studies, n 10 329, b = 22, 16 and 26 g/d); no studies were retrieved for adults. Overall, there was a lack of high-quality studies retrieved. While cross-sectional evidence indicates Na intake was positively associated with adiposity, these findings have not been clearly confirmed by longitudinal studies or RCT.

Is urinary sodium excretion related to anthropometric indicators of adiposity in adults?

Background

Although increasing salt intake is associated with greater odds of obesity, little is known about its relationship with body fat. We investigated the relation of urinary sodium (UNa) with obesity indices, including Clínica Universidad de Navarra-Body Adiposity Estimator (CUN-BAE), a body shape index (ABSI), body mass index (BMI), waist circumference (WC), and waist-to-height ratio (WHtR).

Materials and Methods

A total of 508 free-living adults aged ≥ 19 years were selected through stratified multistage random method as a representative of general population from central parts of Iran and were included in this cross-sectional study. Dietary sodium intake was measured using 24-h UNa (24-UNa) excretion. Weight, height, and WC were measured using standard protocols and calibrated equipment and used to measure obesity indicators, including BMI, WHtR, ABSI, and CUN-BAE. Adjusted univariate multiple logistic regression was used to assess the risk of having greater obesity measures across the tertiles of 24-UNa.

Results

Individuals in the top tertile of 24-UNa in comparison with those in the first tertile had greater body weight (72.02 ± 1.00 vs. 66.02 ± 0.89 kg; P < 0.0001), BMI (26.14 ± 0.33 vs. 24.82 ± 0.29 kg/m²; P = 0.007), and CUN-BAE (29.89 ± 0.42 vs. 28.38 ± 0.78; P = 0.036). There was a trend toward an increment in WC by increasing sodium intake (P = 0.073). After controlling for potential confounders, individuals with greater sodium consumption had greater chance for overweight (odds ratio [OR]: 1.004, 95% confidence interval [CI]: 1.001-1.007; P = 0.015), abdominal obesity (OR: 1.004, 95% CI: 1.00-1.008; P = 0.031), and more body fat (OR: 1.007, 95% CI: 1.003-1.01; P = 0.001). No significant association was found for sodium and WHtR and ABSI.

Conclusion

Greater 24-UNa excretion was associated with greater means of body weight, BMI, WC, and CUN-BAE. Although changes in obesity indices per each additional 24-UNa excretion were small, our findings are relevant because of the rising obesity epidemic.

Metabolites and Hypertension: Insights into Hypertension as a Metabolic Disorder: 2019 Harriet Dustan Award

For over 100 years, essential hypertension has been researched from different perspectives ranging from genetics, physiology, and immunology to more recent ones encompassing microbiology (microbiota) as a previously underappreciated field of study contributing to the cause of hypertension. Each field of study in isolation has uniquely contributed to a variety of underlying mechanisms of blood pressure regulation. Even so, clinical management of essential hypertension has remained somewhat static. We, therefore, asked if there are any converging lines of evidence from these individual fields that could be amenable for a better clinical prognosis. Accordingly, here we present converging evidence which support the view that metabolic dysfunction underlies essential hypertension.

Interactive effect of high sodium intake with increased serum triglycerides on hypertension

Background

A high salt diet is associated with the development of hypertension, one of the most important cardiovascular risk factors. A reduction in sodium intake seems to have an effect on increasing serum triglycerides (TGs). Elevated TGs are independently linked to cardiovascular risk. However, there is limited evidence of a possible interactive effect of sodium intake and serum TGs on high blood pressure (BP).

Methods

We conducted a nationwide, population-based interaction analysis using the Kawasaki method for estimating 24-h urinary sodium excretion (e24hUNaE_Kawasaki) as a candidate indicator of dietary sodium intake. All native Koreans aged 20 years or older without significant medical illness were eligible for inclusion.

Results

A total of 16936 participants were divided into quintiles according to their e24hUNaE_Kawasaki results. Participants in the highest quintile were more obese and hypertensive and had higher white blood cell count, lower hemoglobin, greater glycemic exposure, and poor lipid profiles compared to the same parameters of individuals in other quintiles. Linear regression revealed that e24UNaE_Kawasaki was related to systolic BP, diastolic BP, and TGs. Multiple logistic regression, adjusted for dietary sodium intake and various conventional risk factors for chronic vascular diseases, showed that both e24UNaE_Kawasaki and TGs were significant predictors of hypertension. Our interaction analysis demonstrated that increased sodium intake was associated with higher risk of hypertension in participants with elevated TGs than in those without (adjusted RERI = 0.022, 95% CI = 0.017–0.027; adjusted AP = 0.017, 95% CI = 0.006–0.028; adjusted SI = 1.010, 95% CI = 1.007–1.014).

Conclusion

Our findings suggest that the interaction between a high salt diet and elevated TGs may exert synergistic biological effects on the risk of hypertension.

Cube natural sea salt ameliorates obesity in high fat diet-induced obese mice and 3T3-L1 adipocytes

Sodium is an essential component of the human body, with known influences on obesity. This paper reports the effect of cube natural sea salt (CNS) on the reduction of obesity in high fat diet-induced obese C57BL/6 mice and 3T3-L1 adipocytes, by ameliorating the obesity parameters and obesity-related gene mechanisms. The suppression of high fat diet-induced obesity and differentiated 3T3-L1 adipocytes by sea salt depends on the manufacturing process and mineral content. The manufacturing method using only new sea water (Cube natural sea salt) decreases the magnesium (Mg) and sulfur (S) content in the salt with different crystallization and morphologies, compared to the general manufacturing method (Generally manufactured sea salt, GS). Mg in salt is known to considerably affect obesity; an appropriate concentration of magnesium chloride (MgCl₂) reduces lipid accumulation significantly and regulates the lipogenesis and liver enzyme activity. Our results indicate that sea salt contains an appropriate level of Mg as compared to table salt (purified salt, NaCl), and is important for regulating obesity, as observed in the in vivo and in vitro anti-obesity effects of CNS. The Mg content and mineral ratio of sea salt are important factors that ameliorate the lipid metabolism and liver enzyme activity in high fat diet induced obesity, and contents of Mg in sea salt can be altered by modifying the manufacturing process.

Subacute feeding toxicity of low-sodium sausages manufactured with sodium substitutes and biopolymer-encapsulated saltwort (Salicornia herbacea) in a mouse model

BACKGROUND

Low-sodium sausages were manufactured using sodium substitution and biopolymer encapsulation. A diet comprising 10% treatment sausages (six treatment groups: C (100% NaCl), T1 (55% sodium substitute + 45% saltwort salt), T2 (55% sodium substitute + 45% saltwort salt with chitosan), T3 (55% sodium substitute + 45% saltwort salt with cellulose), T4 (55% sodium substitute + 45% saltwort salt with dextrin), and T5 (55% sodium substitute + 45% saltwort salt with pectin)) was added to a 90% commercial mouse diet for 4 weeks.

RESULTS

Subacute toxicity, hematology, liver function, and organ weight tests in low-sodium sausage groups showed results similar to those of the control group, and all toxicity test levels were within normal ranges.

CONCLUSIONS

All low-sodium sausage types tested are suggested to be safe in terms of subacute toxicity. Moreover, low-sodium sausages can be manufactured by biopolymer encapsulation of saltwort using pectin, chitosan, cellulose, and dextrin without toxicity. © 2019 Society of Chemical Industry.

Higher Sodium Intake Assessed by 24 Hour Urinary Sodium Excretion Is Associated with Non-Alcoholic Fatty Liver Disease: The PREVEND Cohort Study

A higher sodium intake is conceivably associated with insulin resistant conditions like obesity, but associations of non-alcoholic fatty liver disease (NAFLD) with a higher sodium intake determined by 24 hours (24 h) urine collections are still unclear. Dietary sodium intake was measured by sodium excretion in two complete consecutive 24 h urine collections in 6132 participants of the Prevention of Renal and Vascular End-Stage Disease (PREVEND) cohort. Fatty Liver Index (FLI) ≥60 and Hepatic Steatosis Index (HSI) >36 were used as proxies of suspected NAFLD. 1936 (31.6%) participants had an FLI ≥60, coinciding with the increased prevalence of type 2 diabetes (T2D), metabolic syndrome, hypertension and history of cardiovascular disease. Sodium intake was higher in participants with an FLI ≥60 (163.63 ± 61.81 mmol/24 h vs. 136.76 ± 50.90 mmol/24 h, p < 0.001), with increasing incidence in ascending quartile categories of sodium intake (p < 0.001). Multivariably, an FLI ≥60 was positively associated with a higher sodium intake when taking account for T2D, a positive cardiovascular history, hypertension, alcohol intake, smoking and medication use (odds ratio (OR) 1.54, 95% confidence interval (CI) 1.44–1.64, p < 0.001). Additional adjustment for the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) diminished this association (OR 1.30, 95% CI 1.21–1.41, p < 0.001). HSI >36 showed similar results. Associations remained essentially unaltered after adjustment for body surface area or waist/hip ratio. In conclusion, suspected NAFLD is a feature of higher sodium intake. Insulin resistance-related processes may contribute to the association of NAFLD with sodium intake.

Prevalence and risk determinants of metabolic syndrome in obese worksite workers in hill city of Himachal Pradesh, India

OBJECTIVE

We report prevalence and risk factors of metabolic syndrome (MS) in the obese workforce of organized sector in hill city of Himachal Pradesh (HP), India.

METHODS

The cross-sectional survey study of employees of organized sectors in Shimla city of HP, India, was conducted to collect data of demographics, health behavior, psychosocial factors, anthropometry, blood pressure, and blood chemistry to measure blood glucose and lipid profile in fasting state in 3004 employees using validated tools. Out of 3004 subjects screened, data of 418 subjects with body mass index of ≥30 are analyzed to estimate the prevalence of MS and its risk determinants. The association of demographics, health behavior, and psychosocial factors as the risk determinants were analyzed using multivariable logistic regression modeling.

RESULTS

MS was prevalent in 57.6% [95% confidence interval (CI): 52.8%-62.3%]. The central obesity (odds ratio: 10.6, 95% CI: 2.32-48.4) and consumption of frequent or daily alcohol (odds ratio: 1.94, 95% CI: 1.05-3.59),and extra salt (odds ratio: 3.34, 95% CI: 1.09-10.2) were independent risk factors for MS. The consumption of tobacco, vegetables, sugar-sweetened drinks, physical inactivity, and psychosocial factors had no significant association with MS in obese population.

CONCLUSIONS

MS is highly prevalent among obese employees of organized sector. The consumption of alcohol and extra salt were major behavioral risk factors for MS and therefore have important implications in behavioral modifications for prevention of MS among obese employees in organized sectors.

Development of a food-based index of dietary inflammatory potential for Koreans and its relationship with metabolic syndrome

BACKGROUND/OBJECTIVES

Inflammation is known to be a risk factor for metabolic diseases. This study aimed to develop a Food-based Index of Dietary Inflammatory Potential (FBDI) and examine its association with metabolic biomarkers.

SUBJECTS/METHODS

This study analyzed the raw data from the 2012-2014 Korean Genome and Epidemiology Study data of 17,771 people. To analyze the relationship between foods consumed by Koreans and inflammation, we conducted a correlation analysis between 51 food groups and hs-CRP levels. The FBDI was developed from 17 food groups selected by multiple regression method. We examined whether FBDI was associated with metabolic markers (waist circumference, blood pressure, fasting glucose, triglyceride, and HDL-cholesterol) in the 6th Korea National Health and Nutrition Examination Survey (KNHANES). We used binary logistic regression analysis to examine the association.

RESULTS

The FBDI model included seven of the anti-inflammatory food groups and three of the pro-inflammatory food groups. The FBDI formula was calculated by multiplying the intake of food group by β-coefficients derived from the multiple regression model based on the correlation analysis. The FBDI was significantly associated with waist circumference (P < 0.001), blood pressure (P < 0.001), triglyceride level (P < 0.001), and HDL-cholesterol (P < 0.001) level among adults aged 20-64 years in the KNHANES. The prevalence of metabolic syndrome was 2.618 times higher in the group with the highest FBDI than in the group with the lowest one (95% confidence interval: 1.778-3.856, P for trend < 0.001).

CONCLUSIONS

This study established an FBDI reflecting food intake patterns of Koreans, which showed a significant relationship with the prevalence of metabolic syndrome.

Dietary sources of salt intake in adults and older people: a population-based study in a Brazilian town

OBJECTIVE

To assess salt intake and its dietary sources using biochemical and self-report methods and to characterize salt intake according to sociodemographic and disease-related variables in a sample of the Brazilian population.

DESIGN

Population-based cross-sectional survey.

SETTING

Salt intake was assessed by biochemical (24 h urinary Na excretion) and self-report methods (sodium FFQ, 24 h dietary recall, seasoned-salt questionnaire, discretionary-salt questionnaire and total reported salt intake).ParticipantsAdults and older people (n 517) aged 20-80 years, living in Artur Nogueira, São Paulo, Brazil.

RESULTS

Mean salt intake based on 24 h urinary Na excretion and total reported salt intake was 10·5 and 11·0 g/d, respectively; both measures were significantly correlated. Discretionary salt and seasoned salt were the most important sources of salt intake (68·2 %). Men in the study consumed more salt than women as estimated by 24 h urinary Na excretion (11·7 v. 9·6 g salt/d; P&lt;0·0001). Participants known to be hypertensive added more salt to their meals but consumed less salty ultra-processed foods. Waist circumference in both sexes and BMI were positively correlated with salt intake estimated by 24 h urinary Na excretion. In addition, regression analysis revealed that being a young male or having a high waist circumference was a predictor of higher salt intake.

CONCLUSIONS

Salt intake in this population was well above the recommended amount. The main source of salt intake came from salt added during cooking. Salt intake varied according to sex and waist circumference.

Association of dietary sodium:potassium ratio with the metabolic syndrome in Chinese adults

Several epidemiological studies have investigated that Na or K intakes might be associated with the metabolic syndrome (MetS). However, little evidence has evaluated the association between Na:K ratio and the MetS. In this study, we assessed the association between the dietary Na:K ratio and the MetS. The cross-sectional study was conducted among adults aged 18 years and older in Nanjing, using a multi-stage random sampling method, which resulted in a sample size of 1993 participants. Dietary Na and K intakes were assessed by 3 consecutive days of dietary recollection combined with condiments weighing method. Health-related data were obtained by standardised questionnaires, as well as physical examinations and laboratory assessments. The prevalence rate of the MetS was 36·5 % (728/1993). After adjusting for various lifestyle and dietary factors of the MetS, participants in the highest quartile of dietary Na:K ratio were at a higher risk of developing MetS (OR=1·602; 95 % CI 1·090, 2·353) compared with those in the lowest quartile. Each 1-sd increase in dietary Na:K ratio was associated with a higher risk of prevalent MetS (OR=1·166; 95 % CI: 1·018, 1·336). Among the components of the MetS, dietary Na:K ratio was positively associated with high blood pressure (quartile 3 v. quartile 1: OR=1·656; 95 % CI 1·228, 2·256) and hypertriacylglycerolaemia (quartile 4 v. quartile1: OR=1·305; 95 % CI 1·029, 1·655) in multivariate analysis. These results revealed that higher dietary Na:K ratio significantly increased the risk of the MetS in Chinese adults. Further studies are needed to verify this association.

Contemporary Dietary Intake: Too Much Sodium, Not Enough Potassium, yet Sufficient Iodine: The SALMEX Cohort Results

Initiatives to reduce sodium intake are encouraged globally, yet there is concern about compromised iodine intake supplied through salt. The aim of the present study was to determine baseline sodium, potassium, and iodine intake in a sample of workers from our Institution in Mexico City (SALMEX Cohort). Methods. From a cohort of 1009 workers, appropriate 24-h urine and three-day dietary recall was collected in a sample of 727 adult subjects for assessment of urinary sodium, potassium, and iodine concentrations. Median urinary iodine excretion (UIE) was compared across categories of sodium intake of <2, 2–3.6, and ≥3.6 g/day. Results. Average sodium intake was 3.49 ± 1.38 g/day; higher in men than women (4.14 vs. 3.11 g/day, p ≤0.001). Only 10.6% of the population had sodium intake within the recommended range (<2 g/day); 45.4% had high (2–3.6 g/day) and 44% had excessive intake (>3.6 g/day). Average urinary Na/K ratio was 3.15 ± 1.22 (ideal < 1), higher in men (3.42 vs. 3.0, p ≤ 0.001). The multivariate analysis showed that sodium intake was associated with age (p = 0.03), male sex (p < 0.001), caloric intake (p = 0.002), UKE (p < 0.001) and BMI (p < 0.001). Median iodine intake was 286.7 µg/day (IQR 215–370 µg/day). Less than 2% of subjects had iodine intake lower than recommended for adults (95 µg/day); 1.3% of subjects in the recommended range of salt intake had low iodine intake. There is a direct relationship between iodine and sodium urinary excretion (r = 0.57, p < 0.0001). Conclusions. In the studied population, there was an excessive sodium intake and an imbalance between sodium and potassium intake. Only 10.6% of the population had sodium intake within the recommended values, but iodine intake in this group appears to be adequate.

The role of salt for immune cell function and disease

The immune system evolved to protect organisms from invading pathogens. A network of pro- and anti-inflammatory cell types equipped with special effector molecules guarantees efficient elimination of intruders like viruses and bacteria. However, imbalances can lead to an excessive response of effector cells incurring autoimmune or allergic diseases. An interplay of genetic and environmental factors contributes to autoimmune diseases and recent studies provided evidence for an impact of dietary habits on the immune status and related disorders. Western societies underwent a change in lifestyle associated with changes in food consumption. Salt (sodium chloride) is one component prevalent in processed food frequently consumed in western countries. Here we summarize recent advances in understanding the mechanisms behind the effects of sodium chloride on immune cells like regulatory T cells (Tregs) and T helper (T_H ) 17 cells and its implication as a risk factor for several diseases.

Low salt and low calorie diet does not reduce more body fat than same calorie diet: a randomized controlled study

Background

Recent several observational studies have reported that high salt intake is associated with obesity. But it is unclear whether salt intake itself induce obesity or low salt diet can reduce body fat mass. We investigated whether a low salt diet can reduce body weight and fat amount.

Matrials and Methods

The randomized, open-label pilot trial was conducted at a single institution. A total of 85 obese people were enrolled. All participants were served meals three times a day, and provided either a low salt diet or control diet with same calorie. Visceral fat was measured with abdominal computer tomography, while body fat mass and total body water was measured with bio-impedance.

Results

Reductions in body weight (–6.3% vs. –5.0%, p = 0.05) and BMI (–6.6% vs. –5.1%, p = 0.03) were greater in the low salt group than in the control group. Extracellular water and total body water were significantly reduced in the low salt group compared to the control group. However, changes in body fat mass, visceral fat area, and skeletal muscle mass did not differ between the two groups. Changes in lipid profile, fasting glucose, and HOMA-IR did not differ between the two groups.

Conclusions

A two-month low salt diet was accompanied by reduction of body mass index. However, the observed decrease of body weight was caused by reduction of total body water, not by reduction of body fat mass or visceral fat mass.

Associations of Sodium and Potassium with Obesity Measures Among Diverse US Hispanic/Latino Adults: Results from the Hispanic Community Health Study/Study of Latinos

OBJECTIVE

The objective of this study was to evaluate cross-sectional associations of sodium and potassium with BMI, waist circumference (WC), and body fat and to determine whether the nativity and/or duration of United States (US) residence modified these associations.

METHODS

Sodium and potassium were derived from 24-hour diet recalls from 16,156 US participants of the 2008 to 2011 Hispanic Community Health Study/Study of Latinos (HCHS/SOL) and from 24-hour urine in 447 HCHS/SOL participants. BMI, WC, and body fat were measured.

RESULTS

Dietary sodium that was 500 mg/d higher was cross-sectionally associated with a 0.07-kg/m2 higher BMI (P < 0.05) and a 0.18-cm larger WC (P = 0.04). Dietary potassium that was 500 mg/d higher was only associated with lower BMI and smaller WC among those who were foreign-born with 10 + years in the US (-0.13 kg/m2 , P < 0.01 and -0.36 cm, P = 0.01, respectively) and among those who were US-born (-0.62 kg/m2 , P < 0.01 and -1.42 cm, P < 0.01, respectively). Urinary sodium that was 500 mg/d higher was associated with a 0.27-kg/m2 higher BMI (P < 0.01) and 0.54 kg more body fat (P < 0.01).

CONCLUSIONS

Sodium intake was associated with higher BMI, WC, and body fat. Potassium intake was associated with lower BMI and smaller WC among US-born participants and participants with a longer duration of US residence.

Association of sodium intake with insulin resistance in Korean children and adolescents: the Korea National Health and Nutrition Examination Survey 2010

BACKGROUND

This study aimed to evaluate the relationship between sodium intake and insulin resistance indices.

METHODS

A total of 718 Korean children and adolescents (411 boys) aged 10-18 years who participated in the Korea National Health and Nutrition Examination Survey (KNHANES) were included in the study. The urinary sodium to urinary creatinine ratio was used as a surrogate for sodium intake. The homeostatic model assessment of insulin resistance (HOMA-IR) and the quantitative insulin sensitivity check index (QUICKI) were used as indices of insulin resistance.

RESULTS

The mean urinary sodium to urinary creatinine ratio was 11.34 in males and 10.17 in females. The urinary sodium to urinary creatinine ratio was significantly positively correlated with HOMA-IR (r=0.165, p<0.001) and inversely correlated with QUICKI (r=-0.181, p<0.001) in Pearson's correlation analyses. In a multivariate linear regression analysis, the urinary sodium to urinary creatinine ratio was independently and significantly positively associated with HOMA-IR (β=0.073, p=0.018) and significantly inversely associated with QUICKI (β=-0.080, p=0.007) after adjustment for possible confounders. HOMA-IR was independently and significantly positively associated with the urinary sodium to urinary creatinine ratio (β=0.087, p=0.018), whereas QUICKI was independently and significantly negatively associated with the urinary sodium to urinary creatinine ratio (β=-0.097, p=0.009) after controlling for confounders.

CONCLUSIONS

Our results suggest that sodium intake, as estimated by the urinary sodium to urinary creatinine ratio, may be independently associated with insulin resistance in children and adolescents.

Association of the urinary sodium to urinary specific gravity ratio with metabolic syndrome in Korean children and adolescents: The Korea National Health and Nutrition Examination Survey 2010-2013

Objectives

This study aimed to evaluate the association between sodium intake and metabolic syndrome (MetS) in Korean boys.

Methods

A total of 1,738 boys aged 10–18 years were included in this study from the Korea National Health and Nutrition Examination Survey (KNHANES) during the years 2010–2013. Sodium intake was assessed using the urinary sodium excretion to urinary specific gravity ratio (U-Na to U-SG ratio).

Results

The median U-Na to U-SG ratio was 133.27 mmol/L (interquartile range: 95.66–178.50 mmol/L). Significant positive associations were found between the U-Na to U-SG ratio and the TG (P = 0.001 for trend) and TG concentrations, and these concentrations were significantly higher in boys with a U-Na to U-SG ratio in the highest quartile compared with those with a ratio in the lowest (P = 0.001) and second (P = 0.033) quartiles, as demonstrated through analysis of covariance (ANCOVA) after adjustment for possible confounders, including age, BMI standard deviation score, ferritin, vitamin D, house income, smoking, alcohol intake, physical activity, season, total intake, total energy intake, protein intake, fat intake, carbohydrate intake, and water intake. Significant inverse associations were found for the U-Na to U-SG ratio with the HDL-C (P = 0.033 for trend) and HDL-C levels, and these values were significantly lower in boys with a ratio in the highest quartile compared with those with a ratio in the second quartile (P = 0.020), as demonstrated through an ANCOVA. Although the trends did not reach statistical significance, a higher U-Na to U-SG ratio tended to be associated with higher SBP (P = 0.086 for trend), DBP (P = 0.063 for trend), and glucose levels (P = 0.099 for trend), as illustrated through ANCOVA. Boys with a ratio in the highest quartile exhibited a 1.73-fold increased risk for elevated TG (95% CI, 1.19–2.51) and a 2.66-fold increased risk for MetS (95% CI, 1.11–6.35) compared with those with a ratio in the lowest quartile, as demonstrated through multivariate logistic regression analyses after adjusting for confounders.

Conclusions

Our results suggest that high sodium intake may be significantly independently associated with MetS in Korean boys aged 10–18 years.

A high salt diet inhibits obesity and delays puberty in the female rat

BACKGROUND/OBJECTIVES

Processed foods are considered major contributors to the worldwide obesity epidemic. In addition to high sugar and fat contents, processed foods contain large amounts of salt. Owing to the correlations with rising adiposity, salt has recently been proposed to be obesogenic. This study investigated three hypotheses: (i) high salt contributes to weight gain and adiposity in juvenile female rats, (ii) puberty onset would be altered because salt is known to affect neuronal systems involved in activating the reproductive system, and (iii) enhanced adiposity will act synergistically with salt to drive early puberty onset.

DESIGN

Female weanling rats (post-natal day 21, n=105) were fed a low fat/low salt diet, low fat/high salt diet, high fat/low salt diet or a high salt/high fat diet for 24 days. Metabolic measures, including weight gain, food intake, fecal output, activity and temperature were recorded in subsets of animals.

RESULTS

Body weight, retroperitoneal and perirenal fat pad weight, and adipocyte size were all lower in animals fed high fat/high salt compared with animals fed high fat alone. Leptin levels were reduced in high fat/high salt fed animals compared with high fat/low salt-fed animals. Daily calorie intake was higher initially but declined with adjusted food intake and was not different among groups after 5 days. Osmolality and corticosterone were not different among groups. Fecal analysis showed excess fat excretion and a decreased digestive efficiency in animals fed high fat/low salt but not in animals fed high fat/high salt. Although respiratory exchange ratio was reduced by high dietary fat or salt, aerobic-resting metabolic rate was not affected by the diet. High salt delayed puberty onset, regardless of dietary fat content.

CONCLUSIONS

Salt delays puberty and prevents the obesogenic effect of a high fat diet. The reduced weight gain evident in high salt-fed animals is not due to differences in food intake or digestive efficiency.

Biomarkers of the metabolic syndrome: Influence of minerals, oligo- and trace elements

Influences of minerals, oligo- and trace elements on the concentration of biomarkers of the metabolic syndrome (MetS) are reviewed. Since food is a complex mixture of caloric compounds and essential non-caloric food components with multiple interactions and varying bioavailability, it is hard to separate or identify the effect of one single component in a total meal or diet. Moreover the diet contains various non-nutritive biologically active components, which may add some beneficial characteristics. Therefore, conclusions on the effect of components on various biomarkers of MetS are sometimes quite contradictory. Reasons therefore are mentioned. Literature data should be studied in detail to conclude whether a component is related to a reduction of MetS-related symptoms or whether its influence is merely affecting a biomarker.

The Association between Urinary Sodium Excretion and Metabolic Syndrome in Korean Adults from the 2010-2011 Korean National Health and Nutrition Examination Survey

Background

The sodium intake of Koreans was higher than that recommended by the World Health Organization. Urinary sodium, which is correlated with sodium intake, can be easily calculated by the Tanaka's equation. This study aimed to evaluate the association between urinary sodium and metabolic syndrome in Korean adults using the 2010–2011 Korean National Health and Nutrition Examination Survey (KNHANES).

Methods

A total of 5,870 participants from the 2010–2011 KNHANES were included in this study. Twenty-four hour urinary sodium was calculated by the Tanaka's equation using spot urine. Participants were divided into tertiles based on urinary sodium levels. The association between urinary sodium and metabolic syndrome was analyzed using multivariate logistic regression analysis.

Results

The odds ratios (ORs) and 95% confidence intervals (CIs) of metabolic syndrome for the 2nd and 3rd tertile of urinary sodium levels was 1.51 (1.16–1.97) and 1.56 (1.23–1.97) compared to the lowest tertile of urinary sodium in men. The ORs and 95% CIs of metabolic syndrome in women were 1.20 (0.95–1.51) for the 2nd tertile and 2.16 (1.68–2.78) for the 3rd tertile. These associations remained statistically significant, even after adjusting for multiple covariates such as age, education, regular exercise, smoking, and alcohol consumption.

Conclusion

These findings indicate that urinary sodium is significantly associated with metabolic syndrome in Korean adults.

Estimation of salt intake assessed by urinary excretion of sodium over 24 h in Spanish subjects aged 7-11 years

PURPOSE

High intake of salt is associated with early development of cardiovascular risk factors (e.g., hypertension, obesity). In "developed" countries, individuals frequently exceed dietary recommendations for salt intake. Taking into account the limited data on sodium intake by 24-h excretion in urine in schoolchildren, we wished to determine baseline salt intake in Spanish subjects aged 7-11 years.

METHODS

The present study was an observational study involving 205 schoolchildren (109 boys and 96 girls) selected from various Spanish provinces. Sodium intake was ascertained by measuring sodium excretion in urine over 24 h. Creatinine was used to validate completeness of urine collections. The correlation between fat-free mass determined by anthropometry and that determined via urinary excretion of creatinine was calculated (r = 0.651; p < 0.001).

RESULTS

Mean 24-h urinary excretion of sodium was 132.7 ± 51.4 mmol/24 h (salt equivalent: 7.8 ± 3.1 g/day). Hence, 84.5 % of subjects aged ≤10 years had intakes of >4 g salt/day, and 66.7 % of those aged >10 years had intakes of >5 g salt/day. Urinary excretion of sodium was correlated with systolic blood pressure and diastolic blood pressure (r = 0.1574 and r = 0.1400, respectively). Logistic regression analyses, adjusted by sex, showed that a high body mass index (odds ratio = 1.159; 95 % CI 1.041-1.290; p < 0.05) was associated with an increased likelihood of high urinary excretion of sodium.

CONCLUSIONS

Sodium intake, as estimated by 24-h urinary excretion, was (on average) higher than recommended. Reducing the sodium content children's diet is a sound policy to reduce cardiovascular risk.

Sodium and potassium intake in South Africa: an evaluation of 24-hour urine collections in a white, black, and Indian population

Limited number of studies on salt intake has been conducted in the South Africa. The present study established the sodium and potassium excretion (24-hour urine collection) of three different South African populations. In total, 692 successful 24-hour urine collections were analyzed for sodium, potassium, and iodine levels. The median sodium and potassium excretion was 122.9 and 33.5 mmol/d, respectively, and the median salt intake was 7.2 g/d. The majority (92.8%) of the population did not meet the recommended potassium intake/d, and 65.6% consumed more than 6 g of salt/d. Potassium excretion showed a linear relationship with salt intake (P-trend ≤ .001). The median sodium-to-potassium ratio was 3.5. These findings support the South African government's sodium reduction legislation, as well as global initiatives. More consideration should be given to promoting the intake of potassium-rich foods, as this may have a greater public health impact than focusing only on dietary sodium reduction.

Metabolic and Kidney Diseases in the Setting of Climate Change, Water Shortage, and Survival Factors

Climate change (global warming) is leading to an increase in heat extremes and coupled with increasing water shortage, provides a perfect storm for a new era of environmental crises and potentially, new diseases. We use a comparative physiologic approach to show that one of the primary mechanisms by which animals protect themselves against water shortage is to increase fat mass as a means for providing metabolic water. Strong evidence suggests that certain hormones (vasopressin), foods (fructose), and metabolic products (uric acid) function as survival signals to help reduce water loss and store fat (which also provides a source of metabolic water). These mechanisms are intricately linked with each other and stimulated by dehydration and hyperosmolarity. Although these mechanisms were protective in the setting of low sugar and low salt intake in our past, today, the combination of diets high in fructose and salty foods, increasing temperatures, and decreasing available water places these survival signals in overdrive and may be accelerating the obesity and diabetes epidemics. The recent discovery of multiple epidemics of CKD occurring in agricultural workers in hot and humid environments may represent harbingers of the detrimental consequences of the combination of climate change and overactivation of survival pathways.

Elevation of Fasting Ghrelin in Healthy Human Subjects Consuming a High-Salt Diet: A Novel Mechanism of Obesity?

Overweight/obesity is a chronic disease that carries an increased risk of hypertension, diabetes mellitus, and premature death. Several epidemiological studies have demonstrated a clear relationship between salt intake and obesity, but the pathophysiologic mechanisms remain unknown. We hypothesized that ghrelin, which regulates appetite, food intake, and fat deposition, becomes elevated when one consumes a high-salt diet, contributing to the progression of obesity. We, therefore, investigated fasting ghrelin concentrations during a high-salt diet. Thirty-eight non-obese and normotensive subjects (aged 25 to 50 years) were selected from a rural community in Northern China. They were sequentially maintained on a normal diet for three days at baseline, a low-salt diet for seven days (3 g/day, NaCl), then a high-salt diet for seven days (18 g/day). The concentration of plasma ghrelin was measured using an immunoenzyme method (ELISA). High-salt intake significantly increased fasting ghrelin levels, which were higher during the high-salt diet (320.7 ± 30.6 pg/mL) than during the low-salt diet (172.9 ± 8.9 pg/mL). The comparison of ghrelin levels between the different salt diets was statistically-significantly different (p < 0.01). A positive correlation between 24-h urinary sodium excretion and fasting ghrelin levels was demonstrated. Our data indicate that a high-salt diet elevates fasting ghrelin in healthy human subjects, which may be a novel underlying mechanism of obesity.

Association Between Estimated 24-h Urinary Sodium Excretion and Metabolic Syndrome in Korean Adults: The 2009 to 2011 Korea National Health and Nutrition Examination Survey

High sodium intake is 1 of the modifiable risk factors for cardiovascular disease, but in Korea, daily sodium intake is estimated to be double the level recommended by World Health Organization. We investigated the association between the estimated 24-h urinary sodium excretion (24hUNaE) and metabolic syndrome using nationwide population data. In total, 17,541 individuals (weighted n = 33,200,054; weighted men, 52.5% [95% confidence interval, CI = 51.8-53.3]; weighted age, 45.2 years [44.7-45.7]) who participated in the Korean Health and Nutrition Examination Survey 2009 to 2011 were investigated. NCEP-ATP III criteria for metabolic syndrome were used, and sodium intake was estimated by 24hUNaE using Tanaka equation with a spot urine sample. The weighted mean 24hUNaE values were 3964 mg/d (95% CI = 3885-4044) in men and 4736 mg/d (4654-4817) in women. The weighted age-adjusted prevalence of metabolic syndrome was 22.2% (21.4-23.0), and it increased with 24hUNaE quartile in both men and women (mean ± standard error of the mean; men: 22.5 ± 1.0%, 23.0 ± 1.0%, 26.0 ± 1.2%, and 26.0 ± 1.2%; P = 0.026; women: 19.4 ± 0.8%, 17.7 ± 0.8%, 19.8 ± 1.0%, and 23.0 ± 1.1%; P = 0.002, for quartiles 1-4, respectively). Even after adjustment for age, daily calorie intake, heavy alcohol drinking, regular exercise, college graduation, and antihypertensive medication, the weighted prevalence of metabolic syndrome increased with the increase in 24hUNaE in men and women. The weighted 24hUNaE was positively associated with the number of metabolic syndrome components after adjustment for confounding factors in men and women. In subjects without antihypertensive medication, the odds ratio for metabolic syndrome in quartile 4 of 24hUNaE compared with quartile 1 was 1.56 (1.33-1.84, P < 0.001) in the total population, 1.66 (1.34-2.06, P < 0.001) in men, and 1.94 (1.49-2.53, P < 0.001) in women. In this nationwide population study, we observed a significant independent association between high sodium intake, estimated by spot urine sodium excretion, and the presence of metabolic syndrome in men and women.

24-h urinary sodium excretion is associated with obesity in a cross-sectional sample of Australian schoolchildren

Emerging evidence indicates that dietary Na may be linked to obesity; however it is unclear whether this relationship is independent of energy intake (EI). The aim of this study was to assess the association between Na intake and measures of adiposity, including BMI z score, weight category and waist:height ratio (WHtR), in a sample of Australian schoolchildren. This was a cross-sectional study of schoolchildren aged 4-12 years. Na intake was assessed via one 24-h urine collection. BMI was converted to age- and sex-specific z scores, and WHtR was used to define abdominal obesity. In children aged ≥8 years, EI was determined via one 24-h dietary recall. Of the 666 children with valid urine samples 55 % were male (average age 9·3 (sd 1·8) years). In adjusted models an additional 17 mmol/d of Na was associated with a 0·10 higher BMI z score (95 % CI 0·07, 0·13), a 23 % (OR 1·23; 95 % CI 1·16, 1·31) greater risk of being overweight/obese and a 15 % (OR 1·15; 95 % CI 1·09, 1·23) greater risk of being centrally obese. In the subsample of 8-12-year-old children (n 458), adjustment for EI did not markedly alter the associations between Na and adiposity outcomes. Using a robust measure of daily Na intake we found a positive association between Na intake and obesity risk in Australian schoolchildren, which could not be explained by total energy consumption. To determine whether this is a causal relationship, longitudinal studies, with high-quality measures of Na and EI, are required.

Possible deleterious hormonal changes associated with low-sodium diets

The average salt intake of people in Canada, the United States, and Europe is about 3,400 mg of sodium per day, which exceeds the recommended intake levels set by various health organizations. The World Health Organization recommends a worldwide reduction of sodium intake to less than 2,000 mg per day. Most research to date has focused on the negative effects of high-sodium intake; however, little information is available on the metabolic effects of low-sodium intakes. This review focuses on the hormonal changes associated with low-sodium diets, especially the hormones involved in metabolism and cardiovascular and renal function. Based largely on rodent studies, low-sodium diets have been associated with changes in glycemic control, energy metabolism, cardiovascular disease risk, cholesterol concentrations, inflammation, and functioning of the renin-angiotensin-aldosterone system. Overall, research has revealed mixed results regarding the impact of dietary sodium intake on various hormones. Further research is required to assess the effects of sodium reduction on hormones and their associated pathways in order to determine the likelihood of any unintended effects.

High Salt Intake

High salt intake is the major cause of raised blood pressure and accordingly leads to cardiovascular diseases. Recently, it has been shown that high salt intake is associated with an increased risk of obesity through sugar-sweetened beverage consumption. Increasing evidence also suggests a direct link. Our study aimed to determine whether there was a direct association between salt intake and obesity independent of energy intake. We analyzed the data from the rolling cross-sectional study–the UK National Diet and Nutrition Survey 2008/2009 to 2011/2012. We included 458 children (52% boys; age, 10±4 years) and 785 adults (47% men; age, 49±17 years) who had complete 24-hour urine collections. Energy intake was calculated from 4-day diary and misreporting was assessed by Goldberg method. The results showed that salt intake as measured by 24-hour urinary sodium was higher in overweight and obese individuals. A 1-g/d increase in salt intake was associated with an increase in the risk of obesity by 28% (odds ratio, 1.28; 95% confidence interval, 1.12–1.45; P =0.0002) in children and 26% (odds ratio, 1.26; 95% confidence interval, 1.16–1.37; P <0.0001) in adults, after adjusting for age, sex, ethnic group, household income, physical activity, energy intake, and diet misreporting, and in adults with additional adjustment for education, smoking, and alcohol consumption. Higher salt intake was also significantly related to higher body fat mass in both children ( P =0.001) and adults ( P =0.001) after adjusting for age, sex, ethnic group, and energy intake. These results suggest that salt intake is a potential risk factor for obesity independent of energy intake.

Association of Sodium Excretion With Metabolic Syndrome, Insulin Resistance, and Body Fat

Sodium intake was reported to be related to metabolic syndrome (MS). Although a strong association between sodium intake and blood pressure (BP) has been reported, the relationship between sodium intake and other components of MS is unknown. An observational study of 18,146 adults in the Korea National Health and Nutrition Examination Survey IV-V databases (2008-2011) was performed. Estimates of 24-h sodium excretion were made from a single fasting urine sample. A significant positive association was found between sodium excretion and systolic BP and between sodium excretion and diastolic BP in participants with and without hypertension after adjusting for multiple covariates (P < 0.001 for trend). The relationship between triglyceride or glucose levels and sodium excretion was linear (P < 0.005). In both men and women, a positive relationship between sodium excretion and waist circumference and an inverse relationship between sodium excretion and high-density lipoprotein were found (P ≤ 0.001). Body fat percentage, body fat mass, and insulin level were positively related to sodium excretion (P ≤ 0.001), and HOMA-IR was significantly associated with sodium excretion (P < 0.05). The risk of MS was elevated 1.279-fold in the second quartile of sodium excretion (95% CI, 1.088-1.504, P = 0.003), 1.479-fold in the third quartile (95% CI, 1.262-1.734; P < 0.001), and 1.929-fold in the highest quartile (95% CI 1.654-2.249, P <  .001) compared with the lowest quartile. Sodium intake is significantly associated with all components of MS, body fat, and insulin resistance. Therefore, a high-salt diet is a significant risk factor for MS.

Are 24 h urinary sodium excretion and sodium:potassium independently associated with obesity in Chinese adults?

OBJECTIVE

To examine the association of 24 h urinary Na excretion and Na:K with obesity in Chinese adults.

DESIGN

Population-based cross-sectional study using a four-stage stratified sampling strategy.

SETTING

Shandong Province, China.

SUBJECTS

Chinese adults (n 1906) aged 18-69 years who provided complete 24 h urine samples.

RESULTS

Odds of obesity increased significantly across increasing quartiles of urinary Na excretion (1·00, 1·54, 1·69 and 2·52, respectively, for overweight; 1·00, 1·20, 1·50, and 2·03, respectively, for obesity; 1·00, 1·44, 1·85 and 2·53, respectively, for abdominal obesity (assessed by waist circumference); and 1·00, 1·28, 1·44 and 1·75, respectively, for abdominal obesity (assessed by waist-to-height ratio); P for linear trend <0·001 for all). In addition, odds of abdominal obesity, but not odds of overweight and obesity, increased significantly with successive Na:K quartiles. Additionally, for each increment in urinary Na excretion of 100 mmol, odds of overweight, obesity, abdominal obesity (by waist circumference) and abdominal obesity (by waist-to-height ratio) increased significantly by 46 %, 39 %, 55 % and 33 %, respectively. Similarly, with a 1 sd increase in Na:K, odds of abdominal obesity (by waist circumference) and abdominal obesity (by waist-to-height ratio) increased significantly by 12 % and 15 %, respectively.

CONCLUSIONS

These findings suggest that 24 h urinary Na excretion and Na:K might be important risk factors for obesity in Chinese adults.