Salt, blood pressure and cardiovascular risk: what is the most adequate preventive strategy? A Swiss perspective

Ecophysiological and nutritional characterisation of two morphotypes of Cakile maritima subsp. maritima Scop. from Puglia region, Southern Italy

Cakile maritima subsp. maritima Scop. (sea rocket) is a succulent halophyte with significant potential as a nutritious food source, being rich in essential nutrients such as vitamins, minerals, and antioxidants. This annual species exhibits two distinct leaf morphotypes: entire lamina (EL) and pinnatifid lamina (PL). Our understanding of their ecophysiological and nutritional profiles is still limited. The present study investigated the wild EL and PL sea rocket plants from southern Italy during their vegetative stage. The bio-morphological traits (leaf mass area-LMA, dry matter and chlorophyll concentrations), main inorganic ions, key antioxidants (carotenoids, anthocyanins, phenols, flavonoids, glucosinolates, vitamin C as ascorbic and dehydroascorbic acid), and antioxidant activity (by FRAP, DPPH, ABTS assays) were analyzed. Additionally, photosynthetic gas exchange and chlorophyll fluorescence were measured. PL plants showed thicker leaves (higher LMA) and greater accumulation of photo-protective pigments (carotenoids and anthocyanins), despite similar chlorophyll levels. The PL plants also demonstrated higher photosynthetic activity, transpiration rates, and stomatal conductance, with reduced non-photochemical quenching. The EL morphotype had higher cation (K, Mg, Ca, Na) and vitamin C (135.3 mg 100 g-1 FW) concentrations, while no significant disparities were observed between the morphotypes in phenolic concentration (208.5 mg g.a.e. 100 g-1 FW), flavonoids (71.5 mg q.e. 100 g-1 FW), or glucosinolates (61 mg g-1 FW). Interestingly, while the EL type had higher vitamin C, the PL morphotype showed superior antioxidant activity (FRAP, DPPH) and seems to be better adapted to water/nutrient scarcity typical of southern Italy. Both morphotypes offer potential as high-nutritional foods, however, future research should investigate the genotype-specific production of antioxidant compounds in EL and PL plants in response to environmental stresses, including salinity for potential exploitation as a new crop.

Halophytes of the Mediterranean Basin-Underutilized Species with the Potential to Be Nutritious Crops in the Scenario of the Climate Change

Halophyte plants are adapted to saline environments and represent a novel type of crops given their possible uses at both culinary and industrial levels. In this work, the nutritional quality of different Mediterranean halophyte species, Atriplex halimus, Salicornia fruticosa, and Cakile maritima, was evaluated under conditions of high salinity. For this, plants were grown at different NaCl concentrations (0, 100, 200, and 300 mM) and the contents of proteins, total lipids, polyphenols, and mineral elements were analyzed as well as growth. Of the three species, C. maritima was the most sensitive to salt stress and therefore showed the highest phenolic compounds content. By contrast, whereas salinity increased the amounts of proteins and phenolics with respect to the control in A. halimus and S. fruticosa, it decreased them in C. maritima. Plants of A. halimus accumulated higher amounts of Na+ in their leaves, but the level of this ion, considering human consumption, was below that of other culinary halophyte species. In conclusion, all the results indicate that these three halophyte species grown at high salt levels represent optimal crops for-new foodstuff-production as green salt or spice due to their nutritional potential.

Clinical Profiles and Factors Associated with a Low Sodium Intake in the Population: An Analysis of the Swiss Survey on Salt

As a part of the salt controversy, it has been suggested that people with a low sodium intake have an increased risk of cardiovascular events. However, there is no clear explanation for this increased risk. We examined the socio-demographic, clinical profile, and behavioral factors associated with a low sodium intake in the Swiss subjects who participated in the Swiss Survey on Salt. Only 13.3% of the Swiss population eat less than 5 g of salt daily and among them 78.2% are women. Subjects with a low sodium intake eat and drink less as reflected by lower intakes of proteins, potassium, and calcium and a smaller urine volume. In addition, a low blood pressure, a normal body mass index, a low prevalence of obesity, a low serum uric acid, and less alcohol and cigarette consumption characterized this group, suggesting a rather low cardiovascular risk profile. Being single and doing most of the cooking at home are associated with a low intake of sodium, as well as a less frequent consumption of meat and fish when eating less than 5 g salt per day. However, the awareness of the effects of salt on health and cardiovascular risk, health concerns, and physical activity are similar in subjects eating more or less salt. In conclusion, we could not evidence clinical or behavioral factors that could significantly increase the risk of developing cardiovascular events in low salt eaters.

Impaired Daytime Urinary Sodium Excretion Impacts Nighttime Blood Pressure and Nocturnal Dipping at Older Ages in the General Population

The circadian rhythm of urinary sodium excretion is related to the diurnal blood pressure regulation (BP) and the nocturnal dipping pattern. The renal sodium excretion expressed as daytime/nighttime ratio impacts BP, but a limited number of studies have investigated this topic to date. In this cross-sectional study, we aimed to investigate the impact of different daily patterns of sodium excretion (comparing low with high ratios) on BP and nocturnal dipping and to explore the relationship with age. Twenty-four-hour ambulatory BP monitoring and daytime and nighttime urinary sodium collections were used to assess 1062 subjects in Switzerland. Analyses were performed according to the day/night urinary sodium excretion ratio quartiles (Q1-Q4) and by age group (≤50 and ≥50 years). Subjects in Q1 can be considered low excretors of sodium during the daytime since the rate of sodium excretion during the daytime was 40% lower than that of subjects in Q4. Quartiles of the day/night urinary sodium excretion ratio showed that subjects in Q1 were 7 years older and had respectively 6 and 5 mmHg higher nighttime systolic and diastolic BP and a higher nocturnal dipping compared with subjects in Q4 (p-value ≤0.001). Associations found were significant only for subjects older than 50 years (all p < 0.05). The present results suggest that a decreased capacity to excrete sodium during daytime is more prevalent as age increases and that it impacts nighttime blood pressure and nocturnal dipping in older subjects.

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.

Does ENaC Work as Sodium Taste Receptor in Humans?

Taste reception is fundamental for the proper selection of food and beverages. Among the several chemicals recognized by the human taste system, sodium ions (Na⁺) are of particular relevance. Na⁺ represents the main extracellular cation and is a key factor in many physiological processes. Na⁺ elicits a specific sensation, called salty taste, and low-medium concentrations of table salt (NaCl, the common sodium-containing chemical we use to season foods) are perceived as pleasant and appetitive. How we detect this cation in foodstuffs is scarcely understood. In animal models, such as the mouse and the rat, the epithelial sodium channel (ENaC) has been proposed as a key protein for recognizing Na⁺ and for mediating preference responses to low-medium salt concentrations. Here, I will review our current understanding regarding the possible involvement of ENaC in the detection of food Na⁺ by the human taste system.

Trends in Dietary Sodium Intake in the United States and the Impact of USDA Guidelines: NHANES 1999-2016

BACKGROUND

Moderation in sodium consumption is recommended to reduce morbidity and mortality; however, trends in intake and the impact of guidelines have not been examined.

METHODS

Sodium intake data collected from 1999-2016 in the National Health and Nutrition Examination Surveys were analyzed. Trends in sodium intake for individuals aged 18 years or over and in subgroups based on age, sex, race and ethnicity, and sodium-sensitive chronic diseases were examined. Adherence to US Department of Agriculture guidelines was assessed. Multivariable regression analysis was performed to identify predictors of sodium intake from 2011-2016.

RESULTS

A total of 47,509 individuals (median age = 44.0 years, 48.3% male) were included in the study. Median sodium consumption was 3232 mg per day (95% confidence interval [CI], 3210-3255), increasing from 3156 mg per day (95% CI 3,038-3,273) in 1999-2000 to 3273 mg per day (95% CI, 3218-3328) in 2015-2016 (P < .001). Intake declined with age (3427 mg per day for individuals aged 18-50 years, 3101 mg per day for individuals aged 51-70 years, and 2620 mg per day for individuals aged ≥71 years; P < .001) and was greater in males than in females (3827 mg per day vs 2778 mg per day; P < .001). Caucasians, Hispanics, and African Americans consumed 3278, 3117, and 3027 mg of dietary sodium per day respectively (P < .001). Individuals with hypertension, diabetes mellitus, and chronic kidney disease consumed 3073, 3062, and 2658 mg of dietary sodium per day respectively. Population adherence to US Department of Agriculture recommendations declined from 34% to 23% and all high-risk subgroups had < 10% adherence. Daily total calories was the strongest predictor of sodium consumption (overall r² = 0.680).

CONCLUSION

Sodium intake has remained above recommended levels in all segments of the adult population and adherence to guidelines is poor. Novel interventions are needed to reduce sodium intake.

Salt Preference is Linked to Hypertension and not to Aging

BACKGROUND

Seasoning is one of the recommended strategies to reduce salt in foods. However, only a few studies have studied salt preference changes using seasoning.

OBJECTIVES

The aim of this study was to compare preference for salty bread, and if seasoning can change preference in hypertensive and normotensive, young and older outpatients.

METHODS

Outpatients (n = 118) were classified in four groups: older hypertensive subjects (OH) (n = 32), young hypertensive (YH) (n = 25); older normotensive individuals (ON) (n = 28), and young normotensive (YN) (n = 33). First, volunteers random tasted bread samples with three different salt concentrations. After two weeks, they tasted the same types of breads, with seasoning added in all. Blood pressure (BP), 24-hour urinary sodium and potassium excretion (UNaV, UKV) were measured twice. Analysis: Fisher exact test, McNamer's test and ANCOVA. Statistical significance: p < 0.05.

RESULTS

Systolic BP, UNaV, and UKV were greater in HO and HY and they had a higher preference for saltier samples than normotensive groups (HO: 71.9%, HY: 56% vs. NO: 25%, NY; 6%, p<0.01). With oregano, hypertensive individuals preferred smaller concentrations of salt, with reduced choice for saltier samples (HO: 71.9% to 21.9%, and HY: 56% to 16%, p = 0.02), NO preferred the lowest salt concentration sample (53.6% vs. 14.3%, p < 0.01), and NY further increased the preference for the lowest one (63.6% vs. 39.4%, p = 0.03).

CONCLUSIONS

Older and younger hypertensive individuals prefer and consume more salt than normotensive ones, and the seasoned bread induced all groups to choose food with less salt. Salt preference is linked to hypertension and not to aging in outpatients.

Evaluation of an education program based on the theory of planned behavior for salt intake in individuals at risk of hypertension

This study was conducted to evaluate an education program based on the theory of planned behavior (TPB) for salt intake in individuals at risk of hypertension. This randomized controlled trial was conducted from February 2017 to December 2017 in Shahediyeh, Yazd Province, Iran. For this purpose, 140 people were selected and assigned to two groups of 70 each, namely, intervention and control. Data were gathered by a self-administered TPB based questionnaire, and also 24-h urinary sodium and potassium levels and systolic and diastolic blood pressure were measured. The intervention group received TPB based on a training package, while the control group received no intervention. Post-test was administered 2 months after completion of the intervention. Independent and paired t-tests, χ2 and analysis of covariance (ANCOVA) were used for data analysis. All mean scores on TPB constructs increased significantly except motivation to comply and power of control for intervention group. Average salt intake decreased in intervention group compared with the control group (-4.73 g/day �0.73 versus -0.24 g/day �0.94, P < 0.001), but systolic and diastolic blood pressure did not change significantly in intervention group compared with control group. TPB can be implemented along with other approaches in educational programs to reduce salt intake. Code: IRCT201701108803N3.

NFAT5 is differentially expressed in Sprague-Dawley rat tissues in response to high salt and high fructose diets

Current diets contain an increasing amount of salt and high fructose corn syrup, but it remains unclear as to how dietary salt and fructose affect organ function at the molecular level. This study aimed to test the hypothesis that consumption of high salt and fructose diets would increase tissue-specific expression of two critical osmotically-regulated genes, nuclear factor of activated T-cells 5 (NFAT5) and aldose reductase (AR). Fifty Sprague-Dawley rats were placed on a control, 4% NaCl, 8% NaCl, or 64% fructose diet for eight weeks. Fourteen different tissue samples were harvested and snap-frozen, followed by RNA purification, cDNA synthesis, and NFAT5 and AR gene expression quantification by real-time PCR.Our findings demonstrate that NFAT5 and AR expression are up-regulated in the kidney medulla, liver, brain, and adipose tissue following consumption of a high salt diet. NFAT5 expression is also up-regulated in the kidney cortex following consumption of a 64% fructose diet. These findings highlight the kidney medulla, liver, brain, and adipose tissue as being “salt-responsive” tissues and reveal that a high fructose diet can lead to enhanced NFAT5 expression in the kidney cortex. Further characterization of signaling mechanisms involved could help elucidate how these diets affect organ function long term.

A Comparative Study of Iodized Salt Programs: Shanghai and Switzerland

Both Shanghai and Switzerland are developed regions with long-standing salt iodization programs and periodic monitoring. However, the two regions have their own approach to the implementation of the iodized salt policy. In Shanghai, monitoring was carried out every few years, using probability-proportional-to-size sampling technique to select 30 sampling units. Each unit consisted of more than 12 pregnant women and one randomly selected primary school. Urine samples were then taken from the chosen pregnant women and randomly recruited students of that school for iodine test. Data of Switzerland used in this comparative study was extracted from published researches. In Shanghai, the median urinary iodine concentration (UIC) in 2014 was 20% lower than in 1999 (P < 0.05). The median UIC of pregnant women in 2014 was 9.5% lower than that in 2011 (P < 0.05). In terms of iodized salt concentration, opposite to the increasing in Switzerland, it has exhibited a downward trend in Shanghai (P < 0.05). For the years monitored, the iodized salt concentration in Shanghai was significantly (P < 0.05) higher than in Switzerland. Though the UIC of children exhibited a downward trend in Shanghai (P < 0.05), it was still significantly (P < 0.05) higher than in Switzerland over the same monitoring period. However, the UIC in pregnant women was a totally different story, which was significantly (P < 0.05) lower in Shanghai than in Switzerland. Iodized salt is very important for maintaining sufficient iodine level in the population. Appropriate concentration of iodine in fortified salt needs to be decided according to local conditions. Special attention should be paid to the iodine level of pregnant women in Shanghai, and more education about iodine is necessary for the public health.

Inflammasome-Independent NALP3 Contributes to High-Salt Induced Endothelial Dysfunction

Backgrounds and Aims: Na⁺ is an important nutrient and its intake, mainly from salt (NaCl), is essential for normal physiological function. However, high salt intake may lead to vascular injury, independent of a rise in blood pressure (BP). Canonical NALP3 inflammasome activation is a caspase-1 medicated process, resulting in the secretion of IL-18 and IL-1β which lead to endothelial dysfunction. However, some researches uncovered a direct and inflammasome-independent role of NALP3 in renal injury. Thus, this study was designed to investigate the possible mechanisms of NALP3 in high salt induced endothelial dysfunction.

Methods and Results: Changes in endothelial function were measured by investigating mice (C57BL/6J, NALP3^-/- and wild-type, WT) fed with normal salt diet (NSD) or high salt diet (HSD) for 12W, and thoracic aortic rings from C57BL/6J mice cultured in high-salt medium. Changes of tube formation ability, intracellular reactive oxygen species (ROS), and NALP3 inflammasome expression were detected using mouse aortic endothelial cells (MAECs) cultured in high-salt medium. Consumption of HSD for 12W did not affect BP or body weight in C57BL/6J mice. Endothelium-dependent relaxation (EDR) decreased significantly in C57BL/6J mice fed with HSD for 12W, and in isolated thoracic aortic rings cultured in high-salt medium for 24 h. Results from the aortic ring assay also revealed that the angiogenic function of thoracic aortas was impaired by either consumption of HSD or exposure to high-salt medium. NALP3^-/- mice fed with HSD showed a relatively mild decrease in EDR function when compared with WT mice. Tube length of thoracic aortic rings from NALP3^-/- mice was longer than those from WT mice after receiving high-salt treatment. Inhibiting NALP3 with a NALP3 antagonist, small interfering (si) RNA experiments using si-NALP3, and decomposing ROS significantly improved tube formation ability in MAECs under high salt medium. NALP3 expression was increased in MAECs cultured with high salt treatment and inhibiting NALP3 reversed the down-regulation of p-eNOS induced by high salt in MAECs.

Conclusion: High salt intake impairs endothelial function, which is at least in part mediated by increasing NALP3 expression.

The Twin White Herrings: Salt and Sugar

India has the dubious distinction of being a hotspot for both diabetes and hypertension. Increased salt and sugar consumption is believed to fuel these two epidemics. This review is an in-depth analysis of current medical literature on salt and sugar being the two white troublemakers of modern society. The PubMed, Medline, and Embase search for articles published in January 2018, using the terms "salt" [MeSH Terms] OR "sodium chloride" [All Fields] OR "sugar" [All Fields]. India is world's highest consumer of sugar with one of the highest salt consumption per day. Increased salt intake is associated with increased risk of hypertension, left ventricular hypertrophy and fibrosis, cardiovascular events, renal stones, proteinuria, and renal failure. Increased sugar intake is directly linked to increased risk of obesity, fatty liver disease, and metabolic syndrome. Also, increased sugar intake may be indirectly related to the increased risk of type 2 diabetes. Both salt and sugar intake is directly linked to increased systemic and hypothalamic inflammation, endothelial dysfunction, microangiopathy, cardiovascular remodelling, cancers, and death. High fructose corn is especially damaging. There is no safe limit of sugar consumption, as the human body can produce its own glucose. Being nature's gift to mankind, there is no harm in moderate consumption of salt and sugar, however, modest reduction in the consumption of both can substantially reduce the burden of non-communicable diseases. Public health interventions to facilitate this behavioural change must be instituted and encouraged.

Dietary sodium to potassium ratio and the incidence of hypertension and cardiovascular disease: A population-based longitudinal study

OBJECTIVE

There is an interaction between dietary sodium/potassium intake in the pathogenesis of hypertension (HTN) and cardiovascular disease (CVD). The aim of this study was to investigate the association of dietary sodium to potassium (Na/K) ratio and the risk of HTN and CVD in a general population of Iranian adults.

METHODS

In this prospective cohort study, adults men and women with complete baseline data were selected from among participants of the Tehran Lipid and Glucose Study and were followed up for 6.3 years for incidence of HTN and CVD outcomes. Dietary sodium and potassium were assessed using a valid and reliable 168-item food frequency questionnaire. Cox proportional hazards regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between dietary sodium, potassium and their ratio and risk of outcomes.

RESULTS

During the study follow-up, 291 (15.1%) and 79 (5.0%) new cases of HTN and CVD were identified, respectively. No significant association was observed between usual intakes of sodium, potassium and dietary Na/K ratio with the incidence of HTN. There was no significant association between dietary intakes of sodium and potassium per se and the risk of CVD, whereas when dietary sodium to potassium ratio was considered as exposure in the fully-adjusted Cox regression model, and participants in the highest compared to lowest tertile had a significantly increased risk of CVD (HR = 2.19, 95% CI = 1.16-4.14).

CONCLUSIONS

Our findings suggest that high dietary Na/K ratio could contribute to increased risk of CVD events.

Protocol of the Swiss Longitudinal Cohort Study (SWICOS) in rural Switzerland

INTRODUCTION

Increased longevity and consequent major changes in demographics and population lifestyles necessitate new approaches to reduce the burden of ageing-related diseases (including cardiovascular disease) and maintain an optimal quality of life. This study aims to examine and longitudinally follow health status and disease risk factors in a Swiss rural cohort, evaluating all health-related research and practice disciplines to assure development of new implementable and successful preventive strategies for healthy ageing.

METHODS AND OBJECTIVES

Small Swiss villages with low migration rates will be selected for this study. 2 villages (Cama/Lostallo) have already been selected as initial study sites. All residents (age ≥6 years, no upper age limit) are eligible. The target enrolment number per village is 300. Examinations and measurements encompass medical history, anthropometry, cardiac and vascular health, pulmonary function, physical performance, nutritional, mental and emotional status, biochemical and molecular analyses. Follow-up examinations (identical to baseline) will be performed after 5 and 10 years, and in 10-year intervals thereafter. The major objective is to assess, and observe change in, health status over time in a prospective manner. Secondary objectives are to: (1) identify 'hidden' (asymptomatic and/or unrecognised) health problems which enhance risk for chronic diseases; (2) identify barriers to accessing healthcare and adapting health behaviours; (3) evaluate efficacy of present preventive strategies and recommendations; (4) evaluate knowledge and attitude towards ongoing health programmes and public health recommendations; (5) monitor change and progress towards the national health objectives; (6) formulate new preventive strategies and recommendations based on the findings and knowledge base of the past 10 years; (7) formulate models for successful prevention of chronic diseases and for healthy ageing.

ETHICS AND DISSEMINATION

The Ethics Committee of Nordwest-und Zentralschweiz approved this study (EKNZ 2014-209). It is registered at ClinicalTrials.gov (NCT02282748). Findings will be disseminated through scientific articles/presentations and public events.