Associations of Health Literacy with Blood Pressure and Dietary Salt Intake among Adults: A Systematic Review

Health literacy has been recognized as a significant social determinant of health, defined as the ability to access, understand, appraise, and apply health-related information across healthcare, disease prevention, and health promotion. This systematic review aims to understand the relationship between health literacy, blood pressure, and dietary salt intake. A web-based search of PubMed, Web of Science, CINAHL, ProQuest, Scopus, Cochrane Library, and Prospero was performed using specified search/MESH terms and keywords. Two reviewers independently performed the data extraction and analysis, cross-checked, reviewed, and resolved any discrepancies by the third reviewer. Twenty out of twenty-two studies met the inclusion criteria and were rated as good quality papers and used in the final analysis. Higher health literacy had shown to have better blood pressure or hypertension knowledge. However, the relationship between health literacy with dietary salt intake has shown mixed and inconsistent findings. Studies looking into the main four domains of health literacy are still limited. More research exploring the links between health literacy, blood pressure, and dietary salt intake in the community is warranted. Using appropriate and consistent health literacy tools to evaluate the effectiveness of salt reduction as health promotion programs is required.

Tempol Alters Urinary Extracellular Vesicle Lipid Content and Release While Reducing Blood Pressure during the Development of Salt-Sensitive Hypertension

Salt-sensitive hypertension resulting from an increase in blood pressure after high dietary salt intake is associated with an increase in the production of reactive oxygen species (ROS). ROS are known to increase the activity of the epithelial sodium channel (ENaC), and therefore, they have an indirect effect on sodium retention and increasing blood pressure. Extracellular vesicles (EVs) carry various molecules including proteins, microRNAs, and lipids and play a role in intercellular communication and intracellular signaling in health and disease. We investigated changes in EV lipids, urinary electrolytes, osmolality, blood pressure, and expression of renal ENaC and its adaptor protein, MARCKS/MARCKS Like Protein 1 (MLP1) after administration of the antioxidant Tempol in salt-sensitive hypertensive 129Sv mice. Our results show Tempol infusion reduces systolic blood pressure and protein expression of the alpha subunit of ENaC and MARCKS in the kidney cortex of hypertensive 129Sv mice. Our lipidomic data show an enrichment of diacylglycerols and monoacylglycerols and reduction in ceramides, dihydroceramides, and triacylglycerols in urinary EVs from these mice after Tempol treatment. These data will provide insight into our understanding of mechanisms involving strategies aimed to inhibit ROS to alleviate salt-sensitive hypertension.

ROMK channels are inhibited in the aldosterone-sensitive distal nephron (ASDN) of renal-tubule Nedd4-2 deficient mice.

We used whole-cell-recording to examine renal-outer-medullary-K+ channel (ROMK or Kir1.1) and epithelial-Na+-Channel (ENaC) in late-distal-convoluted-tubule (DCT2)/initial-connecting-tubule (iCNT) and in the cortical-collecting-duct (CCD) of kidney-tubule-specific Nedd4-2 knockout mice (Ks-Nedd4-2-KO) and floxed-Nedd4l mice (control). TPNQ-sensitive K+ currents (ROMK) were smaller in both DCT2/iCNT and CCD of Ks-Nedd4-2-KO mice on normal diet than control mice. Neither high-dietary-salt-intake (HS) nor low-dietary-salt-intake (LS) had a significant effect on ROMK activity in the DCT2/iCNT and CCD of control and Ks-Nedd4-2-KO mice. In contrast, high-dietary-K+-intake (HK) increased while low-dietary-K+-intake (LK) decreased TPNQ-sensitive K+ currents in floxed-Nedd4l mice. However, effects of dietary-K+ intake on ROMK channel activity were absent in Ks-Nedd4-2-KO mice since neither HK nor LK significantly affected TPNQ-sensitive K+ currents in DCT2/iCNT and CCD. Moreover. TPNQ-sensitive K+ currents in DCT2/iCNT and the CCD of Ks-Nedd4-2-KO mice on HK were similar to the control mice on LK. Amiloride-sensitive Na+ currents in DCT2/iCNT and CCD were significantly higher in Ks-Nedd4-2-KO mice than floxed-Nedd4l mice on normal-K+-diet. HK increased ENaC activity of DCT2/iCNT only in the control mice but HK stimulated ENaC of the CCD in both control and Ks-Nedd4-2-KO mice. Moreover, HK-induced increase in amiloride-sensitive Na+-currents was larger in Ks-Nedd4-2-KO mice than the control mice. Deletion of Nedd4-2 increased WNK1 expression and abolished the HK-induced inhibition of WNK1. We conclude that deletion of Nedd4-2 increases ENaC activity but decreases ROMK activity in aldosterone-sensitive distal nephron (ASDN) and that HK fails to stimulate ROMK but robustly increases ENaC activity in the CCD of Nedd4-2-deficeint mice.

Association between dietary salt and plasma glucose, insulin and hemoglobin A1C levels among type 2 diabetes patients in Eastern China

Purpose: Type 2 diabetes (T2D) is one of the major public health concerns in China. Studies on the association between dietary salt intake and the glycaemia response of T2D are lacking in China. The aim was to investigate the association between the levels of dietary salt intake and the plasma glucose, insulin and hemoglobin A1c (HbA1c) in T2D patients.Methods: Patients with T2D, who accepted management and treatment by the National Standardized Metabolic Disease Management Center at Ningbo First Hospital from March 2018 to January 2020, were included in this study. Dietary salt was collected through a standardized food frequent questionnaire. Anthropometry, blood pressure and biomarkers were measured by well-trained endocrinology nurses. Generalized linear models (GLM) were used to examine the association.Results: A total of 1145 eligible T2D patients with the mean age of 51.4 years were included in the study. Fasting plasma glucose (FPG), 2h postprandial plasma glucose and 2h postprandial insulin, were significantly increased across dietary salt categories. Generalized linear models further showed that dietary salt >8g/d were positively associated with FPG and HbA1c.Conclusion: Higher daily salt intake was found to be associated with FPG and HbA1c in T2D patients. Lifestyle education and promotion on salt reduction should be provided to T2D patients.

Association between dietary salt and plasma glucose, insulin and hemoglobin A1C levels among type 2 diabetes patients in Eastern China

Purpose Type 2 diabetes (T2D) is one of the major public health concerns in China. Studies on the association between dietary salt intake and the glycaemia response of T2D are lacking in China. The aim was to investigate the association between the levels of dietary salt intake and the plasma glucose, insulin and hemoglobin A1c (HbA1c) in T2D patients. Methods Patients with T2D, who accepted management and treatment by the National Standardized Metabolic Disease Management Center at Ningbo First Hospital from March 2018 to January 2020, were included in this study. Dietary salt was collected through a standardized food frequent questionnaire. Anthropometry, blood pressure and biomarkers were measured by well-trained endocrinology nurses. Generalized linear models (GLM) were used to examine the association. Results A total of 1145 eligible T2D patients with the mean age of 51.4 years were included in the study. Fasting plasma glucose (FPG), 2h postprandial plasma glucose and 2h postprandial insulin, were significantly increased across dietary salt categories. Generalized linear models further showed that dietary salt > 8g/d were positively associated with FPG and HbA1c. Conclusion Higher daily salt intake was found to be associated with FPG and HbA1c in T2D patients. Lifestyle education and promotion on salt reduction should be provided to T2D patients.

Estimation of Salt Intake and its Relation to Knowledge and Attitude Regarding the Dangers of High Salt Intake Among an Urban Omani Population

Objectives: High salt consumption is a major risk factor for hypertension. Studies have shown dietary salt intake to be high in many parts of the world. The aim of this study was to assess the daily salt consumption by the urban population in Oman and to assess their knowledge and attitudes towards dietary salt. Methods: This was a cross-sectional questionnaire-based study conducted between September to December 2017 in Muscat. We used previously validated questionnaires to assess salt intake and the knowledge and attitudes to salt intake. Results: 345 responses were received out of 500 distributed questionnaires (response rate 69%) of which 300 responses (27.88 + 7.9 years, 53.3% male) were included for analysis. 94% of the participants agreed that lowering salt in diet is important and nearly half the participants said that they were taking measures to reduce salt intake. However, the median salt intake was high at 10.5(7.3-15.1) gm salt/day. 90% of those questioned consume more than the maximum recommended amount of salt per day. Salt intake was significantly higher in females and older age group (>40 years of age), There did not appear to be any correlation between awareness of the dangers of salt intake and the amount consumed. Conclusion: The salt intake in our sampled population in Oman is high and does not depend on knowledge. Strategies should be designed to reduce salt intake by health education and increasing knowledge about complications of high salt intake among the urban population. Keywords: dietaray sodium chloride; knowledge attitudes and practices.

Association between dietary salt and plasma glucose, insulin and hemoglobin A1C levels among type 2 diabetes patients in Eastern China

Purpose Type 2 diabetes (T2D) is one of the major public health concerns in China. Studies on the association between dietary salt intake and the glycaemia response of T2D are lacking in China. The aim was to investigate the association between the levels of dietary salt intake and the plasma glucose, insulin and hemoglobin A1c (HbA1c) in T2D patients. Methods Patients with T2D, who accepted management and treatment by the National Standardized Metabolic Disease Management Center at Ningbo First Hospital from March 2018 to January 2020, were included in this study. Dietary salt was collected through a standardized food frequent questionnaire. Anthropometry, blood pressure and biomarkers were measured by well-trained endocrinology nurses. Generalized linear models (GLM) were used to examine the association. Results A total of 1145 eligible T2D patients with the mean age of 51.4 years were included in the study. Fasting plasma glucose (FPG), 2h postprandial plasma glucose and 2h postprandial insulin, were significantly increased across dietary salt categories. Generalized linear models further showed that dietary salt > 8g/d were positively associated with FPG and HbA1c. Conclusion Higher daily salt intake was found to be associated with FPG and HbA1c in T2D patients. Lifestyle education and promotion on salt reduction should be provided to T2D patients.

Current Knowledge and Behavior towards Salt Reduction among Hong Kong Citizens: A Cross–Sectional Survey

Excessive dietary salt intake is prevalent in the Hong Kong community. Over the last decade, the Hong Kong Special Administrative Region Government has been actively promoting community participation to reduce salt intake. The aim of this study was to investigate the current knowledge levels and behaviors relating to dietary salt intake among Hong Kong adults. This cross-sectional survey involved 426 adults in Hong Kong. The findings of this study identified areas of knowledge deficit in the recommended upper limit of daily salt intake for an adult set by World Health Organization (n = 295, 69.2%) indicated a lack of awareness that the overconsumption of salt could cause coronary heart disease (n = 233, 54.7%). Disengagement with salt reduction behavior, such as rarely/never checking the sodium or salt content listed on the food label (n = 252, 59.2%) and rarely/never purchasing food labelled with low salt or no salt content (n = 292, 68.9%), was reported. Excessive salt intake in dietary habits remains an under-recognized non-communicable disease threat by Hong Kong citizens, indicating ineffective responsive risk communication. There is a need to refine existing salt reduction initiatives to aid in making appropriate decisions regarding dietary salt intake among Hong Kong citizens.

Abstract MP22: Dietary Salt Restriction And High Salt Intake Exaggerate Sympathetic Reflexes And Sensitize Central Autonomic Networks: Potential Mechanisms Of The J-shaped Curve

Observational cohort studies suggest that severe salt restriction increases cardiovascular morbidity/mortality, and the relationship between cardiovascular morbidity and dietary salt intake resembles a J-shaped curve. A high salt diet exaggerates sympathetic nerve activity (SNA) and arterial blood pressure (ABP) responses to several cardiovascular reflexes in salt-resistant animals. This study assessed whether salt restriction also exaggerates cardiovascular reflex responses and sensitizes central autonomic networks. To test this hypothesis, male Sprague-Dawley rats were fed low (0.01% NaCl), normal (0.1% NaCl), and high (4.0% NaCl) salt diet for 14-21 days. Baseline mean ABP was not different across groups (low: 104±4, normal: 107±4, high: 107±4mmHg). Activation of sciatic afferents (1ms pulse, 500uA, 5s duration, 2-20Hz) produced significantly greater increases in renal SNA (5Hz; low: 196±12, normal: 136±9, high: 177±8%, n=8, P<0.05) and ABP (5Hz; low: 29±3, normal: 16±1, high: 24±2 mmHg, n=8, P<0.05) of rats fed low and high versus normal NaCl diets. Activation of the aortic depressor nerve (2ms pulse, 500uA, 15s duration, 2-20Hz) produced significantly greater decreases in renal SNA (5Hz; low: -55±9, normal: -34±8, high: -63±13%, n=7-8, P<0.05) and ABP (5Hz; low: -31±3, normal: -15±5, high: -32±5 mmHg, n=7-8, P<0.05) of rats fed low and high versus normal NaCl diets. To test whether dietary salt intake sensitized central sympathetic circuits, microinjection of L-glutamate (0.1-1nmol, 30nL) in the rostral ventrolateral medulla produced significantly greater increases in renal SNA (0.1nmol; low: 212±15, normal: 149±8, high: 183±17%, n=7-8, P<0.05) and ABP (0.1Hz; low: 20±2, normal: 12±2, high: 22±2 mmHg, n=7-8, P<0.05) of rats fed low and high versus normal NaCl diets. Finally, rats fed low or high NaCl versus normal NaCl diets displayed exaggerated cardiovascular responses to cage switch or mild restraint and increased 24-h blood pressure variability. The present findings show that severe salt restriction and excess dietary salt intake exaggerate sympathetic and cardiovascular responses, and may be explained by a parallel change in the sensitivity of central autonomic networks to resemble a J-shaped curve.