Preference for High Dietary Salt Intake Is Associated With Undiagnosed Type 2 Diabetes: The Henan Rural Cohort

Salt Intake in Adults with Diabetes and Hypertension: The Longitudinal Study of Adult Health-Brasil Study

Background and Objective: Hypertension and type-2 diabetes are strong risk factors for cardiovascular diseases, and their management requires lifestyle changes, including a shift in dietary habits. The consumption of salt has increased in the last decades in some countries, but its association with type-2 diabetes remains unknown. Thus, we aimed to estimate the amount of salt intake among adults with and without diabetes and to assess whether concomitant hypertension and diabetes are associated with higher salt intake. Methods: Data from 11,982 adults 35-74 years of age enrolled in the baseline of the Longitudinal Study of Adult Health-Brasil study (2008-2010) were studied. A clinical and anthropometric evaluation was performed, and their daily salt intake was estimated by the overnight 12-hr urine sodium excretion. Results: Salt intake (gram per day) was higher in participants with diabetes as compared with those without diabetes, regardless of sex (men: 14.2 ± 6.4 vs. 12.4 ± 5.6, P < 0.05; women: 10.5 ± 4.8 vs. 9.1 ± 4.1, P < 0.05). However, salt intake is high in participants with fasting glucose ≥126 mg/dL or HbA1c ≥6.5%, but not in participants with blood glucose 2 hr after the glucose tolerance test ≥200 mg/dL. When hypertension and diabetes coexisted, salt consumption was higher than among people without these conditions. The prevalence of hypertension increased with increasing salt intake in women with diabetes, but not in men with this condition. Conclusions: Our findings highlight the high consumption of salt in individuals with diabetes and/or hypertension, and the need for effective strategies to reduce salt consumption in these groups of increased risk for major cardiovascular events, especially in women.

Association of sodium intake with diabetes in adults without hypertension: evidence from the National Health and Nutrition Examination Survey 2009-2018

Background

Sodium is essential for human health, however the prevalence of various diseases is associated with excessive sodium intake, particularly cardiovascular disorders. However, in most countries, salt intake is much higher than the World Health Organization recommends. Several studies in recent years have revealed that high salt intake is associated with diabetes in the general population, but the association is uncertain in people who do not have hypertension. In this study, we aimed to find out whether high sodium intake increases the risk of diabetes in this particular population.

Method

Data were extracted from the National Health and Nutrition Examination Survey (NHANES; 2009-2018). Participants included adults aged over 20 years old who have undergone the diabetes questionnaire, and the hypertension population was excluded. In order to adjust the confounders, multivariate analysis models were built. Finally, subgroup analysis were conducted to investigate the association between sodium intake and diabetes separately.

Result

In the present study, 7,907 participants are included (3,920 female and 3,987 male), and 512 (6.48%) individuals reported diabetes. The median sodium intake of the participants was 3,341 mg/d (IQR: 2498, 4,364 mg/d). A linear association between sodium intake and the prevalence of diabetes was found (p = 0.003). According to the multivariate analysis models, the odds ratio of diabetes for every 1,000 mg sodium intake increment is 1.20 (OR: 1.20, 95% CI 1.07-1.35). The highest sodium intake quartile was 1.80-fold more likely to have diabetes than the lowest quartile (OR: 1.80, 95% CI 1.17-2.76).

Conclusion

Our results suggest that higher sodium intake is associated with an increased risk of diabetes in the population without hypertension, and for every 1,000 mg sodium intake increment, the risk of diabetes increased by 1.20-fold. To sum up, we have provided the clue to the etiology of diabetes and further prospective research is needed to contribute recommendations for the primary prevention of diabetes in the US.

Obesity, Cardiovascular and Neurodegenerative Diseases: Potential Common Mechanisms

The worldwide increase in the incidence of obesity and cardiovascular and neurodegenerative diseases, e.g. Alzheimer's disease, is related to many factors, including an unhealthy lifestyle and aging populations. However, the interconnection between these diseases is not entirely clear, and it is unknown whether common mechanisms underlie these conditions. Moreover, there are currently no fully effective therapies for obesity and neurodegeneration. While there has been extensive research in preclinical models addressing these issues, the experimental findings have not been translated to the clinic. Another challenge relates to the time of onset of individual diseases, which may not be easily identified, since there are no specific indicators or biomarkers that define disease onset. Hence knowing when to commence preventive treatment is unclear. This is especially pertinent in neurodegenerative diseases, where the onset of the disease may be subtle and occur decades before the signs and symptoms manifest. In metabolic and cardiovascular disorders, the risk may occur in-utero, in line with the concept of fetal programming. This review provides a brief overview of the link between obesity, cardiovascular and neurodegenerative diseases and discusses potential common mechanisms including the role of the gut microbiome.

Molecular Mechanisms of Obesity-Induced Development of Insulin Resistance and Promotion of Amyloid-β Accumulation: Dietary Therapy Using Weak Organic Acids via Improvement of Lowered Interstitial Fluid pH

Insulin resistance is one of the etiologies of type 2 diabetes mellitus (T2DM) and has been suggested to contribute to the development of Alzheimer's disease by promoting amyloid-β accumulation. Various causes of insulin resistance have been suggested; however, mechanisms of insulin resistance development remain to be elucidated in many respects. Elucidating the mechanisms underlying the development of insulin resistance is one of the key factors in developing methods to prevent the onset of T2DM and Alzheimer's disease. It has been suggested that the body pH environment plays an important role in the control of cellular functions by regulating the action of hormones including insulin and the activity of enzymes and neurons, thereby maintaining homeostatic conditions of the body. This review introduces: (1) Mitochondrial dysfunction through oxidative stress caused by obesity-induced inflammation. (2) Decreased pH of interstitial fluid due to mitochondrial dysfunction. (3) Development of insulin resistance due to diminution of insulin affinity to its receptor caused by the lowered interstitial fluid pH. (4) Accelerated accumulation of amyloid-β due to elevated activities of β- and γ-secretases caused by the lowered interstitial fluid pH. (5) Diet therapies for improving insulin resistance with weak organic acids that act as bases in the body to raise the pH of lowered interstitial fluid and food factors that promote absorption of weak organic acids in the gut.

Hepatic Transcriptomics Reveals Reduced Lipogenesis in High-Salt Diet Mice

It has been demonstrated that a high salt diet (HSD) increases the risk of cardiovascular disease and metabolic dysfunction. In particular, the impact and molecular mechanisms of long-term HSD on hepatic metabolism remain largely unknown. To identify differentially expressed genes (DEGs) affecting the metabolism of liver tissues from HSD and control groups, a transcriptome analysis of liver tissues was performed in this study. As a result of the transcriptome analysis, the expression of genes related to lipid and steroid biosynthesis (such as Fasn, Scd1, and Cyp7a1) was significantly reduced in the livers of HSD mice. Additionally, several gene ontology (GO) terms have been identified as associated with metabolic processes in the liver, including the lipid metabolic process (GO: 0006629) and the steroid metabolic process (GO: 0008202). An additional quantitative RT-qPCR analysis was conducted to confirm six down-regulated genes and two up-regulated genes. Our findings provide a theoretical basis for further investigation of HSD-induced metabolic disorders.

Role of high-salt diet in non-alcoholic fatty liver disease: a mini-review of the evidence

With the rising incidence of both obesity and diabetes, non-alcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease worldwide. However, lifestyle intervention remains to be an effective approach for NAFLD due to lack of therapeutic medication. Recently, salt, an essential micronutrient free of calories, has raised a global concern owing to its wide-range healthy relevance. Accumulated evidence has suggested that a long-term high-salt diet (HSD) independently increases the risk of NAFLD. In the past decades, a number of studies have been reported regarding the mechanism of much investigation concerning HSD-induced NAFLD. Here, we review the updates in epidemiology and molecular mechanism of HSD-induced NAFLD and provide a novel insight into the role of HSD in the regulation of lipid metabolism.

Trends of Dietary Intakes and Metabolic Diseases in Japanese Adults: Assessment of National Health Promotion Policy and National Health and Nutrition Survey 1995–2019

Health Japan 21 is Japan’s premier health promotion policy encompassing preventive community health measures for lifestyle-related diseases. In this repeated cross-sectional survey, we report 24-year trends of type 2 diabetes mellitus (T2DM), obesity, hypertension, and their association with dietary intakes to evaluate Health Japan 21’s impact and identify gaps for future policy implementation. We analyzed data from 217,519 and 232,821 adults participating in the physical examination and dietary intake assessment, respectively, of the National Health and Nutrition Survey 1995–2019. Average HbA1c and BMI have significantly increased along with the prevalence of T2DM and overweight/obesity among males. Despite a significant decrease in daily salt intake, the decline in the combined prevalence of Grades 1–3 hypertension was non-significant. Seafood and meat intakes showed strong opposing trends during the study period, indicating a dietary shift in the Japanese population. Neither salt nor vegetable/fruit intake reached the target set by Health Japan 21. Metabolic disease trend differences between males and females highlight the need for a gender-specific health promotion policy. Future Health Japan 21 implementation must also consider locally emerging dietary trends.

Association between Dietary Habits and Type 2 Diabetes Mellitus in Yangon, Myanmar: A Case-Control Study

In Myanmar, the escalating prevalence of type 2 diabetes mellitus (T2DM) and impaired glucose tolerance among adults was recently reported, with the highest prevalence in the Yangon Region. The aim of the present study was to identify the risk factors in dietary habits and their relationship with T2DM in urban Myanmar residents. We conducted a case–control study recruiting 300 individuals aged 25–74 years living in the Yangon Region, consisting of 150 newly diagnosed cases attending a diabetes clinic, and 150 controls, who were community residents and free of diabetes. The case group had a significantly higher consumption of noodles, fish, beans, fermented food and pickles, dried food, topping seasonings, and non-dairy milk products than the control group, whereas they had a lower vegetable intake (more than three servings/day) and fruit intake (more than three servings/day) than the control group. Furthermore, the case group exhibited a higher frequency of some dietary behaviors than the control group, such as (1) having meals with family, (2) skipping breakfast, and (3) eating out. The final model showed that topping seasonings (adjusted odds ratio (aOR) 11.23, 95% confidence interval (CI) 3.08–40.90), more than three servings/day of vegetable intake (aOR 0.18, 95% CI 0.05–0.67), and having meals with family (aOR 2.23, 95% CI 1.05–4.71) were associated with diabetes. The study suggests that Myanmar’s characteristic dietary culture of topping their meals with salty seasonings and sauces and eating multiple dishes together as a family are risk factors associated with T2DM. Our findings may contribute recommendations and opportunities for the primary prevention of T2DM in urban Myanmar.

Dietary sodium and cardiovascular morbidity/mortality: a brief commentary on the 'J-shape hypothesis'

The last decade, a growing number of evidence support J-shape or inverse - instead of positive linear -- associations between dietary sodium intake and cardiovascular morbidity/mortality. A careful evaluation of these studies leads to the following observations: less accurate methods for dietary sodium assessment are usually used; most studies included high-risk participants, enhancing the possibility of a 'reverse causality' phenomenon. However, these limitations do not explain all the findings. Few carefully designed randomized clinical trials comparing different levels of sodium intake that address the issue of the optimal and safe range exist; therefore, current guidelines recommend a higher cut-off instead of a safe range of intake. Given the demonstrated harmful effects of very low sodium diets leading to subclinical vascular damage in animal studies, the 'J-shape hypothesis' cannot yet be either neglected or verified. There is a great need of well-designed general population-based prospective randomized clinical trials to address the issue.