Salt and insulin sensitivity after short and prolonged high salt intake in elderly subjects

Effects of dietary salt intake restriction on blood glucose levels: a meta-analysis of crossover study

BACKGROUND/OBJECTIVES

To identify modifiable risk factors for type 2 diabetes mellitus and explore the relationship between diet sodium intake and blood glucose levels.

MATERIALS/METHODS

Based on inclusion and exclusion criteria, we extracted, analyzed, and assessed the available crossover studies of dietary salt intake restriction and insulin resistance in PubMed, Web of Science, MEDLINE, Embase, Wanfang, and CNKI databases.

RESULTS

We included 6 studies with 8 sets of data, covering 485 subjects. I² statistics results showed insignificant heterogeneity among all data (I² = 39.2% < 50%). Thus, a fixed-effect model was adopted for the final pooled effect size. Weighted mean difference and its 95% confidence interval (CI) value was 0.193 (95% CI, 0.129-0.257), and the test of the overall effect showed P < 0.001. The results revealed that the blood glucose levels in the subjects in the low-salt intake group were significantly higher than those in the normal or high-salt intake groups. We also found no significant change occurred after the removal of any study through sensitivity analysis, which confirmed that the outcome we calculated was prudent and credible. The quantitative Egger's test (P = 0.109 > 0.05) indicated that insignificant publication bias existed.

CONCLUSION

This meta-analysis highlights the relationship between dietary sodium intake and blood glucose levels. Our findings show that higher blood glucose levels might be expected in hypertensive or normal people with low-salt consumption compared to those with normal or high-salt consumption, although these differences were not clinically significant.

Trial Registration

PROSPERO Identifier: CRD42021256998.

Effectiveness of carbohydrate counting and Dietary Approach to Stop Hypertension dietary intervention on managing Gestational Diabetes Mellitus among pregnant women who used metformin: A randomized controlled clinical trial

BACKGROUND

Gestational diabetes mellitus (GDM) is one of the most common complication of pregnancy that has significant impacts on both mother and her offspring health. The present study aimed to examine the effect of carbohydrate counting, carbohydrate counting combined with DASH, and control dietary interventions on glycemic control, and maternal and neonatal outcomes.

METHODS

A total of 75 pregnant women with GDM at 24th - 30th week of gestation were enrolled and randomized to follow one of the three diets: control or carbohydrate counting, or carbohydrate counting combined with Dietary Approach to Stop Hypertension (DASH). Only 70 of them completed the study until delivery. Fasting blood samples were taken at baseline and the end of the study to measure fasting blood glucose (FBG), fasting insulin, glycated hemoglobin (HbA1c), and fructosamine. Homeostatic model assessment-insulin resistance (HOMA-IR) score was calculated using HOMA2 calculator program. The participants recorded at least four blood glucose readings per day. Maternal and neonatal outcomes were collected from medical records. Dietary intake was assessed by three-day food records at the baseline and the end of the study.

RESULTS

Adherence to the three dietary interventions, resulted in decreased FBG levels significantly among all the participants (P < 0.05). Consumption of the carbohydrate counting combined with the DASH diet showed significant reduction in serum insulin levels and HOMA-IR score compared to carbohydrate counting group and control group. Means of fructosamine and HbA1c did not differ significantly among the three intervention diet groups. Overall mean of 1-h postprandial glucose (1 h PG) level was significantly lower in the carbohydrate counting combined with DASH group compared with that in the carbohydrate counting group and the control group (P < 0.001). The number of women who were required to commence insulin therapy after dietary intervention was significantly lower in carbohydrate counting group and carbohydrate counting combined with DASH group (P = 0.026). There were no significant differences in other maternal and neonatal outcomes among the three dietary intervention groups.

CONCLUSIONS

The carbohydrate counting and the carbohydrate counting combined with DASH dietary interventions resulted in beneficial effects on FBG and 1 h PG compared with the control diet. The three dietary interventions produced similar maternal and neonatal outcomes in women with GDM.

TRIAL REGISTRATION

This trial was registered on ClinicalTrials.gov under the identification code: NCT03244579. https://clinicaltrials.gov/ct2/show/NCT03244579.

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.

Salts and energy balance: A special role for dietary salts in metabolic syndrome

BACKGROUND

Dietary salts sodium (Na⁺), potassium (K⁺), magnesium (Mg2⁺), and calcium (Ca2⁺) are important in metabolic diseases. Yet, we do not have sufficient understanding on the salts global molecular network in these diseases. In this systematic review we have pooled information to identify the general effect of salts on obesity, insulin resistance and hypertension.

AIMS

To assess the roles of salts in metabolic disorders by focusing on their individual effect and the network effect among these salts.

METHODS

We searched articles in PubMed, EMBASE and Google Scholar. We selected original laboratory research, systematic reviews, clinical trials, observational studies and epidemiological data that focused on dietary salts and followed the preferred reporting items for systematic review in designing the present systematic review.

RESULTS

From the initial search of 2898 studies we selected a total of 199 articles that met our inclusion criteria and data extraction. Alterations in metabolic pathways associated with the sensitivity of sodium, potassium, magnesium and calcium may lead to obesity, hypertension, and insulin resistance. We found that the results of most laboratory research, animal studies and clinical trials are coherent but some research outcome are either inconsistent or inconclusive.

CONCLUSION

Important of salts in metabolic disorder is evident. In order to assess the effects of dietary salts in metablic diseases, environmental factors, dietary habits, physical activity, and the microbiome, should be considered in any study. Although interest in this area of research continues to grow, the challenge is to integrate the action of these salts in metabolic syndrom.

Relationship between urinary sodium-creatinine ratios and insulin resistance in Korean children and adolescents with obesity

BACKGROUND

The prevalence of childhood obesity has significantly increased in Korea. This study aimed to use data from the 2010 Korea National Health and Nutrition Examination Survey (KNHANES) to investigate the association between sodium (Na) intake and insulin resistance in children and adolescents with obesity.

METHODS

The study population consisted of 578 adolescents aged 12-18 years who were enrolled in the 2010 KNHANES. Subjects were classified into the following four groups based on their body mass index (BMI) and homeostatic model assessment-insulin resistance (HOMA-IR) values: normal BMI and HOMA-IR (Group 1), normal BMI and ≥75% HOMA-IR (Group 2), ≥85% BMI and normal HOMA-IR (Group 3) and ≥85% BMI and ≥75% HOMA-IR (Group 4). The groups were further divided into four quartiles (Q1-Q4) based on urinary sodium-creatinine ratios (UNa/Cr) to analyze the association between obesity and metabolic abnormality as a result of increased Na intake.

RESULTS

There were significant differences among the four groups in terms of abdominal obesity (p<0.000), waist circumference (WC) (p<0.000) blood glucose levels (p<0.000), insulin levels (p<0.000) and UNa/Cr, with Groups 2, 3 and 4 having significantly higher UNa/Cr than Group 1 (p=0.002). In addition, there was a significant positive correlation between UNa/Cr and obesity (Q1=1 vs. Q4=3.23, p=0.019) and metabolic abnormality (Q1=1 vs. Q4=2.25, p=0.167).

CONCLUSIONS

Increased Na intake showed a positive statistical correlation with insulin resistance and is associated with an increased risk of insulin resistance and other metabolic abnormalities in obese children and adolescents.

Low Salt Diet and Insulin Resistance

It is well known that high sodium intake is closely associated with the risk of cardiovascular disease, but the effect of low sodium intake on insulin resistance is not clear. In this article, we summarize findings from previous studies focusing on the association between low sodium intake and insulin resistance. While many investigations on this topic have been conducted actively, their major findings are inconsistent, partly due to different study designs. Thus, additional randomized controlled trials with an adequate study period and reasonable levels of low sodium intake are needed.

Dietary sodium reduction does not affect circulating glucose concentrations in fasting children or adults: findings from a systematic review and meta-analysis

BACKGROUND

Although evidence shows that reduced sodium intake lowers blood pressure, some studies suggest that sodium reduction may adversely affect insulin resistance and glucose tolerance.

OBJECTIVES

The objectives were to assess the effects of sodium reduction on glucose tolerance, evaluate strengths and weaknesses of the relevant scientific literature, and provide direction for future research.

METHODS

We searched The Cochrane Library, MEDLINE, EMBASE, CINAHL, and Web of Science through August 2014. Both randomized and nonrandomized intervention trials were included in our meta-analyses. The effects of sodium reduction on glucose tolerance were evaluated in 37 articles, but because of a lack of comparable data, 8 trials were excluded from the meta-analyses.

RESULTS

Participants were 10-79 y old, either primarily healthy or with hypertension. In meta-analyses of 20 randomized, crossover trials (n = 504 participants) and 9 nonrandomized crossover trials (n = 337), circulating glucose concentrations of fasting participants were not affected by reduction in sodium intake. In contrast, in meta-analyses of 19 of the 20 randomized, crossover trials (n = 494), fasting insulin concentrations were 9.53 pmol/L higher (95% CI: 5.04, 14.02 pmol/L higher) with sodium reduction. In 9 nonrandomized trials (n = 337), fasting insulin did not differ with reduced sodium intake. Results differed little when the analyses were restricted to studies with a low risk of bias and duration of ≥7 d.

CONCLUSIONS

This meta-analysis revealed no evidence that, in trials with a short intervention and large reductions in sodium, circulating glucose concentrations differed between groups. Recommendations for future studies include extending intervention durations, ensuring comparability of groups at baseline through randomization, and assessing sodium intakes relevant to population sodium reduction. In addition, analyses on other metabolic variables were limited because of the number of trials reporting these outcomes and lack of consistency across measures, suggesting a need for comparable measures of glucose tolerance across studies.

Salt preferences of normotensive and hypertensive older individuals

The aim of this study was to evaluate the preference for salt in hypertensive and normotensive older individuals. Hypertensive (group 1: n=32, aged 73.7±6.3 years) or normotensive patients (group 2: n=26, aged 71.5±8.0 years) were submitted to a test to determine their preference for bread samples with different salt concentrations: 1.5%, 2.0% (usual concentration), and 2.7%, and were reevaluated 2 weeks later using the same salt concentrations, but with the addition of oregano. Twenty-four-hour urinary sodium excretion (UNaV), blood pressure (BP), and body mass index (BMI) were obtained. Systolic BP, BMI, and UNaV were higher in group 1. In the first analysis, group 1 showed greater preference for the saltiest sample (P=.001). Comparing the first evaluation and the second, a greater preference for less salty samples was observed in both groups (P<.01). Hypertensive older patients consumed more salt and showed a greater salt preference than the normotensive patients. The use of the spice reduced the preference for salt in both groups.

Review: efficacy of alginate supplementation in relation to appetite regulation and metabolic risk factors: evidence from animal and human studies

This review provides a critical update on human and animal studies investigating the effect of alginate supplementation on appetite regulation, glycaemic and insulinemic responses, and lipid metabolism with discussion of the evidence on potential mechanisms, efficacy and tolerability. Dependent on vehicle applied for alginate supplementation, the majority of animal and human studies suggest that alginate consumption does suppress satiety and to some extent energy intake. Only one long-term intervention trial found effects on weight loss. In addition, alginates seem to exhibit beneficial influence on postprandial glucose absorption and insulin response in animals and humans. However, alginate supplementation was only found to have cholesterol-lowering properties in animals. Several mechanisms have been suggested for the positive effect observed, which involve delayed gastric emptying, increased viscosity of digesta and slowed nutrient absorption in the small intestine upon alginate gel formation. Despite reasonable efficacy and tolerability from the acute or short-term studies, we still realize there is a critical need for development of optimal alginate types and vehicles as well as studies on further long-term investigation on alginate supplementation in humans before inferring that it could be useful in the management of obesity and the metabolic syndrome.