Effect of vitamin D3 supplementation on insulin resistance and β-cell function in prediabetes: a double-blind, randomized, placebo-controlled trial

Insight into the Interaction Mechanism of Vitamin D against Metabolic Syndrome: A Meta-Analysis and In Silico Study

As a dietary supplement or functional food additive, vitamin D (VD) deficiency may impact extra-skeletal functions associated with metabolic syndrome (MetS) risk factors. However, the precise effects and mechanisms of VD supplementation on dyslipidemia and insulin resistance in MetS subjects remain controversial. Here, we investigate potential therapeutic targets, pathways and mechanisms of VD against MetS through a comprehensive strategy including meta-analysis, network pharmacology analysis, molecular docking, dynamics simulations, and quantum chemical calculations. Our results reveal that VD supplementation significantly reduces triglyceride levels, fasting glucose, and insulin concentrations in subjects, thereby improving insulin homeostasis to some extent. We theoretically identify 14 core MetS-associated targets. Notably, VD exhibits substantial interactions with three targets (PPARγ, FABP4, and HMGCR) in the PPAR signaling pathway, indicating that VD can modulate this pathway. Van der Waals forces predominantly stabilize the complexes formed between VD and the three targets. Nonetheless, to provide valuable insights for personalized MetS management, further research is necessary to confirm our findings, emphasizing the importance of exploring genetic variability in VD response. In conclusion, our study contributes insights into the mechanisms of VD in preventing and treating MetS through dietary supplementation, promoting the development of VD-based functional foods or nutritious diets.

The Effect of Vitamin D Supplementation on Incidence of Type 2 Diabetes: A Systematic Review

With the clinical increase in Type 2 Diabetes worldwide, several interventions to decrease its incidence have been investigated. One such intervention is Vitamin D supplementation, as it affects Insulin secretion from the pancreas and Insulin receptors in the cells of the body. This systematic review addresses whether or not Vitamin D supplementation has a role in reducing the risk of developing Type 2 Diabetes. Systematic searches were conducted on PubMed, and Cochrane Library mainly but also checked Google Scholar. Randomized controlled trials, systematic trials and cohort studies were retrieved that included keywords pertaining to Vitamin D supplementation and the incidence of Type 2 Diabetes. Exclusion criteria included studies that looked at different forms of Diabetes, studies including patients aged less than 18 or more than 85 years of age and studies that were not English language. For all the trials identified, the incidence of Type 2 Diabetes among the cohort receiving vitamin D supplementation was compared to the cohort receiving placebo medication. Additionally, the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) was analyzed to observe if there was a difference between Insulin resistance among these two cohorts between the start of the trials and the end. Thirteen randomized controlled trials were identified. Seven of these identified incidences of Type 2 Diabetes as a research outcome, out of which six showed no statistically significant impact of vitamin D on the incidence of Type 2 Diabetes. Out of the 13 trials, 10 analyzed the impact of vitamin D supplementation on patients' HOMA-IR. In six of these trials, patients receiving vitamin D supplementation had a decrease in their HOMA-IR, while it increased in 4 trials. In seven of the ten trials that analyzed for HOMA-IR, the HOMA-IR was less in the vitamin D cohort than the placebo cohort. There is insufficient evidence to suggest that vitamin D supplementation significantly reduces the incidence of Type 2 Diabetes despite its effects on insulin resistance. Further research in this area would be helpful in order to influence clinical guidelines on vitamin D supplementation among patients at risk of Type 2 Diabetes.

Controversial Impact of Vitamin D Supplementation on Reducing Insulin Resistance and Prevention of Type 2 Diabetes in Patients with Prediabetes: A Systematic Review

BACKGROUND

Prediabetes has become a worldwide health problem. Multiple clinical trials have been conducted to determine the potential benefits of vitamin D supplementation in preventing the conversion to diabetes, but the results are inconsistent. The aims of this study were to evaluate the current knowledge and to suggest recommendations for researchers on designing future trials regarding that matter.

METHODS

Four databases were searched for randomized control trials from the last 10 years about vitamin D and insulin resistance. The systematic electronic literature search identified 2645 studies, of which thirty-eight qualified for full-text reading and discussion. Finally, eight trials were included.

RESULTS

Final results of seven trials reported that supplementation of vitamin D does not reduce insulin resistance nor reduces the risk of diabetes mellitus type 2 development in prediabetes. Only one trial showed improvements in fasting glucose and HOMA-IR.

CONCLUSIONS

Due to the great variation and biases in study designs, an unambiguous interpretation of the results is not possible. To eliminate those vulnerabilities in the future, we made certain suggestions for study design. Long-term and well-designed studies are still required.

Dietary Consumption on Glycemic Control Among Prediabetes: A Review of the Literature

Introduction

Prediabetes is a condition that, if left unaddressed, can lead to various complications, such as neuropathy, retinopathy, and nephropathy. Among the critical factors contributing to the development of type 2 diabetes mellitus, dietary choices stand out as particularly significant.

Objective

Consequently, our objective is to examine the latest research findings concerning dietary consumption and its impact on glycemic control in individuals with prediabetes.

Methods

A literature review of randomized controlled trials was performed using databases such as PubMed, Scopus, and ScienceDirect with searches conducted from January 2019 to 2023. The primary reviewer assessed the quality of the selected studies for bias risk using the Joanna Briggs Institute critical appraisal method for randomized controlled trials. Initially, 975 articles were identified through the search, but after applying the inclusion criteria, only 9 articles were ultimately selected.

Results

The review found that a carrageenan-free diet, yogurt with Lactobacillus plantarum OLL2712, Allium hookeri extract (AHE), and delta-tocotrienol improve HbA1C levels. However, salmon, zinc supplement, and balanced deep-sea water were not effective on HbA1C. In addition, studies on the effectiveness of vitamin D in controlling blood glucose levels are inconsistent.

Conclusion

Nurses can enhance patient outcomes through collaborative efforts to create individualized dietary strategies. These strategies may encompass the adoption of a carrageenan-free diet, the inclusion of L plantarum OLL2712-enriched yogurt, the utilization of AHE, and the integration of delta-tocotrienol into the dietary plan. This approach is particularly applicable to ambulatory care nurses, health supervisors, and primary care providers.

Bone mineral density and lipid profiles in older adults: a nationwide cross-sectional study

It has been hypothesized that lipid profiles are associated with bone mineral density (BMD), but previous results have been controversial. In this study, serum triglycerides showed a significant inverse association with BMD, and the relationship is thought to correlate with vitamin D status among older adults.

INTRODUCTION

The purpose of this study was to investigate the relationship between lipid profiles and bone mineral density (BMD) in older adults using data from the Korean National Health and Nutrition Examination Survey (KNHANES).

METHODS

We enrolled men older than 50 years and postmenopausal women who participated in the KNHANES 2008-2011. Subjects with liver cirrhosis, thyroid disease, or renal dysfunction and those receiving treatment for hyperlipidemia or osteoporosis were excluded.

RESULTS

A total of 4323 subjects (2286 men and 2037 women) was analyzed. The prevalence of osteoporosis was 8.7% in men older than 50 years and 38.4% in postmenopausal women. Osteopenia and osteoporosis groups were generally older and tended to have a lower body mass index compared to the normal group (p for trend < 0.001). The correlation between each lipid profile and BMD was analyzed in the linear model adjusted for age and body mass index. Total cholesterol and high-density lipoprotein cholesterol showed a negative correlation with BMD in the total population, but there was no significant correlation when analyzed separately for men and women. Triglycerides had a negative association with whole-body BMD in both men and women (p < 0.05). The adjusted odds ratio of logarithmic triglyceride level for osteoporosis was 2.50 (95% confidence interval 1.13-5.51) in women older than 65 years.

CONCLUSION

Serum triglycerides showed a significant inverse association with BMD, and the relationship is thought to correlate with vitamin D status among older adults.

Vitamin D is negatively associated with triglyceride in overweight/obese patients with type 2 diabetes

PURPOSE

Vitamin D has been identified to have a relation to the development of insulin resistance-related diseases, such as type 2 diabetes (T2D). T2D is often associated with obesity and dyslipidemia. Our study aimed to analyze the relationship between vitamin D and lipid profile in patients with T2D.

METHODS

A total of 446 T2D patients who were hospitalized from January 2015 to December 2016 were recruited. Baseline characteristics were recorded, including body mass index (BMI), serum level of 25 hydroxy vitamin D (25(OH)D), and other biochemical indicators. T2D patients were divided into normal-weight group and overweight/obese group according to their BMI. Subgroup analysis was conducted after patients were subdivided using the quartet-method according to serum level of 25(OH)D. Differences in glucose and lipid metabolism indicators were analyzed. The correlation between serum 25(OH)D and lipid profiles was assessed by the multiple linear regression.

RESULTS

The levels of serum 25(OH)D and high-density lipoprotein cholesterol in T2D patients of overweight/obesity group were significantly lower than those in normal-weight group, while the levels of triglyceride (TG) and HOMA-IR were significantly higher (P < 0.05). Subgroup analysis uncovered that total cholesterol (TC) and TG levels were lower with higher 25(OH)D in normal weight T2D patients. In overweight/obese T2D patients, TG level was lower in patients with higher 25(OH)D (P < 0.05). There were no significant differences in low-density lipoprotein cholesterol (LDL-C), fasting blood glucose (FBG), fasting insulin (FINS), and hemoglobin Alc (HbAlc) among Q1-Q4 in both normal weight and overweight/obese groups. Pearson test showed that serum 25(OH)D was positively correlated with high density lipoprotein cholesterol (HDL-C), and negatively correlated with TC and TG. Serum 25(OH)D was unrelated to low density lipoprotein cholesterol (LDL-C) in both groups. Multiple linear regression analysis only demonstrated an independent negative correlation between 25(OH)D and TG levels in the overweight/obese group (P < 0.01).

CONCLUSIONS

In overweight/obese patients with T2D, serum 25(OH)D was independently, negatively correlated with TG. Vitamin D supplementation should be guaranteed in patients with diabetes, especially with obese T2D.

Association between vitamin D3 levels and insulin resistance: a large sample cross-sectional study

Previous studies have shown that vitamin D3 may be a potential factor in insulin resistance, but the relationship between vitamin D3 and insulin resistance still remains controversial. At present, more research is needed to explore the relationship between vitamin D3 and insulin resistance. The samples from 2009 to 2018 in NHANES database were analyzed to Investigate the relationship and the potential mechanism. We performed a cross-sectional study of five periods in the NHANES database. Finally, 9298 participants were selected through strict inclusion and exclusion criteria, Multivariate logistic regression analysis and curve fitting were conducted to explore the relationship between vitamin D3 level and insulin resistance. Moreover, subgroup analysis was used to further prove the association. The results revealed that there was a strong association between vitamin D3 and insulin resistance (OR 0.82, 95% CI 0.72-0.93). However, subgroup analyses indicated that this correlation varied between individuals and races. There was a negative correlation between vitamin D3 level and insulin resistance, which provides a new proof for exploring the influencing factors of insulin resistance. More well-designed studies are still needed to further elaborate on these associations.

Effect of Vitamin D Supplementation in Type 2 Diabetes Patients with Tuberculosis: A Systematic Review

BACKGROUND

Diabetes mellitus (DM) and tuberculosis (TB) have been recognized as reemerging epidemics, especially in developing countries. Among all the risk factors, diabetes causes immunosuppression, increasing the risk of active TB three times. Vitamin D has been found as a link between DM-TB co-morbidity.

OBJECTIVE

Vitamin D affects the immune response, suppresses Mycobacterium tuberculosis (Mtb) growth, and affects insulin secretion. The present systematic review determines the effect of vitamin D supplementation on clinical and therapeutic outcomes of DM-TB patients.

METHOD

A comprehensive literature search was carried out in PubMed, Cochrane, Web of Science, and Scopus database to determine eligible studies from inception to January 2021. Out of the 639 articles retrieved, three randomized controlled trials (RCTs) were included in the systematic review.

RESULT

The effect of vitamin D3 or oral cholecalciferol supplementation was assessed on outcomes, such as duration to sputum smear conversion, TB scores improvement, change in glycemic parameters, including HbA1c, FBS, and PLBS, and laboratory parameters, such as Hb, ESR, and CRP. Duration of sputum smear conversion was decreased by two weeks in the vitamin D3 supplemented group in two studies. TB score improvement and changes in glycemic parameters were inclined towards supplemented group; however, they were not significant.

CONCLUSION

The overall effect of vitamin D3 supplementation on TB patients with DM was not significant. Further studies are required in the future examining the effect of supplementation on outcomes in this population.

Fecal microbiota transplantation reverses insulin resistance in type 2 diabetes: A randomized, controlled, prospective study

OBJECTIVES

Recent studies have shown that fecal microbiota transplantation (FMT) improved the metabolic profiles of patients with type 2 diabetes mellitus (T2DM), yet the effectiveness in reversing insulin resistance and increasing metformin sensitivity in T2DM patients have not been reported. In this study, we evaluated the improvements of T2DM patients and their gut microbiota by FMT alone and FMT plus metformin.

METHODS

A total of 31 patients with newly diagnosed T2DM were randomized to intervention by metformin, FMT, or FMT plus metformin in the study. Patients were followed up at baseline and week 4 after treatment. Blood and stool samples were collected and subject to analyze clinical parameters and microbial communities by metagenomic sequencing, respectively.

RESULTS

FMT alone and FMT plus metformin significantly improved the clinical indicators HOMA-IR and BMI in T2DM, besides fasting blood glucose, postprandial blood glucose, and hemoglobin A1c that were also controlled by metformin. Donor microbiota effectively colonized in T2DM with slightly higher colonization ration in FMT than FMT plus metformin within 4 weeks, resulting in increased microbial diversity and community changes from baseline after treatment. A total of 227 species and 441 species were significantly alerted after FMT and FMT plus metformin, respectively. FMT were significantly associated with the clinical parameters. Among them, Chlorobium phaeovibrioides, Bifidibacterium adolescentis and Synechococcus sp.WH8103 were potential due to their significantly negative correlations with HOMA-IR.

CONCLUSIONS

FMT with or without metformin significantly improve insulin resistance and body mass index and gut microbial communities of T2DM patients by colonization of donor-derived microbiota.

Effect of Vitamin D Supplementation on Glycemic Control in Prediabetes: A Meta-Analysis

Clinical research results of vitamin D supplementation in the improvement of prediabetes remain controversial. Accordingly, a literature search was conducted of PubMed, Embase (Ovid), and Web of Science prior to 9 November 2021. Randomized controlled studies reported that the following indicators were included: body mass index (BMI), fasting blood glucose (FBG), 2 h oral glucose tolerance test plasma glucose (2h-PG), hemoglobin A1c (HbA1c), insulin resistance by homeostasis model assessment (HOMA-IR), homeostasis model assessment of β-cell function (HOMA-B), and fasting insulin (FINS). Twenty-nine articles (N = 3792) were included in the present meta-analysis. Intriguingly, vitamin D supplementation resulted in a vast improvement in FBG (standardized mean difference (SMD) = -0.38; 95%CI: -0.59, -0.16), HbA1c (SMD = -0.14; 95%CI: -0.22, -0.06) and FINS (SMD = 0.18; 95%CI: -0.26, -0.09), but not in other outcomes. However, preferred changes were observed in subgroups, as follows: Asia (SMD_2h-PG = -0.25, 95%CI: -0.45, -0.04), study duration ≥1 year (SMD_HOMA-IR = -0.44, 95%CI: -0.81, -0.06) (SMD_HOMA-B = 0.34, 95%CI: 0.01, 0.66), baseline 25(OH)D < 50 nmol/L (SMD_2h-PG = -0.23, 95%CI: -0.39, -0.06), and baseline 25(OH)D ≥ 50 nmol/L (SMD_HOMA-IR = -0.50, 95%CI: -0.96, -0.03). In conclusion, oral supplementation of vitamin D has shown better effects in improving FBG, HbA1c, and FINS compared with controls among prediabetics; long-term vitamin D supplementation could have additional effects in participants with vitamin D deficiency for 2h-PG, HOMA-IR, and HOMA-B.

Effect of vitamin D supplementation on glycose homeostasis and islet function in vitamin D deficient or insufficient diabetes and prediabetes: a systematic review and meta-analysis

Objective of the present study was to evaluate the effect of vitamin D supplementation on glycose homeostasis, islet function, and diabetes progress. Literatures were searched via electronic databases, websites, and previous reviews from the earliest available time to the end of May 2020. Randomized controlled trials initially designed for diabetes and prediabetes with 25-dihydroxyvitamin D [25(OH)D]<30 ng/ml were included. All data were analyzed and presented based on the Cochrane guidelines and PRISMA guidelines. In total, 27 articles (n = 1,932) were enrolled in this study. Vitamin D supplementation significantly improved fasting blood glucose, postprandial blood glucose, and quantitative insulin sensitivity check index in diabetes and prediabetes with baseline 25(OH)D<30 ng/ml. Higher percentages regressing from prediabetes to normal glucose status [1.60 (1.19, 2.17), p = 0.002, n = 564] and lower percentage progressing from prediabetes to diabetes [0.68 (0.36, 1.27), p = 0.23, n = 569] were found in the supplementation group. The positive effects of vitamin D supplementation on body mass index, waist, HDL-C, LDL-C, and CRP were also demonstrated. In conclusion, modest improvements in vitamin D supplementation on short-term glycose homeostasis, insulin sensitivity, and disease development in diabetes and prediabetes with 25(OH)D<30 ng/ml were demonstrated, but more research needs to be conducted in the future to support the clinical application. (Register ID: CRD42020186004)

Role and Treatment of Insulin Resistance in Patients with Chronic Kidney Disease: A Review

Patients with chronic kidney disease (CKD) and dialysis have higher mortality than those without, and cardiovascular disease (CVD) is the main cause of death. As CVD is caused by several mechanisms, insulin resistance plays an important role in CVD. This review summarizes the importance and mechanism of insulin resistance in CKD and discusses the current evidence regarding insulin resistance in patients with CKD and dialysis. Insulin resistance has been reported to influence endothelial dysfunction, plaque formation, hypertension, and dyslipidemia. A recent study also reported an association between insulin resistance and cognitive dysfunction, non-alcoholic fatty liver disease, polycystic ovary syndrome, and malignancy. Insulin resistance increases as renal function decrease in patients with CKD and dialysis. Several mechanisms increase insulin resistance in patients with CKD, such as chronic inflammation, oxidative stress, obesity, and mineral bone disorder. There is the possibility that insulin resistance is the potential future target of treatment in patients with CKD.

Mechanisms Involved in the Relationship between Vitamin D and Insulin Resistance: Impact on Clinical Practice

Recent evidence has revealed anti-inflammatory properties of vitamin D as well as extra-skeletal activity. In this context, vitamin D seems to be involved in infections, autoimmune diseases, cardiometabolic diseases, and cancer development. In recent years, the relationship between vitamin D and insulin resistance has been a topic of growing interest. Low 25-hydroxyvitamin D (25(OH)D) levels appear to be associated with most of the insulin resistance disorders described to date. In fact, vitamin D deficiency may be one of the factors accelerating the development of insulin resistance. Vitamin D deficiency is a common problem in the population and may be associated with the pathogenesis of diseases related to insulin resistance, such as obesity, diabetes, metabolic syndrome (MS) and polycystic ovary syndrome (PCOS). An important question is the identification of 25(OH)D levels capable of generating an effect on insulin resistance, glucose metabolism and to decrease the risk of developing insulin resistance related disorders. The benefits of 25(OH)D supplementation/repletion on bone health are well known, and although there is a biological plausibility linking the status of vitamin D and insulin resistance supported by basic and clinical research findings, well-designed randomized clinical trials as well as basic research are necessary to know the molecular pathways involved in this association.

Role of Vitamin D in the Metabolic Syndrome

The prevalence of hypovitaminosis D has risen in developed countries over the past few years in association with lifestyle changes and an increase in unhealthy habits. Vitamin D deficiency has been implicated in various diseases, including metabolic syndrome (MetS), which is clinically defined by a set of metabolic and vascular disorders. The objective of this study was to review scientific evidence on the relationship between MetS and vitamin D deficiency to support the development of prevention strategies and health education programs. An inverse relationship has been reported between plasma vitamin D concentrations and the features that define MetS, i.e., elevated serum concentrations of glucose, total cholesterol, low-density lipoproteins, triglycerides, glycosylated hemoglobin, and a high body mass index. Numerous studies have described the benefits of vitamin D supplementation to improve outcomes in individuals with MetS. Interventions to maintain optimal vitamin D concentrations are proposed as a preventive strategy against MetS.

No Association between 25-Hydroxyvitamin D and Insulin Resistance or Thyroid Hormone Concentrations in a Romanian Observational Study

Background and objectives: Vitamin D is involved in insulin resistance through genomic and non-genomic mechanisms. Several observational and randomized studies have discrepant results; some of them showed an improved insulin resistance (IR), and others a neutral effect after vitamin D deficiency is corrected. Materials and Methods: We designed a retrospective observational study that included all women who presented for 33 months in an outpatient clinic in Bucharest, Romania. Results: We analyzed 353 patients with a mean age of 58.5 ± 13.7 years, a mean body mass index (BMI) of 27.36 ± 4.87 kg/m^-2, and a mean level of 25-hydroxyvitamin D (25OHD) of 39.53 ± 15.73 ng/mL. There were no differences in the calculated Homeostatic Model Assessment of Insulin Resistance variants 1 and 2 (HOMA-IR) and the Quantitative Insulin Sensitivity Check Index (QUICKI) between women with vitamin D deficit versus normal values. In multivariate analysis, there was no significant relation between 25OHD and the response variables considered by us. Conclusions: We observed a small positive correlation between a higher level of 25OHD and increased glycosylated hemolobin (HbA1c) or IR indices without clinical significance. Other modifiable or non-modifiable factors override 25OHD influence on IR in adult women with a normal serum level and may contribute to the remainder of the variability observed.

Circulating vitamin D and the risk of gestational diabetes: a systematic review and dose-response meta-analysis

PURPOSE

Several meta-analyses of observational studies revealed a modest increase in the risk of gestational diabetes (GDM) among pregnant women with low levels of serum vitamin D. However, no study examined a dose-response meta-analysis as well as a high versus low analysis in this regard.

METHODS

We systematically searched PubMed, Embase, ISI Web of Science, and Scopus up to August 2019 to find prospective observational studies investigating the association of serum 25(OH)D with the risk of developing GDM. Using a random-effects model, the reported risk estimates were pooled.

RESULTS

Nine cohort studies and six nested case-control studies were included in the final analysis (40,788 participants and 1848 cases). Considering linear analysis, each 10 nmol/L increase in circulating 25(OH)D was associated with a 2% lower risk of GDM (effect size (ES): 0.98; 95% CI: 0.98, 0.99; I² = 85.0%, P < 0.001). highest compared with the lowest category of circulating 25(OH)D was associated with a 29% lower risk of GDM, with low evidence of heterogeneity (I² = 45.0%, P = 0.079).

CONCLUSIONS

In conclusion, lower levels of serum 25(OH)D were associated with a higher chance of GDM. Differential results existed between the overall and subgroup analysis, either based on vitamin D detection methods or based on maternal age, although these subgroups partially lowered the heterogeneity.

The Effect of Vitamin D Supplementation on Insulin Sensitivity: A Systematic Review and Meta-analysis

BACKGROUND

Vitamin D has been suggested to affect peripheral insulin sensitivity. Evidence regarding the effect of vitamin D supplementation on insulin sensitivity is still conflicting.

PURPOSE

This meta-analysis aimed to assess the effect of vitamin D supplementation on insulin sensitivity in humans with or at risk for insulin resistance.

DATA SOURCES AND STUDY SELECTION

PubMed, Web of Science, Embase, CINAHL, and Cochrane Library were systematically searched for randomized controlled trials (RCTs) from 1980 until 31 December 2018 reporting treatment effects of vitamin D supplementation on insulin sensitivity.

DATA EXTRACTION

The main outcome of interest was the change in insulin sensitivity, derived from the gold standard hyperinsulinemic-euglycemic clamp or the Matsuda index derived from the oral glucose tolerance test and insulin sensitivity index from intravenous glucose tolerance test. We extracted data on the standardized mean difference between the vitamin D treatment and placebo groups in change from baseline insulin sensitivity.

DATA SYNTHESIS

Eighteen RCTs were included in this meta-analysis comparing vitamin D supplementation (n = 612) with placebo (n = 608). Vitamin D supplementation had no effect on insulin sensitivity (standardized mean difference -0.01, 95% CI -0.12, 0.10; P = 0.87, I ² = 0%). Visual inspection of funnel plot symmetry did not suggest potential publication bias.

LIMITATIONS

The number of individuals who participated in the included studies was relatively small, possibly due to the invasive character of the measurement (e.g., clamp).

CONCLUSIONS

This meta-analysis provides no evidence that vitamin D supplementation has a beneficial effect on peripheral insulin sensitivity in people with or at risk for insulin resistance.

The relationship between obesity, diabetes, hypertension and vitamin D deficiency among Saudi Arabians aged 15 and over: results from the Saudi health interview survey

BACKGROUND

Obesity and diabetes are related conditions, the prevalence of which has increased globally in recent years. These conditions have been linked to hypertension and vitamin D deficiency though the nature of the relationship remains unclear and is likely to vary between identifiable groups and specific contexts. The aim of this paper is to examine the relationships between obesity, type 2 diabetes, hypertension and vitamin D, among Saudis citizens aged 15 and over.

METHODS

Self-reported and measured data were taken from the 2013 Saudi Health Interview Survey and analysed using a series of seemingly unrelated bivariate probit regression (SURBVP) analyses. Sensitivity analyses were undertaken in which the selection and specification of covariates and outcomes were varied.

RESULTS

In the main analysis data on 957 women and 1127 men were analysed. Differences were evident between men and women in the prevalence of type 2 diabetes, obesity, central obesity, hypertension and vitamin D deficiency. While men were more likely to experience diabetes and hypertension, women were more likely to experience obesity, central obesity and vitamin D deficiency. In multivariable analyses obesity and age were found to significantly predict hypertension risk in women; central obesity to predict diabetes risk in men and women, as well as hypertension risk in men. Vitamin D was not found to predict diabetes risk nor hypertension risk in either sex. Milk consumption and sun exposure were found to predict vitamin D deficiency in women but not men. While there was evidence of unobserved heterogeneity in models predicting diabetes and hypertension, there was no evidence of unobserved heterogeneity between these and those predicting vitamin D deficiency. Results did not materially change over a range of sensitivity analyses.

CONCLUSION

While there is strong evidence of distinct patterns in the relationship between diabetes, hypertension and obesity among men and women in Saudi Arabia and in the risk of vitamin D deficiency, we found no evidence of a relationship between vitamin D levels and risk of either diabetes or hypertension.