Vitamin D supplementation improves waist-to-hip ratio and fasting blood glucose in vitamin D deficient, overweight or obese Asians: A pilot secondary analysis of a randomised controlled trial

Association between serum 25-hydroxyvitamin D and vitamin D dietary supplementation and risk of all-cause and cardiovascular mortality among adults with hypertension

BACKGROUND

The relationship between vitamin D status and mortality among adults with hypertension remains unclear.

METHODS

This prospective cohort study involved a sample of 19,500 adults with hypertension who participated in the National Health and Nutrition Examination Survey (NHANES) from 2001 to 2018. We utilized a weighted COX proportional hazard model to assess the association between vitamin D status and mortality. This statistical model calculates hazard ratios (HR) and their corresponding 95% confidence intervals (95% CI).

RESULTS

The study indicated that lower serum 25(OH)D concentration was associated with an increased risk of all-cause mortality among individuals with hypertension. Specially. Those with concentrations between 25.0 and 49.9 nmol/L (HR = 1.71, 95%CI = 1.22-2.40) and less than 25.0 nmol/L (HR = 1.97, 95%CI = 1.15-3.39) had higher hazard ratios for all-cause mortality. Individuals with hypertension who took vitamin D supplements had a lower risk of all-cause mortality, but not the risk of CVD mortality (HR 0.75, 95%CI 0.54-1.03), compared to those who did not supplement (HR = 0.76, 95%CI = 0.61-0.94). Subgroup analysis further revealed that vitamin D supplementation was associated with a reduced risk of all-cause mortality among individuals without diabetes (HR = 0.65, 95%CI = 0.52-0.81) and individuals without CVD (HR = 0.75, 95%CI = 0.58-0.97), and a decreased risk of CVD mortality among individuals without diabetes (HR = 0.63, 95%CI = 0.45-0.88) and without CVD (HR = 0.61, 95%CI = 0.40-0.92). Furthermore, higher-dose vitamin D supplementation was also associated with a greater reduction in all-cause mortality among hypertensive individuals, and there was the potential synergistic effect of combining normal-dose calcium and vitamin D supplementation, showing a superior effect on mortality compared to low-dose supplementation in adults with hypertension.

CONCLUSIONS

This prospective cohort study demonstrated a significant association between lower serum 25 (OH)D concentration and increased all-cause mortality among adults with hypertension. Furthermore, the study found that vitamin D supplementation had a strong and significantly positive correlation with reduced all-cause and CVD mortality among hypertensive individuals without diabetes or CVD. This positive correlation suggests that vitamin D supplementation could potentially be an effective strategy to reduce the risk of mortality in this specific group of people.

Vitamin D supplementation and exercise for improving physical function, body composition and metabolic health in overweight or obese older adults with vitamin D deficiency: a pilot randomized, double-blind, placebo-controlled trial

PURPOSE

Vitamin D supplementation may have non-skeletal health benefits and enhance exercise responsiveness, particularly in those with low vitamin D levels. We determined whether, compared with placebo, vitamin D supplementation taken prior to and during a 12-week exercise program improves physical function, body composition or metabolic health, in overweight and obese older adults with vitamin D deficiency.

METHODS

Fifty overweight or obese older adults (mean ± SD age: 60 ± 6 years; BMI 30.6 ± 5.7 kg/m²) with vitamin D deficiency (25-hydroxyvitamin D [25(OH)D] < 50 nmol/L) were recruited. Participants were randomly allocated to receive either vitamin D₃ (4000 IU/day) or matching placebo for 24 weeks. Between weeks 12 and 24, all participants completed multi-modal exercise three days per week while continuing with vitamin D/placebo. Mean changes in physical function (primary outcome: gait speed), body composition and biochemical parameters at weeks 12 and 24 were compared between groups.

RESULTS

Vitamin D supplementation, with or without exercise, had no effect on gait speed. From baseline to week 12, vitamin D supplementation increased serum 25(OH)D levels (placebo: 2.5 ± 14.7 nmol/L; treatment: 43.4 ± 18.4 nmol/L; P < 0.001) and reduced stair climb times (placebo: 0.3 ± 1.0 s; treatment: - 0.2 ± 1.0 s; P = 0.046). From 12 to 24 weeks, vitamin D supplementation combined with exercise decreased waist circumference (placebo: 1.3 ± 7.3 cm; treatment: - 3.0 ± 6.1 cm; P = 0.02) and waist-to-hip ratio (placebo: 0.01 ± 0.05; treatment: - 0.03 ± 0.05; P = 0.01) relative to placebo. Vitamin D supplementation, with or without exercise, had no effect on other physical function, body composition or metabolic health outcomes.

CONCLUSION

Vitamin D supplementation had no effect on most physical function, body composition or metabolic health parameters when taken alone, or during exercise, in overweight or obese older adults with vitamin D deficiency. Vitamin D-related improvements in stair climb times and waist circumference suggest that future trials should explore the effects of vitamin D on muscle power, and its effects on body composition when combined with exercise, in populations with moderate or severe vitamin D deficiency.

Vitamin D Deficiency Is Associated with Glycometabolic Changes in Nondiabetic Patients with Arterial Hypertension

Recent evidence indicates that mildly increased fasting and post-oral load blood glucose concentrations contribute to development of organ damage in nondiabetic patients with hypertension. In previous studies, vitamin D deficiency was associated with decreased glucose tolerance. The aim of this study was to examine the relationships between serum 25(OH)D levels and glucose tolerance and insulin sensitivity in hypertension. In 187 nondiabetic essential hypertensive patients free of cardiovascular or renal complications, we measured serum 25-hydroxyvitamin D (25(OH)D) and parathyroid hormone (PTH) and performed a standard oral glucose tolerance test (OGTT). Patients with 25(OH)D deficiency/insufficiency were older and had significantly higher blood pressure, fasting and post-OGTT (G-AUC) glucose levels, post-OGTT insulin (I-AUC), PTH levels, and prevalence of metabolic syndrome than patients with normal serum 25(OH)D. 25(OH)D levels were inversely correlated with age, blood pressure, fasting glucose, G-AUC, triglycerides, and serum calcium and PTH, while no significant relationships were found with body mass index (BMI), fasting insulin, I-AUC, HOMA index, and renal function. In a multivariate regression model, greater G-AUC was associated with lower 25(OH)D levels independently of BMI and seasonal vitamin D variations. Thus, in nondiabetic hypertensive patients, 25(OH)D deficiency/insufficiency could contribute to impaired glucose tolerance without directly affecting insulin sensitivity.

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.

Druggable Sphingolipid Pathways: Experimental Models and Clinical Opportunities

Intensive research in the field of sphingolipids has revealed diverse roles in cell biological responses and human health and disease. This immense molecular family is primarily represented by the bioactive molecules ceramide, sphingosine, and sphingosine 1-phosphate (S1P). The flux of sphingolipid metabolism at both the subcellular and extracellular levels provides multiple opportunities for pharmacological intervention. The caveat is that perturbation of any single node of this highly regulated flux may have effects that propagate throughout the metabolic network in a dramatic and sometimes unexpected manner. Beginning with S1P, the receptors for which have thus far been the most clinically tractable pharmacological targets, this review will describe recent advances in therapeutic modulators targeting sphingolipids, their chaperones, transporters, and metabolic enzymes.

Effects of Vitamin D Status and Supplements on Anthropometric and Biochemical Indices in a Clinical Setting: A Retrospective Study

CONTEXT

Obesity and low vitamin D status are linked. It is not clear that weight loss through lifestyle intervention is influenced by vitamin D status.

OBJECTIVE

The aim of this study was to investigate the effect of baseline vitamin D status and vitamin D supplementation on weight loss and associated parameters for participants on a weight loss program in a primary care setting.

DESIGN

A retrospective analysis of clinical records of patients who underwent an individually tailored weight loss program at a single dietetic clinic in Sydney, Australia.

SETTING

Primary care centers.

PATIENTS

205 overweight and obese men and women aged from 18 to 50 years.

INTERVENTIONS

Patients were referred to a dietetic clinic for a weight loss program. Patients with low serum 25-hydroxyvitamin D (25(OH)D) concentrations at baseline were advised to increase sun exposure and take multivitamins supplemented with 2000 IU or 4000 IU per day of vitamin D3, according to the preference of their primary care physician.

MAIN OUTCOME MEASURES

Clinical parameters of weight, height, waist circumference, and serum 25(OH)D, as well as blood pressure and fasting lipid profile were collected from both baseline and three-month follow-up consultations.

RESULTS

Subjects with sufficient baseline 25(OH)D levels (≥50 nmol/L) experienced significantly greater weight loss (-7.7 ± 5.9 kg vs. -4.2 ± 3.3 kg) and reductions in BMI (-2.6 ± 1.8 kg/m² vs. -1.5 ± 1.1 kg/m²) and waist circumference (-5.2 ± 3.5 cm vs. -3.1 ± 3.1 cm) as compared with those who were vitamin D insufficient at baseline (p < 0.001 for all). Vitamin D insufficient patients who were supplemented with daily 2000 IU or 4000 IU vitamin D experienced significantly greater decreases in weight (-5.3 ± 3.6 kg vs. -2.3 ± 1.6 kg), BMI (-1.9 ± 1.2 kg/m² vs. -0.8 ± 0.6 kg/m²) and waist circumference (-4.2 ± 3.4 cm vs. -1.2 ± 1.3 cm) as compared with those not supplemented (p < 0.001 for all). We also observed a greater decrease in low-density lipoprotein (LDL) cholesterol (-0.4 ± 0.5 mmol/L vs. -0.2 ± 0.5 mmol/L) in subjects insufficient at baseline and supplemented as compared with those insufficient at baseline and not supplemented (p < 0.01).

CONCLUSION

In a weight loss setting in a dietetic clinic, adequate vitamin D status at baseline, or achieved at three months through supplementation, was associated with significantly greater improvement of anthropometric measures. The study has implications for the management of vitamin D status in obese or overweight patients undergoing weight loss programs.