Table 1.
Key findings of reviewed studies.
| Ref. | Year | MetS and Vit D | Objective | Methodology | Findings |
|---|---|---|---|---|---|
| Valero et al. [15] | 2007 | Endogenous and exogenous sources of vitamin D and its role in metabolism. | To investigate the sources where they can take vitamin D from requirements, intake, and effects on health. | Review | Physiological levels of 25(OH)D are required to keep the integrity of immune, bone, and muscular systems. Sunlight exposure is not enough for reaching and keeping acceptable levels of Vit D in some age groups. Artificial addition of Vit D in food has showed its efficacy for reaching these desirable levels, and most of the population would profit from it. For people over 65, calcium addition is also necessary. |
| Mansouri et al. [25] | 2018 | Nutrient deficit and metabolic disorders. | To determine the link between vitamin D and metabolic syndrome. | Cross-sectional study. A total of 352 faculty members. Blood samples for the determination of 25(OH)D concentrations, glycemic indicators, and lipid profile. | Reverse association of 25(OH)D serum levels and risk of abdominal obesity, hypertension, and abnormal glucose homeostasis. No significant association for metabolic syndrome. |
| Schmitt et al. [26] | 2018 | Vitamin D-deficiency and metabolic syndrome in postmenopausal women. | To study vitamin D-deficiency and its association with risk factors for metabolic syndrome in postmenopausal women. | Observational and cross-sectional cohort study. A total of 463 women. Levels of total cholesterol, HDL, LDL, triglycerides, glucose, insulin, and 25(OH)D were measured. | Deficiency of vitamin D in postmenopausal women is related to a higher prevalence of MetS, as well as hypertriglyceridemia and low HDL levels. |
| Wimalawansa et al. [28] | 2018 | Association between vitamin D, insulin resistance, obesity, type II diabetes, and metabolic syndrome. | To investigate the relationship between vitamin D and insulin resistance, obesity, type II diabetes, and metabolic syndrome. | Review | Large number of observational studies point out the improvement of type II diabetes, insulin resistance, obesity, and metabolic syndrome with adequate levels of vitamin D. |
| Mutt et al. [29] | 2019 | 25(OH)D levels and MetS in the elderly population from Northern latitudes. | To investigate the associations between serum 25(OH)D levels and prevalence of MetS and its components and assess the effects of vitamin D supplementation on MetS. | Cross-sectional study. A total of 636 subjects from Oulu45 cohort (263 male, 373 female). Determination of 25(OH)D plasmatic levels and assessment of vitamin D supplements usage. | Low vitamin D levels were associated with a higher prevalence of MetS. People under vitamin D supplementation had a lower incidence of MetS and its components. Low vitamin D levels are a risk factor for MetS among other lifestyle factors among older subjects in the Northern latitudes. |
| Navarro et al. [30] | 2014 | Status of vitamin D levels in the Spanish population. | To determine the levels of vitamin D in Spain. | Review | There is an insufficiency of vitamin D in the Spanish population. There are 50% of the population between 18 and 60 years with this deficiency, and up to 87% in the population over 65 years old. |
| Xu et al. [31] | 2020 | Genetically increased circulating 25(OH)D level and prevention of T2D. | To provide an updated estimate for the causality between vitamin D and T2D. | 2-sample multi-instrument variables MR | A higher genetically instrumented 25(OH)D was causally linked to a reduced risk of T2D risk. They confirm the causal role of vitamin D using 2 synthesis-related single-nucleotide polymorphisms (SNPs). |
| Huang et al. [32] | 2015 | Vitamin D and risk of metabolic syndrome. | To analyze vitamin D levels and the link with the risk of metabolic syndrome in non-diabetic adults. | Cross-sectional study. A total of 335 non-diabetic young adult individuals. Measurement of 25(OH)D, metabolic syndrome, and cardiometabolic parameters. | There is an inverse association between vitamin D and MetS. This link could be related to the joint effects of obesity and insulin resistance in individuals. |
| Lee et al. [33] | 2019 | 25(OH)D levels and MetS in the elderly population. | To evaluate the relationship between 25(OH)D levels and MetS in the elderly Korean urban and rural population. | Cohort study. A total of 2936 men and women. Measurement of 25(OH)D serum levels as well as diagnosis of MetS. | There is an association between low levels of 25(OH)D and MetS. Those levels achieved more association in these variables of MetS: high waist circumference, hypertriglyceridemia, as well as low high-density lipoprotein cholesterol. |
| Zhu et al. [34] | 2018 | Vitamin D and markers of metabolic health. | To investigate the link between vitamin D and markers of metabolic health. | Cross-sectional study. A total of 508 urban residents. Measurement of demographic and anthropometric data, as well as 25(OH)D serum levels, blood glucose, and lipid concentrations. | A higher serum 25(OH)D concentration was linked to a better metabolic profile and less risk for developing MetS. |
| Liu et al. [35] | 2020 | Vitamin D-deficiency and MetS criteria in the elderly population. | To analyze the association between serum 25(OH)D and MetS in elderly Chinese individuals. | Cross-sectional study. A total of 2493 elderly people from eight areas of China. 25(OH)D serum levels as well as antropometric and biochemical measurements were determined | High serum vitamin D concentrations were associated with a low prevalence of MetS according to the Adult Treatment Panel III criteria for adequate versus deficient vitamin D and inadequate versus deficient vitamin D levels. |
| Ganji et al. [36] | 2020 | Vitamin D deficiency and MetS prevalence and markers. | To study the relationship between serum vitamin D concentrations and prevalence of MetS and markers of MetS in Qatari women. | Cross-sectional study. A total of 700 women aged 20–80 years old. Independent variable:serum 25(OH)D concentration-dependent variables:MetS and indicators of MetS defined following the International Diabetes Federation criteria | The study showed an inverse relationship between the prevalence of MetS and serum 25(OH)D in Qatari women. No relationship was observed between serum 25(OH)D and waist circumference, blood pressure, HbA1C, blood glucose, HDL-cholesterol, and serum triglycerides. |
| Pott-Junior et al. [37] | 2020 | MetS parameters and low serum 25-hydroxyvitamin D (25(OH)D) levels. | To investigate the relationship between metabolic parameters and serum 25(OH)D levels in community-living older adults. | Cross-sectional study. n = 265. Adults aged 60 years were assessed for anthropometrics and metabolic measurements, including 25(OH)D, insulin, glucose, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, and inflammatory markers. | Subjects with 25(OH)D deficiency presented higher body weight, body mass index, waist circumference, triglycerides and TNF-α, and higher insulin resistance. MetS was more prevalent among 25(OH)D-deficient subjects. |
| Barbalho et al. [38] | 2018 | Vitamin D and markers of metabolic health. | To investigate the link between vitamin D and markers of metabolic health. | Cross-sectional study. A total of 200 patients (89 men, 111 women). Determination of anthropometric and biochemical parameters, blood pressure, atherogenic indices, and presence of MetS. | Patients with altered values for this vitamin presented significantly higher values for glycemia, HbA1c, total cholesterol, LDL-c, triglycerides, BMI, waist circumference, and atherogenic indices. |
| Vimaleswaran et al. [39] | Vitamin D and arterial blood pressure and hypertension risk. | To test whether 25(OH)D concentration is causally associated with blood pressure and hypertension risk. | MR study | Increased plasma concentrations of 25(OH)D might reduce the risk of hypertension. Each 25(OH)D-increasing allele of the synthesis score was associated with a change of −0.10 mm Hg in systolic blood pressure and a change of −0.08 mm Hg in diastolic blood pressure. | |
| Vimaleswaran et al. [40] | Vitamin D status and obesity. | To explore the causality and direction of the relationship between body mass index (BMI) and 25-hydroxyvitamin D [25(OH)D]. | Bidirectional MR study | Higher BMI leads to lower 25(OH)D, whereas any effects of lower 25(OH)D-increasing BMI are likely to be small. | |
| Zheng et al. [41] | Circulating 25-hydroxyvitamin D metabolites and T2D. | To examine the potential causality of these associations using Mendelian randomization (MR) analysis. | MR study | The findings based on MR analysis in a large sample of European ancestry do not support a causal association of a total of 25(OH)D or 25(OH)D metabolites with T2D and argue against the use of vitamin D supplementation for the prevention of T2D. | |
| Wang et al. [42] | Vitamin D, prediabetes, and T2D. | To explore the causal relationship between 25-hydroxyvitamin D (25(OH)D) and glycemic status and indices. | Biredictional MR | The MR-derived odds ratios of genetically determined 25(OH)D for risk of T2D and prediabetes were 0.985 and 0.982, respectively. Fasting glucose and HbA1c were not significant either. | |
| Mehri et al. [43] | 2019 | Vitamin D and MetS and its components in females. | To determine the relationship between MetS and its components with vitamin D status. | Observational case-control study. Participants were 276 Iranian female teachers (124 in the case group and 152 in the control group). | Authors did not find an association between vitamin D status and MetS. There is a necessity of using prospective studies to link the vitamin D effects in the development of MetS. |
| Teixeira et al. [44] | 2018 | Association between vitamin D-deficiency and obesity. | To analyze vitamin D and metabolic profile in adolescents and adults and their relationship with severe obesity complications. | Observational comparative study. Population: adolescents and adults with severe obesity. Measurement of circumference and BMI. | There was a high prevalence of deficiency and insufficiency of vitamin D and its association with metabolic changes in the adult and adolescent population with obesity. |
| Chen et al. [45] | 25-hydroxyvitamin D cardiometabolic risk factors and MetS. | To test whether genetically lowered vitamin D levels were associated with MS and its metabolic traits. | MR study | Lower measured 25(OH)D levels were associated with MetS after multivariable adjustment. However, the MR-derived odds ratio of genetically determined 25(OH) D for risk of MS was 0.977. |
MetS: metabolic syndrome; BMI: body mass index; LDL: low-density lipoprotein cholesterol; HDL: high-density lipoprotein cholesterol; HbA1c: hemoglobin A1c; TNF-α: tumor necrosis factor-α; MR: Medelian randomization; T2D: type 2 diabetes.