[Full text] Effects of a Single Oral Megadose of Vitamin D3 on Inflammation and Ox

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Introduction

The prevalence of overweight and obesity has increased worldwide and is recognized as a chronic disease of complex management and increased risk of morbidity and mortality.1,2 Early evidence has shown that serum levels of 25-hydroxyvitamin D [25(OH)D] are frequently reduced in obese subjects3–6 and that adipose tissue serves as a reservoir for vitamin D, leading to less bioavailability and reduced serum levels.6,7 An early study demonstrated that obese women have greater adipose stores of vitamin D in subcutaneous and omental comportments.8 Obesity in these women has been associated with low-serum vitamin D levels, increased pro-inflammatory markers and oxidative stress, as demonstrated by increased measures of reactive oxygen species and reduced antioxidant defense.4,6,9

Vitamin D is a lipid-soluble vitamin with steroid-like hormonal functions and with a broad spectrum of action in the body. The two major forms of vitamin D are vitamin D3, also called as cholecalciferol, which is synthesized in the skin from cholesterol upon sun exposure (UVB radiation), and vitamin D2 or ergocalciferol, which is mainly ingested from the diet. Vitamin D plays a fundamental role in mineral homeostasis and skeletal health by normalizing calcium and phosphorus metabolism. It has also been reported in the prevention of cardiovascular disease, diabetes mellitus, hypertension, autoimmune disease and cancer.10,11 Additionally, vitamin D has been shown to downregulate pro-inflammatory markers, to have antioxidant properties4,12 and to reduce the risk of liver cancer.13

A preclinical study demonstrated that vitamin D supplementation for 5 weeks of reduced adipose tissue oxidative stress and inflammatory makers in rats fed on a high-fat diet.14 Even though this was a promising result in these rodents, the anti-inflammatory and anti-oxidant effects of vitamin D supplementation in obese subjects remain uncertain. Recognizing the high prevalence of vitamin D deficiency in obese subjects6 and considering the potential anti-inflammatory and antioxidant role of vitamin D and lack of clinical evidence concerning the potential role of vitamin D in attenuating obesity-induced oxidative stress and inflammation, we aimed to evaluate the impact of the vitamin D3 supplementation on the inflammation and oxidative stress markers in overweight and obese women with deficiency or insufficiency of vitamin D.

Methods

Ethical Aspects

This study was approved by the Ethics Committee for Human Research of the Lauro Wanderley University Hospital of the Federal University of Paraíba, João Pessoa, Brazil (Protocol number 2.455.892). All procedures were in accordance with the institution’s ethical standards, conducted in compliance with Resolution 466/2012 of the National Health Council and International Declaration of Helsinki. After the subjects had given written informed consent, they underwent screening procedures. At the request of the ClinicalTrial.gov, this study was registered with the Brazilian registry of clinical studies under the number, ID RBR-39srtp.

Subjects

Women were recruited from the Food and Nutrition Unit in the Lauro Wanderley University Hospital of the Federal University of Paraiba. The randomization adopted was of the simple type with the participants being randomly assigned to a given group. The eligibility criteria were as follows: women aged 18–59 years with vitamin D deficiency (≤20 ng/mL) or insufficiency (21–29 ng/mL) and with body mass index ≥25 kg/m2. Exclusion criteria were as follows: intake of vitamin D supplements, intake of anticonvulsants or medications to treat the human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS), diagnosis of type I diabetes mellitus, nephrotic syndrome, acute or chronic renal disease, liver diseases, hypothyroidism, hyperthyroidism, history of cerebrovascular accident (CVA) or acute myocardial infarction (AMI) within the last 6 months, smoking and alcohol consumption. The flowchart of the study is shown in Figure 1.

Figure 1 Double-blind, controlled trial flow chart. *One woman with normal weight was removed of trial. **Men were not included in the study.

Sample Size Calculation

Based on the prevalence of 25(OH)D serum level deficiency and insufficiency in a previous study, the sample size calculation considered an α error (Zα) of 5% and a β error (Zβ) of 10%. A standard deviation (δ) of 8 ng/mL was adopted for the concentrations of 25(OH)D15 and a mean difference before and after the impact of the supplementation of 10 ng/mL. Considering the difference between the values, for a coefficient of 95% and test power of 80%, the sample size was estimated at a minimum of 11 participants per group.

In the present study, the screening for 25(OH)D serum levels was administered to 69 participants (men and women), of whom, 39 had a vitamin D insufficiency or deficiency (56.5%). Among the participants with vitamin D deficiency or insufficiency, 9 were men and 30 were women. In agreement with the minimum sample size calculation for the establishment of groups, it was no expedient to test the effects of vitamin D supplementation in the male participants. Among women, one had normal body weight and so was not included in the study. After the initial screening, 29 overweight or obese women with vitamin D deficiency or insufficiency were block randomized and divided into two groups: women receiving placebo (placebo, n=14) or women that received a single oral megadose of vitamin D3 (VD3, n=15).

Study Design

This study was designed as a double-blinded, randomized, placebo-controlled trial. At the first visit, a questionnaire was applied in order to record information regarding age, physical activity, smoking, skin phototype, time of sunlight exposure, use of sunscreen, method of sunscreen use, physical activity when exposed to sunlight, and anthropometric measures.

After the randomization of the overweight and obese women with 25(OH)D deficiency or insufficiency, VD3 supplementation or the placebo was administered. The placebo group (n=14) received a capsule (1g) containing sunflower oil. In the vitamin D group, the women received a single oral megadose of 200.000 IU of vitamin D3 (lots 1877) in oleaginous capsules with identical appearances to the placebo.15 The placebo and VD3 were provided by Leviale (Vila Olímpica, São Paulo, Brazil).

All participants received diet therapy assistance and were instructed to increase foods rich in vitamin D intake (fish, milk, egg yolk, liver, and butter, among others). After 4 weeks of intervention, all participants were asked to return to be revaluated concerning anthropometric variables and fasting blood. Participants and statistician were all blind to which came from the vitamin D and which from the placebo groups.

Skin Phototypes and Exposure to Sunlight

The skin phototypes were classified according to the Fitzpatrick classification, with a variation of one to six types, based on the individual ability to tan as well as on skin sensitivity and redness when exposed to sunlight. Sunlight exposure was defined as the average time of exposure per day without considering seasonal variations.

Anthropometric Parameters

Nutritional status was determined through the Body Mass Index (BMI), obtained from the weight/height2 (kg/m2) ratio, with the following cutoff points being adopted: less than 18.5 kg/m2 (underweight); between 18.5 and 24.9 kg/m2 (normal weight); between 25 and 29.9 kg/m2 (overweight); between 30 and 34.9 kg/m2 (class I obesity); between 35 and 39.9 kg/m2 (class II obesity); and greater than or equal to 40 kg/m2 (class III obesity).

The waist circumference (WC) was measured at the midpoint between the outer side of the last rib and the iliac crest, and classified as level 1 for the WC values ≥80 cm and <88 cm (high risk), and level 2 for WC ≥88 cm (very high risk), considering the metabolic complications associated with obesity in women.16

The waist-to-height ratio (WHtR) is a simple measure for assessing the risk associated with excess weight in adults, with a cutoff point of 0.5 (the waist must be less than half the height) according to the Brazilian Guidelines for obesity in 2016. The waist-hip ratio (WHR) was analyzed to assess peripheral obesity, with the cut-off points to classify individuals or groups being 0.75–0.85 cm for moderate risk and >0.85 cm for high risk.17

Blood Sample and Biochemical Measurements

Blood samples were collected from individuals after a 12-h fasting. Fasting glucose (FPG), aspartate aminotransferase (AST), alanine aminotransferase (ALT) and creatinine were measured with specific commercial kits (Labtest, Minas Gerais, Brazil) in an automated analyzer (Labmax 240 Premium; Labtest, Minas Gerais, Brazil) according to the manufacturer’s instructions. The 25-hydroxyvitamin D serum concentrations were measured through chemiluminescent immunoassay. The classification of 25(OH)D levels was done based on the reference values established by the Endocrine Society, as follows: serum levels of 25(OH)D less than or equal to 20 ng/mL as deficient, 21–29 ng/mL as insufficient and between 30 and 100 ng/mL as sufficient.18 The serum levels of parathyroid hormone (PTH) were assessed through chemiluminescent immunoassay and the serum concentrations of calcium (Ca) were measured through the colorimetric technique. The oxidant activity of malondialdehyde (MDA) was quantified in plasma by the reaction of thiobarbituric acid with the products of decomposition of hydroperoxides.19 Total antioxidant capacity (TAC) was quantified in the plasma by measuring the scavenging activity of the free radical 2.2-diphenyl-1-picrylhydrazyl.20 Plasma concentrations of high-sensitivity C-reactive protein (hs-CRP) and alpha-1- acid glycoprotein (A1GPA) was quantified by immunoturbidimetry using specific commercial kits (Labtest) and an automatic analyzer (LabMax 240 Premium; Labtest) according to the manufacturer’s instructions.

Statistical Analyses

Statistical analyses were performed according to a previous study.21 Values were reported as mean (95% confidence interval) for parametric data or median (maximum − minimum) for nonparametric data. All the data were checked for normal distribution using the Kolmogorov Smirnov test. Data were reported as mean (95% confidence interval) and median (maximum − minimum) since some variables were not normally distributed. Comparison between VD3 and placebo groups at baseline was tested using the unpaired Student’s t test or Mann–Whitney test. The paired Student’s t test or Wilcoxon-matched pairs signed-rank test was used to analyze the differences between the baseline and the endpoint values. The categorical data were analyzed by the chi-square test when the expected minimum was not reached, the Fisher exact test was used. The differences were considered significant when the p value was ≤0.05. Statistical analysis was performed using the computational software Stata Statistical version 14 or Prism 6 (GraphPad Software, San Diego, CA, USA).

Results

Baseline characteristics of participants in each group are shown in Table 1. Before the intervention period, age, skin phototype, time of sunlight exposure and use of sunscreen, practice of physical activity and nutritional status were similar between groups (Table 1). Anthropometric variables (weight, waist circumference; waist–hip ratio, waist–height ratio and body mass index) were similar between the two groups at baseline and after the 8-week intervention (p ≥ 0.05, Table 2).

Table 1 Characteristics of the Sample at the Beginning of the Study

Table 2 Anthropometric Characteristics Among Women Receiving a Single Oral Megadose of VD3 Supplementation (n=14) or a Placebo (n=15) Before and After 4-Week Intervention

Regarding the biochemical variables, overweight or obese women had similar serum levels of 25(OH)D before VD3 supplementation (placebo: 24.2 (22.6–25.7) vs VD3: 23.8 (22.0–25.7) ng/mL, p=0.755, Figure 2A). Subjects that received a single oral megadose of VD3 had a significant increase in serum levels of 25(OH)D after 4 weeks of intervention (before: 23.8 (22.0–25.7) vs week 4: 31.7 (26.2–44.5) ng/mL, p = 0.0004, Figure 2A). Serum levels of calcium, PTH glucose, ALT, AST and creatinine were similar between the two groups at baseline period (p-value ≥0.05, Table 3). The serum levels of calcium augmented after placebo (p=0.0003) or VD3 (p=0.002) supplementation (Table 3). Subjects of placebo group displayed increased PTH serum levels after 4-week intervention (p=0.035), but not after VD3 supplementation (p=0.501, Table 3).

Figure 2 Effects of a single oral megadose of VD3 supplementation on 25 hydroxy-vitamin D and oxidative stress and inflammation variables in overweight and obese women with insufficiency or deficiency of vitamin D. Assessment of the serum levels of hydroxy-vitamin D (A), total antioxidant capacity (B), malondialdehyde (C), high-sensitivity C-reactive protein (D) and alpha glycoprotein (E) in overweight and obese women with insufficiency or deficiency of vitamin D who received a single oral megadose of VD3. Baseline and intervention data were compared by paired t-tests or the Wilcoxon rank-sum test according to the data distribution.

Table 3 Biochemical Variables Among Women Receiving a Single Oral Megadose of VD3 Supplementation (n=14) or the Placebo (n=15) in the Moments Before and After 4-Week Intervention

The VD3 supplementation reduced serum levels of ALT (before: 21.6 (19.0–24.1) vs week 4: 16.1 (14.2–18.1) mg/dL, p<0.0001, Table 3) and AST (before: 22.4 (11.0–46.0) vs week 4: 17.7 (11.0–31.0) mg/dL, p=0.035, Table 3) in overweight or obese women. Regarding creatinine serum levels, a reduction was found after placebo (p<0.0001) or VD3 (p=0.001) supplementation (Table 3). Lastly, placebo or VD3 supplementation did not impact on serum levels of fasting glucose (Table 3).

Concerning oxidative status, total antioxidant capacity (placebo: 26.9 (21.8–32.0) vs VD3: 20.9 (14.6–27.2) %, p=0.116, Figure 2B) and MDA serum levels (placebo: 2.8 (2.4–3.2) vs VD3: 2.7 (2.4–3.0) µmol/L, p=0.556, Figure 2C) were similar between the two groups at baseline period. Following the four-week intervention, it was observed that VD3 group had increased MDA concentration in comparison to baseline condition (before: 2.72 (2.43–3.00) vs week 4: 3.52 (2.50–5.80) µmol/L, p=0.006, Figure 2C), but not in TAC (p=0.378, Figure 2B).

Regarding inflammatory markers, C-reactive protein (placebo: 5.25 (0.40–16.70) vs VD3: 4.27 (0.10 −14.30) mg/dL, p=0.739, Figure 2D) and alpha glycoprotein (placebo: 96.5 (84.5–108.6) vs VD3: 96.2 (84.3–108.1) mg/dL, p=0.967, Figure 2E) were similar between the two groups at baseline period. Following the 4-week intervention, it was observed that VD3 group had increased C-reactive protein in comparison to baseline condition (before: 4.27 (0.10 −14.30) vs week 4: 6.03 (0.40–17.70) µmol/L, p=0.043, Figure 2D), but not in alpha glycoprotein (p=0.285, Figure 2E).

Discussion

In the present study, a single oral megadose of VD3 increased the serum levels of 25(OH)D in overweight and obese women with insufficiency or deficiency of vitamin D. However, the results demonstrated that VD3 supplementation was not effective to improve pro-inflammatory markers, anti-oxidant activity. Further, VD3 augmented plasma concentration of lipid peroxidation, as evidenced by increase in MDA measurement, as well as increased the C-reactive protein serum levels.

Regarding the risk factors associated with the deficiency/insufficiency of 25(OH)D,22 it was found that more than half of the women had a daily exposure to sunlight equal or less than 15 minutes. In our understanding, the low sun exposure combined with overweight be the main cause or contribute to of insufficiency or deficiency of vitamin D in these women.23

In agreement with previous studies, vitamin D supplementation increased serum levels of vitamin D. Different doses of vitamin D supplementation have been used in clinical trials to recover vitamin D deficiency. For example, 1.25-di-dihydroxycholecalciferol, at 50,000 IU/week for 8 weeks is able to recover vitamin D deficiency in patients with diabetic nephropathy.24 Using VD3 supplementation in a daily dose of 5000 IU for 12 weeks, increased 25(OH)D serum levels in patients with type 2 diabetes.25 Lastly, a randomized, double-blind, placebo-controlled trial, carried with 40 elderly women with vitamin D insufficiency, demonstrated that a single oral megadose of 200,000 UI of vitamin D significantly increased serum levels of 25(OH)D.15 Taken together, the studies demonstrated that daily, weekly or a single megadose of vitamin D may be effective to increase serum levels of vitamin D.

Vitamin D deficiency may lead to an increase in serum levels of PTH in order to adjust the calcium serum concentrations.26 Previous studies, however, have demonstrated that vitamin D supplementation decreased parathyroid hormone levels in obese27 and elderly women with vitamin D insufficiency.15 The results from our study showed that vitamin D supplementation neither decreased nor increased parathyroid hormone levels in overweight obese women with vitamin D insufficiency or deficiency.

As a safety measure for the VD3 supplementation, a biochemical monitoring of total serum calcium, hepatic and renal biomarkers was performed with both groups at the beginning of the study and after the 4-week supplementation. Although the serum creatinine level was reduced in placebo group after 4-week intervention, the creatinine values remained within range of standard parameters. Hepatic transaminases were reduced in the VD3 group after 4-weeks, suggesting that liver function may be improved by VD3 supplementation in overweight or obese women. The results of vitamin D supplementation on hepatic variables are conflicting. For example, daily supplementation of 2800 IU vitamin D3 for 8 weeks did not reduce ALT and AST serum levels in cirrhotic patients.28 Similarly, an early study demonstrated that a single oral megadose of VD3 did not alter kidney or liver markers in elderly women.15 On the other hand, daily supplementation of vitamin D 3200 IU for 3 months reduced hepatic transaminases in women with polycystic ovary syndrome.29 A future challenge is to evaluate with wider and longer studies whether vitamin D supplementation in obese subjects exerts beneficial effects on hepatic variables.

The results of this clinical trial demonstrated that a single oral megadose of VD3 increased the serum levels of hs-CRP. In fact, the effects of vitamin D supplementation on inflammatory markers are conflicting and inconclusive. For example, it has been demonstrated that vitamin D supplementation did not improve the hs-CRP level in patients with inflammatory bowel disease.30 A meta-analysis of seven randomized controlled trials carried out in patients with heart failure demonstrated that vitamin D supplementation could lower concentrations of tumor necrosis factor-alpha (TNF-α), but was not effective in reducing hs-CRP, interleukin (IL)-10 or IL-6.31 Another meta-analysis of 13 randomized controlled trials carried with type 2 diabetes mellitus subjects demonstrated that vitamin D supplementation is beneficial for the reduction of hs-CRP but does not have a significant influence on TNF-α and IL-6.32 Lastly, a meta-analysis of 13 randomized controlled trials carried out with overweight and obese subjects demonstrated that vitamin D supplementation did not have a significant influence on changes in the concentration of hs-CRP, TNF-α and IL-6.33

Early study has demonstrated that oxidative stress markers are augmented in obese subjects than healthy controls.34 This suggests that anti-oxidant therapies should be recommended for subjects with an obesity condition. Regarding the effects of vitamin D supplementation on oxidative stress markers, the results of the present study demonstrated that a single oral megadose of VD3 did not affect TAC, but significantly increased lipid peroxidation through the determination of MDA concentrations in overweight and obese women. A recent meta-analysis carried out in 17 randomized clinical trials found that oral vitamin D supplementation had beneficial effects on oxidative stress parameters by significantly decreasing circulating MDA levels as well as significantly enhancing antioxidant defense systems compared to placebo.12 However, no study has been carried on obese subjects for these meta-analyses.

Other antioxidant strategies with the potential to downregulate oxidative stress, inflammation, obesity indices and metabolic dysfunction have been related in early studies. For example, systematic reviews and meta-analysis of randomized controlled trials have demonstrated that berberine supplementation may ameliorate the state of chronic inflammation35 and reduces obesity indices.36 Another systematic review and meta-analysis of randomized controlled trials found that phytosterols supplementation at 1–2 g/day could effectively lower fasting blood sugar and glycosylated hemoglobin.37 Additionally, green tea supplementation associated with a balanced and healthy diet and regular physical exercise has been suggested to improve anthropometric indices in obese subjects.38 Lastly, a systematic review and meta-analysis of randomized controlled trials found that probiotic/symbiotic supplementation can significantly increase serum TAC, glutathione and NO, as well as reduce MDA levels in adults.39

In present study, we highlight that vitamin D supplementation in obese or overweight women who have an insufficiency or deficiency of vitamin D did not improve obesity indices and metabolic variables, indicating that this treatment must be proceeded with caution and following oxidative stress and inflammatory parameters.

Potential limitations:

This was a clinical trial performed with small samples size of women only, due to the fact that males were not recruited for the study. Additionally, the lack of a wash-out or recovery time point could be considered also as potential limitation of study.

Conclusion

The results of this randomized, double-blind, placebo-controlled clinical trial showed that a single oral megadose of VD3 significantly increased the serum levels of 25(OH)D, but did not improve inflammatory and oxidative stress markers.

Data Sharing Statement

After publication, the authors intend to share individual de-identified participant data, for 1 year, when requested for e-mail.

Acknowledgments

The authors thank the all workers who participated in this study, the teams of the Clinical Analysis Laboratory at the HULW/UFPB and the Laboratory for Physical Exercise Studies Applied to Performance and Health (LETFADS), and the Department of Physical Education/UFPB, which enabled the development of the analyses, the nutritionists of the food service units and the students of the nutrition course for their contribution to the development of this study. We thank the research participants and the Federal University of Paraíba for logistical support and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for the financial support of the study.

Disclosure

The authors report no conflicts of interest for this work and declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

References

1. Apovian CM. Obesity: definition, comorbidities, causes, and burden. Am J Manag Care. 2016;22(7 Suppl):s176–85.

2. Carvalho NNC, de Oliveira Junior FA, da Silva G, et al. Impact of arterial hypertension and type 2 diabetes on cardiac autonomic modulation in obese individuals with recommendation for bariatric surgery. Diabetes Metab Syndr Obes. 2019;12:1503–1511. doi:10.2147/DMSO.S204414

3. Vilarrasa N, Maravall J, Estepa A, et al. Low 25-hydroxyvitamin D concentrations in obese women: their clinical significance and relationship with anthropometric and body composition variables. J Endocrinol Invest. 2007;30(8):653–658. doi:10.1007/BF03347445

4. Wimalawansa SJ. Vitamin D Deficiency: effects on Oxidative Stress, Epigenetics, Gene Regulation, and Aging. Biology (Basel). 2019;8(2).

5. Wamberg L, Pedersen SB, Rejnmark L, et al. Causes of Vitamin D Deficiency and Effect of Vitamin D Supplementation on Metabolic Complications in Obesity: a Review. Curr Obes Rep. 2015;4(4):429–440. doi:10.1007/s13679-015-0176-5

6. de Oliveira LF, de Azevedo LG, da Mota Santana J, et al. Obesity and overweight decreases the effect of vitamin D supplementation in adults: systematic review and meta-analysis of randomized controlled trials. Rev Endocr Metab Disord. 2020;21(1):67–76. doi:10.1007/s11154-019-09527-7

7. Wortsman J, Matsuoka LY, Chen TC, et al. Decreased bioavailability of vitamin D in obesity. Am J Clin Nutr. 2000;72(3):690–693. doi:10.1093/ajcn/72.3.690

8. Carrelli A, Bucovsky M, Horst R, et al. Vitamin D Storage in Adipose Tissue of Obese and Normal Weight Women. J Bone Miner Res. 2017;32(2):237–242. doi:10.1002/jbmr.2979

9. Keaney JF Jr, Larson MG, Vasan RS, et al. Obesity and systemic oxidative stress: clinical correlates of oxidative stress in the Framingham Study. Arterioscler Thromb Vasc Biol. 2003;23(3):434–439. doi:10.1161/01.ATV.0000058402.34138.11

10. Bouillon R. Vitamin D and cardiovascular disorders. Osteoporos Int. 2019;30(11):2167–2181. doi:10.1007/s00198-019-05098-0

11. Chun RF, Shieh A, Gottlieb C, et al. Vitamin D Binding Protein and the Biological Activity of Vitamin D. Front Endocrinol (Lausanne). 2019;10:718. doi:10.3389/fendo.2019.00718

12. Sepidarkish M, Farsi F, Akbari-Fakhrabadi M, et al. The effect of vitamin D supplementation on oxidative stress parameters: A systematic review and meta-analysis of clinical trials. Pharmacol Res. 2019;139:141–152. doi:10.1016/j.phrs.2018.11.011

13. Zhang Y, Jiang X, Li X, et al. Serum vitamin D levels and risk of liver cancer: a systematic review and dose-response meta-analysis of cohort studies. Nutr Cancer. 2020:1–9.

14. Farhangi MA, Mesgari-Abbasi M, Hajiluian G, et al. Adipose tissue inflammation and oxidative stress: the ameliorative effects of vitamin D. Inflammation. 2017;40(5):1688–1697. doi:10.1007/s10753-017-0610-9

15. de Medeiros Cavalcante IG, Silva AS, Costa MJC, et al. Effect of vitamin D3 supplementation and influence of BsmI polymorphism of the VDR gene of the inflammatory profile and oxidative stress in elderly women with vitamin D insufficiency: vitamin D3 megadose reduces inflammatory markers. Exp Gerontol. 2015;66:10–16. doi:10.1016/j.exger.2015.03.011

16. Obesity: preventing and managing the global epidemic. Report of a WHO consultation. World Health Organ Tech Rep Ser. 2000;894:i–xii, 1–253.

17. Bray GA, Frühbeck G, Ryan DH, et al. Management of obesity. Lancet. 2016;387(10031):1947–1956. doi:10.1016/S0140-6736(16)00271-3

18. Holick MF, Binkley NC, Bischoff-Ferrari HA, et al. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011;96(7):1911–1930. doi:10.1210/jc.2011-0385

19. Ohkawa H, Ohishi N, Yagi K. Assay for lipid peroxides in animal tissues by thiobarbituric acid reaction. Anal Biochem. 1979;95(2):351–358. doi:10.1016/0003-2697(79)90738-3

20. de Lima Tavares Toscano L, Silva AS, de França ACL, et al. A single dose of purple grape juice improves physical performance and antioxidant activity in runners: a randomized, crossover, double-blind, placebo study. Eur J Nutr. 2020;59(7):2997–3007. doi:10.1007/s00394-019-02139-6

21. Romao da Silva LF, de Oliveira Y, de Souza EL, et al. Effects of probiotic therapy on cardio-metabolic parameters and autonomic modulation in hypertensive women: a randomized, triple-blind, placebo-controlled trial. Food Funct. 2020;11(8):7152–7163. doi:10.1039/D0FO01661F

22. Maeda SS, Borba VZC, Camargo MBR, et al. Recommendations of the Brazilian Society of Endocrinology and Metabology (SBEM) for the diagnosis and treatment of hypovitaminosis D. Arq Bras Endocrinol Metabol. 2014;58(5):411–433. doi:10.1590/0004-2730000003388

23. Pereira-Santos M, Costa PRF, Assis AMO, et al. Obesity and vitamin D deficiency: a systematic review and meta-analysis. Obes Rev. 2015;16(4):341–349. doi:10.1111/obr.12239

24. Barzegari M, Sarbakhsh P, Mobasseri M, et al. The effects of vitamin D supplementation on lipid profiles and oxidative indices among diabetic nephropathy patients with marginal vitamin D status. Diabetes Metab Syndr. 2019;13(1):542–547. doi:10.1016/j.dsx.2018.11.008

25. Yiu YF, Yiu K-H, Siu C-W, et al. Randomized controlled trial of vitamin D supplement on endothelial function in patients with type 2 diabetes. Atherosclerosis. 2013;227(1):140–146. doi:10.1016/j.atherosclerosis.2012.12.013

26. Khundmiri SJ, Murray RD, Lederer E. PTH and Vitamin D. Compr Physiol. 2016;6(2):561–601.

27. Wamberg L, Kampmann U, Stødkilde-Jørgensen H, et al. Effects of vitamin D supplementation on body fat accumulation, inflammation, and metabolic risk factors in obese adults with low vitamin D levels – results from a randomized trial. Eur J Intern Med. 2013;24(7):644–649. doi:10.1016/j.ejim.2013.03.005

28. Pilz S, Putz-Bankuti C, Gaksch M, et al. Effects of vitamin D supplementation on serum 25-hydroxyvitamin D concentrations in cirrhotic patients: a randomized controlled trial. Nutrients. 2016;8:5. doi:10.3390/nu8050278

29. Javed Z, Papageorgiou M, Deshmukh H, et al. A randomized, controlled trial of vitamin D supplementation on cardiovascular risk factors, hormones, and liver markers in women with polycystic ovary syndrome. Nutrients. 2019;11:1. doi:10.3390/nu11010188

30. Jun JC, Yoon H, Choi YJ, et al. The effect of vitamin D administration on inflammatory markers in patients with inflammatory bowel disease. Intest Res. 2019;17(2):210–217. doi:10.5217/ir.2018.00081

31. Rodriguez AJ, Mousa A, Ebeling PR, et al. Effects of vitamin D supplementation on inflammatory markers in heart failure: a systematic review and meta-analysis of randomized controlled trials. Sci Rep. 2018;8(1):1169. doi:10.1038/s41598-018-19708-0

32. Yu Y, Tian L, Xiao Y, et al. Effect of vitamin D supplementation on some inflammatory biomarkers in Type 2 diabetes mellitus subjects: a systematic review and meta-analysis of randomized controlled trials. Ann Nutr Metab. 2018;73(1):62–73. doi:10.1159/000490358

33. Jamka M, Woźniewicz M, Walkowiak J, et al. The effect of vitamin D supplementation on selected inflammatory biomarkers in obese and overweight subjects: a systematic review with meta-analysis. Eur J Nutr. 2016;55(6):2163–2176. doi:10.1007/s00394-015-1089-5

34. Gaman MA, Epîngeac ME, Diaconu CC, et al. Evaluation of oxidative stress levels in obesity and diabetes by the free oxygen radical test and free oxygen radical defence assays and correlations with anthropometric and laboratory parameters. World J Diabetes. 2020;11(5):193–201. doi:10.4239/wjd.v11.i5.193

35. Beba M, Djafarian K, Shab-Bidar S. Effect of Berberine on C-reactive protein: a systematic review and meta-analysis of randomized controlled trials. Complement Ther Med. 2019;46:81–86. doi:10.1016/j.ctim.2019.08.002

36. Xiong P, Niu L, Talaei S, et al. The effect of berberine supplementation on obesity indices: A dose- response meta-analysis and systematic review of randomized controlled trials. Complement Ther Clin Pract. 2020;39:101113. doi:10.1016/j.ctcp.2020.101113

37. Salehi-Sahlabadi A, Varkaneh HK, Shahdadian F, et al. Effects of Phytosterols supplementation on blood glucose, glycosylated hemoglobin (HbA1c) and insulin levels in humans: a systematic review and meta-analysis of randomized controlled trials. J Diabetes Metab Disord. 2020;19(1):625–632. doi:10.1007/s40200-020-00526-z

38. Lin Y, Shi D, Su B, et al. The effect of green tea supplementation on obesity: A systematic review and dose–response meta-analysis of randomized controlled trials. Phytother Res. 2020;34(10):2459–2470. doi:10.1002/ptr.6697

39. Pourrajab B, Fatahi S, Sohouli MH. et al. The effects of probiotic/synbiotic supplementation compared to placebo on biomarkers of oxidative stress in adults: a systematic review and meta-analysis of randomized controlled trials. Crit Rev Food Sci Nutr. 2020:1–18. doi:10.1080/10408398.2020.1821166

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