Vitamin D,selenium,and antidiabetic drugs in the treatment of type 2 diabetes mellitus with Hashimoto's thyroiditis

BACKGROUND Diabetes and thyroiditis are closely related.They occur in combination and cause significant damage to the body.There is no clear treatment for type-2 diabetes mellitus(T2DM)with Hashimoto's thyroiditis(HT).While single symptomatic drug treatment of the two diseases is less effective,combined drug treatment may improve efficacy.AIM To investigate the effect of a combination of vitamin D,selenium,and hypoglycemic agents in T2DM with HT.METHODS This retrospective study included 150 patients with T2DM and HT treated at The Central Hospital of Shaoyang from March 2020 to February 2023.Fifty patients were assigned to the control group,test group A,and test group B according to different treatment methods.The control group received low-iodine diet guidance and hypoglycemic drug treatment.Test group A received the control treatment plus vitamin D treatment.Test group B received the group A treatment plus selenium.Blood levels of markers of thyroid function[free T3(FT3),thyroid stimulating hormone(TSH),free T4(FT4)],autoantibodies[thyroid peroxidase antibody(TPOAB)and thyroid globulin antibody(TGAB)],blood lipid index[low-density lipoprotein cholesterol(LDL-C),total cholesterol(TC),triacylglycerol(TG)],blood glucose index[fasting blood glucose(FBG),and hemoglobin A1c(HbA1c)]were measured pre-treatment and 3 and 6 months after treatment.The relationships between serum 25-hydroxyvitamin D3[25(OH)D3]level and each of these indices were analyzed.RESULTS The levels of 25(OH)D3,FT3,FT4,and LDL-C increased in the order of the control group,test group A,and test group B(all P<0.05).The TPOAB,TGAB,TC,TG,FBG,HbA1c,and TSH levels increased in the order of test groups B,A,and the control group(all P<0.05).All the above indices were compared after 3 and 6 months of treatment.Pre-treatment,there was no divergence in serum 25(OH)D3 level,thyroid function-related indexes,autoantibodies level,blood glucose,and blood lipid index between the control group,test groups A and B(all P>0.05).The 25(OH)D3 levels in test groups A and B were negatively correlated with FT4 and TGAB(all P<0.05).CONCLUSION The combination drug treatment for T2DM with HT significantly improved thyroid function,autoantibody,and blood glucose and lipid levels.

Association of Serum Folate and Vitamin B_(12) Concentrations with Obesity in Chinese Children and Adolescents

Objective This study aimed to evaluate the associations of serum folate and/or vitamin B12 concentrations with obesity among Chinese children and adolescents.Methods A cross-sectional study was conducted including 3,079 Chinese children and adolescents,aged 6 to 17 years,from Jiangsu,China.Anthropometric indices,such as,children's body mass index(BMI),BMI z-scores,waist circumference,and waist-to-height ratio were utilized.Multivariable linear regression and generalized additive models were used to investigate the associations of serum folate and vitamin B12 levels with anthropometric indices and odds of obesity.Results We observed that serum vitamin B12 concentrations were inversely associated with all anthropometric indices and the odds of general obesity[odds ratio(OR)=0.68;95%confidence interval(CI)=0.59,0.78]and abdominal obesity(OR=0.68;95%CI=0.60,0.77).When compared to participants with both serum vitamin levels in the two middle quartiles,those with both serum folate and vitamin B12 levels in the highest quartile were less prone to general(OR=0.31,95%CI=0.19,0.50)or abdominal obesity(OR=0.46,95%CI=0.31,0.67).Conversely,participants with vitamin B12 levels in the lowest quartile alongside folate levels in the highest quartile had higher odds of abdominal obesity(OR=2.06,95%CI=1.09,3.91).Conclusion Higher serum vitamin B12 concentrations,but not serum folate concentrations,were associated with lower odds of childhood obesity.Children and adolescents with high levels of vitamin B12 and folate were less likely to be obese.

Selenium,Type-2 Diabetes,and the Possible Protective Role of Vitamin D

Diabetes is a pervasive and serious global health issue.According to the International Diabetes Federation report,463 million adults worldwide were living with diabetes in 2019,and this number is projected to reach 700 million in 2045^([1]).

Association of plasma vitamin A level with type 2 diabetes mellitus:a community aging population-based cross-sectional study

Recent studies indicated that vitamin A(VA)might be involved in the pathology of type 2 diabetes mellitus(T2DM).This cross-sectional study was conducted to explore the association between circulating VA level and T2DM.A total of 1818 subjects aged 50 years old and above were recruited from the community.Binomial logistic regression and restricted cubic spline(RCS)were applied to analyze the association of plasma VA level with the risk of T2DM.Serum VA and lipid-adjusted VA levels of T2DM patients were significantly higher than that of non-T2DM subjects(P<0.05).The ratios of plasma VA/total cholesterol(TC),VA/high-density lipoprotein cholesterol(HDL-c)and VA/low-density lipoprotein cholesterol(LDL-c)were positively associated with the risk of T2DM in the aging population(P<0.05).Compared with the Q1 level,subjects with Q2 to Q3 levels of plasma VA/triglyceride(TG)have decreased risk of T2DM(odds ratio(OR)Q2=0.68,P_(Q2)=0.021;ORQ3=0.59,P_(Q3)<0.01).Our results indicated that the imbalance of circulating lipids and VA might affect the relationship between VA and T2DM.The middle and aging subjects with higher ratios of plasma VA/TC,VA/HDL-c,and VA/LDL-c displayed increased risk for T2DM,but the moderate ratio of VA/TG might protect against risk of T2DM.

Vitamin A regulates mitochondrial biogenesis and function through p38 MAPK‑PGC‑1α signaling pathway and alters the muscle fiber composition of sheep

Background Vitamin A(VA)and its metabolite,retinoic acid(RA),are of great interest for their wide range of physiological functions.However,the regulatory contribution of VA to mitochondrial and muscle fiber composition in sheep has not been reported.Method Lambs were injected with 0(control)or 7,500 IU VA palmitate into the biceps femoris muscle on d 2 after birth.At the age of 3 and 32 weeks,longissimus dorsi(LD)muscle samples were obtained to explore the effect of VA on myofiber type composition.In vitro,we investigated the effects of RA on myofiber type composition and intrinsic mechanisms.Results The proportion of type I myofiber was greatly increased in VA-treated sheep in LD muscle at harvest.VA greatly promoted mitochondrial biogenesis and function in LD muscle of sheep.Further exploration revealed that VA elevated PGC-1αmRNA and protein contents,and enhanced the level of p38 MAPK phosphorylation in LD muscle of sheep.In addition,the number of type I myofibers with RA treatment was significantly increased,and type IIx myofibers was significantly decreased in primary myoblasts.Consistent with in vivo experiment,RA significantly improved mitochondrial biogenesis and function in primary myoblasts of sheep.We then used si-PGC-1αto inhibit PGC-1αexpression and found that si-PGC-1αsignificantly abrogated RA-induced the formation of type I myofibers,mitochondrial biogenesis,MitoTracker staining intensity,UQCRC1 and ATP5A1 expression,SDH activity,and enhanced the level of type IIx muscle fibers.These data suggested that RA improved mitochondrial biogenesis and function by promoting PGC-1αexpression,and increased type I myofibers.In order to prove that the effect of RA on the level of PGC-1αis caused by p38 MAPK signaling,we inhibited the p38 MAPK signaling using a p38 MAPK inhibitor,which significantly reduced RA-induced PGC-1αand MyHC I levels.Conclusion VA promoted PGC-1αexpression through the p38 MAPK signaling pathway,improved mitochondrial biogenesis,and altered the composition of muscle fiber type.

Causal relationship between circulating vitamin C and 25-hydroxyvitamin D concentrations and common mental disorders-a Mendelian randomization study

Mental disorders seriously affect people’s health and social stability.This Mendelian randomization(MR)study was designed to investigate the causal relationship between circulating vitamin C(VC)or 25-hydroxyvitamin D(25(OH)D)levels and mental disorders.The data used for the MR analysis were derived from the summary genome-wide association studies(GWAS)database for VC and 25(OH)D and from the Finn Gen consortium for fourteen mental disorders.Based on the inverse variance weighted(IVW)method,we found a potential causal association between circulating VC and anxiety disorders(IVW:OR=1.139,95%CI:1.023-1.269,P=0.018).However,no causal association was found between VC or 25(OH)D and other mental disorders(P>0.05).In the reverse MR analysis,individuals with Alzheimer’s disease was causally associated with higher concentrations of circulating VC(P=0.012),while individuals with anxiety disorders had a negative association between the concentrations of 25(OH)D(P=0.012).However,the current evidence does not support a causal relationship between VC or 25(OH)D and other mental disorders.In addition,there was no causal association between circulating VC and 25(OH)D(P>0.05).Future studies are needed to confirm these findings and to elucidate the mechanisms of potential causality.

Effects of vitamin family members on insulin resistance and diabetes complications

The following letter to the editor highlights the article“Effects of vitamin D supplementation on glucose and lipid metabolism in patients with type 2 diabetes mellitus and risk factors for insulin resistance”in World J Diabetes 2023 Oct 15;14(10):1514-1523.It is necessary to explore the role of vitamin family members in insulin resistance and diabetes complications.

Vitamin D and selenium for type 2 diabetes mellitus with Hashimoto’s thyroiditis:Dosage and duration insights

This letter discusses the publication by Feng et al.Iodine,selenium,and vitamin D are closely associated with thyroid hormone production in humans;however,the efficacy of selenium and vitamin D supplementation for type 2 diabetes mellitus(T2DM)patients with Hashimoto’s thyroiditis(HT)remains controversial.In the retrospective study we discuss herein,the authors highlighted significant improvements in thyroid function,thyroid antibodies,blood glucose,and blood lipid in T2DM patients with HT following addition of vitamin D and selenium to their antidiabetic regimens,underscoring the value of these supplements.Our team is currently engaged in research exploring the relationship between micronutrients and HT,and we have obtained invaluable insights from the aforementioned study.Based on this research and current literature,we recommend a regimen of 4000 IU/day of vitamin D and 100-200μg/day of selenium for over three months to six months for patients with HT,particularly for those with concurrent T2DM.

Vitamin D, selenium in type 2 diabetes and Hashimoto's thyroiditis: Is it effective?

The study by Feng et al,explores treatment approaches for these coexisting conditions.It emphasizes the potential advantages of selenium and vitamin D supplementation but also raises methodological and patient selection concerns.Findings indicate a complex interplay between interventions and disease markers,prompting the need for further research.Despite limitations,the study offers valuable insights into managing the intricate relationship between type 2 diabetes mellitus and Hashimoto's thyroiditis.The authors'contributions shed light on potential treatment avenues,although careful consideration of study design and patient characteristics is warranted for future investigations in this domain.

Vitamin D, Parathyroid Hormone, Insulin Sensitivity and Islet β-Cell Secretory Function in Diabetic Patients from South Kivu in the Democratic Republic of Congo: Cross-Sectional Study

Background: The role of vitamin D and parathyroid hormone in the metabolic profile of type 2 diabetes mellitus in sub-Saharan Africa has not been adequately assessed. The aim of this study was to determine the prevalence of low vitamin D level and secondary hyperparathyroidism and their association with insulin sensitivity and β-cell secretory function among Congolese type 2 diabetics. Methodology: Fasting glycaemia, fasting insulin, 25OH D3 and human parathyroid hormone (hPTH) were measured in one hundred and eighty-four type 2 diabetic patients followed as outpatients in South Kivu. Levels of 25OH D3 65 pg/ml defined low vitamin D and elevated parathyroid hormone levels, respectively. The HOMA model was used to measure insulin sensitivity and β-cell secretory function. Results: Medians (IQR) were 25.3 (20.4 - 32.4) ng/ml for 25OH D3 and 53.7 (38.4 - 115.7) pg/ml for hPTH. 58.7% of diabetics had insulin resistance, 126 (68.5%) had low vitamin D and 80 (43.5%) had hyperparathyroidism. In multivariate analysis, hPTH (partial r = −0.28;p = 0.0002) and 25OH D3 (partial r = 0.16;p = 0.03) showed an independent association with insulin sensitivity after adjustment for body mass index and waist circumference. Finally, hPTH (partial r = 0.27;p = 0.0002) was the sole determinant of β-cell secretory function. Conclusions: This study confirms the high prevalence of low vitamin D level and secondary hyperparathyroidism and their association with insulin resistance and impaired islet β-cell secretory function among Congolese with type 2 diabetes mellitus. Vitamin D and calcium supplementation should be envisaged for cases of deficiency in this region.

Role of nutrition in diabetes mellitus and infections

In this editorial,we have commented on the article that has been published in the recent issue of World Journal of Clinical Cases.The authors have described a case of unilateral thyroid cyst and have opined that the acute onset of infection may be linked to diabetes mellitus(DM).We have focused on the role of nutrition in the association between DM and infection.Patients with DM are at a high risk of infection,which could also be attributed to nutrition-related factors.Nutritional interventions for patients with diabetes are mainly based on a low-calorie diet,which can be achieved by adhering to a low-carbohydrate diet.However,dietary fiber supplementation is recommended to maintain the diversity of the gut microbiota.Furthermore,high-quality protein can prevent the increased risk of infection due to malnutrition.Supplementation of vitamins C,vitamins A,vitamins D,and folic acid improves blood sugar control and facilitates immune regulation.Mineral deficiencies augment the risk of infection,but the relationship with diabetes is mostly U-shaped and a good intake should be maintained.

Research Progress on the Mechanism of Correlation Between Vitamin D and Thyroid Cancer

Vitamin D is a kind of fat-soluble vitamin,which is mainly involved in the metabolism of calcium and bone in the human body.As a metabolic substance,it also has a certain impact on the cellular microenvironment,and vitamin D also inhibits the proliferation of tumor cells.25(OH)D is considered the best index to evaluate the vitamin D level in the human body because of its relatively stable characteristics in the circulation.Thyroid cancer is a common malignant tumor that develops from malignant thyroid nodules.A large number of studies have found that the lower the serum 25(OH)D level,the higher the risk of thyroid nodules.A large number of studies have found that the lower the serum 25(OH)D level,the higher the risk of thyroid nodules.

Effect of Phosphorus on the Content of Vitamin E in Different Soybean Cultivars

[Objective] This study aimed to explore the effects of phosphorus on the contents of vitamin E in different cultivars of soybean grains and find the optimum application amount of phosphorus for different genotypes of soybean cultivars,in order to increase the contents of vitamin E in soybean grains and improve the qualities.[Method] Three soybean cultivars were selected as experimental materials,including Heinong 48（high-protein cultivar）,Heinong 37（intermediate cultivar） and Heinong 44（high-oil cultivar）.The soybeans were planted in pots,with 0.033 g/kg soil of N and K2O,four phosphorus treatments were set,respectively applied with 0（P1）,0.033（P2）,0.067（P3） and 0.100（P4） g/kg soil of P2O5,and the total contents of vitamin E in different cultivars of soybean grains were determined by high-performance liquid chromatography method.[Result] The total contents of vitamin E in the same cultivar of soybean grains in P3 treatment were significantly higher than that in the other three treatments,the total contents of vitamin E in Heinong 37,Heinong 44 and Heinong 48 in P3 treatment had increased by 11.96%,16.55% and 14.02%,compared with the control;among the three soybean cultivars in P2 treatment,the content of vitamin E in Heinong 37 was the maximum;among the 12 treatment combinations,the total contents of vitamin E in Heinong 44 in P3 treatment was the maximum.The contents of vitamin E in three soybean cultivars significantly varied among the various cultivars and different phosphorus treatments.[Conclusion] Application of phosphorus could affect the contents of vitamin E in three soybean cultivars,appropriate application amount of phosphorus is advantageous to improve the contents of vitamin E in soybean grains.

Role of vitamin D in diabetes mellitus and chronic kidney disease

Approximately 30%-50% of people are recognized to have low levels of vitamin D,and insufficiency and deficiency of vitamin D are recognized as global health problems worldwide.Although the presence of hypovitamin D increases the risk of rickets and fractures,low vitamin D levels are also associated with hypertension,cancer,and cardiovascular disease.In addition,diabetes mellitus(DM) and chronic kidney disease(CKD) are also related to vitamin D levels.Vitamin D deficiency has been linked to onset and progression of DM.Although in patients with DM the relationship between vitamin D and insulin secretion,insulin resistance,and β-cell dysfunction are pointed out,evidence regarding vitamin D levels and DM is contradictory,and well controlled studies are needed.In addition,vitamin D influences the renin-angiotensin system,inflammation,and mineral bone disease,which may be associated with the cause and progression CKD.There is increasing evidence that vitamin D deficiency may be a risk factor for DM and CKD;however,it remains uncertain whether vitamin D deficiency also predisposes to death from DM and CKD.Although at this time,supplementation with vitamin D has not been shown to improve glycemic control or prevent incident DM,clinical trials with sufficient sample size,study periods,and optimal doses of vitamin D supplementation are still needed.This review focuses on the mechanism of vitamin D insufficiency and deficiency in DM or CKD,and discusses the current evidence regarding supplementation with vitamin D in patients with these diseases.

Protective links between vitamin D,inflammatory boweldisease and colon cancer

Vitamin D deficiency has been associated with a wide range of diseases and multiple forms of cancer including breast, colon, and prostate cancers. Relatively recent work has demonstrated vitamin D to be critical in immune function and therefore important in inflammatory diseases such as inflammatory bowel disease(IBD). Because vitamin D deficiency or insufficiency is increasingly prevalent around the world, with an estimated 30%-50% of children and adults at risk for vitamin D deficiency worldwide, it could have a significant impact on IBD. Epidemiologic studies suggest that low serum vitamin D levels are a risk factor for IBD and colon cancer, and vitamin D supplementation is associated with decreased colitis disease activity and/or alleviated symptoms. Patients diagnosed with IBD have a higher incidence of colorectal cancer than the general population, which supports the notion that inflammation plays a key role in cancer development and underscores the importance of understanding how vitamin D influences inflammation and its cancer-promoting effects. In addition to human epidemiological data, studies utilizing mouse models of colitis have shown that vitamin D is beneficial in preventing or ameliorating inflammation and clinical disease. The precise role of vitamin D on colitis is unknown; however, vitamin D regulates immune cell trafficking and differentiation, gut barrier function and antimicrobial peptide synthesis, all of which may be protective from IBD and colon cancer. Here we focus on effects of vitamin D on inflammation and inflammation-associated colon cancer and discuss the potential use of vitamin D for protection and treatment of IBD and colon cancer.

Correlation between serum vitamin B12 level and peripheral neuropathy in atrophic gastritis

AIM To explore the correlation between serum vitamin B12 level and peripheral neuropathy in patients with chronic atrophic gastritis(CAG). METHODS A total of 593 patients diagnosed with chronic gastritis by gastroscopy and pathological examination fromSeptember 2013 to September 2016 were selected for this study. The age of these patients ranged within 18-to 75-years-old. Blood pressure, height and weight were measured in each patient, and the body mass index value was calculated. Furthermore, gastric acid, serum gastrin, serum vitamin and serum creatinine tests were performed, and peripheral nerve conduction velocity and Helicobacter pylori(H. pylori) were detected. In addition, the type of gastritis was determined by gastroscopy. The above factors were used as independent variables to analyze chronic gastritis with peripheral neuropathy and vitamin B12 deficiency risk factors, and to analyze the relationship between vitamin B12 levels and peripheral nerve conduction velocity. In addition, in the treatment of CAG on the basis of vitamin B12, patients with peripheral neuropathy were observed. RESULTS Age, H. pylori infection, CAG, vitamin B9 and vitamin B12 were risk factors for the occurrence of peripheral nerve degeneration.Furthermore,CAG and H. pylori infection were risk factors for chronic gastritis associated with vitamin B12 deficiency. Serum vitamin B12 level was positively correlated with sensory nerve conduction velocity in the tibial nerve(R = 0.463). After vitamin B12 supplementation, patients with peripheral neuropathy improved. CONCLUSION Serum vitamin B12 levels in patients with chronic gastritis significantly decreased, and the occurrence of peripheral neuropathy had a certain correlation. CAG and H. pylori infection are risk factors for vitamin B12 deficiency and peripheral neuropathy. When treating CAG, vitamin B12 supplementation can significantly reduce peripheral nervous system lesions. Therefore, the occurrence of peripheral neuropathy associated with vitamin B12 deficiency may be considered in patients with CAG. Furthermore, the timely supplementation of vitamin B12 during the clinical treatment of CAG can reduce or prevent peripheral nervous system lesions.

Is there a relationship between vitamin D with insulin resistance and diabetes mellitus?

Available data suggest a possible link between abnormalvitamin D level and abnormal glucose homeostasis,two of the most common chronic medical conditions.Both conditions are associated with inflammation,and the exact mechanism for role of either on the other is not well clear.Literature investigating the link between vitamin D and either pre-diabetic states or diabetes is reviewed.Vitamin D deficiency is detrimental to insulin synthesis and secretion in animal and human studies.In humans,it has been shown by majority of observational studies,that vitamin D is positively correlated with insulin sensitivity and its role is mediated both by direct mechanism through the availability of vitamin D receptors in several tissues and indirectly through the changes in calcium levels.Large number of,but not all,variable samples cross sectional human trials have demonstrated an inverse relation between vitamin D status and impaired glucose tolerance,insulin resistance or diabetes.To compliment this conclusively,evidence from intervention studies is critically warranted before we can frankly state that vitamin D plays a role in diabetes prevention or treatment.Absence of both sizable prospective observational trials utilizing 25(OH)D as the main variable and the non-availability of randomized studies specifically designed to assess the effects of vitamin D on pre-diabetes and diabetes states,are the main obstacles to draw solid and conclusive relationships.

Association between Vitamin D Insufficiency and the Risk for Gestational Diabetes Mellitus in Pregnant Chinese Women

Objective To investigate the association between vitamin D deficiency and risk of gestational diabetes rnellitus （GDM） in pregnant Chinese women. Methods A nested case-control study was conducted. Clinical and biochemical data were analyzed for 200 subjects with GDM and 200 subjects with normal glucose tolerance （NGT）. Results The median （interquartile range） serum 25-hydroxyvitamin D （25OHD） levels were 22.39 （17.67, 29.38） and 25.86 （19.09, 34.88） nmol/L in the GDM and NGT groups, respectively. Rates of 25OHD deficiency or insufficiency were significantly higher in the GDM group than in the NGT group. Subjects with 25OHD levels 〈25 nmol/L had a 1.g-fold higher risk of GDM compared with subjects with higher vitamin D levels. In the GDM group, serum 25OHD was independently associated with HbAlc and insulin resistance after adjusting for confounding factors. In the NGT group, serum 25OHD was independently associated with fasting plasma glucose and systolic blood pressure after adjusting for maternal age and other confounding factors. Conclusion 2SOHD insufficiency is very common in Chinese women. Low 25OHD status may be associated with insulin resistance and act as a risk factor for GDM.

Vitamin A administration at birth promotes calf growth and intramuscular fat development in Angus beef cattle

Background: Marbling, or intramuscular fat, is an important factor contributing to the palatability of beef. Vitamin A, through its active metabolite, retinoic acid, promotes the formation of new fat cells(adipogenesis). As intramuscular adipogenesis is active during the neonatal stage, we hypothesized that vitamin A administration during the neonatal stage would enhance intramuscular adipogenesis and marbling.Methods: Angus steer calves(n = 30), in a completely randomized design, were randomly allotted to three treatment groups at birth, receiving 0, 150,000, or 300,000 IU of vitamin A at both birth and one month of age.A biopsy of the biceps femoris muscle was collected at two months of age. After weaning at 210 d of age, steers were fed a backgrounding diet in a feedlot until 308 d of age, when they were transitioned to a high concentrate finishing diet and implanted with trenbolone/estradiol/tylosin mixture. Steers were harvested at an average of 438 d of age. All diets were formulated to meet nutrient requirements.Results: Weaning weight and weight during the backgrounding phase were linearly increased(P < 0.05) by vitamin A level, though no difference in body weight was observed at harvest. Intramuscular fat of steers at 308 d of age, measured by ultrasound, quadratically increased(P < 0.05) with vitamin A level from 4.0±0.26 % to 4.9±0.26 %.Similarly, carcass marbling score in the ribeye quadratically increased(P < 0.05).Conclusion: Administration of vitamin A at birth increased weaning weight and enhanced marbling fat development.Thus, vitamin A administration provides a practical method for increasing marbling and early growth of beef cattle.

Association between vitamin D and hepatitis C virus infection: A meta-analysis

AIM:To evaluate the association between 25-hydroxyvitamin D[25(OH)D]and sustained virological response(SVR)in hepatitis C virus(HCV)infected individuals.METHODS:Relevant studies were identified by systematically searching MEDLINE databases up to March2012 and abstracts of the European and American Congress of Hepatology conducted in 2011.Studies must provide information on SVR and the levels of 25(OH)D3and/or 25(OH)D2[henceforth referred to as 25(OH)D]in sera samples from HCV infected individuals.The inclusion criteria were:clinical studies that included HCV infected patients aged older than 18 years regardless of HCV genotype or ethnic group;provided information on SVR rates;and were reported in the English languageas full papers.Due to the heterogeneity of studies in categorizing serum vitamin D levels,a cut-off value of30 ng/mL of serum 25(OH)D was used.Heterogeneity was assessed using I2statistics.The summary odds ratios with their corresponding 95%CI were calculated based on a random-effects model.RESULTS:Overall,11 studies(8 observational and 3interventional)involving 1575 individuals were included and 1117 HCV infected individuals(71%)showed low vitamin D levels.Most of the studies included monoinfected HCV individuals with the mean age ranging from 38 to 56 years.Four studies were conducted in human immunodeficiency virus/HCV infected individuals.Regarding vitamin D measurement,most of the studies employed radioimmunoassays(n=5)followed by chemiluminescence(n=4)and just one study employed high performance/pressure liquid chromatography(HPLC).Basal vitamin D levels varied from 17 to43 ng/mL in the studies selected,and most of the HCV infected individuals had genotype 1(1068/1575)with mean viral load varying from log 4.5-5.9 UI/mL.With regard to HCV treatment,most of the studies(n=8)included HCV individuals without previous treatment,where the pooled SVR rate was 46.4%.High rates of SVR were observed in HCV individuals with vitamin D levels above 30 ng/mL(OR=1.57;95%CI:1.12-2.2)and those supplemented with vitamin D(OR=4.59;95%CI:1.67-12.63)regardless of genotype.CONCLUSION:Our results demonstrated high prevalence of vitamin D deficiency and high SVR in individuals with higher serum vitamin D levels or receiving vitamin D supplementation.