Serum 25-hydroxyvitamin D and markers of insulin resistance in a Japanese working population

Association between vitamin D serum levels and insulin resistance assessed by HOMA-IR among non-diabetic adults in the United States: Results from NHANES 2007-2014

Insulin resistance, a pathological response to insulin hormone in insulin-dependent cells, is characterized by the presence of high glucose and insulin concentrations. The homeostasis model of insulin resistance (HOMA-IR) is one of the most used indexes to estimate insulin resistance by assessing the fasting glucose and insulin levels. An association was observed between vitamin D levels and insulin resistance, which varied in different ethnic groups, and there is some evidence that vitamin D supplementation could contribute to the improvement of insulin resistance. This study assessed the association between 25-hydroxyvitamin D (25[OH]D) concentration and HOMA-IR in American adults aged 20 years and older, without diabetes and other chronic diseases that can influence insulin resistance. The data from the National Health and Nutrition Examination Survey (NHANES) 2007–2014 were used by exploiting the free and publicly-accessible web datasets. Linear regression models were performed to evaluate the association between serum 25(OH)D concentration and HOMA-IR, and a negative association was observed, which remained significant following the adjustment for age, gender, race/ethnicity, education, body mass index (BMI), physical activity, the season of examination, current smoking, hypertension, the use of drugs which can influence insulin resistance, serum bicarbonates, triglycerides, and calcium and phosphorus levels. Only in non-Hispanic Blacks was this inverse association between vitamin D and HOMA-IR not observed in the fully adjusted model. Further studies are needed to explain the mechanisms of the observed ethnic/racial differences in the association of vitamin D levels with HOMA-IR.

Serum, Dietary, and Supplemental Vitamin D Levels and Insulin Resistance in 6294 Randomly Selected, Non-Diabetic U.S. Adults

The primary aim of this study was to determine the associations between serum, dietary, and supplemental vitamin D levels and insulin resistance in 6294 non-diabetic U.S. adults. A total of 8 years of data from the 2011−2018 National Health and Nutrition Examination Survey (NHANES) and a cross-sectional design were utilized to answer the research questions. Serum vitamin D levels were quantified using high-performance liquid chromatography−tandem mass spectrometry. Dietary and supplemental vitamin D intakes were assessed using the average of two 24 h dietary recalls taken 3−10 days apart. The homeostatic model assessment (HOMA), based on fasting glucose and fasting insulin levels, was employed to index insulin resistance. Demographic covariates were age, sex, race, and year of assessment. Differences in physical activity, body mass index (BMI), cigarette smoking, body weight, season, and energy intake were also controlled statistically. Serum levels of vitamin D differed significantly, and in a dose−response order, across quartiles of HOMA-IR, after adjusting for year, age, sex, and race (F = 30.3, p < 0.0001) and with all the covariates controlled (F = 5.4, p = 0.0029). Dietary vitamin D levels differed similarly across HOMA-IR quartiles, but to a lesser extent, respectively (F = 8.1, p = 0.0001; F = 2.9, p = 0.0437). Likewise, supplemental vitamin D levels also differed across the HOMA-IR quartiles, respectively (F = 3.5, p = 0.0205; F = 3.3, p = 0.0272). With all the covariates controlled, the odds of having insulin resistance were significantly greater for those in the lowest quartile of serum and supplemental vitamin D intake compared to the other quartiles combined. In conclusion, in this nationally representative sample, serum, dietary, and supplemental vitamin D were each predictive of insulin resistance, especially in those with low serum levels and those with no supplemental intake of vitamin D.

Vitamin D Deficiency Is Inversely Associated with Homeostatic Model Assessment of Insulin Resistance

The study was conducted to comprehensively assess the association of the concentration of vitamin D in the blood and insulin resistance in non-diabetic subjects. The objective was to pool the results from all observational studies from the beginning of 1980 to August 2021. PubMed, Medline and Embase were systematically searched for the observational studies. Filters were used for more focused results. A total of 2248 articles were found after raw search which were narrowed down to 32 articles by the systematic selection of related articles. Homeostatic Model Assessment of Insulin Resistance (HOMAIR) was used as the measure of insulin resistance and correlation coefficient was used as a measure of the relationship between vitamin D levels and the insulin resistance. Risk of bias tables and summary plots were built using Revman software version 5.3 while Comprehensive meta-analysis version 3 was used for the construction of forest plot. The results showed an inverse association between the status of vitamin D and insulin resistance (r = -0.217; 95% CI = -0.161 to -0.272; p = 0.000). A supplement of vitamin D can help reduce the risk of insulin resistance; however further studies, like randomized controlled trials are needed to confirm the results.

Insulin Resistance Is Inversely Associated with the Status of Vitamin D in Both Diabetic and Non-Diabetic Populations

Vitamin D has been implicated in the regulation of glucose metabolism and insulin resistance. We designed this study to provide evidence that insulin resistance is dependent on the concentration of vitamin D in the body. Forty observational studies of both type 2 diabetes mellitus patients and healthy subjects were included in this meta-analysis. Related articles were searched from Embase, PubMed, and Medline through January 2021. Filters for search were used to obtain more focused results. We used Comprehensive Meta-Analysis Version 3 for the construction of forest plots. RevMan software version 5.3 was used to build the risk of bias tables and summary plots. The observational studies included in this systematic review and meta-analysis showed an inverse relationship of insulin resistance with the status of vitamin D both in non-diabetic (r = -0.188; 95% CI = -0.141 to -0.234; p = 0.000) and diabetic (r = -0.255; 95% CI = -0.392 to -0.107, p = 0.001) populations. From the meta-analysis we concluded that hypovitaminosis D is related to increased levels of insulin resistance in both type 2 diabetes patients and the healthy population all over the world.

New Insights on Low Vitamin D Plasma Concentration as a Potential Cardiovascular Risk Factor

The role of Vitamin D hormone in human health and disease is still debated. Recently, growing attention has been paid to its putative role in cardiovascular system homeostasis with several studies that suggested a correlation between low vitamin D levels and increased cardiovascular risk. Several mechanisms are involved in the development of cardiovascular diseases: systemic inflammation, endothelial dysfunction, arterial hypertension and insulin resistance. In the present paper, we have revised the current literature supporting a role for vitamin D in the development of these pathogenetic processes. Finally, we have evaluated the current evidence linking vitamin D to atherosclerosis and its natural consequence, cardiovascular diseases.

Vitamin D levels and deficiency with different occupations: a systematic review

Background

Vitamin D deficiency is prevalent worldwide, but some groups are at greater risk. We aim to evaluate vitamin D levels in different occupations and identify groups vulnerable to vitamin D deficiency.

Methods

An electronic search conducted in Medline, Embase, the Cochrane Central Register of Controlled Trials, and CINAHL Plus with Full Text generated 2505 hits; 71 peer-reviewed articles fulfilled the inclusion criteria. Occupations investigated included outdoor and indoor workers, shiftworkers, lead/smelter workers, coalminers, and healthcare professionals. We calculated the pooled average metabolite level as mean ± SD; deficiency/insufficiency status was described as % of the total number of subjects in a given category.

Results

Compared to outdoor workers, indoor workers had lower 25-hydroxyvitamin D (25-(OH)D) levels (40.6 ± 13.3 vs. 66.7 ± 16.7 nmol/L; p < 0.0001). Mean 25-(OH)D levels (in nmol/L) in shiftworkers, lead/smelter workers and coalminers were 33.8 ± 10.0, 77.8 ± 5.4 and 56.6 ± 28.4, respectively. Vitamin D deficiency (25-(OH)D < 50 nmol/L), was high in shiftworkers (80%) and indoor workers (78%) compared to outdoor workers (48%). Among healthcare professionals, medical residents and healthcare students had the lowest levels of mean 25-(OH)D, 44.0 ± 8.3 nmol/L and 45.2 ± 5.5 nmol/L, respectively. The mean 25-(OH)D level of practising physicians, 55.0 ± 5.8 nmol/L, was significantly different from both medical residents (p < 0.0001) and healthcare students (p < 0.0001). Nurses and other healthcare employees had 25-(OH)D levels of 63.4 ± 4.2 nmol/L and 63.0 ± 11.0 nmol/L, respectively, which differed significantly compared to practising physicians (p = 0.01), medical residents (p < 0.0001) and healthcare students (p < 0.0001).

Rates of vitamin D deficiency among healthcare professionals were: healthcare students 72%, medical residents 65%, practising physicians 46%, other healthcare employees 44%, and nurses 43%. Combined rates of vitamin D deficiency or insufficiency (25-(OH)D < 75 nmol/L) were very high in all investigated groups.

Potential confounders such as gender and body composition were not consistently reported in the primary studies and were therefore not analyzed. Furthermore, the descriptions of occupational characteristics may be incomplete. These are limitations of our systematic review.

Conclusions

Our review demonstrates that shiftworkers, healthcare workers and indoor workers are at high risk to develop vitamin D deficiency, which may reflect key lifestyle differences (e.g. sunlight exposure). This may help target health promotion and preventive efforts.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-017-4436-z) contains supplementary material, which is available to authorized users.

Vitamin D and its effects on cardiovascular diseases: a comprehensive review

Vitamin D is a molecule that is actively involved in multiple metabolic pathways. It is mostly known for its implications related to calcium metabolism. It has also been determined that it actively participates in the cardiovascular system, influencing blood pressure, coronary artery disease and other vascular diseases, such as heart failure and atrial fibrillation. Furthermore, it has been established that this vitamin is extensively involved in the regulation of both the renin angiotensin aldosterone system and the immune system. In this review, we present the different vitamin D metabolic pathways associated with the cardiovascular pathophysiology, and we include studies in animal and human models, as well as some of the controversies found in the literature. This review also incorporates an overview of the implications in the molecular biology and public health fields.

Serum 25-Hydroxyvitamin D Concentration Is Independently Inversely Associated with Insulin Resistance in the Healthy, Non-Obese Korean Population

BACKGROUND

We evaluated the associations between 25-hydroxyvitamin D (25(OH)D) concentrations in serum and insulin resistance in the healthy Korean population.

METHODS

We conducted this cross-sectional analysis in 1,807 healthy Korean people (628 men and 1,179 women) aged 30 to 64 years in the Cardiovascular and Metabolic Disease Etiologic Research Center study. All participants were assessed for 25(OH)D, fasting glucose, and insulin levels, and completed a health examination and lifestyle questionnaire according to standard procedures. Insulin resistance was defined as the homeostasis model assessment insulin resistance higher than the 75 percentile.

RESULTS

Compared to those in the highest tertile (≥14.3 ng/mL), the odds ratio (OR) for insulin resistance was 1.37 (95% confidence interval [CI], 1.01 to 1.86) for the 1st tertile (<9.7 ng/mL) and 1.19 (95% CI, 0.08 to 1.62) for the 2nd tertile (9.7 to 14.3 ng/mL) after adjusting for age, gender, waist circumference, alcohol consumption, smoking status, physical exercise, season, and cohort. After stratification of the subjects by adiposity, these associations remained only in non-obese subjects (lowest tertile vs. highest tertile, multivariable OR, 1.64; 95% CI, 1.05 to 2.56).

CONCLUSION

Serum 25(OH)D has an independent inverse association with insulin resistance in the healthy, non-obese Korean population, even among people with vitamin D insufficiency.

Circulating ferritin concentrations are differentially associated with serum adipokine concentrations in Japanese men and premenopausal women

PURPOSE

Increased iron storage, as measured by circulating ferritin, has been linked to an increased risk of various diseases including diabetes. We examined the association of circulating ferritin with serum adiponectin, leptin, resistin, plasminogen activator inhibitor-1 (PAI-1), and visfatin levels.

METHODS

We conducted a cross-sectional study among 429 Japanese employees (284 men and 145 premenopausal women, mean age: 42.5 ± 10.5 years). Serum adipokines were measured using Luminex suspension bead-based multiplexed array, and serum ferritin was determined using a chemiluminescence immunoassay. Multivariable regression analysis was performed to calculate mean concentrations of adipokine according to the tertile of ferritin concentrations with adjustment for potential confounders.

RESULTS

Leptin and visfatin concentrations increased with increasing ferritin concentrations in men after multivariable adjustment of physical activity, smoking, alcohol use, and body mass index (P for trend = 0.02 and 0.01 for leptin and visfatin, respectively). Serum ferritin concentrations were inversely and significantly associated with adiponectin in women (P for trend = 0.01). Resistin and PAI-1 were not appreciably associated with ferritin concentration.

CONCLUSIONS

Increased iron storage may be associated with higher circulating concentrations of leptin and visfatin in men and with lower concentrations of adiponectin in women.

Vitamin D inadequacy is widespread in Tunisian active boys and is related to diet but not to adiposity or insulin resistance

BACKGROUND

Vitamin D inadequacy is widespread in children and adolescents worldwide. The present study was undertaken to assess the vitamin D status in active children living in a sunny climate and to identify the main determinants of the serum concentration of 25-hydroxyvitamin D (25-OHD).

METHODS

This cross-sectional study included 225 children aged 7-15 years practicing sports in a football academy. Anthropometric measures were performed to calculate body mass index (BMI), fat mass, and maturity status. A nutritional enquiry was performed including 3-day food records and food frequency questionnaire. Plasma 25-OHD and insulin were assessed by immunoenzymatic methods ensuring categorization of vitamin D status and calculation of insulin sensitivity/resistance indexes. A logistic regression model was applied to identify predictors for vitamin D inadequacy.

RESULTS

Vitamin D deficiency (25-OHD<12 µg/L) was observed in 40.9% of children and insufficiency (12<25-OHD<20 µg/L) was observed in 44% of children. In a multivariate analysis, vitamin D deficiency and insufficiency were associated with a lower dietary intake of vitamin D, proteins, milk, red meat, fish, and eggs. However, no significant relationship was observed with maturation status, adiposity, or insulin resistance.

CONCLUSIONS

Tunisian children and adolescents are exposed to a high risk of vitamin D inadequacy despite living in a sunny climate. Circulating 25-OHD concentrations are related to the intake of vitamin D food sources but not to maturation status or body composition. Ensuring sufficient and safe sun exposure and adequate vitamin D intake may prevent vitamin D inadequacy in children from sunny environments.

Serum 25-hydroxyvitamin D and metabolic syndrome in a Japanese working population: The Furukawa Nutrition and Health Study

OBJECTIVE

Increasing evidence has suggested a protective role of vitamin D on metabolic syndrome (MetS). However, studies addressing this issue are limited in Asia and it remains unclear whether calcium could modify the association. We examined the association of serum 25-hydroxyvitamin D (25(OH)D) status with MetS, and the potential effect modification by calcium intake in a Japanese working population.

METHODS

Study subjects were 1790 workers, ages 18 to 69 y, who participated in a health survey at the time of periodic checkup. MetS was defined according to the joint interim statement. Serum 25(OH)D was measured by a protein binding assay. Multilevel logistic regression was used to estimate the odds ratio (OR) with adjustment for potential confounding variables.

RESULTS

An inverse trend was observed between 25(OH)D and MetS. Compared with those with a 25(OH)D of <20 ng/mL, multivariable adjusted OR (95% confidence interval) for MetS was 0.79 (0.55-1.15) and 0.52 (0.25-1.04) for those with a 25(OH)D of 20 to 29 ng/mL and ≥30 ng/mL, respectively (P for trend = 0.051). Similar association was observed in the analysis using quartile categories of 25(OH)D; the OR in the highest quartile of 25(OH)D compared with the lowest quartile was 0.61 (0.36-1.01) (P for trend = 0.046). This association was noted only in older subjects (≥44 y). The inverse association between serum 25(OH)D and MetS was more pronounced in subjects with high calcium intake. The inverse association between 25(OH)D and MetS appears to be linear according to restricted cubic spline regression. There was inverse, but statistically nonsignificant, associations between 25(OH)D and each component of MetS.

CONCLUSION

Our results suggest that higher circulating vitamin D is associated with decreased likelihood of having MetS among Japanese adults.

Association between serum 25-hydroxyvitamin D level and insulin resistance in a rural population

PURPOSE

A low serum 25-hydroxyvitamin D [25(OH)D] level in the blood has been correlated with an increased risk of diabetes mellitus; however, the association between serum 25(OH)D level and insulin resistance has not been established in a Korean rural population. The aim of this study was to investigate the independent association between serum 25(OH)D level and insulin resistance in rural Korean adults.

MATERIALS AND METHODS

This study used data from the Korean Genome Epidemiology Study-Kangwha Study. In the 2011 study, 1200 adults completed health examinations. In an ancillary study, serum 25(OH)D level was measured in a subsample (n=813). After excluding those taking vitamin D supplements, a cross-sectional analysis was carried out on 807 participants (324 men and 483 women) aged 40 to 89 years old. Measured from overnight fasting blood samples, glucose and insulin levels were used to calculate the homeostasis model assessment for insulin resistance (HOMA-IR). Measures of glucose, insulin, and HOMA-IR were log-transformed for parametric tests.

RESULTS

Serum 25(OH)D level was inversely associated with HOMA-IR (β=-0.003, p=0.039) in a univariate analysis. However, the association was not significant after adjustment for sex and age (β=-0.002, p=0.123) or after adjustment for sex, age, body mass index, smoking status, alcohol intake, and regular exercise (β=-0.003, p=0.247).

CONCLUSION

Our findings suggest that vitamin D is not independently associated with insulin resistance in Korean men and women.

Vitamin D3 supplementation during weight loss: a double-blind randomized controlled trial

BACKGROUND

Vitamin D deficiency is associated with obesity; whether repletion supports weight loss and changes obesity-related biomarkers is unknown.

OBJECTIVE

We compared 12 mo of vitamin D3 supplementation with placebo on weight, body composition, insulin, and C-reactive protein (CRP) in postmenopausal women in a weight-loss intervention.

DESIGN

A total of 218 overweight/obese women (50-75 y of age) with serum 25-hydroxyvitamin D [25(OH)D] ≥10 ng/mL but <32 ng/mL were randomly assigned to weight loss + 2000 IU oral vitamin D3/d or weight loss + daily placebo. The weight-loss intervention included a reduced-calorie diet (10% weight loss goal) and 225 min/wk of moderate-to-vigorous aerobic activity. Mean 12-mo changes in weight, body composition, serum insulin, CRP, and 25(OH)D were compared between groups (intent-to-treat) by using generalized estimating equations.

RESULTS

A total of 86% of participants completed the 12-mo measurements. The mean (95% CI) change in 25(OH)D was 13.6 (11.6, 15.4) ng/mL in the vitamin D3 arm compared with -1.3 (-2.6, -0.3) ng/mL in the placebo arm (P < 0.0001). Changes in weight [-7.1 (-8.7, -5.7) compared with -7.4 (-8.1, -5.4) kg], body mass index (in kg/m(2): both -2.8), waist circumference [-4.9 (-6.7, -2.9) compared with -4.5 (-5.6, -2.6) cm], percentage body fat [-4.1 (-4.9, -2.9) compared with -3.5 (-4.5, -2.5)], trunk fat [-4.1 (-4.7, -3.0) compared with -3.7 (-4.3, -2.9) kg], insulin [-2.5 (-3.4, -1.7) compared with -2.4 (-3.3, -1.4) μU/mL], and CRP [-0.9 (-1.2, -0.6) compared with -0.79 (-0.9, -0.4) mg/L] [corrected] were similar between groups (all P > 0.05). Compared with women who achieved 25(OH)D <32 ng/mL, women randomly assigned to vitamin D who became replete (ie, 25(OH)D ≥32 ng/mL) lost more weight [-8.8 (-11.1, -6.9) compared with -5.6 (-7.2, -5.0) kg; P = 0.05], waist circumference [-6.6 (-9.3, -4.3) compared with -2.5 (-4.6, -2.0) cm; P = 0.02], and percentage body fat [-4.7 (-6.1, -3.5) compared with -2.6 (-3.9, -2.2); P = 0.04]. Among women with complete pill counts (97% adherence), the mean decrease in CRP was 1.18 mg/mL (46%) in the vitamin D arm compared with 0.46 mg/mL (25%) in the placebo arm (P = 0.03).

CONCLUSIONS

Vitamin D3 supplementation during weight loss did not increase weight loss or associated factors compared with placebo; however, women who became replete experienced greater improvements. This trial was registered at clinicaltrials.gov as NCT01240213.

Habitual consumption of coffee and green tea in relation to serum adipokines: a cross-sectional study

PURPOSE

Coffee and green tea consumption may be associated with circulating adipokines, but data are inconsistent, scarce or lacking. We examined the association of coffee and green tea consumption with serum adiponectin, leptin, visfatin, resistin and plasminogen activator inhibitor-1 (PAI-1) among a Japanese working population.

METHODS

The authors analyzed data (n = 509) from a cross-sectional survey among Japanese workers aged 20-68 years. Serum adipokines were measured using a Luminex suspension bead-based multiplexed array. Coffee and green tea consumption was assessed using a validated diet history questionnaire, and caffeine consumption from these beverages was estimated. Multiple regression analysis was performed with adjustment for potential confounding variables.

RESULTS

Coffee consumption was significantly, inversely associated with leptin and PAI-1 (P for trend = 0.007 and 0.02, respectively); compared with subjects consuming <1 cup per day, those consuming ≥4 cups per day had 13 and 10 % lower means of leptin and PAI-1, respectively. Similar associations were observed for caffeine consumption (P for trend = 0.02 for both leptin and PAI-1). Additionally, we noted a significant positive association between coffee consumption and adiponectin in men (P for trend = 0.046), but not in women (P for trend = 0.43, P for interaction = 0.11). Moreover, there was a positive association between coffee consumption and resistin in current male smokers (P for trend = 0.01), but not in male non-smokers (P for trend = 0.35, P for interaction = 0.11). Green tea consumption was not associated with any adipokine.

CONCLUSIONS

Higher consumption of coffee and caffeine but not green tea was associated with lower serum levels of leptin and PAI-1 in Japanese adults.

Does insulin resistance in type 2 diabetes alter vitamin D status?

AIMS

Data on changes of vitamin D due to insulin resistance are conflicting. We assessed vitamin D concentrations and parameters of glycemia and mineral homeostasis in patients with insulin resistant type 2 diabetes and in matched normal controls.

METHODS

Sixty-nine patients with type 2 diabetes and 60 matched normal control subjects were studied. After an overnight fast, blood was collected for measuring the parameters of glycemia (glucose, insulin and HbA1c), mineral profile (corrected calcium, phosphate and alkaline phosphatase), total 25(OH) vitamin D and parathyroid hormone (PTH) levels.

RESULTS

Patients had significantly elevated fasting glucose (P=0.0001), insulin (P=0.0003) and HbA1c (P=0.0005) than the controls had. They had significantly raised calculated insulin resistance compared with control subjects (P=0.0001). Patients and controls had similar levels of serum corrected calcium and ALP, whereas serum phosphate was significantly lower in the patients compared with controls (P=0.001). Patients and controls had similar levels of 25(OH)D, but the levels of 25(OH)D in both were in the deficiency range. Intact PTH was similar in the patients and controls. Levels of 25(OH)D did not demonstrate any relation with fasting insulin, insulin resistance, or HbA1c, but correlated negatively with intact PTH (r=-0.4, P=0.02).

CONCLUSION

This study demonstrated prevalent vitamin D deficiency in insulin resistant type 2 diabetic and normal subjects. Insulin resistance did not influence the status of vitamin D.

A novel approach localizes the association of vitamin D status with insulin resistance to one region of the 25-hydroxyvitamin D continuum

Vitamin D status has been implicated in insulin resistance, type 2 diabetes mellitus, and hypertension, but the range of vitamin D status values over which the association can be found is unknown. Our objective was to define this range in a cohort of nondiabetic adult Canadians. We used a regression modeling strategy, first adjusting insulin-response variables and systolic and diastolic blood pressure for BMI, waist circumference, weight, age, and sex. The resulting residuals were regressed against serum 25-hydroxyvitamin D [25(OH)D] concentration using successive 40% data blocks ranging from the 0th to the 60th percentile of 25(OH)D values. All of the predictor variables were significantly associated with each of the dependent variables, with BMI and waist circumference accounting for >98% of the explained variance. The vitamin D association was localized to the serum 25(OH)D range extending from ∼40 to ∼90 nmol/L (16-36 μg/L). We conclude that vitamin D status is inversely associated with insulin responsiveness and blood pressure. Consistent with the threshold response characteristic typical of nutrients, the association was strongest in a circumscribed region of the range of 25(OH)D values. There was no association at 25(OH)D values >80-90 nmol/L (32-36 μg/L), indicating that the vitamin D association applied principally to values below that level. The differences observed, if they can be further confirmed in prospective studies, are of a magnitude that would be clinically important.

Relationship between vitamin D and nonalcoholic fatty liver disease

Vitamin D is an important secosteroid hormone with pleiotropic effects, including regulation of cell proliferation, differentiation, apoptosis, and immunomodulation. Recently certain evidence has indicated that insufficiency of vitamin D or vitamin D deficiency is related to nonalcoholic fatty liver disease (NAFLD). Subjects with NAFLD have lower serum vitamin D levels than controls, and low vitamin D levels are closely associated with histologic severity of steatosis, necrosis, inflammation and fibrosis in NAFLD. Vitamin D-deficient diet aggravated high fat diet-induced hepatic inflammation in NAFLD models, while vitamin D supplementation improved hepatic histopathology. Vitamin D may act as a regulator in NAFLD through activating VDR and controlling various genes. Modulating hepatic stellate cells is an important mechanism underlying the antifibrotic effect of vitamin D in NAFLD. Vitamin D is a potential drug for treatment for NAFLD, and further prospective RCT studies are required to acquire sufficient evidence.