nonalcoholic fatty liver disease ( nafld ) is one of the most common chronic liver diseases in the worldwide and it is associated with chronic diseases such as diabetes and heart disease .
nafld is associated with insulin resistance and is defined as fat accumulation in liver , exceeding 5% of liver weight , in the absence of ethanol intake > 10 g / day .
the first one is about the development of insulin resistance that explains the effect of insulin resistance in nafld .
the second theory is increased inflammation which can lead to nafld . in a study conducted in japan
, a significant relationship was observed between the level of serum c - reactive protein ( crp ) and risk of nafld .
however , in another study , no significant correlation was seen between serum crp and nafld .
vitamin d is a fat - soluble vitamin that exists in a number of food products such as oils and dairy products .
vitamin d is traditionally known as a regulator of calcium and phosphorus metabolism , but in recent years a significant relationship has been observed between serum levels of vitamin d and risk of chronic diseases such as diabetes and cardiovascular diseases .
vitamin d receptors are present in more than 38 tissues and its receptors affect genes controlling oxidative stress and inflammation .
there are several lines of evidence demonstrate an association between vitamin d and liver disease .
however , in several studies , there were no association between vitamin d concentration and severity of fatty liver .
the effect of vitamin d on its receptor in these cells regulates and balances the inflammation and oxidative stress .
moreover , several studies have confirmed the relationship between serum vitamin d levels and inflammation . due to the role of inflammation in nafld ,
hence , the purpose of this study was to investigate the effect of vitamin d supplementation on inflammation in patients with nafld .
a randomized double - blind placebo - controlled clinical trial was conducted on 60 patients ( 30 - 70 years ) with nafld .
samples were calculated with a confidence interval of 95% and 80% power of the test by below formula ( s = 1.7 , d = 0.7 ) .
this study was conducted in metabolic liver disease research center in isfahan university of medical sciences , isfahan , iran .
the study was performed with the approval of isfahan university of medical sciences local ethics committee .
exclusion criteria in our study were defined as acute illnesses , chronic kidney disease , hyperparathyroidism , hypoparathyroidism , chronic heart failure , hepatitis c or hepatitis b , wilson syndrome , history of chronic liver diseases , or disorders that affect gallbladder and bile ducts , pregnancy or history of taking any drugs affecting levels of alt including ( valproic acid , tamoxifen , 3-hydroxy-3-methylglutaryl - coenzyme a reductase inhibitors , metformin , angiotensin - converting enzyme 1 and angiotensin - converting enzyme - related 1 ) .
subjects should not intake oral vitamin d / calcium / multivitamin supplementation in the previous study .
participants were divided into two groups using permuted block randomization : ( a ) 30 patients in vitamin d group ( capsules containing 50,000 iu vitamin d ) , ( b ) 30 patient in the placebo group .
intervention period followed for 10 weeks and patients received vitamin supplements or placebo capsules every week . to evaluate the acceptability of vitamin d supplementation , serum 25-hydroxy vitamin d level was measured at the beginning and end of the study .
dietary records were collected every 2 weeks , and intakes were determined based on estimated values in household measurements . to obtain nutrient intakes of participants on the basis of these 5-d food diaries , nutritionist iv software ( version 7.0 ; n - squared computing , salam , or , usa ) , which was modified for iranian food items were used .
physical activity levels estimated as metabolic equivalent of task hours per week ( met - hr / wk ) .
met - hr / wk for each exercise program calculated ( days per week  hours of exercise each time  met equivalent of exercise ) and summed of all met - min / wk values for each patient evaluated .
height and body weight were measured while the subjects were in a standing position at baseline and 10 week .
25-hydroxy vitamin d was assessed by using a commercial elisa kit ( immuno diagnostic systems ) . at the beginning and the end of the study .
ast and alt serum levels were measured through enzymatic photometric method ( ifcc ) with a sensitivity of 2 u / l and a coefficient of variation of 14% ( alt , ast , and alkaline phosphatase ( alp ) were measured by commercially available enzymatic reagents ( pars azmoon ) on a bt-3000 ( biotechinica ) autoanalyzer .
crp serum was measured by high - sensitivity enzyme ( test pars tehran , tehran , iran ) .
level of liver esteatosis was assessed by using ultrasonography with esaote medical ultrasound machine ( convex 3.5 mhz ) at the beginning and the end of the study .
us performed by the same expert radiologist with the same instrument in the begging and the end study .
hepatic ultrasonography was conducted by someone who is unaware of the objectives of the study .
patients for ultrasound should be fasting for 8 h. ultrasonography is performed in the supine position .
echogenicity the liver , the presence or absence of bulky tumors cystic or solid and calcification was assessed .
independent - samples student 's t - test was used to detect differences in general characteristics and dietary intakes between two groups . in this analysis
chi - square test for comparison the grades of fatty liver between two groups of placebo and intervention used and paired t - test used to assess the within group comparison of quantitative variables .
all statistical analyses conducted using statistical package for the social sciences ( spss ) , version 16 ( spss inc . , chicago , usa ) .
a randomized double - blind placebo - controlled clinical trial was conducted on 60 patients ( 30 - 70 years ) with nafld .
samples were calculated with a confidence interval of 95% and 80% power of the test by below formula ( s = 1.7 , d = 0.7 ) .
this study was conducted in metabolic liver disease research center in isfahan university of medical sciences , isfahan , iran .
the study was performed with the approval of isfahan university of medical sciences local ethics committee .
exclusion criteria in our study were defined as acute illnesses , chronic kidney disease , hyperparathyroidism , hypoparathyroidism , chronic heart failure , hepatitis c or hepatitis b , wilson syndrome , history of chronic liver diseases , or disorders that affect gallbladder and bile ducts , pregnancy or history of taking any drugs affecting levels of alt including ( valproic acid , tamoxifen , 3-hydroxy-3-methylglutaryl - coenzyme a reductase inhibitors , metformin , angiotensin - converting enzyme 1 and angiotensin - converting enzyme - related 1 ) .
subjects should not intake oral vitamin d / calcium / multivitamin supplementation in the previous study .
participants were divided into two groups using permuted block randomization : ( a ) 30 patients in vitamin d group ( capsules containing 50,000 iu vitamin d ) , ( b ) 30 patient in the placebo group .
intervention period followed for 10 weeks and patients received vitamin supplements or placebo capsules every week . to evaluate the acceptability of vitamin d supplementation , serum 25-hydroxy vitamin d level was measured at the beginning and end of the study .
dietary records were collected every 2 weeks , and intakes were determined based on estimated values in household measurements . to obtain nutrient intakes of participants on the basis of these 5-d food diaries , nutritionist iv software ( version 7.0 ; n - squared computing , salam , or , usa ) , which was modified for iranian food items were used .
physical activity levels estimated as metabolic equivalent of task hours per week ( met - hr / wk ) .
met - hr / wk for each exercise program calculated ( days per week  hours of exercise each time  met equivalent of exercise ) and summed of all met - min / wk values for each patient evaluated .
height and body weight were measured while the subjects were in a standing position at baseline and 10 week .
25-hydroxy vitamin d was assessed by using a commercial elisa kit ( immuno diagnostic systems ) . at the beginning and the end of the study .
ast and alt serum levels were measured through enzymatic photometric method ( ifcc ) with a sensitivity of 2 u / l and a coefficient of variation of 14% ( alt , ast , and alkaline phosphatase ( alp ) were measured by commercially available enzymatic reagents ( pars azmoon ) on a bt-3000 ( biotechinica ) autoanalyzer .
crp serum was measured by high - sensitivity enzyme ( test pars tehran , tehran , iran ) .
level of liver esteatosis was assessed by using ultrasonography with esaote medical ultrasound machine ( convex 3.5 mhz ) at the beginning and the end of the study .
us performed by the same expert radiologist with the same instrument in the begging and the end study .
hepatic ultrasonography was conducted by someone who is unaware of the objectives of the study .
patients for ultrasound should be fasting for 8 h. ultrasonography is performed in the supine position .
echogenicity the liver , the presence or absence of bulky tumors cystic or solid and calcification was assessed .
normality of studied variables was evaluated using kolmogorov  smirnovtest or probability - probability plot . for nonnormal variables ,
independent - samples student 's t - test was used to detect differences in general characteristics and dietary intakes between two groups . in this analysis
chi - square test for comparison the grades of fatty liver between two groups of placebo and intervention used and paired t - test used to assess the within group comparison of quantitative variables .
all statistical analyses conducted using statistical package for the social sciences ( spss ) , version 16 ( spss inc . , chicago , usa ) .
the study flow chart shows the screening , randomization and follow - up of the participants [ figure 1 ] . in this study , 29 men and 31 women participated .
data shows that 23.6% and 10.9% of our subjects have abnormal alt and ast levels at baseline , respectively .
compliance with the treatments was good in both groups and no side - effects were presented . on the basis of 5-d dietary intake and physical activity records , no significant differences were seen between the two groups [ table 3 ] . the comparison of subclinical characteristics at baseline and after intervention of study adjusted changes in metabolic variables in nafld who received either vitamin d supplements or placebo fatty liver grades in nafld who received either vitamin d supplements or placebo dietary intakes and physical activity of nafld who received either vitamin d supplements or placebo throughout the study vitamin d supplementation resulted in an increase of serum 25(oh ) d concentrations in inter group ( p < 0.05 ) and intra - group ( p < 0.05 ) . at the end of study , in the intervention group , tg and crp reduced significantly compare with baseline ( p < 0.05 ) .
a significant increase was seen in calcium serum in the intervention group in comparison with baseline ( p < 0.05 ) and compared with the placebo group ( p < 0.05 ) . after adjusting for baseline values , levels of alt ,
ast , tg and crp were reduced in the intervention group in comparison with the placebo group , but these changes were not significant between two groups after intervention .
this study was the first one that investigated the effect of vitamin d supplementation on inflammation in patients with nafld . in this study ,
vitamin d supplementation did not reduce inflammation in patients with nafld in the intervention group compared with the control group .
in addition , vitamin d supplementation did not significant effect on serum tg levels and liver enzymes .
several studies have shown significant relationship between low serum vitamin d and increase inflammatory markers . in a study conducted by grossmann et al .
, 12 weeks of vitamin d supplementation caused a significant decrease in the levels of inflammatory factors in patients with cystic fibrosis . in another study
on 328 african - american patients , vitamin d supplementation significantly decreased systemic inflammation in these patients . in another study ,
the effect of vitamin d supplementation was investigated on inflammatory markers in patients with type 2 diabetes . in this study ,
vitamin d supplementation significantly decreases systemic inflammation and crp concentration in patients with type 2 diabetes .
however , in several studies , vitamin d supplementation had no effect on systemic inflammation and crp .
vitamin d affects through receptors on these organs and regulates pro - inflammatory and systemic inflammation in the body .
in addition , vitamin d with binding to its receptors in monocytes can reduce pro - inflammatory cytokines .
the first one was use of ultrasound method for diagnosis of fatty liver disease , while for accurate diagnosis of fatty liver , liver biopsy should be used .
the second limitation was a small sample size of participants , especially in grades one and three .
vitamin d supplementation had no effect on crp and other variables in the intervention group compared with the placebo group .
further studies with strong design and more sample must conduct to demonstrate the effect of vitamin d supplementation on inflammation in patients with nafld .
 background : nonalcoholic fatty liver disease ( nafld ) is the most common chronic liver disease in the worldwide . 
 it is associated with chronic disorders such as diabetes and heart diseases . 
 inflammation is one of the basic causes of metabolic diseases . 
 several studies have shown that vitamin d can reduce inflammation . 
 the purpose of this study was to investigate the effect of vitamin d supplementation on inflammation in patients with nafld.methods:this study involved 60 nafld patients , divided equally into two intervention and placebo groups . during 10 weeks 
 , patients in the intervention group receive vitamin d ( capsules containing 50,000 iu vitamin d ) , weekly . 
 vitamin d levels , c - reactive protein ( crp ) , triglyceride ( tg ) , aspartate aminotransferase ( ast ) and alanine aminotransferase ( alt ) levels were measured at the beginning and end of the study . 
 data were analyzed using analysis of covariance tests . 
 analyses were done using spss software ( version 16 ) ( spss inc . , 
 chicago , usa ) . 
 p < 0.05 set as significant level.results:vitamin d supplementation resulted in an increase of serum 25(oh ) d concentrations in inter group ( p < 0.05 ) and intra - group ( p < 0.05 ) in intervention group . at the end of the study , in the intervention group , 
 tg and crp reduced significantly compare with baseline ( p < 0.05 ) . 
 a significant increase was seen in calcium serum in the intervention group in comparison with baseline ( p < 0.05 ) and compared with the placebo group ( p < 0.05).conclusions : vitamin d supplementation had no effect on crp and other variables in the intervention group compared with the placebo group . 
 further studies with strong design and more sample must conduct to demonstrate the effect of vitamin d supplementation on inflammation in patients with nafld . 