Discussion
NAFLD, fatty liver, abdominal obesity, Milk, milk reduced hepatic apoptosis
FATTY LIVER, OBESE, BLIND, VITAMIN D DEFICIENCY
This study was the first study that assessed the effects of low-fat dairy products fortified with nano-encapsulated vitamin D on liver function parameters in adults with abdominal obesity. After ten weeks of intervention, treatment with vitamin D fortified dairy products was associated with a significant, increase in serum vitamin D concentrations, although serum 25(OH)D levels did not reach a sufficient serum concentration (> 30 ng/ml). A significant reduction from baseline levels was observed in serum ALP in both the fortified dairy groups compared to unfortified dairy products. This finding was consistent with previous studies [Nam et al. reported that the activity of aminotransferases was positively correlated with serum levels of vitamin D, and it has been shown that vitamin D deficiency is an independent risk factor for elevated aminotransferases in obese individuals [In our study, the ALT and AST were reduced in all groups except for fortified yogurt. This finding was in contrast with the findings of the mentioned studies. In contrast, few studies reported no association between serum levels of vitamin D and AST and ALT in patients with NAFLD who were supplemented with oral capsule consisting of 50,000 IU vitamin D3 [It might also be hypothesize that the improvement in ALT and AST in our study might be due to the effect of consumption of dairy products, not vitamin D supplementation. Animal studies reported that branched-chain amino acids (BCAAs) from casein in milk reduced hepatic apoptosis in Sprague Dawley rats. Hepatocyte function was altered by BCAAs, which was observed by the improvement of hepatocyte aminotransferases activity [The observed changes in liver function biomarkers may be caused via the VDR on the liver. VDR has been widely detected in the liver, and the performance pattern of this receptor is through connection to its own ligand and entering the nucleus from the cytoplasm [Milk has been known for its myotropic effects due to its various nutritional components; although, this effect is obtained by high amount of intake along with exercise [The sample size and the design of this study (total blind RCT) can be considered as the strengths of this study. Furthermore, this study was the first study to investigate the efficacy of low-fat dairy products fortified with nano-encapsulated vitamin D on liver function and relative enzymes.One of the limitation points of this study was not investigating the presence of fatty liver in participants. This factor could be effective in interpreting the results. However, this restriction did not significantly affect our results as evidenced by similar findings reported by previous studies. Study duration might be another limitation of our study. Since the data in this study were obtained from a larger study with a different objective, the duration of the study could not be altered. There is a need for further studies to assess the effects of vitamin D supplementation on liver function biomarkers for longer periods. Furthermore, this study only evaluated the final outcome of vitamin D fortification on liver enzymes in abdominally obese individuals. Therefore, there is a need for further studies to evaluate the possible mechanisms of this effect.