Vitamin D can affect liver function through the vitamin D receptor (VDR). VDR is naturally present in liver cells and its increased expression can reduce inflammation in chronic liver diseases (Benetti et al. Vitamin D also has antifibrotic, proliferative, and inflammatory effects on the liver. The pleiotropic effects of vitamin D indicate a relationship between its deficiency and numerous chronic diseases, such as DM, cardiovascular, autoimmune and infectious diseases, several types of cancer, and chronic liver diseases.
Vitamin D synthesized from skin and dietary sources can be stored in adipocytes or undergo liver 25-hydroxylation. The association between vitamin D levels and non-alcoholic fatty liver disease (NAFLD) has been increasingly identified in recent research. Another important point to consider in relation to vitamin D levels is that low vitamin D levels may be due to a probable sedentary lifestyle, and no questions were asked to the patient or the control group about their lifestyle. It is well known that intestinal absorption of vitamin D could be affected in the presence of cholestasis, since dietary absorption of vitamin D depends on bile salts.
In fact, clinical studies suggest that these parameters may improve with vitamin D supplementation; however, prospective, randomized, placebo-controlled studies are required to establish firm conclusions. Patients with fatty liver disease had a significant decrease in serum levels of 25 (OH) and D compared to patients without this disease and, in addition, as the stage of the disease increased, vitamin D levels decreased significantly. Vitamin D is an important secosteroid hormone with a known effect on calcium homeostasis, but lately it is increasingly recognized that vitamin D is also involved in cell proliferation and differentiation and has immunomodulatory and anti-inflammatory properties. Finally, the association between vitamin D deficiency and the prognosis of liver diseases, such as progression to NASH or the onset of HCC, should be addressed through prospective studies.
Patients with NAFLD have low serum vitamin D concentrations, suggesting that vitamin D may play a role in the development of NAFLD. Therefore, the objective of this study was to determine the relationship between the serum level of vitamin D evaluated by 25-hydroxyvitamin D3 (25 (OH), D and NAFLD in adults. Vitamin D promotes the immune system's innate response and has a “self-regulatory effect” by limiting the adaptive response. In addition, it is highly recommended to conduct future studies that compare vitamin D levels in different liver diseases.