Does Vitamin D Independently Lower the Severity of Nonalcoholic Fatty Liver Disease? A Case-Control Study in Khuzestan Province, Iran

Abstract

Background: A global pandemic of hypovitaminosis D is emerging. Vitamin D is essential for metabolic processes, particularly those involving free fatty acids (FFA), which transition from peripheral tissues to the liver. Consequently, its deficiency could promote the production of hepatocyte fat. Objectives: This study investigated the hypothesis that vitamin D levels, as an independent factor, directly impact nonalcoholic fatty liver disease (NAFLD) in individuals of varying grades, ages, and genders in Khuzestan province, Iran. Methods: Serum 25(OH)D levels were retrospectively assessed in 400 individuals, comprising 200 NAFLD patients and 200 healthy controls. Vitamin D deficiency was defined as serum 25(OH)D levels below 20 ng/mL. The study aimed to exclude any potential confounding variables that could have affected the relationship between vitamin D and NAFLD. In this investigation, the receiver operating characteristic (ROC) curve was utilized. Results: Twenty percent of controls and 70% of NAFLD patients had vitamin D deficiency. Serum 25(OH)D levels were significantly lower in NAFLD patients compared to healthy controls, with a mean of 24.95 ± 9.16 ng/mL versus 31.28 ± 12.52 ng/mL (P < 0.001). Those with NAFLD had significantly higher than normal liver enzyme [alanine transferase (ALT)] values (P < 0.001). The ROC curve analysis revealed that a blood 25(OH)D level below 26.4 ng/mL increases the risk of NAFLD with a 63.5% sensitivity and 66.5% specificity. Among female NAFLD patients, 28.8% had vitamin D deficiency, while 44.9% of male patients were deficient. The findings demonstrated that, in contrast to age, a greater Body Mass Index (BMI), gender, and vitamin D deficiency were significantly associated with an elevated risk of NAFLD. Conclusions: Regardless of any confounding variables, low levels of 25(OH) vitamin D are independently linked to NAFLD, and 26.4 ng/mL was identified as the precise cutoff value for vitamin D associated with an elevated risk of NAFLD.