Objective: To demonstrate the effect of vitamin D replacement on liver enzymes and inflammatory markers in non-alcoholic fatty liver disease (NAFLD) patients.

Materials and Methods: A randomized, double-blind, placebo-controlled trial was conducted at liver clinic at Vajira Hospital. Sixty eligible NAFLD participants, who have alanine transaminase (ALT) elevation with vitamin D insufficiency, were randomly enrolled into 2 groups and assigned to receive either a 40,000 IU per week of vitamin D replacement or a placebo for 20 weeks. Serum ALT, inflammatory markers, and transient elastography (TE) were compared before and after the 20-week vitamin D replacement period to evaluate the anti-inflammatory effect of vitamin D.

Results: At the beginning of the study, there were no statistical differences between the 2 groups of patients on the baseline characteristics, including gender, age, body mass index (BMI), ALT, inflammatory markers, transient elastogram and bioelectrical impedance analysis except diabetes and metformin use. At the end of the present study, ALT (-27.4+24.6 U/L, p<0.001), IL-6 (-0.5+1.1 pg/mL, p = 0.036) and ferritin (-52.8+96.3 ng/mL, p = 0.006) decreased significantly in the vitamin D group, while CAP (-4.8+26.1 dB/m), hsCRP (-0.4+1.7 mg/L) were non-significantly decreased. In addition, the decrease of serum ALT in the vitamin D group was significantly greater than in the placebo group (-27.4+24.6 U/L vs. -12.7+25.5 U/L, respectively, p = 0.026). Furthermore, all patients in the vitamin D group did not experience any side effects from hypervitaminosis D or hypercalcemia.

Conclusion: Oral vitamin D replacement could significantly reduce ALT in vitamin D insufficiency NAFLD patients with previous ALT elevation, which may mediate via alleviation of inflammatory mechanisms, without evidence of short-term adverse effects.