Vitamin D deficiency is a major public health problem worldwide. Some previous studies showed this condition may play a role for development of NAFLD. However the data in this context are inconsistent. This study was conducted to determine the association between vitamin D levels and NAFLD.

We utilized the data of 4276 participants 18 years and more in phase 2 of our cohort study conducted in 2016-2017. NAFLD and its grade were evaluated by ultrasound. Vitamin D levels were measured and categorized. A level ≥30 ng/dl was considered normal, 20-29 ng/dl considered vitamin D insufficiency and less than 20ng/dl considered vitamin D deficiency. Mean vitamin D levels and the frequency of normal level, vitamin D insufficiency and vitamin D deficiency were estimated based on various degrees of NAFLD. Simple and multiple multinomial logistic regression analyses were performed in which NAFLD considered outcome and the vitamin D level independent variable. In multiple multinomial logistic regression analysis age, BMI, CRP levels, season and history of vitamin D supplement use were considered potential mediators.

Mean vitamin D levels in men without NAFLD, with grade 1 of NAFLD, grade 2 of NAFLD and grade 3 of NAFLD was 22.62 ±15.76, 20.47±11.95, 20.19±13.87 and 18.51±12.42 (p-value<0.001), respectively. In women the related values were 19.20±18.53, 19.99±18.79, 21.66±21.82 and 20.31±16.27, respectively (p-value=0.157). The prevalence of a normal vitamin D (based on percent) in men without NAFLD, with grade 1 of NAFLD, grade 2 of NAFLD and grade 3 of NAFLD was 17.34 (95%CI=15.11-19.58), 13.18 (95%CI=10.19-16.18), 8.94 (95%CI=5.77-12.12) and 10.28 (4.43-16.13) [p-value<0.001]while this prevalence in women was 16.31 (95%CI=13.82-18.81), 16.91 (95%CI=13.52-20.30), 17.49 (95%CI=12.87-22.11) and 19.15 (95%CI=7.47-30.83) [p-value=0.816], respectively. Although, there was only a significant relationship between vitamin D levels and NAFLD in simple multinomial logistic regression analysis in men, no independent relationship was detected between them in multiple multinomial analyses both in men and women.

Although a relationship was detected between serum vitamin D level and NAFLD in men, no independent association was detected between them both in men and women.