Researchers from CHA University assessed 1,812 subjects above the age of 18, all of whom had participated in the Sixth Korea National Health and Nutrition Examination Survey (KNHANES VI) conducted by the Korea Centers for Disease Control and Prevention (CDC).
Of the 1,812 subjects, 22.6% (409) were found to have non-alcoholic fatty liver disease. 56.7% of these patients were male, and 57.2% had higher BMI (above 28), as well as a greater incidence of metabolic syndrome.
However, the proportion of those who had vitamin D insufficiency did not differ between the patients and non-patients (77.5% versus 77.4%).
While previous studies had produced inconsistent results on the relationship between vitamin D insufficiency and non-alcoholic fatty liver disease, this study discovered that "vitamin D insufficiency was not related" to the risk or prevalence of the disease.
Instead, BMI, diabetes and triglyceride levels were pinpointed as risk factors for non-alcoholic fatty liver disease, even among subjects who were not obese or who did not have metabolic syndrome.
Additionally, the study used the BMI, AST / ALT Ratio, Diabetes (BARD) score to determine liver fibrosis in its subjects, and found that the "proportion of significant fibrosis by BARD score did not differ according to vitamin D status".
While vitamin D insufficiency and deficiency have been associated with illnesses such as cancer and heart and brain diseases, any association it might have with non-alcoholic fatty liver disease has been less consistent.
Although earlier studies said vitamin D insufficiency was related to the "presence, severity, and / or progression" of non-alcoholic fatty liver disease, more recent studies have said otherwise. In fact, one study even reported that vitamin D supplementation induced progression of the disease in mice on high-fat diets.
A recent RCT on the effect of oral vitamin D supplementation on non-alcoholic fatty liver disease patients found that vitamin D supplements "did not have any beneficial effect on hepatic steatosis and metabolic or cardiovascular parameters".
Furthermore, previous studies on the link between vitamin D and non-alcoholic fatty liver disease had limited data due to the small number of subjects involved, or the participation of subjects who already exhibited risk factors for the disease, such as obesity or diabetes.
The study concluded that "traditional risk factors such as higher BMI, and diabetes correlated with the presence" of non-alcoholic fatty liver disease, not vitamin D insufficiency; this was the case even in non-obese patients.
“The Association between Vitamin D Insufficiency and Nonalcoholic Fatty Liver Disease: A Population-Based Study”
Authors: Yeonjung Ha, Seong Gyu Hwang, Kyu Sung Rim