Abstract
BACKGROUND: The association between vitamin C and the risk of developing non-alcoholic fatty liver disease remains controversial. The aim of the present study is to examine any correlation between serum vitamin C and the risk of non-alcoholic fatty liver disease. METHODS: Our study enrolled 3374 participants aged ≥ 20 years from the National Health and Nutritional Survey (2003-2006). Nonalcoholic fatty liver disease was defined as the US Fatty Liver Index ≥ 30 in the absence of other chronic liver disease. Multivariate logistic regression and the fitted smoothing curves were adopted for analyzing the correlation between serum vitamin C levels and the risk of developing non-alcoholic fatty liver disease. RESULTS: After adjusting for all the covariates, it was discovered that serum vitamin C was negatively correlated with the risk of nonalcoholic fatty liver disease (odds ratio: 0.664, 95% CI: 0.512-0.860, P = .002). Through smooth curve fitting, it was further noticed that the relationship between serum vitamin C and the risk of non-alcoholic fatty liver disease was non-linear. The inflection point was 0.92, and to its left, a negative correlation was seen between vitamin C and non-alcoholic fatty liver disease (odds ratio: 0.451, 95% CI: 0.288- 0.706, P = .001). To the right of the inflection point, however, the correlation between vitamin C and non-alcoholic fatty liver disease was not found to be significant. CONCLUSION: The correlation was non-linear between serum vitamin C levels and the risk of developing non-alcoholic fatty liver disease. Serum vitamin C was negatively correlated with the risk of non-alcoholic fatty liver disease when its level was less than 0.92 mg/dL.