Relationship between urinary cotinine and serum vitamin A levels in Korean adults: the Korea National Health and Nutrition Examination Survey (KNHANES), 2016-2018

Objective To examine the relationship between urinary cotinine and serum vitamin A levels in Korean adults. Methods A total of 4445 adults (age >= 19 years) participating in the Korea National Health and Nutrition Examination Survey (KNHANES) from 2016 to 2018 were classified by sex and as smokers/electronic cigarette users (SE) or non-smokers (NS). Data were analyzed using complex sample general linear models. Results There were no differences in dietary intake of vitamin A, carotene, or retinol between the SE and NS groups. Adjusted mean serum vitamin A levels were higher in the SE group compared with those in the NS group (0.63 mg/L vs 0.60 mg/L among men; 0.55 mg/L vs 0.51 mg/L among women). Among all participants, urinary cotinine and serum vitamin A levels were positively correlated (R-2 = 0.037). However, no correlation was observed in either the SE or NS groups individually. In a model adjusted for age, body mass index, sex, frequency of binge drinking, and dyslipidemia, a stronger correlation was observed (R-2 = 0.244). Conclusion In Korean adults, urinary cotinine levels were positively associated with serum vitamin A levels. Mean serum vitamin A levels were significantly higher in the SE group compared with the NS group.