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.