Triple Tobacco Users Show Higher Liver Enzyme Levels in Korean Survey

Adults who smoke cigarettes and also use e-cigarettes and heated tobacco products show measurably higher levels of the liver enzyme alanine aminotransferase (ALT) than people who use no tobacco products at all, according to a cross-sectional analysis of the Korea National Health and Nutrition Examination Survey (KNHANES) covering 2019 to 2022. The study, published in BMC Public Health by Chaeeun Kang and Kyeezu Kim, is among the first to examine how combined use of non-cigarette tobacco or nicotine products relates to liver function in a large national sample. Non-cigarette products such as electronic cigarettes and heated tobacco devices have been marketed as less harmful alternatives to conventional cigarettes, but their short time on the market has left their safety profile, particularly for liver health, insufficiently studied.

Research on people who use several different tobacco products simultaneously has also been limited. To address this gap, the researchers classified 19,374 adults into five groups based on whether they had ever used cigarettes, e-cigarettes, or heated tobacco products: non-users of any product; cigarette-only smokers; cigarette smokers who also used e-cigarettes but not heated tobacco; cigarette smokers who also used heated tobacco but not e-cigarettes; and triple users who had used all three. The team built linear regression models adjusting for demographic and health-related variables, and then stratified the analyses by sex and by body mass index (BMI) status.

Because the design is cross-sectional, the findings show associations at a single point in time and cannot establish that tobacco use caused the enzyme changes. The clearest signal emerged for ALT. Compared with non-users, triple users had the greatest ALT levels in the fully adjusted model (β = 1.57, p < 0.001), followed by cigarette-plus-e-cigarette users (β = 1.09, p = 0.044) and cigarette-plus-heated-tobacco users (β = 1.00, p = 0.035).

In other words, the more product types a person had used, the higher their ALT tended to be, with the combination of all three products standing out most strongly. The association was more clearly visible in men, where the pattern resembled that seen in the total sample. BMI stratification added a further nuance.

When participants were split by body mass index, the elevated ALT association appeared only among triple users with normal BMI status (β = 2.11, p = 0.003). The authors propose a possible mechanism: additional use of heated tobacco products was related to higher serum ALT levels, especially in males, possibly because heated tobacco devices deliver nicotine in a way that increases nicotine absorption. As an observational, cross-sectional study, the analysis identifies associations rather than proven causal effects, and the results reflect the Korean adult population surveyed between 2019 and 2022.

Subject of Research: Association between combined use of cigarettes, e-cigarettes and heated tobacco products and liver function in Korean adults

Article Title: Combined use of alternative tobacco products and liver function: findings from the Korea National Health and Nutrition Examination Study 2019–2022

Article References: Kang, C., & Kim, K. (2026). Combined use of alternative tobacco products and liver function: findings from the Korea National Health and Nutrition Examination Study 2019–2022. BMC Public Health. https://doi.org/10.1186/s12889-026-29642-w

Image Credits: AI Generated

DOI: 10.1186/s12889-026-29642-w

Keywords: liver function, ALT, e-cigarettes, heated tobacco products, tobacco, nicotine, KNHANES, cross-sectional study, BMC Public Health, South Korea, public health, triple users