A new study using zebrafish is raising fresh concerns about the potential hidden health impacts of e-cigarettes, suggesting that vaping can disrupt delicate gut bacteria and alter behaviour, even without nicotine.
Researchers from Kyushu University in Japan exposed the small tropical fish – a common model in biomedical research due to genetic similarities to humans – to e-cigarette vapour in their water for seven days, mimicking typical vaping conditions.
Tse Ka Fai William, Associate Professor at Kyushu University’s Faculty of Agriculture said: ‘The gut microbiome is sensitive to environmental exposure, and its balance and stability are closely linked to overall health. We therefore investigated how e-cigarette vapor changes bacterial communities and what that might mean for the organism.’
The findings revealed that the heated vaping liquids produced known harmful byproducts such as formaldehyde. More significantly, the exposure scrambled the fish’s gut microbiome, the community of bacteria crucial for overall health. The balance of bacteria shifted as some types declined and others, known for breaking down toxins, became dominant.
The paper’s first author Thi Ngoc Mai Dong, from the Kyushu University’s Graduate School of Bioresource and Bioenvironmental Sciences. said: ‘Some bacteria become dominant and replace others, forming a new microbial community. The changes suggest that the fish, or rather the bacteria, can ‘feel’ the toxic substances in the water and want to adapt to the new environment.’
These gut changes were seen to occur with both nicotine and nicotine-free vapours. The team also observed behavioural changes in the exposed fish, including impaired escape responses, hinting at a possible link between gut disruption and brain function.
Tse added: ‘This research was partly motivated by our international students, who noticed e-cigarette use becoming more common among their peers, not only in Japan but worldwide.
‘We hope these findings can make consumers aware that e-cigarettes produce harmful substances, and support more transparent risk communication and regulation.’
While the results from fish cannot be directly applied to humans, they provide important biological clues. The study highlights that vaping introduces a complex mix of chemicals, many from undisclosed flavourings, into the body. This research aims to spark broader public and regulatory discussion about the potential long-term risks of e-cigarettes, which are often marketed as a safe alternative to smoking but whose full health profile remains under intense scientific scrutiny.
The research can be accessed here.
Photo: Nery Zarate
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