Flavourings added to e-cigarettes and other tobacco products appear to harm the endothelial lining of blood vessels, say the authors of a recent paper.
The in-vitro study showed that exposing endothelial cells to flavouring compounds led to an increase in inflammation and impaired nitric oxide production, both of which are markers for endothelial damage.
“Increased inflammation and a loss of nitric oxide are some of the first changes to occur leading up to cardiovascular disease and events like heart attacks and stroke, so they are considered early predictors of heart disease,” said the lead author, Jessica Fetterman of the Whitaker Cardiovascular Institute, Boston, Massachusetts. “Our findings suggest that these flavouring additives may have serious health consequences.”
The research, published in Arteriosclerosis, Thrombosis, and Vascular Biology
, explored the effects of the flavouring compounds menthol or eugenol (clove flavouring) exposure on vascular endothelial cells from nine non-smokers matched to six menthol and six non-menthol cigarette smokers.
They found that cells from smokers of either type of cigarette already exhibited impaired stimulated nitric oxide production and exposure to menthol or eugenol induced a similar response in cells from non-smokers.
They then exposed commercially available human aortic endothelial cells to the flavourings vanillin, menthol, cinnamaldehyde, eugenol, dimethylpyrazine (strawberry), diacetyl (butter), isoamyl acetate (banana), eucalyptol and acetylpyridine (burnt) for 90 minutes at various concentrations.
The team found that, at biologically relevant concentrations, vanillin, menthol, cinnamaldehyde, eugenol and acetylpyridine all induced both impaired nitric oxide production and increased inflammation.
The researchers said that future research would need to look at the effects of heating on the toxicity of these compounds, and establish their concentrations in bloodstream after e-cigarette use.
In 2017, an EU directive created increased restrictions on the sale of flavoured cigarettes, which will be completely unavailable in the UK from 2020. However, different rules apply to e-cigarettes.
This latest piece of research follows a statement from the Forum of International Respiratory Societies calling for e-cigarettes to be regulated in the same way as tobacco to minimise harm to children and young people.
 Fetterman JL, Weisbrod RM, Feng B et al. Flavorings in tobacco products induce endothelial cell dysfunction. Arteriosclerosis, Thrombosis, and Vascular Biology. 2018;38(6). doi: 10.1161/ATVBAHA.118.311156