Wednesday, 29 May 2019 01:08

By Dr Farsalinos

A new study published in the well-known Journal of the American College of Cardiology (JACC) identified that e-cigarette flavorings, particularly cinnamon, can be toxic to the heart by having oxidative and pro-inflammatory properties. Researchers used human-induced pluripotent stem cell–derived endothelial cells (iPSC-ECs) which were exposed to six commercially-available e-cigarette liquids (which were not vaped, they were used in liquid form). They identified increased cytotoxicity, oxidative stress and inflammatory response, particularly with cinnamon and menthol flavored liquids. Another part of the study examined the acute effects of using e-cigarette or tobacco cigarette by collecting serum from 5 smokers and 4 e-cigarette users (2 of whom were dual users) and measuring several markers of inflammation and response of endothelial cells in vitro. This part of the study is of limited value since it is irrelevant to flavors effects and included very few participants. I wonder, however, how hard it is to find exclusive e-cigarette users in the US so that you can avoid combining exclusive and dual users into one group.

I marked with bold letters above that e-cigarette liquids were used in their original liquid form instead of being used with an e-cigarette. This means that the effects observed by the authors were not related to the heating process that can produce thermal degradation products. Therefore, it is interesting to look at the literature on the effects of cinnamaldehyde on inflammatory processes and oxidative stress. Interestingly enough, there is a lot of literature about cinnamaldehyde having anti-oxidant, anti-inflammatory, anti-cancer properties, anti-diabetic and cardioprotective effects. For example, cinnamaldehyde has been found to reduce plasma glucose levels by increasing (i.e. improving) insulin sensitivity and increasing glucose uptake by cells, and to improve lipid homeostasis in diabetic rats (here). Cinnamaldehyde is also reported to have antimicrobial properties through various mechanisms, and these properties can be used to inactivate pathogens in food, protect farm animals and poultry from infections and perhaps even contribute to the treatment of drug-resistant bacterial infections (here). Cardioprotective effects of cinnamaldehyde include prevention of cardiac remodeling, fibrosis and hypertrophy (here), reduction in ischemic myocardial injury by reducing oxidative stress and increasing anti-oxidant activity (here), reducing endothelial dysfunction induced by high glucose (here), having antithrombotic properties and reducing platelet aggregation (here), and promoting vasodilation, both endothelium-dependent (here) and independent (here). Anti-oxidant and anti-inflammatory properties of cinnamaldehyde were found applicable to other disease conditions such as rheumatoid arthritis too (here). Cinnamaldehyde was also found to have anti-cancer and neuroprotective activity (for Alzheimer disease – here).

I am not suggesting that cinnamaldehyde is the miracle drug of the 21st century. All the above are mainly in vitro cell or animal studies. I am also not suggesting that it is safe, harmless or beneficial to vape cinnamon-flavored liquids. I will emphasize, however, once again that the study published in JACC used e-cigarette liquids in liquid form. Thus, cinnamaldehyde in the cinnamon-flavored liquids was not different from cinnamaldehyde present in food. In fact, if the observed effects are attributed to cinnamaldehyde, then cinnamaldehyde in food products must be equally toxic to endothelial cells.

In conclusion, cell and animal studies show conflicting results on the effects of cinnamaldehyde. It is possible, however, that the effects observed in the recent study were irrelevant to cinnamaldehyde and could be attributed to other compounds in the liquids. Still, I don’t think that this in vitro study can truly represent a model to understand the cardiovascular effects of e-cigarette flavorings.