This is what concerns me. Nicotine appears to be linked to the formation of podosome rosettes in cardiovascular tissues. Podosome rosettes are sort of like stalactites (those icicle-like rock formations in caves) which cause plaque build up in those tissues. This plaque build up is a well-known heart disease called atherosclerosis, hence my concern with the link between nicotine and heart disease. This implication would apply to nicotine patches/lozenges as well, not just e-cigs.
My general stance is that too much of anything can be bad for you. I feel that this is especially true for ingesting things that our bodies have not naturally evolved to ingest, particularly when it's done repeatedly and over long periods of time. As a result, I'm just as concerned of the FDA-approved flavorings as I am of the nicotine itself, since inhaling substances is not the same as digesting them.
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On a side note, I do feel healthier since having switched from cigs to e-cigs. Coughing has been reduced significantly, I don't get that "morning flem" in the shower like I used to, and don't get as winded when walking up flights of stairs, jogging, etc. There has got to be health benefits to not inhaling all of that carcinogenic crap found in tobacco cigarettes, I'm just a little dubious about long-term vaping not having any sort of health repercussions.