I agree with your second point, however, respectfully, your first point is incorrect (I was going to call it absolute bloody bullshit, but that would be the amphetamines talking).
Here's a better breakdown of carcinogens in cigarette smoke (same book, same author)[0]. The most lethal way tobacco smoking impacts health is through carcinogenic by-products created from metabolizing said tobacco.
"PAH, N-nitrosamines, aromatic amines, 1,3-butadiene, benzene, aldehydes, and ethylene oxide are probably the most important carcinogens because of their carcinogenic potency and levels in cigarette smoke."[0]
To elucidate on one of your points: nicotine isn't on any of the "carcinogens in tobacco" lists, because it, nor any of its metabolites, aren't carcinogens at any dosage that is practically applicable to humans.[1]
> The most lethal way tobacco smoking impacts health is through carcinogenic by-products created from metabolizing said tobacco.
Maybe, we're misunderstanding each other. But all those compounds you listed are directly present in smoke itself. I.e. they're not metabolic byproducts.
In fact they're not even related to tobacco specifically. (With the major exception of N-nitrosamine). Cannabis smoke (gram for gram) contains equivalent of higher levels of PAH, benzene, 1,3-butadiene, aldehyde, and aromatic amines.[1] These are all pretty much universal byproducts of burning any type of dried plant material, and the same reason that exposures are similar for wood-burning fireplaces.[2]
The paper describes finding an enzyme that can cleave catecholamine precursors. OK? There's literally only one catecholamine precursor that's used medically, and that's L-DOPA.
We know Parkinson's medications work, and very effectively. L-DOPA is used effectively, despite being metabolized by gut flora.
Major nitpick: Dopamine isn't the "feel good" chemical.
Endorphins are more accurately "feel good" chemicals.
Dopamine is involved in motivation through reward reinforcement, movement, and cognition in the human nervous system.
Another nitpick: L-DOPA isn't a building block of dopamine. It's dopamine with an extra molecule attached to it that makes it "inactive." This molecule gets snapped off by the AADC enzyme, which "activates" it. L-DOPA is the precursor to dopamine.
Third nitpick: We can understand how these gut flora affect ingestion of L-DOPA, and neurotransmitter precursors, by looking at how it's used in medical treatments. Most notably, Parkinson's patients. Suffice to say, it really makes no fucking difference, and orally-administered L-DOPA (with a dehydroxylaze inhibitor) is effective.
Whatever L-DOPA is stolen by gut-flora, can be augmented with a higher dosage. If for some strange reason, the converted L-DOPA -> Dopamine gets released into the digestive tract, and absorbed by the body, it's readily broken down in the blood. L-DOPA converts to dopamine in the blood-stream anyway, so it makes absolutely no difference.
I wanted this paper to be novel, but after reading it, it's not.
If we're nitpicking, endorphins act on opioid receptors of GABAergic neurons, inhibiting the release of GABA, which in turn disinhibits the release of dopamine in reward pathways.
That dopamine release is what is directly responsible for pleasure and euphoria associated with endorphin release.
1. LARPing is nomenculture in the infosec (netsec/"cybersecurity") world. It means someone is taking security a bit too seriously, like they're in a James Bond movie. They've fallen into delusions and paranoia that everyone has the capability of a state actor, and that all systems and all actions should be considered with this notion in-mind.
If someone is running TailsOS/Whonix/Qubes as their daily driver OS, and only browses from TOR, connected through a VPN/cellphone tether/coffee shop WiFi, with full hard-drive encryption using VeraCrypt+hidden partitions with a killswitch to zero out the harddrive if a certain password is entered, and runs their laptop with no battery, with a CoreBoot/LibreBoot flashed BIOS -- then they are taking this shit way too seriously and will be chided as a LARPer.
Yes yes, I understand security is important -- I used to be a vulnerability researcher who transitioned to "red teaming" for a government agency -- but the above is taking things too far, especially if you're just a layman that barely makes it on anybody's radar.
That's LARPing. It's like when a script kiddie buys a DDoS service, and calls themself a "hacker," for overloading a server (AnonSec/Anonymous I'm looking at you, morons). It's roleplaying, it's childish, and it will get ridiculed for its self-aggrandizing.
2. I don't know why, but everytime someone mentions that they're offended or miffed about something someone else said, especially on the internet, I have a very hard time taking them seriously.
I believe it's because I grew up on hearty banter, and anyone that couldn't hang was, in my eyes, a chode. No disrespect, but I wanted to share that insight with you. Maybe it'll come in-handy somewhere down the line.
1. To the outside world, a LARPer might be indistinguishable from someone that actually needs perfect opsec. Maybe that LARPer in the coffee shop is Ross Ulbricht.
2. If one day you actually need real encryption, it will help if you've LARPed in the past.
Here's a better breakdown of carcinogens in cigarette smoke (same book, same author)[0]. The most lethal way tobacco smoking impacts health is through carcinogenic by-products created from metabolizing said tobacco.
"PAH, N-nitrosamines, aromatic amines, 1,3-butadiene, benzene, aldehydes, and ethylene oxide are probably the most important carcinogens because of their carcinogenic potency and levels in cigarette smoke."[0]
To elucidate on one of your points: nicotine isn't on any of the "carcinogens in tobacco" lists, because it, nor any of its metabolites, aren't carcinogens at any dosage that is practically applicable to humans.[1]
[0] https://www.ncbi.nlm.nih.gov/books/NBK53010/ [1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4553893/