Nicotine and the increased cholinergic activity it causes have been shown to impede apoptosis, which is one of the methods by which the body destroys unwanted cells (programmed cell death). Since apoptosis helps to remove mutated or damaged cells that may eventually become cancerous, the inhibitory actions of nicotine may create a more favourable environment for cancer to develop, though this remains to be proven.
Also women who use nicotine gum and patches during the early stages of pregnancy face an increased risk of having babies with birth defects, according to a study of around 77,000 pregnant women in Denmark. The study found that women who use nicotine-replacement therapy in the first 12 weeks of pregnancy have a 60 percent greater risk of having babies with birth defects, compared to women who are non-smokers.
Nicotine is a very powerful constrictor and decreases the flow of blood to the periphery of the body. It has been measured and found that there is a 29 percent blood-flow decrease to the thumb after smoking two cigarettes.
Cigarette smoke has a number of carcinogens in it. While nicotine itself is not known to be a carcinogen [0] it does inhibit programmed cell death [1]. Thus, nicotine promotes carcinogenic activity in the lungs and in other bodily tissues.
Interestingly, THC seems to have the exact opposite effect promoting programmed cell death rather than inhibiting it [2]. This may lead to a low risk of lung cancer when smoking marijuana as compared to a high risk of lung cancer when smoking cigarettes [3].
"This may lead to a low risk of lung cancer when smoking marijuana as compared to a high risk of lung cancer when smoking cigarettes"
Many people roll tobacco and marijuana into joints. So this probably isn't true in many cases. It would be true if marijuana were to be smoked on it's own in a joint.
Additionally, people tend to hold the marijuana smoke in a lot longer than they do tobacco, so (while I don't have any evidence), I imagine that also makes it more dangerous.
Nicotine demethylates when heated into nornicotine. This reacts with saliva to form the carcinogenic N-nitrosonornicotine -- which is also found in any variety of cured tobacco.
While not itself carcinogenic, it is incredibly hard to separate nicotine from cancer, unfortunately.
From memory, I believe one line of thinking is that vasoconstrictors (of which nicotine is one), in the course of chronic exposure / activity, promote rigidity aka hardening of blood vessels.
I see now what you mean, although I think the brevity and nature of the comment made it easier to do so. Upvoting your comment (I did not downvote it, before).
