Tobacco and nicotine: effect on the human body

Tobacco, the variety of which Nicotiana tabacum, is a solanaceous plant cultivated from a northern latitude of 60° to a southern latitude of 40°. Its consumption, and therefore its cultivation, are exclusively due to its production of nicotine, an insecticide alkaloid, which, by structural analogy with a physiological molecule in humans, acetylcholine, will activate the specific receptors of the latter called nicotinic cholinergic receptors.

These receptors are present throughout the body, and particularly in the brain at the level of the reward system of the limbic system whose purpose is to ensure the survival of the individual and its reproduction through the intake of food, drink and sexual activity by providing a feeling of pleasure. This feeling of pleasure is linked, in large part, to the release of dopamine which results from the activation by nicotine of these nicotinic cholinergic receptors.

Nicotine is a psychoactive substance because its administration, as defined by the World Health Organization, alters mental processes, such as cognitive functions or affect. Thus, nicotine consumption can improve, for example, attention and learning or reduce the feeling of hunger.

In addition to having psychoactive effects, nicotine is a drug, the simplest definition of which is the subject's loss of control over the use of the substance, which smokers describe well by confiding "it's stronger than me". This drug leads to a very strong addiction, even one of the strongest, which explains why tobacco consumption is by far the most widespread drug addiction in the world and why its withdrawal is one of the most difficult.

To date, nicotine consumption is mainly through tobacco smoke, because its inhalation results in a massive and very rapid flooding of the nicotinic cholinergic receptors (7 to 8 seconds between the start of inhalation and the arrival of nicotine in the brain). This explains the power of this addiction and the difficulties in getting rid of it, especially since its consumption remains, to a large extent, socially accepted as commonplace.

The inhalation of nicotine present in tobacco smoke is accompanied by that of several thousand other substances, some of which are toxic to the body, which explains why its consumption is the leading preventable cause of Non-Communicable Diseases (NCDs) such as cancers and cardiovascular and respiratory diseases.