Over the years, the human species has had the strange habit of finding dangerous substances in plants and then starting to consume them.
Caffeine is harmful to most insects and is believed to have arisen as a plant repellent against herbivorous insects.
Capsaicin and other spicy molecules (found in chili peppers and jalapeños, for example) aim to produce a burning sensation to repel herbivorous mammals.
And nicotine, the addictive substance in tobacco, is a poison that functions as a natural insecticide in plants. We are the multiple exception to these rules.
Nicotine and tobacco are two closely related concepts. The term “tobacco” is commonly used to refer both to various plants in the Nicotiana genus and to the products made from the leaves of these plants.
Although several species are used for the commercial production of cigarettes and other smoking products, they are usually made from Nicotiana tabacum. Between 1% and 3% of this plant’s leaves are nicotine.
The leaves are harvested and processed to produce the tobacco that will be consumed. Between 0.6% and 3% of the final weight of dried tobacco is nicotine.
Interesting fact: nicotine is not exclusive to these plants. Potatoes and tomatoes also contain nicotine. It is also true that a potato has 2.25 micrograms and a tomato has 7.1 micrograms of nicotine. For comparison, a single typical cigarette contains between 11,900 and 14,500 micrograms, of which approximately 1,000-2,000 are absorbed by the body when smoked.
The Mysteries of Nicotine
Nicotine is an alkaloid, a natural molecule with nitrogen, that interacts with the nicotinic acetylcholine receptors in the human body. Normally, these receptors are activated by acetylcholine, but nicotine also has this capability.
This activity stimulates the release of several neurotransmitters, mainly catecholamines and serotonin. The effect is quick; nicotine can reach the brain, crossing the blood-brain barrier that surrounds it, within 10-12 seconds of the first inhalation. The peak nicotine level in the blood is reached within 6-10 minutes. After 2 hours, more than half will have metabolized, mainly by the liver.
Nicotine has some positive effects on the consumer: it improves precise movements in hands and fingers, and both long-term and short-term memory. It helps maintain alertness and attention and decreases hunger. It has been studied for its potential therapeutic value in some nervous diseases such as Parkinson’s.
However, one thing needs to be clear from the beginning: despite this, by definition, it is a neurotoxin. In fetuses, children, and adolescents, due to its effect on nicotinic receptors, it can modify their development and regulation, making them especially dependent on tobacco. In adults, it would be quite harmless if not for one detail: addiction.
Nicotine is highly addictive. Dependence is both physical and psychological. Additionally, tolerance is created, meaning the person feels less stimulation from the same dose of tobacco, with negative effects in its absence. Smoking addiction is more like nicotine addiction.
The person feels irritability, anxiety, stress, concentration and memory problems, and difficulty falling asleep. These effects last until the nicotine peak in the blood is regained, or enough time passes for normality to return.
Many smokers need other sources of nicotine when they quit smoking to maintain the addiction. Additionally, social and psychological components of addiction often accompany nicotine.
There are other compounds to quit smoking that do not contain nicotine, such as bupropion, which increases extracellular dopamine levels, an effect both substances have in common.
One Cigarette, Hundreds of Compounds
Why do people quit smoking but continue consuming nicotine? Because nicotine is what hooks you, but it’s the tobacco and the cigarette that actually kill you.
A cigarette has approximately 600 ingredients. Its combustion releases about 7,000 different chemicals, of which at least 70 are carcinogenic.
In addition to nicotine, there are toxic gases (carbon monoxide, ammonia), heavy metals (lead, cadmium, arsenic), and other compounds of varying risk (acetone, acetaldehyde, toluene, methanol…).
In this blog, we have encountered smoking as a common risk factor in the pathologies we discuss. In the collective imagination, we associate it with respiratory and cardiovascular diseases such as lung cancer, chronic obstructive pulmonary disease, or stroke.
However, its effects of smoking addiction are systemic. It decreases fertility in both men and women, causes premature births and babies in poorer health, increases the risk of type 2 diabetes, causes eye damage, and is related to practically every cancer that exists, no matter how distant, such as pancreatic cancer.
The complete pack of poisons. Impossible to talk about so many in such a small space.
The effect of tobacco on people’s DNA and genome is well known. We have already mentioned that smoking releases carcinogenic substances and is a constant risk factor in all cancers.
But did you know that genes also affect addiction to smoking?
Is Smoking Hereditary?
The behavior of smoking is hereditary and is associated with 15% of deaths globally.
Of course, it is not something due to a single gene. It is, as with complex diseases, multiple genetic variants that make a person more susceptible to becoming addicted to nicotine. But among the reasons and causes for smoking addiction are genes.
No gene will make you start smoking against your will. But the right combinations can make you more susceptible to smoking and a faster and/or stronger dependence on nicotine.
So far, many of the genetic variants involved in smoking have been found in genes that encode information for the subunits of the nicotinic receptor.
For example, the CHRNA5 gene, which carries information for a subunit of the nicotinic receptor, has a version that increases nicotine addiction. Researchers found that this new receptor softened the negative effects of nicotine, making the first experiences with cigarettes less unpleasant for non-smokers.
In 2022, one of the most ambitious studies was conducted, using data from 3.4 million people, 21% of whom were non-Europeans (a problem with these studies is sometimes the homogeneity of the sample if all participants belong to the same genetic population).
In that study, they found almost 2,500 genetic variants associated with smoking, spread across 1,346 loci (a fixed, physical, and specific area of the genome). They detected another 39 variants related to the age of smoking initiation, 206 with the ability to quit smoking, and 243 with the number of cigarettes smoked daily.
Thanks to the inclusion of individuals from different ancestries, they found among others 721 completely new variants associated with smoking. Some of these genetic variants were from genes involved in nervous system functions such as NRXN1 or GRIN2A.
It should be noted that tobacco addiction tests, like the tellmeGen DNA kit, calculate genetic predisposition to nicotine addiction. It does not mean that the person will inevitably smoke. A person who has never tried nicotine cannot become addicted to it.
And, in general, we recommend not trying it.
