Addictive, yes, but nicotine was otherwise thought to be the least harmful ingredient in tobacco — that is until recently.
Now some experts are beginning to question whether nicotine is really as benign as thought, or whether its adverse effects have simply been masked by the fact that other toxins in cigarettes are so much worse.
And this also raises questions about vapes — the ‘safer’ alternative to cigarettes — as these also often contain nicotine.
Scientists have started looking at nicotine because while smoking levels are at their lowest since records began (in the 1940s), vaping is on the rise.
Every day, more than 270 people in the UK die from smoking-related conditions such as heart attack, lung disease and cancer.
This toll is largely due to a toxic brew of harmful chemicals in cigarettes.
Nicotine was otherwise thought to be the least harmful ingredient in tobacco — that is until recently (stock image)
These include 1,3-butadiene (used to make rubber and which can cause certain blood cancers); cadmium (found in batteries and linked with lung cancer); and chromium VI (used to make paints and dyes, also linked to lung tumours).
In fact, there are thousands of harmful chemicals in cigarettes — some occur naturally in the tobacco plant, others are added during manufacturing to boost flavour or increase the absorption of smoke in the lungs (to get more into the bloodstream and then the brain for a better ‘hit’).
But the innocent party in tobacco’s deadly effect on human health was always thought to be nicotine — the addictive ingredient that produces the ‘high’ that smokers crave, but that’s been considered relatively safe.
However it’s come under the spotlight because of the rising popularity of e-cigarettes, which give users the same nicotine ‘hit’ as tobacco but without exposure to harmful chemicals — although there are separate concerns about possible carcinogenic effects of gases, called volatile organic compounds, in vapes.
More than four million people in the UK now vape and, according to latest estimates, e-cigarette users will outstrip smokers within the next couple of years.
As a means of quitting tobacco, vaping has the backing of charities such as the British Heart Foundation and Action on Smoking and Health, while the NHS website says vaping doubles the chance of stopping smoking compared to nicotine gum or patches.
Nicotine occurs naturally but in tiny quantities in many plants — including tomatoes, potatoes and aubergines. But in tobacco plants, where it acts as an in-built insecticide, levels are at their highest.
Its effect on the brain is well known — within 20 seconds of inhalation, it triggers the release of chemical messengers such as dopamine, associated with reward and pleasure. But it also increases heart rate and blood pressure and makes blood vessels constrict. This is because nicotine triggers the release of the hormone adrenaline. The big question is whether there is any long-term impact.
‘Nicotine does have physiological effects on the body,’ says John Britton, a professor of epidemiology at Nottingham University and former chairman of the Royal College of Physicians’ Tobacco Advisory Group. ‘It changes blood pressure and heart rate and has similar effects to caffeine.’
The problem has been a lack of evidence on nicotine alone.
Professor Britton says one of the few large-scale studies to tease out the effects of nicotine specifically was led by scientists at the Karolinska Institute in Sweden, who looked at data on more than 130,000 men who were regular users of snus.
This is a tea-bag style tobacco product that’s placed under the top lip to allow the nicotine to seep into the bloodstream through the tiny blood vessels in the inner surface of the mouth. (Snus is very popular in Scandinavia and while banned from sale in the UK, it’s not illegal to use it.)
The study results found that regular users of snus were no more likely to have a heart attack than non-users, reported the European Journal of Epidemiology in 2012.
But now more recent research — by a different team of scientists at the Karolinska Institute — casts doubt on these findings.
The researchers looked at the effect of snus on the arteries of otherwise healthy men. They did this by temporarily shutting off blood supply to the forearm once the snus had been taken, then measuring how much the arm ‘shrank’, before allowing blood to flow again to see how quickly the arm returned to its original diameter. The quicker this happens, the more stretchy the arteries.
The researchers found that the nicotine from snus made the arteries much stiffer — reducing blood flow and potentially increasing the chances of heart disease down the line, according to results published in the journal PloS One in June last year.
Some experts are beginning to question whether nicotine is really as benign as thought, or whether its adverse effects have simply been masked by the fact that other toxins in cigarettes are so much worse
Other studies put rates of peripheral arterial disease — restricted blood flow in the legs and feet — from nicotine exposure through snus on a par with those from cigarette smoking.
In September, the UK’s Professional Footballers’ Association announced an inquiry into reports of the rising use of snus — top football players have reportedly been spotted taking it — warning that it has been linked to heart problems and reduced physical performance.
Separately, research presented at the American Heart Association conference in October last year showed e-cigarette users regularly exposed to nicotine consistently performed worse than non-vapers on treadmill tests designed to predict heart disease risk — with the damaging effects similar to those seen with cigarettes.
Laboratory studies have also suggested a possible link with some types of cancer.
For instance, nicotine has been shown to fuel the growth of pancreatic cancer cells in mice, while a 2021 study at Wake Forest School of Medicine in the U.S. found that nicotine promotes the spread of breast cancer cells to the lungs — altering the environment in the airway so that it’s more conducive to tumour growth, reported the journal Nature Communications.
Dr Marina Picciotto, a neuroscientist at Yale University, has been studying the effect nicotine has on young adults’ brains and is particularly concerned about young vapers’ exposure during their crucial years of neuro-cognitive development.
She told Good Health: ‘We know from both pre-clinical and human studies that nicotine disrupts normal activity in the brain’ — specifically, in areas associated with memory, learning, attention and arousal.
Nearly one in 20 children in the UK aged between 11 and 15 regularly vapes, rising to around one in six older teens, according to Action on Smoking and Health.
Campaigners fear that the fact some vapes are designed to attract young palates, with flavours such as blackberry sour, means a new generation is being exposed to nicotine.
Dr Picciotto says that although nicotine is potentially less harmful than other toxins in tobacco, ‘my worry is we will only find out more about the consequences of nicotine vaping in years to come — just as the consequences of smoking can take decades to show up’.
But Professor Britton says the risks are minimal.
‘Being addicted to nicotine all your life is probably on a par with drinking coffee every day. The evidence connecting it to serious illness is sparse and in humans is still compounded by tobacco and the many things in smoke.
‘The real harm is from the stuff you have to take with it to get the effect — toxins in tobacco and the other chemicals in e-cigarettes.
‘If one of my kids said they were going to start vaping, I’d say ‘no, over my dead body’ — why become addicted to something unnecessarily? But if they said they were going to vape instead of smoke, I’d say ‘yes, absolutely’ — it’s a no-brainer.’
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