The tobacco plant Nicotiana tabacum, is probably the most loved and hated member of the vegetable kingdom. The smoking of tobacco in various forms provides many millions of people with a seemingly innocent and pleasurable pastime. But the most common form of tobacco use – the cigarette – has doctors united in calling cigarette smoking the largest single preventable cause of death and disease in the developed world. Even with this knowledge, only a minority of smokers succeed in giving up, and most do not begin to try.
The addictive power of tobacco is not obvious when compared with the strong effects of alcohol, heroin or other drugs. People smoke tobacco and nothing much happens. A good starting point in explaining smoking is to ask smokers why they do it.
Why do smokers smoke?
Part of the attraction for young people is that smoking is seen as an adult behaviour. There is also simple curiosity, and offering or exchanging cigarettes is a good way to make friends and feel part of a group. For all smokers there is the pleasant smell and taste of smoke, something to occupy your hands, and the attraction of having something on which to suck. It is possible to enjoy all of these aspects of smoking without drawing smoke into the lungs. Almost all cigarette smokers inhale smoke, however, which suggests there is more to the habit than social behav-iour and sensory satisfaction. Smokers have to learn to inhale. This takes time, and is initially unpleasant. Once smokers have learned to inhale, very few of them stop. This is because inhalation is a fast and efficient way of getting a drug to the brain, taking fewer than seven seconds. The only drug of any sig-nificance in tobacco smoke is nicotine. Smoking is, therefore, a way of dosing with nicotine.
Tobacco as a hazard to health
The contention that smoking damages the health is almost as old as the habit of smoking itself. The first official condemnation of tobacco, entitled ‘A Coun-terblaste to Tobacco’, was issued in 1604 by King James I of England. One of the first studies pinpointing the detrimental effects of tobacco was published in 1859. It showed that each.of 68 patients who had been admitted to a hospital in Montpellier, France, suffering from various forms of mouth cancers, had used tobacco at some time in their lives. Interest in the relationship between smoking and health declined until after World War II when smoking had become more widespread. Health authorities reported that in countries where cigarette smoking was popular, death from lung cancer and related diseases was climbing at an alarming rate. The results of many subsequent studies have inspired government bodies to issue health warnings on cigarette packets, and to ban television advertisement of tobacco.
The effects of nicotine
Nicotine was first isolated as the active ingredient of tobacco in 1828, when it was named after Jean Nicot, a sixteenth-century tobacco enthusiast and French ambassador to Portugal. Another century passed before people realized that nicotine was very similar to one of the body’s own biochemicals, acetylcholine, which plays an essential role in the transmission of nerve impulses. Acting as a kind of skeleton key, nicotine unlocks the biochemical systems normally controlled by acetylcholine, and this action is responsible for its subtle but significant effects on the brain. Recent experiments on the performance of both animals and people show that nicotine can act either as a stimulant or as a sedative. In small doses it reduces fatigue, and in larger doses counters the disruptive effects of stress. In these respects, smokers are right about the benefits of tobacco, at least in the early stages of the habit and when people do not smoke too frequently. The problem, as with any drug, is that the body responds to the presence of nicotine by trying to compensate for its effects. When the drug is no longer present, the body functions less effectively, and there are unpleasant side-effects. Regular smokers deprived of nicotine complain of anxiety, poor concentration, fatigue and depression, as well as changes in appetite and physical symptoms such as altered bowel function and weight gain. These effects can be removed immediately by taking a further dose of nicotine, which creates a vicious circle and the smoker becomes an addict. Despite producing useful changes in the physiological and psychological state, nicotine and its power as an agent of addiction is the main reason people smoke. Nicotine is probably also responsible for some of the damage caused by smoking. It increases blood pressure, hence the risk of stroke; it changes the pattern of blood flow, making coronary artery disease worse and provoking angina chest pains; and nicotine causes blood vessels in the extremities to constrict (smokers may notice that their fingers are often cold).
Any organic material that burns produces a vast range of different chemicals. Tobacco smoke is a cocktail of many harmful substances. The most important from the health point of view are the oily tars, irritant gases such as oxides of nitrogen, and carbon monoxide. The tars cause cancer, as can be shown by taking the residues of cigarette smoke and painting them on the skin of a laboratory animal.
Lung cancer is probably the most common and most feared consequence of smoking. In Britain, the worst affected country, one smoker in ten dies from the disease.
Tar, together with irritant gases, is also responsible for other lung diseases, progressing from smoker’s cough to chronic bronchitis. Foreign substances are normally removed from lung tissue by the cilia. These are fine hairs that line the airways and continuously sweep particles and debris from the lungs in secreted mucus (phlegm). As smoke passes along the airways, it may gradually destroy some of the cilia. This causes an increased secretion of mucus, and the lungs be- come chronically inflamed and susceptible to infections such as bronchitis – severe forms of which may result in death. Emphysema is a disorder that also occurs far more commonly among smokers. In this disease, the walls forming the tiny air sacs at the base of the lungs break down, reducing the body’s ability to absorb oxygen. This is a progressive condition for which there is no known cure; it can also be fatal.
Carbon monoxide is almost equally as damaging. It reduces the supply of oxygen to body tissues by becoming firmly attached to haemoglobin, the red oxygen-transporting pigment in the blood. By reducing oxygen supply to the fetus during pregnancy, carbon monoxide is responsible for low birth weight and complications. So pregnant women are especially advised not to smoke.
Carbon monoxide also seems to encourage the accumulation of atheroma in the arteries, leading eventually to their obstruction. When this affects the arteries carrying blood to the heart muscle, the result is a heart attack, which is more likely to be fatal in heavy smokers than in other people.
The damage smoking causes is plain. Smokers have chosen to take the risk, but there is increasing concern that exposure to ‘second-hand’ smoke is also harming non-smokers. This is the problem of ‘passive smoking’. The evidence is not yet clear, but non-smokers exposed to smoky atmospheres for long periods may suffer some of the same lung damage that is caused to smokers, although to a much smaller degree.
How to stop smoking
A great deal of effort has been put into persuading people to stop smoking, although there are few effec-tive ways of helping them to do so. Smoking clinics offer advice and social support, and may provide minor stimulant or tranquillizing drugs to ease initial withdrawal. Many attempts have been made to develop ‘non-smoking pills’ but the main effects of such pills are to give the smoker something oral to do; mint sweets are just as effective. Psychologists have tried to treat smoking using behaviour therapy in which the habit is associated with unpleasant stimuli such as electric shocks or the sight of pictures showing the diseases it causes. Success has been limited. The usual pattern is for many smokers to give up initially, with half of those who have given up still not smoking six months after treatment was stopped. Four out of five, however, normally return to smoking before the end of a year. The recent development of nicotine-flavoured chewing gum has improved matters. The drug is absorbed through the membranes lining the mouth. This allows the smoker time to break the habit of using cigarettes, without the unpleasant experience of nicotine withdrawal symptoms at the same time. Smokers using the gum are almost twice as likely to give up permanently as those using other methods. The idea for nicotine gum came from Sweden, and extends the traditional Scandinavian interest in using tobacco without smoking. It is still common in these countries to chew tobacco, or smear it on the gums in the form of a paste called ‘snus’, or inhale it as snuff, as a finely ground powder. Nicotine can be absorbed through the linings of the mouth and nose but absorption is not as fast as with inhalation of smoke.
Pipes and cigars
Pipe and cigar smoking does not usually involve smoke being drawn into the lungs, one reason being the harshness of the smoke from burning pipe or cigar tobacco, which makes it almost impossible to breathe it directly into healthy lungs. The tobacco is dried, or ‘cured’ by a longer and more natural process than that used in cigarettes, and produces a smoke with an alkaline rather than a acidic composition. This means that nicotine can be absorbed through the mouth membranes, and smoke does not have to be taken into the lungs.
There are relative ‘advantages’ for health by smoking pipe or cigar tobacco. No deposits of tar clog the lungs, so there is little risk of lung cancer, and no carbon monoxide is absorbed. Even so, pipe and cigar smokers are still in danger of developing cancers of the mouth, tongue and lips.
Smokers who cannot stop
Cigarette smokers who cannot give up smoking would do better to switch to a pipe or cigars. They must remember not to inhale, however, which is something many find difficult at first. For those who wish to remain with cigarettes, the advice is to smoke fewer of them, and to leave a longer butt of unsmoked tobacco – because tar becomes more concentrated towards the end of the cigarette. Filter cigarettes are less dangerous than untipped brands; a good filter traps around half the tar. There is some indication that the widespread use of filter brands which started about thirty years ago, is now becoming apparent in the falling rates of lung cancer. There may also be some advantage in smoking cigarettes that are low in tar content. Most low-tar brands are also low in nicotine. It is, however, proven that in cigarettes which are low in nicotine, the amount of nicotine in the smoke is higher than in cigarettes with a higher nicotine content. Because of this, benefits from low-tar cigarettes are likely to be less than suggested. This is especially true if the low-tar brands lead smokers to inhale more deeply and so absorb more carbon monoxide. The only certain medical advice is that if you smoke you should stop, and if you do not smoke you should never start.