IELTS Academic Reading Practice Test 387

At the beginning of the sixteenth century, a European doctor treating a sick patient had little to offer beyond the teachings of the Greek physician Galen, who had died fourteen centuries earlier. Illness was explained as an imbalance of four bodily fluids, or humours, and treatment consisted of restoring the balance by bleeding, purging or changing the patient's diet. Medicines were compounded from dozens of ingredients, and a remedy might contain so many substances that nobody could say which of them, if any, was doing good. It was against this system, and against the authority that sustained it, that a Swiss physician named Paracelsus rebelled.

Paracelsus was born in 1493 or 1494 in the village of Egg, near Einsiedeln in what is now Switzerland, the son of a physician who also had a keen interest in chemistry. After studying at the university in Vienna and, by his own account, at several other institutions, he spent years travelling through Europe, possibly working as an army surgeon. He later claimed to have learned more from peasants, midwives and craftsmen than from professors, and there is no doubt that much of his knowledge of metals and minerals came from the mines and smelting works of the Alps.

He took the name Paracelsus, meaning 'beyond Celsus', a reference to a Roman medical writer, apparently to signal that he intended to surpass the ancients. His central claim was that the authority of Galen, and of the physician Avicenna, counted for nothing beside the evidence of experience. Accounts written by his contemporaries describe how, in 1527, he publicly threw a copy of Avicenna's work into a bonfire in Basel. Whether or not the scene occurred exactly as described, it captured his attitude: a doctor should trust what he observed at the bedside and in the workshop, not what a long-dead author had written.

Paracelsus replaced the four humours with a different scheme. He argued that everything, including the human body, was composed of three principles: sulphur, which accounted for whatever burned; mercury, which gave substances their fluidity and volatility; and salt, which provided solidity. Disease, on this view, was not a general disturbance of the whole body but a specific disorder with its own external cause, and each disorder therefore required a particular remedy. He was scornful of medicines designed to suit every patient, and he searched for what he called specifics, substances that would act on one disease and no other.

Chemistry supplied those specifics. Paracelsus and his followers developed a set of techniques, known as spagyric medicine, for distilling, extracting and purifying substances so that their active parts could be separated from the rest. He favoured mineral remedies at a time when most physicians preferred plants, and mercury and antimony in particular were used against syphilis and other conditions. Such substances are highly toxic, and Paracelsus was well aware of the danger. In a work of 1538 he observed that nothing is without poison and that only the quantity determines whether a substance harms or heals, and he therefore paid close attention to how much of a remedy he administered.

His career was as turbulent as his opinions. In 1527, with the support of influential friends in Basel, he was appointed city physician and given permission to lecture at the university. He promptly scandalised his colleagues by teaching in German rather than in Latin, and by criticising the treatments his fellow physicians prescribed. His quarrel with the medical faculty deepened, and in 1528 he left the city abruptly. For the rest of his life he moved from town to town, practising medicine and writing, but he never again held a secure academic post.

Among his writings from this period is a short treatise on the diseases of miners, based on observations made in the mining districts of central Europe. Paracelsus described the breathlessness and wasting illness that afflicted men who worked underground, and connected it with the dust and fumes they breathed and with the metals they handled. The book, which appeared in print only after his death, is often described as an early study of what would now be called occupational medicine, since it treated a disease as the product of a particular working environment rather than of the patient's constitution.

He died in Salzburg in September 1541, at about the age of forty-seven, after a short illness; the circumstances are uncertain, and some writers have suggested that he was attacked. Most of his work was published after his death, much of it by followers who edited and rearranged his manuscripts, so that it is not always easy to tell which ideas were his and which belonged to his disciples.

His influence on medicine was nonetheless considerable. The physician Jan Baptist van Helmont, writing in the following century, acknowledged a debt to Paracelsus while rejecting much of his system, and the tradition of iatrochemistry, which sought to treat disease through chemical processes, owed a great deal to his example. Some of his notions now look merely strange, such as his proposal that a wound could be healed by applying ointment to the weapon that had caused it. But his insistence that diseases have specific causes, that remedies must be matched to them, and that the amount given matters, points towards the pharmacology that emerged three centuries later.

Nothing in the pharmacy is entirely free of risk. The same substance that relieves a headache can, in sufficient quantity, destroy the liver, and the same molecule that lowers blood pressure can, at a higher concentration, stop the heart. Even water and oxygen, which are essential to life, become dangerous when taken to excess: too much water dilutes the salts in the blood, and pure oxygen under pressure damages the lungs. Toxicologists sum up the point in a sentence that has become a cliché of the discipline: the dose makes the poison. It is not a claim that all chemicals are equally hazardous, nor that anyone need be alarmed by the trace quantities found in food. It is a reminder that the question 'is this substance safe?' cannot be answered without two further pieces of information: how much, and for how long.

To answer those questions, scientists rely on the idea of a dose-response relationship. As the amount of a substance increases, the effect on the body generally increases too, although not always in a straight line. For many substances there is a threshold below which the body's defences cope and no harm results; above it, damage appears and then worsens as the dose rises. The classic measure of acute toxicity is the LD50, the dose at which half of a group of test animals dies, expressed in milligrams per kilogram of body weight. It is a blunt instrument, recording one kind of harm over a short period. The figure can differ markedly between species and between routes of exposure: a chemical swallowed may be far less dangerous than the same chemical inhaled. Nor does it say anything about the effects of low doses continued over years.

Between the dose swallowed and the damage caused lies the body's own chemistry. A substance must be absorbed, carried in the blood and often converted by enzymes in the liver before it can act, and it is the concentration reaching a particular organ that determines the harm. The liver's processing may make a substance safer by breaking it down, or considerably more dangerous by turning it into something more reactive than the original. Paracetamol, among the most widely used medicines in the world, is a well-studied example. At the recommended dose the liver disposes of it safely, but in a large overdose the usual routes of breakdown are overwhelmed, a reactive by-product accumulates faster than the body can neutralise it, and the result can be fatal liver failure. Such overdoses are a familiar problem in hospital emergency departments.

The same quantity of a substance may be harmless to one person and hazardous to another, because the effective dose depends on the body that receives it. Body mass matters, which is why children's medicines are calculated by weight; so does age, since the liver and kidneys of a newborn baby or a very old patient may clear a chemical more slowly. Genetic differences in liver enzymes mean that some people break a drug down rapidly and others slowly, and pregnancy alters the way many substances are handled. Interactions with other chemicals add a further layer: grapefruit juice, for instance, blocks an enzyme that normally dismantles a number of common medicines, so that a normal dose remains in the bloodstream longer, and at higher concentrations, than intended.

Beyond these general principles lie areas of genuine uncertainty. Most safety data concern one substance at a time, yet people are exposed to hundreds of compounds simultaneously, in food, in air and in household products, and the effects of these mixtures are poorly understood. Long-term exposure at low levels is difficult to study, because any harm may take decades to appear and cannot ethically be tested on people. Some substances, including certain carcinogens that damage DNA directly, are assumed to have no safe threshold at all, while others produce effects in laboratory animals that have never been confirmed in humans. Extrapolating from a few thousand mice to billions of people is a statistical convenience as much as a scientific certainty, and how such exposures ought to be regulated remains disputed.

Regulators translate these ideas into numbers. For a food additive or a pesticide residue, they first establish the highest dose at which no observable harm occurs in animal studies, then divide that figure by a safety factor, usually a hundred, to allow for differences between species and between individuals. The result is an acceptable daily intake, a level considered safe if consumed every day for a lifetime. Safety margins of this kind are a response to ignorance as much as to knowledge: they cannot guarantee that a substance is harmless, but they make serious error less likely. Whether a hundredfold margin is generous or barely adequate remains a matter of debate, and the same arithmetic underlies public arguments about almost every chemical in the food supply.

Walk into any pharmacy and you will find shelves of products that advertise their contents as natural, plant-based or free from chemicals. The appeal is easy to understand. Herbal medicine is felt to be older, gentler and more harmonious with the body than the products of a laboratory, and its advocates often describe it as a tradition rather than an industry. Behind the marketing lies an assumption that deserves examination: that a remedy's origin tells us something reliable about how safe it is. Toxicology suggests that this assumption is mistaken, and that the distinction it rests on may be the least useful way of thinking about risk.

Plants are not gentle. Unable to run away, they defend themselves chemically, manufacturing an extraordinary range of compounds to deter insects, fungi and grazing animals, and many of these compounds are poisonous to humans as well. Green potatoes contain solanine; cassava, a staple food for millions of people, must be processed to remove cyanide-releasing substances; castor beans contain ricin, one of the most lethal substances known; and moulds growing on stored peanuts and maize produce aflatoxins, among the most potent natural carcinogens identified. Natural does not mean harmless. It means only that the chemistry was assembled by an organism rather than in a factory.

None of this denies the value of the plant kingdom. Some of medicine's most important drugs were first found in plants or in the knowledge of people who used them. Willow bark, recommended for pain and fever since antiquity, yielded salicin and eventually aspirin; the foxglove gave digitalis, still used to strengthen a failing heart; the opium poppy gave morphine; and in the 1970s Chinese researchers investigating a herb used against fever, Artemisia annua, isolated artemisinin, which became a cornerstone of treatment for malaria. The lesson is not that plants are safe but that they are pharmacologically active, and that traditional use can point scientists towards molecules worth studying.

The difficulty for anyone taking a herbal product is knowing what is in it. The quantity of active compound in a plant depends on the species and variety, the soil, the weather and the method of preparation, so two bottles of the same remedy may differ considerably. Analyses of marketed products have repeatedly found wide variation, and some have found contamination with heavy metals or with species not listed on the label. The consequences are not theoretical. In the 1990s, women in Belgium who took a slimming preparation containing the wrong species of Aristolochia suffered severe kidney damage, and the plant was subsequently banned in many countries.

Regulation reflects a different standard of proof. A new pharmaceutical must pass laboratory tests and then clinical trials demonstrating that it works and that its risks are acceptable before it can be licensed. Herbal products rarely face anything comparable. In the United States they are generally sold as dietary supplements, a category created by legislation in 1994, under which a product may be marketed without evidence of effectiveness and without the safety testing required of a drug. In the European Union a simplified registration scheme introduced in 2004 allows remedies with a long history of traditional use to be sold on that history rather than on clinical evidence.

Defenders of the present arrangements point out, reasonably, that synthetic medicines are not free of danger either. Reactions to properly prescribed drugs are a recognised cause of hospital admission, and the history of pharmaceutical regulation is a history of failures corrected. Thalidomide, prescribed in the late 1950s for morning sickness and for insomnia, caused severe birth defects before it was withdrawn, and the scandal led to far stricter requirements for testing new medicines. That is the point, however: the system is not worthless, since it is the reason such effects are now detected early, and it makes the risks of licensed drugs visible in a way that the risks of herbal products are not.

The argument from nature runs into a more fundamental difficulty. A molecule has the same structure wherever it comes from: the salicylic acid in a willow and the equivalent made in a factory are indistinguishable to the body, which has no way of knowing which it has received. What determines the effect is the amount reaching the tissues, not the biography of the substance. Appeals to nature therefore smuggle in a conclusion that does not follow from the premise. That a remedy has been used for centuries is evidence about its popularity, not about its safety, and history is full of treatments that were trusted and harmful.

None of this argues for abandoning herbal medicine. It argues for treating it seriously. Doctors should ask patients what they are taking, including remedies bought without prescription, because some herbs alter the way the body handles other drugs: a preparation that accelerates the breakdown of a medicine can make it ineffective at its normal dose. Manufacturers should be required to show that their products contain what the label claims, batch after batch. And research that turns traditional knowledge into tested medicine should continue, since it has already produced drugs that no laboratory programme would have predicted.

The question, then, is badly framed. There is no reason to think that natural remedies are safer than synthetic ones, or more dangerous; there are safe and dangerous examples of both, and chemistry does not take sides. What distinguishes a good medicine from a bad one is evidence: that it works for the condition it is sold for, that the dose is controlled and known, that the product is what it claims to be, and that its risks have been measured and judged acceptable. Herbal remedies should be held to those standards in proportion to the claims made for them, rather than exempted from them because they are old.