Herbal medicine is the use of plants as medicines. Herbal medicine is also known as phytotherapy (especially in Europe; from Greek phyton meaning plant), botanical medicine, medical herbalism and herbology (USA). More specifically, the term herbal medicine refers to the therapeutic use of relatively crude and therefore chemically complex plant extracts, or simply the herb in its dried form. In this way herbal medicines are distinct from plant-derived pharmaceutical drugs, which contain single chemical compounds extracted from plants in their pure form.
All human societies of which we have any knowledge have availed themselves of plants for use as medicines. Herbal medicine in the widest sense is therefore a global form of medicine, which exists in a vast (albeit declining) diversity, forming a dynamic part of the rich cultural tapestry of our planet. Some of the most successful and sophisticated systems of herbal medicine prevailing today are Chinese Herbal Medicine (an integral part of Traditional Chinese Medicine) and the herbal medicine that forms part of the Ayurveda, the traditional system of medicine/health from India. These systems are treated elsewhere in this book.
This chapter is concerned with the type of herbal medicine that is prevalent in industrialised, western societies (in particular English-speaking countries), as distinct from both Chinese and Ayurvedic herbal medicine. Often referred to as ‘western herbal medicine’ (for want of a better term), this form of herbal medicine can best be defined as the therapeutic use of medicinal plants within a holistic context. Apart from being practised as a stand-alone therapeutic modality, it also forms part of the practice of naturopathy in English-speaking countries. Western herbal medicine is, as will be outlined below, essentially European in origin with significant influences from herbal traditions from other parts of the world, most notably North America and Asia (Wohlmuth et al. 2002).
It is important to be aware that the word ‘herb’ means different things to different people. To a botanist a herb is a herbaceous, that is, non-woody, plant, in contrast to shrubs and trees, both of which have woody stems. At the grocery store the term ‘herb’ is likely to be interpreted as meaning a culinary additive such as chives, parsley or dill. In herbal medicine, however, ‘herb’ is synonymous with ‘medicinal plant’ or, to be specific, the medicinal part(s) of a medicinal plant species, regardless of whether the plant is woody or not. The herb cascara is thus the bark (medicinal part) of Frangula pursbiana, which happens to be a tree, just as the herb lemon balm consists of the above-ground parts of the herbaceous (non-woody) plant Melissa officinalis.
Theoretical foundations of western herbal medicine
The roots of western herbal medicine are ancient, yet at the start of the twenty-first century the modality finds itself vying for a place in mainstream healthcare in industrialised countries. At the same time, herbal medicine is becoming increasingly science based and as a result the theoretical foundations of the discipline are to some extent in a state of flux. Today’s practitioners of western herbal medicine occupy a broad spectrum as far as theoretical foundations are concerned.
At one end of the spectrum are the traditionalists with strong philosophical allegiance to Thomsonian and physiomedical traditions and their vitalistic approach. At the other end of the spectrum are those who accept the biomedical model but see real value in the holistic approach to health and disease and the therapeutic qualities of herbal medicines. In this context it may be worth pointing out that it is entirely possible to use herbal medicines in a non-holistic, reductionist manner. Doing so, herbal practitioners would argue, does not amount to true herbal medicine but rather to allopathic medicine practised with plant-based medicines. Thus, the holistic approach is central to the practice of contemporary western herbal medicine. In a holistic framework, the emphasis is on treating the patient rather than their disease. The patient is viewed as comprising a physical body, with mental, emotional and spiritual aspects, all of which potentially influence the individual’s state of health. In addition, the patient is viewed in the wider context of personal relationships, community and environment, and it is recognised that each of these could play a role in the person’s health.
The practice of western herbal medicine
The initial visit to a practitioner of western herbal medicine (be it a herbalist or a naturopath) is likely to last for at least an hour. The practitioner will take a comprehensive case history and may carry out a physical examination as appropriate. The case history will include the patient’s presenting complaint, medical history and family history, diet, lifestyle, social situation, emotional wellbeing, use of pharmaceutical drugs and supplements and so on. If biomedical diagnostic tests are required, the practitioner will refer the patient to a general practitioner. Well-trained practitioners will base their clinical diagnosis on biomedical diagnostics, while some may also use unproven diagnostic tools such as iridology.
Once a diagnosis has been made, the practitioner will provide the patient with dietary and lifestyle advice and determine the appropriate herbal treatment. The treatment may be aimed at different therapeutic outcomes. Part of the treatment may aim to provide symptomatic relief and make the patient feel better in the short term, while another aspect of the treatment may address the perceived causes of the problem (thus honouring the fundamental principle of ‘treat the cause, not just the symptoms’). Yet another part of the treatment may be constitutional in nature, that is, aimed at treating underlying weaknesses (acquired or inherited). Treatment aimed at providing symptomatic relief should not be undervalued. After all, the patient’s most immediate concern is usually to feel better, and short-term improvement is the most effective way of ensuring that the patient returns for follow-up consultations, where underlying issues and causative factors can be addressed.
A second visit will normally take place one or two weeks after the first and will nearly always be shorter in duration. Herbal treatment can vary from days to years, depending on the nature of the patient’s health problems. As in other holistic healthcare modalities, there is an emphasis on actively involving the patient in their treatment and healing process, rather than being a passive recipient of a treatment prescribed by the practitioner. The practitioner’s role as educator and motivator is important in encouraging the patient to take responsibility for their own health. This approach is a core tenet of the therapeutic relationship in holistic medicine, and it contrasts with the rather more paternalistic relationship between doctor and patient that traditionally has prevailed in conventional western medicine. Another characteristic of holistic medicine is the emphasis on prevention, and this approach is incorporated into herbal practice whenever possible.
The herbal treatment
Herbal treatment is characterised by the fact that it is tailored to the specific needs of the individual patient. Therefore, two patients with the same medical diagnosis would rarely be given identical herbal treatments. For example, two patients may present with osteoarthritis; one may also suffer from frequent digestive upsets while the other is experiencing bouts of anxiety. Although the herbal medicines aimed at treating the osteoarthritis may be the same for both patients, the holistic herbal prescriptions would differ. This emphasis on individualised treatment is often expressed in the maxim ‘treat the patient, not the disease’.
In accordance with traditional principles herbal treatment is often supportive and normalising in nature. The body’s eliminative functions and the digestive system (including liver function) tend to receive particular attention, reflecting the importance placed on healthy digestion.
A western herbal medicine practitioner will generally prescribe medicines based on their actions rather than their indications. The term ‘action’ refers to a pharmacological or physiological property (e.g. sedative, diaphoretic or anti-inflammatory), whereas the term ‘indication’ refers to a condition or disease state for which the medicine can be used (e.g. insomnia, the common cold or tendonitis). This mode of prescribing facilitates a holistic treatment of the patient rather than an exclusive focus on the treatment of their disease.
Herbal medicines are dispensed in a variety of ways. When dispensed by a practitioner the medicine commonly contains extracts of several different herbs. For this reason practitioners tend to favour the use of liquid extracts, which allow for the convenient blending of individualised formulations from single-herb stock extracts in the practitioner’s dispensary. In recent years the use of standardised botanical extracts in capsule or tablet form has become increasingly common. These preparations have the advantages of a consistent chemical composition and being easy and convenient to take, although they do not allow the practitioner to make up an individualised formula for the patient. Most western herbal medicine practitioners have a dispensary in their clinic from where the prescription will be made up and dispensed. Dietary advice is also a common part of herbal treatment.
Patient compliance is an important issue in herbal therapy, as it is in any other kind of therapy. If the patient does not take the prescribed medicine and follow other recommendations provided, a successful treatment outcome cannot be expected. The use of liquid herbal extracts presents particular challenges in terms of compliance, especially owing to their taste. Patients who are not familiar with herbal medicines may find the strong taste (exacerbated by the alcohol content) a major barrier to compliance. This problem can often be overcome by taking the extract in a little fruit juice. The inconvenience of the medicine being in liquid form can also compromise compliance, especially if the patient is required to take the medicine in the middle of the day. Prescribing a medicine to be taken twice daily (morning and evening) rather than three times daily tends to result in better compliance. The key to good patient compliance is motivation and the setting of attainable goals for the patient. Asking a patient to make drastic and immediate changes to diet and lifestyle is far less likely to succeed than a more long-term plan that involves gradual change. Encouraging the patient to take responsibility and gain control of their own health is also an important strategy to obtain good compliance.
Safety issues in herbal medicine
The view held by some that herbal medicines are inherently safe because they are ‘natural’ is of course false. Nature abounds with very poisonous plants; one only needs to think of a plant like hemlock (Conium maculatum), the ‘state poison’ used for executions in ancient Greece, to be reminded of the power of plant poisons. While many poisonous plants were used in conventional medicine in days gone by, contemporary western herbal medicine does not employ the use of plants with significant toxic potential. In most countries legislation prevents the use of highly toxic plants in herbal medicine.
The safety issue in herbal medicine has a scope that extends far beyond poisonous plants. It includes side effects and other types of adverse reactions, interactions with pharmaceutical drugs, the use of herbal medicines in pregnancy and lactation and a range of issues arising from inadequate quality assurance.
Available evidence suggests that western herbal medicine is very safe. Safety data obtained from clinical trials consistently show that herbal medicines are safe and associated with only mild side effects compared with pharmaceutical drugs. When the number of serious adverse events arising from the use of herbal medicines is related to the number of people in the community using these preparations one can only conclude that the risk associated with herbal medicines is minimal. Given that adverse reactions arising from herbal medicines are less likely to be reported than adverse reactions to pharmaceutical drugs, the evidence still suggests that herbal medicines are generally safe. Serious but very rare adverse reactions to herbal medicines may be liver toxicity or severe allergic reactions, but most reported adverse events are mild and transient in nature.
Many cases of adverse reactions to herbal medicine arise from a lack of good manufacturing practice rather than as a result of plant toxicity. Failure of good manufacturing practice may involve botanical misidentification, substitution, adulteration, contamination (e.g. with micro-organisms or heavy metals), incorrect preparation or incorrect recommended dosage.
Herbal medicines have the potential to interact with pharmaceutical drugs and modify their pharmacological effects in the body. The opposite is of course equally true: drugs can interact with herbal medicines. Interactions can compromise treatment and can in some cases put the patient at serious risk.
Based on knowledge of the chemical constituents in medicinal plants it is possible to hypothesise about a vast number of potential herb-drug interactions. The clinical experience suggests, however, that such interactions present less of a problem than could be expected. For this reason it is important to differentiate between hypothetical interactions, of which there are many, and documented interactions, of which there are relatively few.
Knowledge of herb-drug interactions is still in its infancy and there is no doubt that more cases will be documented in the future. Increased knowledge and documentation of interactions is a positive development for western herbal medicine as it provides for safer and more effective practice. Recent years have seen a marked increase in our understanding of herb-drug interactions, and clinical trials are now being conducted with the specific purpose of investigating potential interactions between herbal medicines and drugs. Currently, the most detailed information about interactions pertains to St John’s wort (Hypericum perforatum). Extracts of this plant can interact with pharmaceutical drugs through several mechanisms. One of these involves stimulation of drug-metabolising enzymes, resulting in reduced bioavailability and efficacy of certain drugs, when these are co-administered with St John’s wort.
Herbal medicine in pregnancy, lactation and childhood
In pregnancy, especially during the first three months, the intake of any medicine, be it herbal or conventional, should be minimised as information about the effects on the human foetus is limited. For herbal medicines the knowledge about the safety (or lack thereof) of herbal medicines comes from traditional use, sometimes supplemented with data from animal studies.
The most widely used herbal medicine in pregnancy is probably raspberry (Rubus idaeus) leaf, which is considered a facilitator of labour and commonly taken as a tea during the last trimester of pregnancy. While its efficacy remains to be conclusively proven there is nothing to suggest that this use is unsafe.
Morning sickness is a common problem in early pregnancy and herbal medicines such as ginger (Zingiber officinale), German chamomile (Matricaria recutita) and fennel (Foeniculum vulgare) tea have been safely employed to provide relief for centuries.
Many medicinal plants are regarded as unsafe in pregnancy and their use is avoided. Included in this category are plants that present a risk of inducing spontaneous abortion, such as pennyroyal (Mentha pulegium) and juniper (Juniperus communis). Despite many herbs having been assigned ‘abortifacient’ properties in the past, no herbal medicine can be used safely and effectively to induce abortion.
In breastfeeding it should be considered that most compounds absorbed by the mother will end up in the breast milk and therefore be ingested by the baby, albeit in lowered concentrations. This is particularly important in newborns, whose ability to metabolise and excrete foreign compounds is incompletely developed. In general, western herbal medicine is well suited to the treatment of children. Qualified practitioners select mild-acting herbs dispensed in appropriate doses, to which children tend to respond extremely well.
Herbal Medicine: Conclusion
Contemporary western herbal medicine has evolved from an ancient system of traditional medicine dating back more than 2000 years, to the time of Hippocrates. As the discipline evolved, it benefited from numerous influences. Major early influences were Greek and Roman medicine followed by Central European and British herbal traditions. The eighteenth and nineteenth centuries saw the incorporation of many medicinal plants of North American origin, knowledge of which was mostly gleaned from North American indigenous peoples.
During the latter part of the twentieth century science played an increasing role in the development of the major herbal traditions, including western herbal medicine. Although this has led to concerns about the future of herbal medicine in some sections of the herbal profession, it also promises to make the practice of herbal medicine increasingly evidence-based in terms of both safety and efficacy. This, combined with the persistent demand for a range of natural healthcare options by a large section of the community, has seen herbal medicine move towards becoming an accepted part of mainstream healthcare in many western countries in recent years.
This move towards the mainstream brings with it new challenges. Preserving a holistic approach to health and disease is paramount if herbal medicine is to survive as a distinct medical system. The increasingly scientific approach must be employed in a way that prevents the herbal medicine of the future from becoming conventional medicine practised with plant-based pharmaceuticals. Science has immense potential to further the use and acceptance of herbal medicine, but it must be applied in a manner that respects the holistic philosophy so crucial to the successful practice of herbal medicine.
Quality control is another area that presents itself as a challenge for the future. Complex natural products such as herbal medicines pose inherent problems in terms of quality and safety, and the herbal medicine industry must successfully address these problems if herbal medicine is to become a viable part of mainstream healthcare in the future.
The continuing development of herbal medicine relies heavily on research. Research is expensive, and it is more difficult to protect intellectual property relating to herbal medicines than pharmaceutical drugs. This in turn makes it harder for the herbal industry to recuperate its investments in research and development, and adequate funding for future herbal medicine research will require financial commitments from both industry and governments.
Herbal medicine is already responding to these new challenges, and the resurgent interest in plants as medicines from the public, healthcare professionals and scientists leaves little doubt that herbal medicine will take its rightful place in the medicine of the future.