THE HISTORICAL USE OF PLANTS AS MEDICINE

It is certainly true that humans have employed various medicinal plants, often in association with magic or religious tenets, to treat their ailments and presumably those of their animals. Therefore, one argument used in favor of the use of herbal and botanical medicine is an appeal to the longevity of the therapy. Otherwise stated, herbal medicines are said to have withstood the “test of time” and should therefore be employed. Both practitioners and owners may believe that such remedies are safe and effective, even though they have not seriously questioned whether this is true (Ernst, 1995a).

It should be immediately noted that the “test of time” standard is inadequate when it comes to assessing the reliability of any human endeavor, including those involving the practice of medicine (Ernst, 1998a). Some notoriously unreliable enterprises have been associated with humankind for many thousands of years. For example, people have used astrology—the attempt to foretell one’s future by looking at the stars—for thousands of years, although there is no credible evidence for its usefulness and ample evidence to refute it. Similarly, therapeutic phlebotomy (bleeding) is one of the oldest known medical interventions; it has generally been abandoned only in the last century or so (except for its use in a very few conditions) and is still used in some societies. Curiously, and in keeping with the general response of some modern herbalists to scientific criticisms of their remedies, even when bleeding was finally shown to be ineffective, it was not bleeding itself, but the new type of controlled trial, that was doubted (Lilienfeld, 1982). Finally, even medications that were used for thousands of years have subsequently been shown to have serious adverse effects. For example, a traditional Oriental formula, Sho-saiko-to, was said to have been used for 2000 years in China without adverse effects, but it came to be associated with serious liver damage in Japan in a case report of 4 patients (Itoh, 1995). Thus, the “test of time” is not a reliable indicator of safety or efficacy.

Nevertheless, some evidence for the use of herbal and botanical medicines dates back to the Neanderthal period (Kleiner, 1995). Once historical records began, prescriptions for the use of various plants became part of the medical tradition of virtually every society. Even today, herbal medicines are an important component of traditional medicine in virtually every culture (Vickers, 1999). Once traditions of plant medicine were established, they eventually became more developed. So, for example, the 16th century saw European medical schools creating botanical gardens to grow medicinal plants (Akerele, 1993). When the European expansion occurred, beginning in the late 15th century, European explorers encountered medicinal plants from other cultures and began to send them back to Europe. These plants, originating from Central and South America, profoundly influenced European treatments of the 16th and 17th centuries (Duran-Reynals, 1946). As America became colonized, housewives of the colonial period would gather plants and wild herbs, such as sarsaparilla, horehound, and dandelion, and hang them to dry for future use (Blanton, 1930). Indeed, until the 20th century, most medicinal remedies were botanicals, and, through trial and error, a few were considered to be helpful.

Over time, more formal programs involving the use of herbal and botanical remedies arose. For example, in the United States between 1836 and 1911, 13 physiomedical colleges, which substituted botanical medicines for pharmaceutical drugs and promoted beliefs in a “vital force” that permeated the body and to which healing powers were attributed, opened and then closed their doors (Haller, 1997). In the United States and to a lesser extent in Europe, the Thomsonian movement of the mid-1800s became popular by endorsing herbal remedies for health and medicine (in addition to advocating steaming the body to overcome the “power” of cold). However, contrary to assertions that herbal remedies are time honored, the influence of herbalists and their remedies, as well as the power of the other medical sects, waned over time. This likely occurred because these practitioners could no longer match the advances of science and accompanying improvements in medicine, which removed them from the public trust that developed as those advances continued.

The history of veterinary applications of herbals and botanicals is perhaps as long as, but somewhat less well documented than, that of similar applications in human medicine (Haas, 2000). For example, black and white hellebore treatments (Helleborus niger and Veratrum album, respectively) were used by Pliny in the first century ad. as a seton (drain) through the ears of horses or sheep; in the early 20th century, they were used as purgatives, emetics, anthelmintics, and parasiticides (although they caused death in many animals). Historical prescriptions for herbal use—such as pounded apricot kernels combined with pig fat for the treatment of animals with hoof ailments, or guang barley combined with food chewed by a child for the treatment of animals with hoof wounds—can be found in 6th century Chinese Qimin yaoshu (Ramey, 2001). The medicinal practices of native North Americans are a rich source of veterinary herbal prescriptions (Vogel, 1970). Botanical “horse medicines” were provided for the treatment of horses during the American Civil War (Merillat, 1935). Even as late as 1957, popular books continued to list such substances as aconite, belladonna, cinchona, ipecac, nux vomica (strychnine), and tobacco for veterinary use (Hiscox, 1957). However, such titles became scarcely evident until the latest revival of interest in the use of herbal and botanical veterinary remedies.

HISTORICAL REALITY CHECK

The fact that herbal and botanical products have been used throughout history may suggest, to some, that such products are effective medicines; however, a critical look reveals that such an assertion is not correct. In my opinion, an approach to medical therapy that relies on crude botanicals and botanical preparations is not likely to be, and has not been, useful for the treatment of patients with disease or the maintenance of health.

When thes historical efficacy of herbal medications is discussed, the salient question is, “Effective compared with what?” In fact, during the heyday of herbal and botanical medicine, other medical treatments, such as bleeding or prescribing large doses of mercury salts (calomel), were largely ineffective—even toxic. Thus, the use of a plant product that was not acutely toxic would have been expected to be of less obvious harm to the patient compared with other interventions and, therefore, more desirable. Furthermore, the fact that herbal medications were widely used may simply reflect that plants were readily available for use by all, and that outside health care was simply not affordable or available for many humans or animals.

Throughout history, it cannot be asserted that herbal and botanical medicines were responsible for any measurable improvement in human or animal health. Mortality curves remained surprisingly similar over thousands of years and under diverse cultural conditions (Cairns, 1986). For example, examination of skeletons from a 40,000-year-old Paleolithic society in Morocco shows that 50% of the population had died before age 38. Before the advent of modern pharmacology in the 20th century, life was “poor, nasty, brutish, and short” (Thomas Hobbs, 1588–1679). When compared with the mortality curves of preagrarian societies, those of 19th century cities were largely identical, although death rates spiked during years of infectious epidemics. In 1900, Western life expectancy was 45 years.

By 1996, this expectancy had increased to 76.1 years. The high rates of morbidity and short life spans that are consistent throughout history and across cultures were due, at least in part, to the inability to prevent or effectively treat infectious diseases (Huxtable, 1999). The dramatic changes in life expectancy that occurred in the 20th century were largely due to clean water, vaccination, and the ability to control infection via effective pharmaceuticals.

In addition, historical assessments of herbal therapies must be made in light of vast differences between historical and current use of the products. In the past, the emphasis for the use of herbal medications was on treatment of symptoms, rather than underlying disease conditions (which had yet to be identified). Ironically, and particularly so in light of the holistic claims that may be made currently for herbal preparations, elimination of the symptom, rather than elimination of the underlying problem, was the criterion used for treatment “success.” For example, if a fever abated because the patient ingested willow bark, the treatment would have “worked,” although the disease process that caused the fever might have been unaffected. In addition, herbal and botanical remedies were generally applied for vague, all-encompassing conditions (e.g., liver malfunction), rather than for specific indications.

Again, the vague nature of such historical prescriptions should not be surprising in light of the fact that these remedies were prescribed in an era when the causes of disease were uncertain, when different diseases with the same symptoms could not be differentiated, and when the treating doctor had few tools at his or her disposal. In addition, the long-standing use of plants as medicine did not lead to an overall increase in knowledge about their use, nor was such use codified in any meaningful way. Throughout most of history, whether in China, India, or European societies, no effective way of conveying useful information had been developed. As a result, historical herbalists copied extensively from one another over millennia and mixed accurate (by modern standards) information with nonsense, misconceptions, and inaccuracies.

In fact, the true usefulness of historical texts as guides for modern practice is extremely limited. In historical texts, true plant identities are doubtful, in regard to both genus and species. Furthermore, if such treatments failed when they were applied, this was not likely to be noted—the societal acceptability of risk in the treatment of patients with disease was higher (Huxtable, 1999). In fact, the only way to separate the beneficial from the useless or hazardous was through anecdotes relayed mainly by word of mouth (Angell, 1998). Nor would the appearance of such information necessarily have been useful; even when they became available, most people lacked the means, the literacy, and the mobility to obtain or read textbooks.

Given those limitations, the history of botanical preparations does not provide a good template for modern medical prescription. The nature of the historical claims made for efficacy of various plants and the vague nature of the conditions treated makes it exceedingly difficult to objectively evaluate the true utility of the remedies employed today. Furthermore, the historical “successes” attributed to botanicals carried a cost. As noted, the indications for using a given botanical were poorly defined. Dosages were unavoidably arbitrary and ill defined because concentrations of active ingredients were unknown. Any number of contaminants may have been present. It is most important to note that, as with many other tools used in the historical practice of medicine, many of the remedies simply did not work; some were harmful or even deadly. Accordingly, although historical records of the use of medicinal plants may make for interesting reading, such records cannot be used as accurate guides for many currently advocated uses of herbal and botanical products.

THE HISTORICAL USE OF PLANTS AS DRUGS

Limitations of the historical use of plants aside, it is inarguable that the active ingredients of some currently used pharmaceuticals are identical to, or derived from, plants that were used historically as historical folk remedies. Herbal and botanical sources may be the origin of as many as 30% of all modern pharmaceuticals (Kleiner, 1995). For example, aspirin (acetylsalicylic acid) is derived from salicylic acid, which, as salicin (salicyl alcohol plus a sugar molecule), occurs in the flower buds of the meadowsweet (Filipendula, formerly Spirea) and in the bark and leaves of several poplars and willows, notably the white willow (Salix alba). Historically, it was noted that white willow bark extracts had some effectiveness as a pain remedy; indeed, the seminal Greek physician Hippocrates reportedly prescribed willow bark and leaves for fever and the pain of childbirth. Other cultures have soaked willow leaves and applied them topically for use as a painkiller. Digoxin, another pharmacologically active compound, is derived from the foxglove plant, Digitalis spp. (at least 12 varieties of the plant are known). Historically, foxglove was found to be helpful for “dropsy” (ascites or edema). Quinine, first isolated from the bark of the cinchona tree (Cinchona calisaya) in 1820, was an important antipyretic. As the cost declined and as it became more readily available, quinine was used for the treatment of fever of virtually any origin (“fever” being a common reason for the prescription of plant preparations throughout history). Indeed, the use of quinine as an antipyretic became so widespread in the days after the Civil War that the American Medical Association (AMA) tried unsuccessfully to convince the federal government to grow the cinchona tree in the United States (Ackernecht, 1943).

However, simple facts about the historical use of plants as medicine may not reveal other important considerations that may have led to their decline. After all, it is highly unlikely that people would abandon safe, effective, readily available, and inexpensive medications for no reason. As such, although salicin (the parent of salicylate drugs) was first isolated in the 19th century and was used in crude form as willow bark long before that, to ingest 1 g of salicin from willow bark, a person must ingest at least 14 g of the bark. In addition, the tannins in willow bark (as well as salicin itself) are very irritating to the stomach lining; however, this consideration may not have been important in the historical use of plant preparations because adverse effects were an accepted part of historical medical therapy (Huxtable, 1998). Furthermore, as with many plant preparations when compared with the pharmaceutical products derived from them, salicin is only about half as potent as aspirin.

The use of digitalis preparations for the treatment of patients with heart disease carried its own set of problems. According to detailed descriptions from historical texts, each of the 12 varieties of digitalis plants had active compounds, although the quality of those compounds varied. Seeds of the plant have at least six different biologically active chemical variations, with cardiac and other effects. The potency of digitalis preparations deteriorated rather quickly over a few months, even when the preparations were kept hermetically sealed. Additional difficulties arose because various digitalis compounds had different rates of absorption from the gastrointestinal tract. Finally, variations from batch to batch depended on growing conditions (Osol, 1955).

The use of quinine declined simply because newer and better products were developed. In the 1880s, research with coal tars led to the development of synthetic antipyretics. These products quickly took the place of quinine. Over time, this trend has continued, and plant preparations have essentially disappeared from the mainstream therapeutic armamentarium because newer synthetic drugs gave greater consistency and more targeted efficacy.

THE MYTH OF “NATURAL”

Historical usage notwithstanding, popular modern herbalism has achieved much of its popularity through bombastic claims, such as that its therapies are safer, holistic, or more “natural.” Many promoters of natural herbal products promote the myth that they are somehow superior to the same products produced synthetically in a laboratory. No scientific basis exists for such claims. A chemical is a chemical. For example, no difference has been discerned in the vitamin C that is obtained from natural biosynthetic processes in rose hips and that which is made in the laboratory of a chemical manufacturer. The word “natural” implies only the source and does not indicate that the product is, in fact, superior. Rather, it appears to be used mostly as a marketing term.

Nor does “natural” imply that herbal medications are safe. Many people think that herbal medicines, because they are natural, are harmless (Ernst, 1995b). This is wrong. Nothing about herbs automatically makes them nontoxic simply because they are natural. Natural toxins have the same mechanisms of toxicity as synthetic toxins. For example, cabbage and broccoli contain a chemical whose breakdown products act in the same manner as those of dioxin—one of the most feared industrial contaminants. Dioxin is carcinogenic and teratogenic in rodents in extremely small amounts; however, the quantities ingested by humans are far lower than the lowest amounts that have been shown to cause cancer and reproductive damage in rodents (Ames, 1990a).

One reason why herbs may have a reputation for lack of toxicity may be that the concentrations of pharmacologic compounds in herbs are frequently very low, that is, very little of the active ingredient in an herbal preparation is actually delivered; all toxic effects are dose related. Regardless, drug receptors in an animal’s body cannot distinguish whether a molecule comes from a chemical laboratory or from the plant kingdom. The toxic potential of an herbal remedy does not depend on its origin; rather, it is related to the pharmacologic characteristics and dose levels of its active ingredients.

MODERN HERBALISM—A NEW AND INVENTIVE FRONTIER

Current usage of botanicals is quite different from historical usage. Historically, even if they were unable to assist in the resolution of a disease process, herbal medicines may have served to make the patient feel cared for, and perhaps even helped to relieve some symptoms. However, when compared with modern usage, herbs were historically used in lesser amounts, for specific disease indications (as opposed to the modern practice of using herbs prophylactically, in an effort to prevent health problems), in crude form (as opposed to concentrated extracts), and by themselves, that is, not in association with other medications, such as pharmaceuticals, thereby obviating concerns about herb–drug interactions (Huxtable, 1999).

Although modern herbalism in the treatment of patients with disease conditions or symptoms may differ from historical usage, it also differs from conventional pharmacotherapy in its prescription. Whereas conventional medications are given primarily to treat disease, herbal medications may be offered for many more indications, including the treatment of healthy individuals. Herbal prescriptions may be offered for maintenance, well-being, or health, and may be prescribed to support, enhance, or stimulate various body processes (although the precise nature of such herbal activity is undefined but generally assumed to be good). Prescribing substances to improve health, rather than to treat disease, allows for an entirely different medical paradigm—one that is largely free of the constraints of evidence and objectivity.

Indeed, the English language appears to have been stretched to its ingenious limits in the attempt to ascribe health benefits to herbal products. The creative linguistics used to promote herbal medications appears to be designed solely for marketing the products—often ignoring truth in the process. For example, it cannot be said that the herb Echinacea, commonly used to treat or prevent the human cold, has ever been shown to be effective; indeed, there is good evidence that it is ineffective (Bent, 2004). However, it may be claimed that Echinacea has natural antibiotic actions and is considered an excellent herb for infections of all kinds. Ginseng—a genus with many different species—has long been promoted as an energy booster, for example, yet the military, in studies of possible energy enhancements for troops, has found it worthless (Lieberman, 2001). As such, the veracity of modern herbal marketers who may ignore such real data and continue to make prescriptions under false pretenses must be questioned. Furthermore, it is curious that even though herbal medications may be promoted as “natural,” in fact, advocating the concept of regular ingestion of substances to promote health in individuals in whom no disease is apparent could be construed as anything but natural.

However, in addition to such philosophical differences and linguistic legerdemain, herbal prescribing diverges from modern pharmacotherapy primarily in three important areas:

TABLE 9-1 Example of an Herbal Prescription for Osteoarthritis