Herbal medicine

From SkepticWiki

1 Definition
2 Origins
3 Discussion
4 References

[edit] Definition

Datura, from an early 19th century American herbal.[1]

Herbal medicine is the use of plants for medicinal purposes. A related term, Herbalism, refers to the practice of using whole plants to treat disease. In Herbalism, it is generally believed that the whole plant or part of the plant must be used, rather than refined extracts.

[edit] Origins

Herbal medicine is probably as old as the human species itself. A controversial branch of science, zoopharmacognosy, suggests that it may be even older. There have been some observations that chimpanzees eat rolled leaves which reduce the number of intestinal parasites. Other animals, such as deer, have been observed seeking out plants with psychoactive substances to eat. This suggests the possibility that beneficial substances in some plants may have evolved for the benefit of animals. Other plant substances, such as penicillin and many antifungals, benefit the plant itself by killing or driving off pests and infections and are useful for similar pests and infections of humans.

Herbal medicine today is in international industry with a turnover estimated at over US $20,000,000,000 per year, with up to 34% of American adults having consulted a natural health practitioner in 1990.

[edit] Discussion

Many of the substances in modern pharmacology are derived from plants. According to Professor E. O. Wilson [1], 40% of pharmaceuticals prescribed in the USA have active ingredients originating in plants; and academic and industrial scientists put a great deal of research in investigating traditional herbal medicines, as well as testing plants which have no particular medical traditions attached to them. Aspirin was originally derived from the bark of the willow tree. Digitalis originated in foxglove. Many strong painkillers are derived from the poppy flower. The near certainty of finding many useful plants in the rainforests is often used by scientists as a pragmatic justification for preserving these and other wilderness areas.

Herbalists often claim that researchers of scientific medicine deny the medicinal properties of herbs. This is a strawman argument against science and critical thinking and is far from the truth. Modern pharmacologists study herbs and extract the active substances, isolating them from other, possibly harmful substances. Herbalists insist that this process removes some sort of ill defined goodness from the natural plant. An herbalist would insist that, for example, willow bark is superior to aspirin for pain relief. The opposite is usually the case. Willow bark preparations can damage the stomach. The refinement of the active ingredient, salicylic acid, by adding an acetyl group, drastically reduces the damaging effects while preserving the beneficial properties.

Skeptics raise a number of issues about herbalism:

[edit] Safety

One popular misconception is that “herbal” equals “natural” equals “safe”, often combined with the scientifically illiterate idea that conventional medicines contain chemicals and herbal medicines do not.

As we have seen, conventional medicines often contain exactly the same active ingredients as plants do, or are manufactured from plant extracts: these conventional medicines are no less safe than the herbs on which they are based and are frequently safer.

The very fact that herbs have real and powerful effects means that they can have side-effects which are disagreeable in some cases and fatal in others. One case in point is Black Cohosh (also known as Black Snake Root, Bugwort, Bugbane, Squawroot, Rattleweed, Rattle Root, and Cimicifuga). Prescribed for menopausal symptoms, it has been implicated in causing cancer [3], which seems a heavy price to pay for avoiding hot flushes: yet it is still available from herbalists, and is bought, presumably, by women who think that herbal medicine is necessarily safe.

Anyone considering taking herbal medicines should seek some reputable source on the dangers the particular herb presents, and the contra-indications: like a more conventional medicine, a given herb may be unsuitable for people with kidney problems, or asthma, or immune disorders, etc.

Besides the safety problems that herbal medicines share with conventional medicines, there are some issues which relate only to herbal medicines.

One problem is that the herb may have been grown using toxic pesticides, or on land contaminated with heavy metals. Very few herbs are sold giving a guarantee of their provenance. Another problem specific to herbal medicines is that they may vary greatly in the quantity of the active ingredient, with the potency of a particular herb varying from season to season, subspecies to subspecies, soil to soil, climate to climate. By contrast, the manufacture of pharmaceuticals is rigorously controlled in this regard. Similar remarks apply to quality control: an herbal medicine, like an illegal drug, may be “cut” with some other substance. A commission reporting to the UK Parliament found that most ill-effects from herbal medicines are caused by poor quality control [4].

Finally, herbal medicines are simply not subjected to the lengthy and rigorous process of testing that pharmaceuticals must go through. Other things being equal, an effective pill which has been tested for safety is more likely to be safe than an equally effective herb which has not undergone such testing.

[edit] Effectiveness

A new drug will be tested, not only to guarantee that it is safe and effective, but also to see if it is safer or more effective than the existing leaders in the field. By contrast, an herb may be touted as a cure based on nothing more than anecdotal evidence, the placebo effect, regression to the mean, or the “intuition” of a healer. The result is that the patient may end up paying for a herb which doesn’t work rather than a pill which does.

Moreover, the drugs available are the result of the testing of literally thousands of substances, including plants from all over the globe. It is unlikely that any particular herb known only to one ethnic group with a much narrower range of substances to choose from will be more effective than the pharmaceuticals prescribed for the same condition. It is, of course, possible, which is why scientists still go on investigating new plants. But the odds are very much against it, which is why so many herbs undergo scientific scrutiny for every drug that comes to market.

[edit] Green issues

The hope of finding herbs in the rainforest has, as noted, been used as a standard environmentalist argument, but some thought should also be taken for the fate of the medicinal plant once it has been discovered.

For example, the African Devil’s Claw plant is being uprooted from the Kalahari desert at an estimated rate of 15 million plants per year. In America, the overharvesting of American ginseng has driven it onto the endangered species list. Even plants which can easily be cultivated, such as oregano, are threatened in the wild by overharvesting. This is not a new phenomenon. The favorite herbal remedy of the ancient Greeks, sylphium, was driven into extinction by overharvesting: in South America the cinchona tree (source of quinine, used against malaria) was under threat in the nineteenth century from overharvesting. However, the scale of the problem today is greater than ever. Two thirds of herbal remedies on sale are produced by harvesting wild plants. A recent report by Plantlife International, the wild plant conservation charity[2], claimed that 4,000 to 10,000 herbs worldwide are endangered by the herbal medicine industry. This is despoliation on a scale which makes the “ecological footprint” of a pharmaceutical company seem modest and innocuous.

[edit] Profit

Modern scientific medicine is criticized by many herbalists as being motivated by profit and neglecting plants for that reason, because a natural plant cannot be patented. From the size of the industry, however, it does not appear that the producers of herbal products will starve any time soon. Furthermore, modern scientific medicine continues to make profit from products that cannot be patented or from products whose patents have long since expired.