|
TASTE AND ACTION OF CHINESE HERBS Traditional and Modern Viewpoints Since ancient times, Chinese herbalists have classified medicinal materials according to their tastes (Chinese: wei). The taste was understood to have a relationship to the effect of the herb when ingested. This relationship was seen as having great importance in guiding the combining of herbs within formulas. In most traditional Chinese herb books, taste was the first property of an herb to be mentioned, helping to orient the reader to the information that followed. There are five tastes—sweet, salty, sour, bitter, and acrid (sometimes called pungent or spicy)—consistent with the five element concept. Additionally, some herbs are said to be bland in taste, meaning that there is hardly any taste sensation on the tongue when the herb is tested. This term “bland,” however, doesn’t quite capture the Chinese meaning: that the taste is natural, unspoiled, or pure. The bland taste is sometimes considered a subdivision of the sweet taste. Whereas sweet herbs can contribute to accumulation of dampness if taken in too great a quantity, the bland tasting herbs tend to be diuretic, a property that counteracts dampness. There is additionally the designation astringent, which is often considered a subcategory of the sour taste. Some materials—especially minerals and shells—can be astringing without an obvious sour sensation on the tongue, while most sour tasting herbs also have an astringent action. In some texts, astringent taste is added to the basic group of five flavors plus bland herbs, thus yielding seven categories. It is reasonable to raise the question whether or not the tastes really have a strong correlation with herbal effects now that there is so much more known about the actions of herbs as the result of long historical experience and modern research methods. The answer to this might influence modern herbalists in their decisions about which herbs are appropriate to combine within a formulation. Unless noted otherwise, the traditional designation of taste for herbs mentioned in this article comes from Oriental Materia Medica (1). In several instances, other texts may provide different designations; this is most often the case when an herb is said to have two or more tastes. 1. SWEET TASTEThe sweet taste of herb materials—and foods—is traditionally associated with a tonic effect. The main sweet tasting constituents in nature are now known to be carbohydrates (including simple sugars, complex starches, pectins, and polysaccharides) and proteins. There are some rare exceptions, such as the glycyrrhizin in licorice which is about 50 times as sweet as sugar but is not a type of sugar; still this relatively rare exception basically proves the rule that sweets are sugars, simple or complex. Raw licorice is often used as a detoxicant and anti-inflammatory, as one would do with bitter herbs (see below), and licorice does contain bitter components. To fully utilize licorice as a tonic herb, it is first baked with a substantial amount of honey—adding considerable sugar and possibly neutralizing some of the bitter, cooling, and anti-inflammatory components. The sweet taste is one of the few in nature that is inherently pleasing to all, young and old and regardless of culture. This situation is no doubt a biological survival mechanism by which humans are “directed” to consume nutritious substances as food: of the three basic macro-substances needed in nutrition, sugar and protein tend to be sweet, while the third, fat, appears to elicit appreciation for other flavors, especially sweetness. In nature, fat usually accompanies protein (as in nuts and meat), and thus the food with substantial fat is usually sweet. It is rare that sweet tasting natural substances are poisonous, which is why it is the only inherently pleasing taste (especially to young children who are exposed first to the sweet taste of mother’s milk). Although the full range of tastes are associated with a relatively limited non-toxic part of our natural environment, most of them are acquired tastes, things that are first approved by those who have survived eating them, and then, with some convincing, passed on to the next generation. Green vegetables, with their slight to strong bitter component, are normally avoided by children, and by quite a large portion of the adult population in America, despite persisting pressure to eat them because of their healthful value. In a modern culture inundated by isolated sugars, it may be hard to imagine how sweet tasting things can be considered beneficial to health, but in the native culture of China there was little in the way of isolated sweets or even overly sweet native foods. Thus, the sweet tasting food substances in Chinese culture were usually starches (such as rice), which have a very mild sweet taste, and meats (mainly chicken and pork). Relying on a natural diet, one tends to be more sensitive to the sweetness of complex sugars (a perception which seems to vanish with the experience of refined sugars), and more appreciative of their healthful qualities. Most modern research regarding dietary simple sugars is aimed at showing their negative impact, because of the large amounts consumed. Complex carbohydrates are repeatedly demonstrated to be of benefit (at least up to a certain proportion of the diet), and that focus of dietary research comes, in part, from our modern reliance on refined simple sugars replacing complex carbohydrates as the sweet part of the diet. Actually, both types of sugars can be beneficial in the appropriate amounts. Too much of some complex carbohydrates can be detrimental. Very simple sugars, such as glucose, fructose, and sucrose, are not only nutrients, but they are calming to the body. That is one reason why they are so often sought out now in the form of “treats.” In modest amounts, they not only calm agitation, they also invigorate basic energy as a fundamental nutrient. Sugars also soothe irritated membranes and are thus used successfully in making cough syrups, throat lozenges, and the like. In China, simple sedative formulas are made from jujube, wheat, licorice, maltose, and other sweet herbs; honey-based cough syrups have been used since ancient times. The modern experience of children becoming uncontrollable when consuming sweets reflects two problems: disharmony in the child’s body and carbohydrate consumption that far exceeds the amounts that would provide a soothing effect. Complex sugars are even better at soothing irritated membranes, and they also bind water in such a way that they can help treat mild diarrhea. Pueraria starch and the pectin-like materials of hoelen are examples. Certain complex sugars interact with cell membranes and promote immune functions: these are polysaccharides that have been of growing interest since their isolation and testing in the late 1960’s. Astragalus has been a major source of such sugars. As an illustration of the connection between traditional and modern approaches to taste and medicinal activity, at a 1981 international conference in Harbin, China, a researcher described how she had decided to test astragalus polysaccharides, one of several types of the herb’s active constituents for immune-promoting. She said that in traditional Chinese medicine, the tonic quality of astragalus was associated with the sweet taste; she reasoned that the sweet taste would likely be made up of sugars, and so she isolated various saccharides, and tested them for a tonic action, namely, for increasing resistance to disease as measured by specific immunological tests. Her studies showed that the astragalus polysaccharides had a marked effect on several immune responses; this work was followed up in the U.S. and became the basis of recommending astragalus for treatment of cancer patients suffering from chemotherapy-induced leukopenia. Plant parts that have a notable sweet taste are usually fruits and roots/rhizomes/tubers. The reason fruits are sweet is that this attracts fruit eaters among the animals who will then deposit the seeds at some distance from the plant on which the fruit grew, giving a sort of mobility to the plant that it would not otherwise have. The sweet fruit may also attract certain kinds of bacteria and fungi into the process of decay when the fruit falls, providing useful nutrients to the plant. Sweet roots and tubers are storing sugars for the plant to use in growing in the early spring. These roots usually become large and sweet in the late summer or autumn. Given the natural roles of polysaccharides as a medium for energy metabolism, as a structural material, and as a means of storage under difficult conditions, it is not surprising that the sweet tasting materials are “tonic” in effect when ingested: energizing, building, and storing. Protein is the structural substrate for biological activity. It is the substance of enzymes, muscles, and neurotransmitters. A substantial amount of protein in the human diet is usually obtained from animal sources. Legumes and nuts are the main edible plant sources of protein. Seeds and other reproductive materials (e.g., pollen) have high amounts of protein; it is utilized to initiate the growth process. Some seeds are too tough to eat and others are poisonous (biological mechanisms to aid survival in some cases), so we usually rely on a limited range of them. The taste of the meats, legumes, and nuts are mildly sweet; it is common practice to add salt to them in order to broaden the taste experience in meals. Most of the foods that are consumed in substantial quantity (e.g., grains, beans, meats, many fruits) are classified by the Chinese as having a sweet taste (they may have other tastes as well) and a tonic nature. They are considered by Chinese diet specialists as tonic to the spleen system (though the different foods can also be subdivided according to benefits to each of the five zang), which is the organ system responsible for distributing the qi from food. That is, good food benefits the spleen and builds up the qi. Our modern understanding of sweet tasting herbs has close correspondence with the traditional classifications:
Of 71 tonic herbs listed as such in Oriental Materia Medica, 38% are roots, rhizomes, and tubers, 21% are animal materials, 13% are seeds, and 11% are fruits, and 17% are from all other types of materials combined, including two mushrooms and maltose (a simple natural sugar product). Since edible animals, fruits, and seeds are more commonly listed in diet therapy rather than in herb therapy, one can understand why this herb book mainly lists the roots, rhizomes, and tubers. Not all the items in the tonic sections mentioned here have a sweet taste: of the 58 items (82% of the total materials listed) with a sweet taste, 34% are roots, rhizomes, and tubers, 21% are animal materials, 12% are fruits, 11% are seeds and 22% are all other materials combined. Some tonic herbs with sweet taste as the sole classification given (e.g., not sweet and bitter):
2. SOUR TASTE The sour taste is relatively rare among the herbs of the Chinese Materia Medica, but is fairly prominent in foods, specifically fruits. A variety of organic acids common to the fruits contribute the presence of sour flavor. These include citric, malic, and ascorbic acids. It is also the fruits that mostly contribute a sour flavor among the herbs in the Oriental Materia Medica (examples of fruit and fruit rind herbs with sour taste are mume, schizandra, terminallia, rubus, rose, cornus, pomegranate, crataegus, chaenomeles, and phaeseolus. Wine (with tartaric acid) and vinegar (mainly comprised of acetic acid) are sometimes used to process herbs that are to be utilized as liver and blood tonics because of their influence on the herb properties that is similar to that of other sour materials. Some herbs have a sour taste due to ingredients other than organic acids. Alum, haloysite, and oxycalcite are classified sour tasting minerals. Roots and stems, such as peony, achyranthes, sanguisorba, and cistanche, have a variety of complex active components that produce a sour taste. There are two major connotations of the sour taste in Chinese medical theory:
Herbs with Sour Taste Among the items mentioned above are minerals which astringe fluid discharge and numerous fruits. 3. BITTER TASTEThe bitter taste is the most common one found among medicinal herb ingredients, especially among the plant materials. It has been suggested that the bitter taste is generally unpleasant because it warns of potentially toxic ingredients. These toxins are strong medicines, and it is because of this that they become common among the ingredients of herbal medicines. Alkaloids, which often affect the nervous system, are consistently bitter, and glycosides, which usually affect the circulatory system, are frequently bitter; so are most flavonoids, which have broad beneficial health effects if taken in sufficient quantities. There are two basic qualities associated with bitter taste:
There are so many bitter herbs that one could hardly begin to list them. However, it is in the category of “fire-purging” herbs that the bitter taste is most frequently found. Some of the intensely bitter herbs include:
These herbs inhibit infections, reduce inflammation, and, in many cases, inhibit tumors. 4. ACRID TASTEThe acrid taste indicates a certain burning or numbing sensation of the tongue, which is elicited by a variety of ingredients, but most frequently by essential oils. Most of the essential oils are highly volatile, giving them a notable fragrance and a dispersing quality. Essential oils may cause the surface blood vessels to dilate, causing sweating and changes in the circulation in the skin and joints. They also tend to stimulate mucus secretion and movement in the lungs and sinuses (see: The use of aromatic agents for regulating qi, vitalizing blood, and relieving pain for additional information about applications and constituents). There are five sections of the Materia Medica that contain a large percentage of acrid herbs, with one section dominated by acrid tasting herbs: the surface-relieving category. Although not all the herbs that relieve the surface contain essential oils as active constituents (ma-huang is an obvious exception, it has an alkaloid as the principal effective ingredient), the majority are rich in essential oils that stimulate circulation and, with adequate dosage and proper administration, induce perspiration. Among the acrid herbs for relieving the surface with essential oils as dominant ingredients are:
The other associations of acrid taste in traditional Chinese medicine are:
From a Western perspective, we know that essential oils are penetrating and have circulation-altering actions. 5. SALTY TASTEThe salty taste has two predominant associations in traditional Chinese medicine:
From a Western perspective, we have come to associate salt (sodium chloride) as being harmful to the kidneys and a cause of fluid retention. However, the primary activity of salty tasting herbs is usually not the result of adding substantial amounts of sodium salts to the body. According to the philosophy of the Nei Jing, herbs with a salty taste are directed to act upon and benefit the kidney, while consumption of large amounts of salt will harm the kidneys. The herbs for resolving swellings (in most cases, these are not the kidney tonics) usually have a cold nature, and are thus to be used cautiously in persons with cold syndromes, including yang-deficiency diarrhea. They are considered somewhat deleterious if taken over a long period of time by persons with weak stomach/spleen functions. The salty kidney tonic herbs are predominantly of warm nature (turtle and tortoise shell are exceptions) and they should be used cautiously in persons with deficiency fire syndromes. Herbs with Salty Taste It is unclear, from the modern viewpoint, how a salty taste fits with the above listed herbal properties, except that large amounts of salts, as found in the seaweeds, could have an impact on clumping of cells and other phenomena that might yield swellings and could affect diuresis. Assigned Tastes Anyone who has tasted ginseng roots recognizes the strong bitter flavor, and may feel hard pressed to note the sweet taste, apart from those fresh roots that have been preserved with sugar. The ginseng root contains a substantial amount of starch and sugar, and a small amount of the immune-enhancing polysaccharides. The bitter taste derives from its content of saponin glycosides—the principle active constituents at usual dosages; the more glycosides a root has, the more potent the root is, in terms of tonification. A saponin is a steroid-like molecule and a glycoside is a combination of a complex molecule, such as a steroid, with a sugar (which often has the effect of enhancing absorption). The sweet taste may have been attributed to ginseng for any number of reasons, including the possibility that when the taste was first assigned in an herbal text, the available roots were from a different plant species (one like codonopsis) which are sweeter than the current ones. No matter the original designation, the reputation of ginseng as a spleen tonic and the description of ginseng as a sweet tasting herb (with mild, bitter quality), coincides with the dogma that the sweet taste is tonic, and especially that it tonifies the spleen. Therefore, the emphasis on ginseng’s sweet taste remains. In similar manner, the essentially white ginseng roots are described as being yellow, consistent with the five element systematic correspondence of the yellow color and the spleen. By contrast with ginseng, astragalus and codonopsis are notably sweet in taste (like many herbs, they also have some bitter quality). These two herbs, like ginseng, are said to tonify the spleen and lung. Although ginseng is considered the “stronger” qi tonic, it is not sweeter than the others. Thus, the degree of sweetness of an herb is not necessarily associated with the traditionally described degree of tonic effect. Nor is the degree of sweetness by tasting necessarily associated with the degree of sweetness described by herbalists: maltose is a sugary material that is listed in Oriental Materia Medica as having only mild sweetness (others list it as sweet), while tremella, a polysaccharide-rich mushroom, has barely detectable sweetness, but is described in Oriental Materia Medica as being sweet (not mildly so). Ganoderma is an example of a tonic herb (it is classified as a tonic sedative in some books) that is said to have a sweet, mild flavor. Anyone who has tasted the ganoderma extracts notes that it is extremely bitter. This is because of its content of triterpenes, which are molecules quite similar to the saponin glycosides of ginseng. In this herb, both the immune-promoting polysaccharides and the triterpenoids play key roles in providing a healing action. The triterpenoids are responsible for the sedative effect, as well as some other actions, including better oxygen utilization (hence improving energy), and the bitter components of ginseng do the same. The description of ganoderma as a sweet herb may follow, rather than precede, its description as a tonic agent. Thus, while traditional herbalists were able to properly associate the sweet tasting component of herb materials with tonic effects that we can now confirm experimentally, there are considerable limitations to this simple system based on general observations of nature. Modern investigations raise questions about the emphasis on describing, for example, a sweet taste as a designation of tonic properties of several herbs. The tastes assigned to herbs has sometimes changed over time, and, even today, herb specialists may debate about which designation is correct. In the Zhenzhu Nang (Bag of Pearls), written around 1200 A.D., siler (fangfeng) is described simply as being sweet (not sweet and acrid as it is today), and its effects are described as eliminating wind from the body, especially wind that is moving upwards (3). The acrid quality of siler is emphasized in modern texts, which matches with the dispersing (wind-dispelling) properties that are still attributed to it. According to Heiner Fruehauf, all the traditional texts, in designating the wei of an herb, are referring to the immaterial function rather than the material basis of the herbs. Therefore, when translating wei to taste, one finds many discrepancies because the word usually implies, to Westerners, only the effect of the substance on the tongue. In sum, one can find modern confirmation of at least some of the traditional assignment of taste as a characteristic associated with herb action. One can also find many situations in which the traditional designations do not seem to make very much sense in light of common knowledge. At least partial resolution of some of the apparent discrepancies may lie in the interpretation of the Chinese term wei; but some of the designations remain the subject of debate among herbal authorities. Changing Views “When heaven and earth had already been separated, the creation of all things was due solely to the five qi [this is like the six qi of hot, cold, wind, damp, etc.]. After the five qi had been determined, the five tastes arose. Following the genesis of the five tastes, the thousand transformations and ten thousand changes continued without end. Thus it is said that the qi bring forth things, and the tastes complete them. That which was created individually becomes a pair when complete; that which was created as a pair becomes an individual entity when complete. Cold hardens; thus the corresponding taste [salty] can be used to draw things together. Hot influences draw things together, thus the corresponding taste [bitter] hardens things. The influence of wind disperses; thus the corresponding taste [sour] can be used to gather. The influence of dryness gathers; thus the corresponding taste [acrid] can be used to disperse. The zhong influences [central] originate in the soil. They are able to harmonize everything; thus the corresponding taste [sweet] can be used to soothe. If the qi is firm, strength results. For this reason, the qi [circulating in the body] can be nourished by bitter things. If the vessels are drawn together, they are in harmony. Thus, the vessels can be nourished with salty things. If the bones are gathered together, they are strong. Therefore, the bones can be nourished with sour things. If the muscles are dispersed, they are not cramped. Thus, the muscles can be nourished with acrid things. If the flesh is soothed, it can not be blocked. Therefore, flesh can be nourished with sweet things. If a soothing effect is wanted, the sweet things should be used; if soothing is not wanted, the sweet things should not be used. No applications may be exaggerated; excessive amounts can also cause illness. Anyone in ancient times who wanted to nourish life and cure suffering first had to understand what has been said here. Only very rarely is suffering relieved without such understanding.” While some of the above statements correspond to traditional dogma conveyed today, some of them do not. Though practitioners do not often think of salty things drawing together in the most general sense, calcined oyster shell and alum are examples of salty astringents used to tighten up membranes and stop dripping of fluid. Most practitioners probably don’t think of qi being nourished by bitter things, vessels being nourished by salty things, or bones being nourished by sour things; these represent areas where the associations have changed. Here is a description in the Tangye Bencao, written during the 13th century (3): If the liver suffers from tensions, sweet herbs should quickly be taken in order to relieve these tensions. Licorice is advisable in this case. If one wishes to disperse obstructions, acrid herbs should be taken quickly. Cnidium is advisable in this case. With acrid herbs, one replenishes the liver, asarum is appropriate. With sour herbs, one drains the liver; peony is appropriate....Bitter herbs replenish the kidneys; rehmannia and phellodendron are appropriate. These descriptions seem somewhat at odds with the dogma of today’s traditional approach. Liver tensions are often treated with bitter herbs (such as bupleurum and chih-shih); asarum would be deemed inappropriate for a liver deficiency syndrome; the sour herb peony is described as nourishing the blood and astringing the yin, rather than draining; and bitter herbs are used to deplete kidney fire rather than replenish the kidney, though by reducing the deficiency fire, the yin can be naturally restored. Some of the apparent discrepancies and variations might be explained by applications of different aspects of the five elements system (which includes the nurturing and controlling relationships), but others simply represent differing views that arose during the long history of Chinese medicine. Using Taste Designations Today In the 1995 publication Advanced Textbook of Traditional Chinese Medicine and Pharmacology (4), this is said: “Since the flavors of drugs have an intrinsic relationship with their efficacies, understanding the characteristics of the five tastes is of great importance in guiding the administration of drugs.” Yet, despite this statement, the relationship is not raised again after the single page that includes a few examples of taste associated with therapeutic effect. One example from this page is that “Drugs such as perilla leaf and mentha for inducing perspiration and relieving exterior syndrome and citrus and saussurea for activating qi are all acrid.” Yet, in the text describing individual herbs, the section on surface-relieving includes the non-acrid cicada skin (salty and slightly sweet), morus leaf (bitter and sweet), and chrysanthemum flower (sweet and bitter); the section on activating qi includes the non-acrid melia (bitter). While the majority of herbs in these two sections have an acrid taste (often combined with another taste), these exceptions do not elicit any commentary. In the U.S., the taste of an herb is one of the required pieces of information for students to learn, yet descriptions of taste and effect rarely crop up in the American literature, except as simple recitation of the current standard dogma. Herb tastes is a subject left out of the portion of the NCCA examination devoted to herbs that most American acupuncturists now take. Undoubtedly, persons who strongly respect the traditional methods would argue that there is still be too little known about the herbs to disregard the taste as a distinguishing feature. By contrast, persons who follow the modern scientific approach to herbalism may suggest that it is the actions of the main active constituents that determine the effect of a formula, and it does not matter what the actual taste is, since the taste can be influenced by so many different ingredients within the material, some of them not seemingly relevant to the effects. Thus, for example, the lignans of schizandra are deemed especially important components by modern researchers, but these contribute only a bitter taste to the “five flavored fruit.” The sour flavor, conferred by organic acids as found in many other fruits, probably contributes relatively little medicinal action except, possibly, when high dosage decoctions (or dried decoctions) are relied upon. Observing modern practitioners of traditional Chinese medicine designing treatments for patients reveals two patterns of behavior that suggest there is actually less emphasis on taste than when it was suggested, several centuries ago, as a critical factor in attaining success. First, many doctors use large prescriptions, containing a dozen or more herbs, and with such large prescriptions, one usually finds a complex mix of all five tastes regardless of the therapeutic action intended; it is not clear that an effort was made to coordinate the tastes in coming up with the final formulation. By contrast, taste of herbs in a formula is often raised in descriptions of small ancient prescriptions, such as Cinnamon Combination and Rehmannia Six Formula. Second, it is common to see a base formula developed for treatment of a disease condition which is then modified by various added ingredients for specific symptoms, constitutional patterns, or signs. The additions clearly alter the taste of the formula, but it does not seem to be the case that the taste of the additions is a major consideration; rather, it is their defined actions based on either modern or ancient indications. Still, disregarding taste may be one of the steps, like so many others taken in modern times, that isolates the herb practitioner from an important interaction of humans with nature: experiencing and responding to a fundamental sensory perception and leaving behind the traditional methods of describing natural phenomena (such as herb actions). It is easy to be overwhelmed by the power of clinical experience and modern research. Without disregarding what has become available through the modern efforts, one may wish to keep aware of the traditional methods with regard to taste and formulation. At the least, one should examine the traditional ideas—in all their variations over time and among authors—until something more definitive can be established by the work that is currently underway to determine how herbs affect human health. REFERENCES
October 2010
|