Taste is traditionally linked to herbal energetics, since according to all the principal herbal traditions the action exerted by each herb is strongly connected to its taste (or tastes).
The tastes formally recognized as such by modern science are: sweet, salty, bitter, acid and, since not long, also umami (which we can think of as the “taste of proteins”) and fatty.
When we speak of taste within the context of traditional medicines, we have to refer both to the real, formally-recognized tastes and to the flavors and “sensations” that the drugs elicit in our mouth and on our tongue, not necessarily through the taste buds. This is the case of astringency, for instance, that is not a real taste, but rather a sensation. The same applies for that tingling sensation that we perceive when we chew a little bit of Echinacea: it is not a real taste but the result of a kind of stimulation exerted upon the nerve endings located within the oral cavity, and it is a special case of the so-called pungent taste.
Taste is traditionally linked to the fundamental qualities of matter (i.e., the Four Elements and the Four Qualities of the Hippocratic-Galenic medicine, the Five Movements of the Traditional Chinese medicine, and so on) and, for such reason, it is considered one of the most important (if not the single most important) indicator of herbal actions, so much that often drugs are classified on the basis of taste rather than of their effects (or actions).
Comparing the various traditions, some inconsistencies (or at least they seem so, at a first glance) emerge. If we look more carefully, we realize that such inconsistencies are indeed mostly formal and due to the details of the reference model rather than to the taste properties on their own.
With this article, first of a series dedicated to the topic, we begin to a make a (critical) summary of the information coming from:
- the Traditional Mediterranean Medicine (TMM) or Hippocratic-Galenic Medicine [Giannelli. Giannelli2],
- the Traditional Chinese Medicine (TCM)
- the Ayurvedic Medicine, and
- the western herbalism [Wood, Wood2].
In doing so, in order to correctly “position” all the concepts that come from the various traditions, we need to work out a kind of “extended” energetic model. Here, we chose to derive our own directly from the Hippocratic-Galenic one. So, certainly we can find in our model the concepts of Yellow Bile (responsible of the body Heat processes), Phlegm (that represents all that is liquid and nourishes), Blood (responsible of the processes related to Heat and Dampness together) and Melancholy (the “manager” of the solidification processes in the whole body).
In order to accommodate information missing from the Hippocratic-Galenic model, like the concept of Qi coming from TCM, the concepts of status strictus and status laxus of the Greek Methodists and the Constriction and Relaxation tissue states coming from western herbalism (see [Wood], [Wood2]), we introduce into our model the concept of Tension, that roughly corresponds to the vital energy (or, if we prefer, to the functional ability) of the body and internal organs. In relation to it, we define: a Tension stagnation, a condition analogous to Qi stagnation; a Tension deficiency, corresponding to the Qi deficiency, the status laxus of Greek Methodists and/or to the Relaxation tissue state according to Matthew Wood; a Tension excess, that we can define as a state in which the whole body is “stuck” in a kind of functional hyperactivity (it corresponds to status strictus of Greek Methodists and to the Constriction tissue state according to Matthew Wood).
In this humoral model, we will distinguish between primary and secondary tastes. The latter can be seen as derived someway from the former and participating of the nature and characteristics of the primary taste they derive from. The primary tastes are: pungent, aromatic, salty, bitter, sweet, unctuous, acid, astringent, bland. The secondary ones are: acrid-bitter, bitter due to cyanogenetic glycosides, sour-unripe and pontic; each of them is treated within the paragraph that deals with the corresponding primary taste.
Different and even apparently opposite tastes can coexist in the same herb; in such case, they don’t cancel out with each other but rather each of them exerts its own effect independently, at most smoothing the effects of each other. For instance, cinnamon, that is mucilaginous (bland), aromatic and astringent, works at the same time with its mucilaginous, aromatic and astringent components; certainly, the mucilage (moistening) can limit the collateral effects (e.g., excessive dryness) of astringency. The coexistent tastes can show their effects in a more or less pronounced manner, according to the administration conditions (nature of condition and prescription, time of the day, weather conditions, and so on) and/or the patient conditions. The same happens when two or more herbs are combined in a formula: the respective tastes don’t cancel each other out, but act together, possibly “mitigating” the collateral effects of each other.
Within our model, as in the Hippocratic-Galenic one, each taste derives formally from one of the Four Elements. The most accentuated tastes are connected to Dryness (that accentuates and carries to the extreme) while the most delicate ones are connected to Dampness (that mitigates). So Fire, combination of Heat and Dryness (thus the maximum expression of Heat), produces the strongest tastes (pungent, aromatic, salty and bitter, together with its secondary tastes); Earth, combination of Cold and Dryness (thus the maximum expression of Cold), produces cold but still very intense tastes (acid, astringent and the intermediate tastes sour-unripe and pontic); Air, combination of Heat and Dampness generates delicate tastes (sweet and unctuous) that can however be felt, thanks to their albeit modest degree of Heat; Water, combination of Cold and Dampness, prevents any taste and flavor to come out (so that the only taste that can be associated to this Element is a non-taste: bland).
Each taste is associated to a directional tendency, that can be expressed as “centrifuge”, “centripetal”, “upward” or “downward”. This feature can be more or less pronounced in an herb, so that, for instance, we can speak of “strongly centrifugal” herbs rather than herbs that tend “slightly upward”.
Here we also introduce the consequent actions, that are similar to supplementing and draining functions of Chinese medicine and to Ayurvedic viapakas. They can be:
- reducing (it purifies and reduces tissues and/or secretions),
- nutritive (it tonifies and increases tissues and/or secretions ) and
- intermediate (it tonifies the body but reduces or does not increases tissues and secretions).
Hot/dry: Heat and Dryness are both very intense and can reach the extreme degrees.
It warms (but, according to the nature of plant, may also cool); puts into motion, diffuses and externalizes (opens the pores); dissipates and thins, dries, resolves stagnations (of both energy and matter).
Centrifugal and upward.
Deficiency and Stagnation of Yellow Bile; Deficiency, Excess and Stagnation of Tension; Stagnation of Phlegm, Blood, Melancholy
It dispels Tension, dries, inflames.
Within the various medicine systems, the words pungent, spicy and acrid are used sometimes interchangeably and sometimes with different meanings.
These tastes (whatever be the meaning we give them) are sensations rather than true tastes: indeed, they are characterized by their ability to induce a burning or tingling sensation on the tongue and within the oral cavity. Different classes of substances can produce this taste:
- essential oils: it’s the case of cloves, cinnamon, mint and several other spices;
- molecules, different from essential oils, that stimulate specific nerve receptors on the tongue and in the oral cavity or that modulate their response (see also the box “Pungency and receptors” below): it’s the case of alcohol, of the capsaicin contained in hot pepper, of the thiocyanates contained in the plants that belong to the Allium genera or Brassicacee family, of the N-alkylamides contained in some Asteraceae like Echinacea and Acmella, etc.; the most part of plants that produce a tingling sensation belongs to this group;
- molecules that exert a real irritating or injurious action upon tissues: it’s the case, for instance, of the saponins contained in plants such as English Ivy, soapwort, chickweed, or of the protoanemonin contained in the Ranunculacee; it’s also the case of plants like lobelia, valerian, Iris (fresh root), catnip, and some Viburnum
In order to avoid confusion, here we distinguish among:
- pungent aromatic taste, that is, the taste of plants that are pungent due to their essential oil content;
- hot taste or hotness, that is, the taste of drugs containing molecules different from essential oils that stimulate specific nerve receptors on the tongue;
- acrid taste or acridity, that is, the sensation caused by tissue-irritating or tissue-injuring molecules;
- pungent taste or pungency (without further specifications), meaning any one of the previous cases (or all three indistinctly).
Acrid is the only completely unpleasant taste: unlike bitter, that, though being naturally one of the less pleasant at all, may even become pleasant with time (we speak of “acquired taste”), we cannot acquire a habit to acrid. It can be diluted someway (for instance with the sweet taste), but never completely “fixed up”. This notwithstanding, people that decidedly need this taste due to their conditions may find it even pleasant in small quantity.
Clearly, the classification above is generally valid but special cases exist. Sometimes, for instance, pungency is due to the presence at the same time in the same plant of more than one of these kinds of molecules: let’s think, for instance, to black pepper that contains both piperine and essential oil. In such cases, we still speak of pungent aromatic taste if aromaticity is decidedly important and/or contributes significantly to the pungency. On the contrary, hot plants may also possess a certain aroma (i.e., hot pepper), but pungency in them is mostly conferred by substances other than the aromatic ones, and/or aromaticity is not particularly intense. Obviously, intermediate cases can occur for which we cannot make a clear distinction.
Often pungency is due to essential oils and, unfortunately, this sometimes leads to mistaking pungent drugs for aromatic ones and vice versa. Indeed, not all pungent drugs are aromatic and not all aromatic drugs are also pungent. Indeed:
- the pungent taste, as we have already told, may also be due to substances other than essential oils;
- the aromaticity may be due to substances other than essential oils (for instance, vanillin);
- not all essential oil bearing plants are (or can be classified as) pungent, either because the essential oil they contain is too scarce or because of the specific molecules contained in the essential oil: this is the case, for instance, of roses, that are aromatic but not at all pungent, so much that the TCM classifies them, according to the species, as bitter and astringent (Flos Rosae Multiflorae), sweet (Flos Rosae Chinensis) or sweet and bitter(Flos Rosae Rugosae), but not pungent.
According to the degree, the pungent taste can: warm, move and diffuse, externalize (because it opens the pores) and dissipate/thin. The strongly pungent substances (classified as pungent in the 4.th degree) can cause burning on the skin and mucous membranes. Because it opens the pores, it’s diaphoretic and so it can moisten the surface, but it can also dry the interior of the body (a function that belongs to the thinning action). It moves and regulates energy (Tension) and matter, resolving congestions and stagnations. Thanks to these properties, it resolves infections, putrefactions and the syndromes caused by external factors (fevers, catarrhs, …).
The pungent taste on its own is classified as hot and dry, but the degree of hotness and dryness can vary. Indeed, some traditions (e.g., TCM) distinguish between hot and cold (or cool) pungent herbs. The hot pungent herbs mostly participate of the sole nature of Heat and so they warm; the cold pungent herbs (mint, eucalyptus, lemon balm, …) participate of both the natures of Heat (inasmuch as they are pungent) and Cold, in a more or less high degree. For this reason, the cold pungent herbs are ambivalent with respect to the Hot/Cold polarity and produce both the effects of Heat (in a lesser degree with respect to the hot pungent herbs) and the effects of Cold. The hot pungent herbs are most suited to those conditions in which the body needs to be warmed (e.g., cold diseases), while the cold pungent herbs are most suited when the body is already hot (e.g., hot diseases). Among the cold pungent herbs, we can find the plants that contain essential oils that stimulate the cold receptors (e.g., TRPM8) or that modulate the response of some of the nociceptive stimuli nerve receptors (e.g., TRPA1, see box “Pungency and receptors” below).
It may seem strange that Heat and Cold can coexist in a plant; indeed, in this context they are not different degrees of the same phenomenon, but rather they are qualities that can exist independently from each other. If we think to peppermint, for instance, we instinctively know that it’s decidedly hot (it suffices to think to mint candies) but yet it’s able to cool at the same time (it can also be used to soothe the irritation of skin and mucous membranes). In such cases, the plant is said to be ambivalent with respect to the Heat/Cold polarity: hotness on its own is always a hot quality, but the nature of the whole plant participates of a certain degree of Cold, too.
Some properties of essential oils
From a western point of view, essential oils are able to: cross the cell membranes, penetrating quickly into the tissues; modulate dilatation and contractility of both deep and peripheral blood vessels, so “altering” someway the superficial circulation and favoring or inhibiting sweating; act upon bronchial contractility; thin and move mucus; counteract infections, thanks to their antiseptic action. All these properties account, at least partially, for all the activities traditionally linked to pungent plant rich in essential oils.
Another very important property of essential oils is their ability of acting upon the nervous system, modulating its activity in different ways according to the plant species they are extracted from. Often, indeed, pungent aromatic drugs act on the ability of coping with stress, on mood and on the “nervous” reactivity in general.
Pungent plants are diffusive. Some of the plants with this taste (particularly the ones that make the tongue tingle) act specifically as lymphatics.
The pungent taste has a dispersing action upon Tension excess and stagnation. Indeed, herbs for regulating Qi according to TCM are pungent and hot and often aromatic too. This action is particularly relevant with the acrid taste: acrid herbs are strongly relaxant, decidedly antispasmodic and often they act as parasympathomimetic and/or sympatholytic drugs. So, the acrid taste can be useful in case of excessive neuromuscular tension with spasms, stiffness and/or chronic contractures, hypersympatheticotony or, on the contrary, syndromes due to parasympathetic deficiency (e.g., “adrenal insufficiency”, burn-out, etc.).
The pungent taste is also able to warm and activate (that is, to tonify Yellow Bile and sometimes also Tension). So, pungent herbs can be stimulating and so be able to “increase” the body and tissue activity, relaxing, that is, able to reduce the resistances to this activity (i.e., resolve the Tension excess and stagnation), or they can even be both stimulating and relaxing at the same time. Some pungent drugs are more stimulating, others are more relaxing; some are strongly stimulating and relaxing at the same time (e.g., Monarda fistulosa). The hot pungent herbs are often stimulant, and the cold pungent ones are often relaxing, but this correspondence doesn’t always hold.
All the pungent herbs help to thin and expel Phlegm, but the acrid ones in particular are decidedly apt to act this way, especially in case of thickened Phlegm. This happens both with saponin-rich plants (e.g.., English Ivy and sopawort, excellent mucolytics indicated for thick mucus), and with plants that contains acrid principles other than saponins (e.g., Iris species, used both in Western and Hippocratic-Galenic medicines and powerful phlegmagogues; Pulsatilla, indicated for thick yellow or greenish mucus, or for thick and white mucus with yellow-greenish spots or blood streaks; Lobelia spp., used in the American and Chinese pharmacopoeias as expectorant drugs; Clematis spp. that, according to homeopathy, are indicated for mucus in the urine, and which rhizomes are used in TCM for Wind-Damp syndromes and as diuretics; also homeopathic Aconitum napellus has, among its indications, vomiting of bloody mucus or expectoration of thick white mucus or red-colored or red-streaked mucus due to presence of blood [Boger], even if these are not the remedy most important symptoms). The acrid taste, besides “preparing” the thickened Phlegm for expulsion (that is, thinning it), directly stimulates its expulsion, typically due to its irritating action upon the tissues and mucous membranes.
According to the Five Movements systematic correspondence of TCM, the pungent taste is associated to the Lungs, the organs that are responsible, among other things, of regulating the Wei Qi (Defensive Qi), the superficial circulation of Qi and fluids, and so also the opening of skin pores. Pungent drugs, indeed, are also able to modulate sweating (diaphoretic, anti-diaphoretic or ambivalent drugs, like garden sage, that stimulates sweating when taken hot, and reduces it when taken cold), while some of them alleviates coughing and/or wheezing (Aster root, Tussilago flower, Perilla and Lepidium seeds) by ensuring the correct downward direction of Lung Qi. According to the taste/action association, pungent herbs activate the circulation of Qi and disperse accumulated moisture [ITMOnline]. Some pungent herbs are specifically used for these purposes (for instance, citrus fruits).
As a general rule in TCM, most herbs used to induce sweating and to move and regulate Qi are pungent and/or aromatic and are mostly used to release the exterior, expel Wind-Dampness, transform Dampness, warm the interior, warm and transform Phlegm-Cold, open the orifices and for disorders due to Qi and Blood stagnation (to regulate Qi, move the Blood and dispel stasis).
Pungency and receptors
Sometimes, pungency is the result of the stimulation of specific receptors located on the free nerve ending of the tongue, among which for instance:
The most part of pungent substances are also aromatic. Their ability to act upon thermal receptors of heat (TRPV1) or cold (TRPM8) explains, in physiological terms, why some traditional medicines (TMC, for instance) distinguish among hot and cold (or cool) aromatic substances.
The TRPA1 receptors are really interesting because they are activated by very heterogeneous stimuli and because they are the receptors most sensible to the ROS (Reactive Oxygen Species) presence. For this reason, they are involved in the generation of pain sensations caused by a lot of stressors. The ligands of such receptors (for instance, the sulphurous substances contained in the various species of Allium and Brassicaceae, limonene, trans-anethole, etc.) are able to modulate the sensitivity of such receptors, so modulating also the pain sensation. For instance, limonene, contained in several essential oils, among which those of lemon and lemon balm, when taken systemically, is able to reduce the pain sensations mediated by the TRPA1 receptors, acting in fact as a real analgesic [Kaimoto]. Probably, the vegetal drugs that tastes more or less “lemony” (here we are referring to flavor, not acidity) are more or less cooling also for this reason.
 Receptors for fatty acids, especially the long chain ones, are present on the tongue.
 It corresponds more or less to the pungent vipaka of Ayurvedic Medicine.
 It corresponds more or less to the sweet vipaka of Ayurvedic Medicine.
 It corresponds more or less to the acid vipaka of Ayurvedic Medicine.
 Such molecules irritate and produce a burning sensation in the throat, oral cavity and sometimes also in the stomach.
 Some essential oils stimulate specific receptors (i.e., mint essential oil), but in such case the taste is still classified as pungent aromatic rather than hot.
 The so called diffusive drugs act mostly through a stimulation of the nervous system, and produce a strong sensation that can be perceived by the senses and that can quickly diffuse throughout the body [Wood].
 They act, for instance, both as muscular relaxant and as nervous system relaxant.
 Stimulation and relaxation are not opposite activities, but rather complementary ones: indeed, relaxing drugs do not reduce the body activity, but rather reduce the resistances to this activity. For this reason, the same drug can exercise both the activities at the same time.
 Within TCM, indeed, relaxing drugs, that is, drugs that dispel the Qi stagnation, are typically hot and pungent.
 Sometimes, the phlegmagogue term is used (even though not always appropriately) to describe these drugs.
 Saponins possess also a certain diuretic activity (they eliminate phlegm through the kidneys) and enhance the intestinal absorption of the other substances with which they are co-administrated, since they are able to lose the intestinal tight junctions.
 Lobelia chinensis is also used in TCM to promote diuresis and dispel swelling [Li Wei].
 We can expect that all the chemically and structurally similar molecules (e.g., geranial rather than geraniol) produce also similar effects.
 It is not currently clear whether the TRPA1 receptors participate, in humans, to the reaction to cold or heat, since the thermoactivation of such receptors seems to be strongly species-dependent and modulated by the biochemical state of the environment of the receptors.
 According to the TMM, all the aromatic substances are hot. Lemon balm and mint, for instance, are classified as hot according to the MTM and as cool according to the TCM (mint) and the western (American) herbalism.
[Giannelli] Luigi Giannelli, “Medicina Tradizionale Mediterranea”, Ed. Tecniche Nuove (2006)
[Giannelli2] Giannelli, Di Stanislao et al., “Fitoterapia comparata”, Ed. Massa, Napoli (2001)
[Wood] Matthew Wood, “The Practice of Traditional Western Healing”, North Atlantic Books (2004)
[Wood2] Matthew Wood, “The Earthwise Herbal – A Complete Guide to New World Medicinal Plants”, North Atlantic Books (2009)