THE stimulating and refreshing action of coffee is mainly due to the presence of caffeine and a volatile oil. Caffeine belongs to the group of substances known as alkaloids, which as a class have usually a bitter taste and are only slightly soluble in water. Amongst other well-known alkaloids are cocaine, the active principle obtained from coca leaves ; morphine, codeine, and narcotine, the essential constituents of opium ; quinine and cinchonine, to which the bark of cinchona owes its properties theobromine contained in cacao. Theine, the alkaloid of tea, is practically identical with caffeine, and both are very similar to theobromine. Paraguay tea, or maté, and kola nuts contain caffeine.
The quantity of caffeine present varies greatly in different species of coffee. It is never very large in amount, slightly under 20 per cent. of the dry seeds being the highest recorded. Analyses of Arabian coffee show a range of between 0.7 and P6 per cent., whilst Liberian coffee varies from about 10 to P5 per cent. The wild Sierra Leone coffee (Coffee stenophylla) contains about P5 per cent. Four species of coffee, natives of Madagascar or of the neighbouring islands, do not contain any caffeine.
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In the Chinese medical-dietary system, the green bean of coffee would be classified as an herb that regulates liver qi, which is its therapeutic route to strong energy stimulation (attributed chemically to caffeine's action on the nervous system). The green bean is of the color of the wood element (associated with liver); more important to classification, however, is the concept that when the liver qi is constrained, the entire body energy becomes depressed.
By vigorously dredging the stagnated liver qi, a strong sense of mental and physical vitality is experienced. The early use of coffee beans to regulate menstruation is consistent with the Chinese medical approach of regulating menstruation by dredging stagnant liver qi. The green coffee bean also cools the constrained liver qi. When the bean is roasted, it retains its basic medicinal properties, but transforms from a cooling herb to a warming herb. Roasting herbs is a common processing method used in China.
Coffee not only regulates the liver qi, but also purges the gallbladder. In fact, modern research in Chinese medicine suggests that most herbs that regulate liver qi have this effect on the gallbladder as an integral part of the qi-dispersing action, but some herbs have greater gallbladder purging effects than others. The liver (and gallbladder) regulating properties of coffee explain its ability to protect against formation of gallstones and its ability to alleviate constipation. This action has been attributed to chlorogenic acid and other constituents found in coffee.
When liver qi is dredged, its natural tendency is to flow upward; when the gallbladder is purged, its natural tendency is to move downward. Thus, consumption of coffee has a blended upward and downward action. Healthy individuals will experience this as a balanced action, but individuals with certain health problems may experience either an excessive upward or excessive downward reaction.
The bright red berry that encases the coffee bean signifies this herb as a treatment for the heart. Coffee has the effect of opening the orifices, it thus has the action of stimulating and focusing mental activity, something like the effect attributed to the medicinal herb acorus (shichangpu). The bitter taste of the coffee bean signifies its detoxicant qualities. Its effects are comparable to that of dandelion (pugongying), which disperses accumulations by purging the gallbladder and promotes urination (as do caffeine-containing beverages).
The coffee taste, although obviously bitter, is also partly sweet. We know this because addition of a small amount of sugar or other sweetener quickly makes the beverage sweet tasting, which does not occur with strictly bitter-tasting herbs. The sweet taste is associated in Chinese medicine with a tonic effect, particularly for the spleen. As mentioned in the Indian Materia Medica, coffee "assists assimilation and digestion." Thus, coffee can help ameliorate liver-spleen disharmony associated with liver qi stagnation and spleen weakness. On the other hand, its liver dredging effect is strong and its tonic effect is weak, so a person with severe liver qi stagnation and weakness of the spleen may have the adverse experience of released liver qi impinging on the weakly resistant spleen/stomach system, causing gastro-intestinal distress.
In sum, coffee dredges the liver to regulate the flow of liver qi, purges the gallbladder, opens the heart orifices, warms the blood circulation, detoxifies, and gently tonifies. However, while coffee dredges the liver qi, it does not necessarily smooth or soothe the liver qi. Therefore, one has to be cautious about the amount consumed and certain individuals will find the otherwise desirable effects distressing: releasing stagnated qi but not regulating its flow.
As with other Chinese herbs, coffee would best be used in combination with herbs to moderate and enhance its effects. As an example, peony root (baishao) is often used to "soften" the liver, and smooth the flow of qi. Because coffee is consumed as a flavorful beverage, to pursue such an approach would best be done by having additional herbs taken in a form that wouldn't alter the taste of the coffee, such as in pills. Excessive amounts of coffee will agitate the liver yang and even stimulate internal wind. Prolonged use of excessive amounts could thereby damage the blood, but for moderate amounts it serves as a valuable therapy for stagnated liver qi, with constricted circulation of blood, and constrained gallbladder function, with constricted elimination of damp and heat.
What I find most interesting about the near excessive consumption of coffee, at least in Canada is the tendency to add large, sometimes horrifying amounts of refined white sugar to the drink. What I beleive to be a decent, good for you drink, seems to get polluted with the addition of this white poison. So, drinking your Joe black or with a bit of cream, I would think would be the way to go, in moderation, of course. ;D