These findings are contradicted by other studies showing that bitters taken by healthy subjects with a normal appetite do not increase digestive secretions beyond the reflex secretions that normally occur during the cephalic phase of digestion. The secretory mechanism as a whole is already functioning at an optimum level, and the administration of bitters cannot produce any significant change. In conditions where the reflex secretion of gastric juice is inhibited, however, the administration of bitters can initiate the
necessary reflex, leading to gastric secretion of the same intensity and duration (2-3 h) as normal reflex secretion.
There is a definite psychological component to the efficacy of bitters. This was demonstrated by a study in which bitters markedly improved appetite in patients with gastric achylia, despite the fact that increased gastric acid secretion cannot be induced in these patients (Moller, 1947).
Bitters do not invariably act as appetite stimulants. Animals, for example, tend to prefer sweet-tasting foods and avoid bitter-tasting ones (Nachmann and Cole, 1971). Humans are ambivalent toward bitter-tasting foods and bev- erages, tending to prize the flavor of artichokes, beer, grapefruit, liquors, etc. while disliking the sour taste of pickles and heat-preserved citrus juices. There is a psychological tendency, moreover, to associate a bitter taste with the bitterness of an unpleasant experience.
Bitter herbs can be ranked according to the intensity of their bitter taste Bitters that are used medicinally to stimulate appetite and digestive secretions are not merely herbs with a bitter taste; they are herbs that can produce a pleasant taste sensation in conjunction with their bitter flavor. Another criterion is that medicinal bitters must cause no systemic side
effects when used in the proper concentration. Large amounts of bitters reduce gastric secretions, partly by their direct action on the gastric mucosa, and cause appetite suppression. Very strong wormwood tea, for example. can spoil the appetite. Other constituents in bitter herbs are important determinants of taste, and several types of bitter herb are differentiated on that basis.
• Simple bitters such as gentian (Gentiana lutea), bogbean, and centaury (Centaurium minus)
• Aromatic bitters that contain volatile oils, such as angelica root, blessed
thistle, bitter orange peel, and wormwood.
• Astringent bitters that contain tannins, such as cinchona bark and con-
• Acrid bitters such as ginger and galangal.
Besides their action on the digestive glands, bitter principles act reflexly on the cardiovascular system, causing a decrease in heart rate and cardiac stroke volume. Taking bitters for several weeks can engender an aversion to certain bitter herbs, accompanied by loss of appetite. The taste of bitter herbs cannot be corrected with raw sugar or other sweeteners. As for adverse effects, bitters occasionally cause headache in susceptible users, and overdoses can induce nausea or vomiting. Because bitters stimulate digestive secretions, they are contraindicated in patients with gastric or duodenal ulcers.