Herbs, spices and gut health 153
10.2.1 Experimental assays
The digestive stimulant action of spices has been examined in animal and human
studies. In animal studies, the effect of spices on bile secretion has been examined in
the laboratory using experimental rats. In these animal models, bile was systematically
collected following the spice treatment and the influence of spices was examined as
a result of both continued intake through the diet for a period of time and as a one-
time exposure orally (Platel and Srinivasan, 2004). In human studies, patients with
functional dyspepsia or other gastric disorders assessed their symptom intensity during
and after a treatment period of receiving a certain spice (Thompson Coon and Ernst,
2002; Bortolotti et al., 2002; Lee et al., 2004).
10.2.2 Mechanisms of action – active compounds
Many of the herbs and spices such as red pepper, ginger, gentian, capsicum, black
pepper and mustard, act as digestive stimulants and help in digestion by enhancing
the secretion of saliva and the activity of salivary amylase in humans, thus stimulating
gastric secretions (Glatzel, 1968; Blumenthal, 1988). Others have reported that paprika,
black pepper and cinnamon increased the acid secretion while mustard, celery, nutmeg
and sage did not have any such effect (Sanchez-Palomera, 1951). Among all the
spices, onion has been reported to have a favourable influence on most digestive
enzymes of both the pancreas and small intestine. It has been noted also that the
stimulatory influence of the component spices of the spice mixes on digestive enzymes
of the pancreas and small intestine is not additive (Platel et al., 2002). Curcumin,
capsaicin (the active principles of turmeric, red pepper) ginger and fenugreek, onion,
mint, cumin, fennel and ajowan, also stimulate bile acid production by the liver and
its secretion into bile (Bhat et al., 1984, 1985; Platel and Srinivasan 2001a; Sambaiah
and Srinivasan, 1991; Srinivasan, 2005).
The analgesic properties of capsaicin have been known for more than a century.
Capsaicin (the red pepper is used in functional dyspepsia) can impair selectively the
activity of nociceptive C-type fibres carrying pain sensations to the central nervous
system (Lynn, 1990; Holzer, 1991).
Many herbal extracts used in medicine alter gastric motility in a dose-dependent
and region-specific manner not only in the stomach but in all segments of the
gastrointestinal tract (Hohenester et al., 2004). The improvement in gastric motility
is crucial for the pathogenesis of dyspeptic symptoms and may be specifically useful
in patients suffering from dysmotility-like functional dyspepsia. Other herbs referred
to that improve the symptoms of non-ulcer dyspepsia, such as turmeric, greater
celandine, peppermint, caraway, have a direct antispasmolytic action on smooth
muscle or inhibit smooth muscle contraction (Forster et al., 1980; Hills and Aaronson,
1991).
Extensive animal studies have revealed that generally the mechanism of digestive
stimulant action of most spices is mediated through stimulation of bile secretion with
an enhanced bile acid concentration (ingredients essential for fat digestion and
adsorption). This activity is usually followed by an appropriate stimulation of the
activities of digestive enzymes of pancreas and small intestinal mucosa – lipase,
amylase and proteases, disaccharidases, alkaline phosphatase, which play a crucial
role in digestion (Sharathchandra et al., 1995; Platel and Srinivasan, 1996, 2001a,b;
Srinivasan, 2005). Concomitant with such a stimulation of either bile secretion or
activity of digestive enzymes by spices, leading to an accelerating digestion, a reduction