Chapter 18
Health Benefits of Green Tea Catechins: Improvement of Intestinal Conditions Yukihiko Hara
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Food Research Laboratories, Mitsui Norin Company, Ltd., Miyabara, Fujieda City 426-0133, Japan
Green tea catechins were confirmed to have a marked antioxidative as well as antibacterial and antiviral activity. When green tea beverage or catechin capsules are consumed, these materials will contribute to the prevention of various life style related or age related diseases. Green tea catechins have roles in the prevention of these diseases as well as keeping the entire digestive tract healthy. In order to make the best use of the health promoting functions of tea catechins, it is imperative to confirm the safety as well as the distribution and metabolism of green tea catechins after oral intake.
While the benefits of tea drinking have long been cited, there has been no mention of tea polyphenols until a few decades ago. Tea catechins are the major component in tea (Camellia sinensis L.), and approximately 100 mg may be consumed in one cup. Drinking a cup of green tea is somewhat synonymous with consuming tea catechins. Tea catechins have been fractionated and purified in significant quantity to pursue animal experiments at our laboratory over the last 20 years. Various in vitro and in vivo experiments have been carried out with these compounds, the results of which have led us to conclude that tea catechins are most likely effective in preventing a number of life-style related, age-related diseases of humans, such as cancer, hyperlipidemia, hypertention, hyperglycemia, etc. At present, the actual fate of catechins after oral intake has been only partly elucidated. It is assumed that a portion of the catechins taken orally are absorbed from the small intestine into the portal vein and subjected to metabolism in the liver, undergoing methylation or forming conjugates of glucronide or sulfate (1,2,3). The majority of catechins, presumably more than 80%, are thought to remain in the intestinal tract and to be excreted into the feces (4). While in the large intestine, catechins influence the intestinal flora in a very favorable way.
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The Importance of Intestinal Flora on Human Health Intestinal flora are influenced by the diet or various exogenous factors and in a similar fashion the flora will influence the health of the host in various ways. Unhealthy dietary habits will induce unhealthy flora by which various undesirable compounds will be produced. These decomposition products (ammonia, sulfide, amine, phenol, indole, etc), bacterial toxins, carcinogenic compounds (nitroso compounds, epoxides etc.) or secondary bile acids may eventually take their toll on the host in the form of cancer, aging, atherosclerosis, hypertension, liver disfunction, auto-immune diseases, lowered immune response, i f such undesirable exogenous factors are not rectified. In various human studies with fecal specimens, it was shown to be likely that in the intestines of sick people the so-called 'good' bacteria such as Bifidobacteria or Lactobacilli tend to decrease and the so-called 'bad' bacteria such as Clostridium tend to increase as compared to those of healthy people. The increase of Bifidobacteria or Lactobacilli in the intestines of human host occurs along with the concomitant decrease of Clostridium microorganism. Recently, various kinds of oligo-saccharides have become popular as dietary supplements since oligomeric sugars are mainly utilized by Bifidobacteria and not by other intestinal bacteria. Based on these findings, we are now encouraged to consume yogurt, oligo-saccharides or the powder of Bifidobacteria on a daily basis in order to maintain intestinal health. How tea catechins influence the intestinal flora is the topic of this paper.
Antibacterial Potency of Tea Catechins The minimum inhibitory concentrations (MIC) of the catechins in green tea against well known strains of foodborne pathogenic bacteria and 6 strains of lactic acid bacteria are shown in Table I. Results showed that tea catechins act antibacterially against Staphylococcus aureus, Clostridium botulinum, Clostridium perfringens, Bacillus cereus, Vibrio strains, Plesiomonas shigelloides and Aeromonas sobria. The growth of those bacteria was inhibited at a catechin concentration less than that contained in a normal cup of tea, that is ranging from 500 to 1,000 ppm. The foodborne pathogenic bacteria which are inhibited by tea catechins are largely those which have been responsible for a number of incidences of food poisoning. Consequently, tea catechins may possibly be used to prevent bacterial foodborne diseases. Moreover, tea catechins showed virtually no activity against such lactic acid bacteria as Bifidobacteria or Lactobacilli at the concentration of 1,000 ppm. The fate of tea catechins in the digestive tract after oral intake and their activity in the gut is of interest at present.
The Fate of Tea Catechins in the Digestive Tract Among the four kinds of tea catechins, (-)-Epigallocatechin gallate (EGCg) is quantitatively the major component (more than 50%) and physiologically the most potent. Therefore, we traced the fate of E G C g in the digestive tract in rats. Fifty mg of
Parliment et al.; Caffeinated Beverages ACS Symposium Series; American Chemical Society: Washington, DC, 2000.
167 Table I. Minimum Inhibitory Concentrations of Tea Catechins Against Foodborne Pathogenic and Enteric Bacteria
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Bacteria Staphylococcus aureus I A M 1011 Vibrio fluvialis J C M 3752 V. parahaemolyticus IFO 12711 V metschnikovii I A M 1039 Clostridium perfringens J C M 3816 Clostridium botulinum A , Β mix. Bacillus cereus J C M 2152 Plesiomonas shigelloides IID No. 3 Aeromonas sobria J C M 2139 Lactobacillus brevis subsp. gravesensis J C M 1102 L. brevis subsp. brevis J C M 1059 L. brevis subsp. otakiensis J C M 1183 Bifidobacterium bifidum J C M 1255 B. adolescent is J C M 1275 B.longum J C M 1217
Polyphenon 450
MIC EC >800
(ppm) ECg 800
EGC 150
EGCg 250
300 500
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>1000 >1000
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>1000 400
Polyphenon: mixture of individual catechins (purity>80%); E C : (-)-epieateehin; E C g : (-)-epicatechin gallate; E G C : (-)-epigallocatechin; E G C g : (-)-epigallocatechin gallate (major catechin in tea).
E G C g was administered orally to fasted rats, then after 1, 2, 5, 8, 12, 16 and 20 hours the residual content of E G C g in the stomach, small intestine, large intestine as well as in the feces was determined. As shown in Figure 1, within a few hours after administration the level of E G C g in stomach decreased rapidly and increased in the small intestine. The amount of E G C g in the large intestine began to increase sharply as the amount in the small intestine decreased, and was at its highest about 8 hours after ingestion, at which time only a trace amount remained in the other organs. E G C g appeared in the feces 12 hours after ingestion and increased gradually thereafter. Two
Parliment et al.; Caffeinated Beverages ACS Symposium Series; American Chemical Society: Washington, DC, 2000.
Parliment et al.; Caffeinated Beverages ACS Symposium Series; American Chemical Society: Washington, DC, 2000.
I. Residual
EGCg
Time (hrs) in different section of the digestive tract of rats
10
20
1995 MultiMedia Healthcare/Freedom, L L C . )
administered 50 mg of EGCg. (Reproduced with permission from reference 6. Copyright
Figure
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hours after administration, when a small amount of E G C g was already in the large intestine, about 20% of the E G C g was lost (ie. unrecoverable). We concluded that this 20% disappearance of E G C g was the amount absorbed into the body through the small intestine. This assumption is supported by a previous study which confirms that E G C g does not undergo any degradation in the stomach or small intestine (unpublished data). In addition the experimental results of Hattori et al. (5) show that when gallated catechins (EGCg, ECg) are incubated anaerobically with the content of the large intestine of rats or with those of humans, there is no degradation of catechins for 48 hours with rats, and some appreciable degradation with human feces. These data imply that the majority of catechins, at least 50%, will remain intact or undergo reactions with microflora in the large intestine and pass into the feces. In light of these factors an investigation is warranted into the influence of tea catechins on the intestinal flora in humans.
Experimental
Feeding of Catechins by Gastroenteral Tube Feeding In order to evaluate the effects of tea catechins on the intestinal flora and the fecal metabolites in humans, residents in long-term care facilities in and around Hamamatsu, Japan, who were receiving gastroenteral liquid alimentation via nasogastric or gastric tubes were administered tea catechins and their fecal specimens were analyzed (6). The subjects studied were 10 females and 5 males, ranging in age from 51 to 93 years (average, 70.3 years) and their body weight ranged from 28 kg to 56 kg (average, 41kg). A l l subjects received 1,000 kcal of the same nutrition daily, supplemented with 300 mg of catechins, which was divided into three doses a day and mixed in the liquid alimentation for a period of three weeks. Tea catechins used were "Polyphenon 60" provided by Mitsui Norin Co. (Fujieda City, Japan), which contains 62% catechins. A daily dose of 300 mg of catechins is equivalent to 484mg of "Polyphenon 60" powder, which will correspond to 4 to 6 cups of green tea. Freshly voided fecal specimens were collected on days 0 (before administration), 7, 14, and 21 of administration and day 7 postadministration. The fecal measures of microfloral populations, pH, moisture content, ammonia, sulfide, other odorous metabolites, and organic acids, were analyzed at each collection. Results indicated remarkable improvement of bowel conditions. As shown in Figure 2, following the administration of tea catechins, levels of Bifidobacteria and Lactobacilli increased significantly whereas those of Bacteroidaceae, Eubacteria, Enterobacteriaceae and Clostridia decreased significantly. Figure 3 shows other parameters. Fecal pH and ammonia decreased significantly whereas sulfide and fecal odorous metabolites (phenol, cresol, ethyl phenol, indole, and skatol) increased at day 7 and then significantly decreased at
Parliment et al.; Caffeinated Beverages ACS Symposium Series; American Chemical Society: Washington, DC, 2000.
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day Ο day 7 day 14 day 21 day 7 After Before During administration administration administration Graph is expressed as m e a n ± S D . *; Significant difference
