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Green-tea extract in petfood

April 2020

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An unspecified, petfood database shows that green-tea extract was declared as ingredient by almost 10% of the dry dog and cat foods. It was found in less than 1% of the wet foods (1, Notes 1 and 2). The front of a dog-food bag reads "contains green tea" and "enriched with catechins". The package also illustrates the basic structural formula of catechins (2), or the supposed active principles of green tea that are touted as anti-aging, cancer-fighting and immune-boosting antioxidants. All tea is made from leaves of the tea shrub in all its rich variety. Leaves for black or oolong teas undergo withering, maceration and warmth-induced darkening. Leaves for green tea are steamed briefly, cooled down quickly, and dried before fermentative breakdown occurs. That process preserves the polyphenolic catechins in the leaves. The major component is EGCG (epigallocatechin gallate), which makes up about 10% of dried leaves and 60% of authentic, green-tea extract. Daily intake of up to 0.8 g EGCG per day is safe for a 20-kg dog. That intake is equivalent to about 0.24% EGCG or 0.4% unadmixed, green-tea extract in complete dry food. Kibbled dog foods listing green-tea extract as ingredient normally contain far less than 0.4% (Note 3). The EGCG absorbed from such foods is adequately converted by the dog and then excreted with urine and bile. For cats there is no available information about maximum safe intake and metabolic handling of EGCG. Practical amounts of ingested green-tea extract may not increase antioxidant capacity of canine blood, which erodes the foundation of the EGCG-related health claims made by dog tablets, treats and foods. Likewise, there is no scientific proof that green-tea catechins reduce inflammation of gums in dogs and cats. The anti-aging claim is almost unprovable in dogs, but green-tea extract was not life-prolonging in mice (3). Catechins: structures Catechins form a class of flavanoids. They are composed of a heterocycle (five carbons, one oxygen atom) fused and bound with benzene rings A and B. Catechin (C) and epicatechin (EC) are enantiomers, consisting of dihydroxylated A and B rings and a monohydroxylated heterocycle with a chiral carbon. In gallocatechin (GC) and epigallocatechin (EGC), the B ring has a third hydroxyl group. In both epicatechin gallate (ECG) and epigallocatechin gallate (EGCG) the hydroxyl group of the heterocycle is esterified with gallate (3,4,5-trihydroxybenzoate), but EGCG has a trihydroxylated B ring.

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Green-tea extract in petfood

An unspecified, petfood database shows that green-tea extract was declared as ingredient by

almost 10% of the dry dog and cat foods. It was found in less than 1% of the wet foods (1, Notes 1

and 2). The front of a dog-food bag reads “contains green tea” and “enriched with catechins”. The

package also illustrates the basic structural formula of catechins (2), or the supposed active

principles of green tea that are touted as anti-aging, cancer-fighting and immune-boosting

antioxidants.

All tea is made from leaves of the tea shrub in all its rich variety. Leaves for black or oolong teas

undergo withering, maceration and warmth-induced darkening. Leaves for green tea are steamed

briefly, cooled down quickly, and dried before fermentative breakdown occurs. That process

preserves the polyphenolic catechins in the leaves. The major component is EGCG (epigallocatechin

gallate), which makes up about 10% of dried leaves and 60% of authentic, green-tea extract.

Daily intake of up to 0.8 g EGCG per day is safe for a 20-kg dog. That intake is equivalent to about

0.24% EGCG or 0.4% unadmixed, green-tea extract in complete dry food. Kibbled dog foods listing

green-tea extract as ingredient normally contain far less than 0.4% (Note 3). The EGCG absorbed

from such foods is adequately converted by the dog and then excreted with urine and bile. For cats

there is no available information about maximum safe intake and metabolic handling of EGCG.

Practical amounts of ingested green-tea extract may not increase antioxidant capacity of canine

blood, which erodes the foundation of the EGCG-related health claims made by dog tablets, treats

and foods. Likewise, there is no scientific proof that green-tea catechins reduce inflammation of

gums in dogs and cats. The anti-aging claim is almost unprovable in dogs, but green-tea extract

was not life-prolonging in mice (3).

Catechins: structures

Catechins form a class of flavanoids. They are composed of a heterocycle (five carbons, one oxygen

atom) fused and bound with benzene rings A and B. Catechin (C) and epicatechin (EC) are

enantiomers, consisting of dihydroxylated A and B rings and a monohydroxylated heterocycle with a

chiral carbon. In gallocatechin (GC) and epigallocatechin (EGC), the B ring has a third hydroxyl group.

In both epicatechin gallate (ECG) and epigallocatechin gallate (EGCG) the hydroxyl group of the

heterocycle is esterified with gallate (3,4,5-trihydroxybenzoate), but EGCG has a trihydroxylated B

ring.

Dietary catechins

On a dry-matter basis, fresh green-tea leaves contain 16-30% total catechins and 7-13% EGCG (4,

Note 4). Black-tea leaves may only have 0.2% EGCG (5). Catechins were undetectable in broiler meat

(6) and rice (7). Per kg, wheat was found to contain 17 mg catechin equivalents (8), while faba beans

held 494 mg total catechins, but no EGCG (7). Dry food containing 30% faba beans, 25% rice and 30%

poultry meal would thus include 148 mg total catechins/kg.

EGCG makes up about 60% of pure green-tea extract (9), but the contents of commercial

preparations range between 4 and 44%, due to admixing (10). Two complete, dry dog foods with

green tea in their names declare 0.4% green tea (11, 12). According to their declarations, a dry and

canned, veterinary dog food (13) contain 932 and 780 mg green-tea polyphenols/kg air-dry dry

matter. Practically, green tea inclusion levels are little disclosed. The recommended doses for three

dog supplements with green-tea extract (14-16, Note 5) correspond with amounts below 718 mg

EGCG/kg dry food.

Catechin metabolism

Dogs may absorb 20% of ingested EGCG as based on administration of 4-[3H]-EGCG in saline by

intravenous and oral routes (17, Note 6). Four times more of the absorbed radioactivity was

excreted by feces than by urine. After oral administration of green-tea extract (Note 7), EGCG and

ECG were present in blood, but not in urine, at 90- and 120-min post dosing (9). EGC-sulfate was

found in urine, but not in blood. Both bodily fluids contained EGC-glucuronide, EC-glucuronide and

EC-sulfate.

Beagle dogs were given a single, oral dose of 200 mg capsulated green-tea extract (18). As from 30

min after dosing, blood samples were taken. The five catechins were detected again, having

maximum concentrations at about 60 min after dosing. The data point to predominant biliary

excretion of EGCG (Note 8) and ECG. Two other catechins in green-tea extract, EC and EGC, were

conjugated prior to excretion with urine, which might also apply to their biliary excretion.

Safety: dogs and cats

In four (sub)chronic, oral toxicity studies (19-22), Beagle dogs received purified green-tea

preparations at levels corresponding with 0-650 mg EGCG/kg body weight.day. Comparability of the

outcomes is hampered by different experimental conditions, but particularly by high variability in

individual sensitivity, in combination with small sample size and fasted or fed states of the dogs

(Note 9). On a conservative estimate, 40 mg EGCG/kg body weight.day is safe for dogs, which equals

2400 mg EGCG/kg dry food (Note 10). No abnormalities were reported for cats fed a diet with 333

mg total green-tea catechins (142 mg EGCG)/kg for 45 days (23).

Green-tea effects

Based on the cat study (23), and on dogs fed a similar diet (24), it was concluded that the

supplemental green-tea extract effectively reduced gingivitis, but the trials were uncontrolled. Diets

containing either 4610 mg EGCG (25) or 5000 mg tea polyphenols/kg dry food (26) did not affect or

raised dogs’ blood antioxidant capacity (Note 11). EGCG may increase insulin sensitivity in obese

dogs (27, Note 12).

Note 1

Green tea can be considered label friendly to the petfood purchaser. Therefore, green tea may be

added not only as marketing tool for antioxidant-related health claims, but also as extra antioxidant

for petfood preservation. As preservative, green tea extracts may be blended into a powder or liquid

mixture and then added to the basic part or the coating of kibbled food (28).

Note 2

The European Register of Feed Additives lists tea extract from Camellia sinensis (L.) as additive,

falling into the subclassification of botanically defined, natural products (29). An application for

authorization has been submitted.

Note 3

A prudent point of departure is that 40 mg EGCG/kg body weight.day is safe for dogs (Note 9). That

amount equals 0.8 g EGCG/day for a 20-kg dog (20 x 0.04) or 2.4 g EGCG/kg dry food (0.8 x

1000/334; food intake = 334 g/day), or 4.0 g green-tea extract/kg dry food ( for extract with 60%

EGCG). Thus, 0.4% unadmixed, green-tea extract in complete dry food can be considered safe.

In the ingredient statement of complete, dry dogs foods with green-tea extract, the extract is

normally found near the bottom of the list, below the vitamin preparations (cf. 30, 31), implying an

inclusion level way less than 0.4%. Moreover, the green-tea extracts used may contain less than 60%

EGCG. It is assumed here that EGCG determines the toxicity of green-tea extract. Clearly, that

assumption is debatable.

A dry cat food (32) declares green-tea extract in the region of the middle of the ingredient list, but

far after taurine, pointing to a level less than 0.2%.

Note 4

Apart from about 36% total polyphenols, fresh green-tea leaves also contain 15% crude protein, 2%

crude fat, 7% lignin, 25% carbohydrates and 5% ash in the dry matter (4). Fresh leaves hold about 70

% moisture.

Note 5

Three dog supplements declare their green-tea component as “decaffeinated green tea (leaf)

extract” (14), “green tea powder” (15) and “green tea extract (decaffeinated)” (16). Based on the

stated contents per capsule or tablet, and the feeding directions, the dosages correspond with 1.1,

3.2 and 12.0 mg EGCG/kg body weight.day. It is assumed that the green-tea components contain

60% EGCG. For a 20-kg dog consuming 334 g dry food per day, the dosage rates amount to 66, 192

and 718 mg EGCG/kg dry food.

Two supplements declaring either “green tea leaf extract [95% phenols/70% catechins/45% ECGC]”

(33) or “green tea/decaffeinated” (34) provide incomplete information so that the recommended

EGCG dose cannot be calculated.

Note 6

Intestinal absorption of EGCG was assessed by determination of plasma radioactivity after

intravenous and oral administration of 4-[3H]-EGCG in saline (17). Absorption efficiency was

calculated as the total area under the plasma EGCG concentration (μg-equivalents EGCG/ml) after

oral administration divided by that after intravenous administration. The 3H label on EGCG was

found stable toward in-vivo exchange with water.

The intestinal epithelial transport of EGCG and EGCG-loaded niosomes has been studied in

monolayers of human Caco-2 cells (35). The niosomal carrier increased EGCG uptake by a factor of

two. The data collected indicate that the flux of EGCG across the Caco-2 monolayer involves an

active mechanism and is energy-dependent.

Note 7

The green-tea extract used to measure catechin metabolites in blood plasma and urine of dogs

consisted of 62.2% EGCG, 10.4% EC, 9.3% ECG and 4.7% EGC (9).

Note 8

The demonstration of the biliary, excretory pathway for EGCG may imply that a modest increase in

EGCG intake leads to a new steady state. However, for that reasoning there is no clear experimental

evidence. Dogs were administered re-crystallized EGCG at doses of 0, 50, 300 or 500 mg/kg body

weight.day (21). The total daily doses were divided into twice-daily, equal administrations with

gelatin capsules. The capsules were given at one hour after each feeding, which was done twice

daily, for 13 weeks. The authors (21) stated that pre-dosing plasma concentration of EGCG on day 78

showed a dose-dependency, but with low values, indicating the absence of EGCG accumulation. The

data are not disclosed.

Note 9

As based on four (sub)chronic, oral toxicity studies with dogs, no-observed-adverse-effect-levels

(NOAELs) have been reported. Under fed conditions, the values were 300 mg EGCG/kg body

weight.day (21) and 500 mg for a highly purified green-tea extract (22). Under fasting conditions,

200 mg extract was toxic (22) and the NOAEL was 50 mg for re-crystallized EGCG (21). Purity of the

re-crystallized EGCG was 80% so that the NOAEL would be 40 mg/kg body weight.day.

Administration took place after a minimum of 15 hours fasting and 3-4 hours prior to feeding the

dogs.

Note 10

Chronic toxicity of EGCG and green-tea extract preparations involved lethal liver, gastrointestinal

and renal abnormalities. The studies had 8 dogs (four males and four females) per treatment. There

was extreme variation in toxic response within the treatment groups. Thus, it is prudent to accept

the lowest NOAEL of 40 mg/kg body weight.day (Note 9) as lower toxicity threshold.

The EFSA ANS Panel concluded: The NOAEL in fasted dogs was 40 mg EGCG/kg body weight per day,

which was 10 times lower than the NOAEL identified in fed dogs (36). There is some evidence that

the lowest NOAEL holds only for fasted dogs, or administration of EGCG/green-tea extract on an

empty stomach. That difference in toxicity has been explained tentatively by higher systemic

exposure to EGCG (21, 22) or greater vulnerability of target organs (37) under fasting conditions.

However, both speculations are diminished by the high variation within treatment groups.

Note 11

Feeding a dry diet with 4610 mg EGCG/kg did not affect blood antioxidant capacity in dogs, but

markedly lowered the concentration of oxidized glutathione (25). The decrease in oxidized

glutathione agrees with the polyphenol EGCG acting as electron donor, but the lack of effect on

blood antioxidant capacity is contradictory.

The study lasted three months and toxicity signs were not reported (25). EGCG intake was higher

than the conservative NOAEL, which underlines its prudence. In another 3-month study, dogs’ dry

food contained 5000 mg tea polyphenols/kg (26) and toxicity was not reported either.

Note 12

In obese dogs, administration of green-tea extract, equivalent to 733 mg EGCG/kg dry food,

increased insulin sensitivity and lipoprotein lipase expression, and lowered fasting plasma

triglycerides (27). In mice, oral co-administration of EGCG and starch reduced postprandial glucose

levels, while EGCG inhibited pancreatic amylase activity in vitro (38).

Note 13

Dogs, on average weighing 10.5 kg, were fed a dry food and orally received twice daily capsules with

green-tea EGCG at a rate of 77 mg/dog per day (39), or 440 (1000/175 x 77) mg/kg dry food. Blood

was sampled before and after the experimental period of three months. When compared with the

control group, supplemental EGCG altered gene expression by leukocytes.

Note 14

Black and milk chocolate have been reported to contain 460 and 163 mg total catechins/kg, but

EGCG was not detectable (7).

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Aug 2020

Anton Beynen

Carob is the fruit, in the form of a pod, of an evergreen tree that is cultivated mainly in the Mediterranean area (Note 1). The ingredient panels of several canine nutritional products list carob, mostly with suffix, such as pods, meal, powder, chips or gum. Carob treats for dogs are generally positioned as chocolate replacers (Note 2). Two supplements and four complete dry foods make claims, based on their carob ingredient, going from digestive support to diarrhea management (Notes 3, 4). Carob gum is a thickening agent that is occasionally found in wet foods (Note 5). Carob pods have a wrinkled, leathery surface and softer inner portion that surrounds and separates the seeds. Pods can be divided into two parts: pulp (70-90%) and seeds. Carob pulp may undergo drying and grinding. It can also be dehulled, ground, roasted and milled into a powder, serving as chocolate substitute. During the roasting process the pulp obtains a cacao-like aroma. Isolated seeds' endosperm (nutritive tissue for the embryo/germ) serves as carob gum, also called locust-bean gum. Carob contains tannins, polyphenols that can bind proteins in the intestinal lumen and make them resistant to digestion. Dry dog foods with carob generally contain less than 3% pulp, which brings in tannin levels that slightly reduce net protein digestion, but do not jeopardize protein supply. There are no published dog studies providing any evidence for dietary carob as promoter of digestive health or as controller of diarrhea. Roasted carob pulp is used as chocolate replacer because of near comparable appearance and taste. Contrary to cacao in chocolate, carob does not contain theobromine, which can be toxic for dogs. Acute, chocolate poisoning in dogs occurs frequently, the signs being vomiting, diarrhea, excessive thirst, lack of coordination and irregular heartbeat. There is wide variation between individual dogs in their sensitivity to theobromine. Thus, keeping all dogs away from chocolate is prudent (Note 6). Some dog owners appear to fill the abstention with carob treats (Note 7), given their market supply (Note 2). Proximate composition Size, pulp:seed ratio and proximate compositon of carob pods depend on cultivar and horticultural condition (1-3). As a rough guide, carob pulp contains 5% crude protein, 1% crude fat, 7% crude fiber, 3% ash, 8% moisture and 76% soluble carbohydrates (nitrogen-free extract). The pulp's carbohydrate fraction has about 60% sucrose and 5% pinitol (4, Note 8). Seeds' germ and endosperm may contain 57 and 6% crude protein and 18 and 91% soluble carbohydrates (5, 6). The carbohydrates of endosperm (carob gum) comprise about 80% galactomannans (6), which provide gelling capacity.

Enhanced uptake and transport of (+)-catechin and (−)-epigallocatechin gallate in niosomal formulation by human intestinal Caco-2 cells

Article

Full-text available

May 2014

The aim of this study was to evaluate (+)-catechin and (−)-epigallocatechin gallate (EGCG) cellular uptake and transport across human intestinal Caco-2 cell monolayer in both the absence and presence of niosomal carrier in variable conditions. The effect of free drugs and drug-loaded niosomes on the growth of Caco-2 cells was studied. The effects of time, temperature, and concentration on drug cellular uptake in the absence or presence of its niosomal delivery systems were investigated. The intestinal epithelial membrane transport of the drug-loaded niosomes was examined using the monolayer of the human Caco-2 cells. The kinetics of transport, and the effect of temperature, adenosine triphosphate inhibitor, permeability glycoprotein inhibitor, multidrug resistance-associated protein 2 inhibitor, and the absorption enhancer on transport mechanism were investigated. It was found that the uptake of catechin, EGCG, and their niosomes by Caco-2 cells was 1.22±0.16, 0.90±0.14, 3.25±0.37, and 1.92±0.22 μg/mg protein, respectively (n=3). The apparent permeability coefficient values of catechin, EGCG, and their niosomes were 1.68±0.16, 0.88±0.09, 2.39±0.31, and 1.42±0.24 cm/second (n=3) at 37°C, respectively. The transport was temperature- and energy-dependent. The inhibitors of permeability glycoprotein and multidrug resistance-associated protein 2 and the absorption enhancer significantly enhanced the uptake amount. Compared with the free drugs, niosomal formulation significantly enhanced drug absorption. Additionally, drug-loaded niosomes exhibited stronger stability and lower toxicity. These findings showed that the oral absorption of tea flavonoids could be improved by using the novel drug delivery systems.

Evaluation of Resveratrol, Green Tea Extract, Curcumin, Oxaloacetic Acid, and Medium-Chain Triglyceride Oil on Life Span of Genetically Heterogeneous Mice

Article

Full-text available

Mar 2012
J GERONTOL A-BIOL

The National Institute on Aging Interventions Testing Program (ITP) was established to evaluate agents that are hypothesized to increase life span and/or health span in genetically heterogeneous mice. Each compound is tested in parallel at three test sites. It is the goal of the ITP to publish all results, negative or positive. We report here on the results of lifelong treatment of mice, beginning at 4 months of age, with each of five agents, that is, green tea extract (GTE), curcumin, oxaloacetic acid, medium-chain triglyceride oil, and resveratrol, on the life span of genetically heterogeneous mice. Each agent was administered beginning at 4 months of age. None of these five agents had a statistically significant effect on life span of male or female mice, by log-rank test, at the concentrations tested, although a secondary analysis suggested that GTE might diminish the risk of midlife deaths in females only.

Dietary tea catechins and iron-induced lipid oxidation in chicken meat, liver and heart

Article

Full-text available

Nov 2000
MEAT SCI

The effects of dietary tea catechins (TC) supplementation at levels of 50 (TC 50), 100 (TC 100), 200 (TC 200), and 300 (TC 300) mg kg(-1) feed on susceptibility of chicken breast meat, thigh meat, liver and heart to iron-induced lipid oxidation were investigated. Day old chicks (n=200) were randomly divided into six groups. Chicks were fed diets containing either basal (C), or α-tocopheryl acetate supplementation at a level of 200 mg kg(-1) feed (VE 200), or TC supplementation for 6 weeks prior to slaughter. Lipid oxidation was assessed by monitoring malondialdehyde formation with 2-thiobarbituric acid (TBA) assay. TC supplementation at all levels exerted antioxidative effects for all tissues with the exception of 50 mg kg(-1) feed for breast meat. TC supplementation at levels of 200 and 300 mg kg(-1) feed were found to be significantly (P<0.05) more effective in retarding lipid oxidation in all tissues, compared to the control. TC supplementation at a level of 300 mg kg(-1) feed was also found to be significantly (P<0.05) superior to vitamin E supplementation at a level of 200 mg kg(-1) feed (VE 200) for oxidative stability in chicken thigh meat, but it was inferior to VE 200 in chicken liver and heart. TC supplementation at a level of 50 mg kg(-1) feed was found to be pro-oxidative in breast meat, but this did not occur in chicken thigh meat, liver and heart. The variation of TC antioxidative properties in different tissues may be explained by the uneven distribution of lipid, iron and TC accumulation in tissues.

Effect of Japanese Green Tea Extract on Canine Periodontal Diseases

Article

Mar 1994
Microb Ecol Health Dis

Asaccharolytic pigmented Porphyromonas strains were isolated from the plaque of dogs with gingivitis and periodontitis. Various species of Porphyromonas , including P. endodontalis , P. gingivalis , P. circumdentaria and unclassified species, were detectable. Canine Porphyromonas were sensitive to Japanese green tea extract (JGTE). We examined the effects of dietary JGTE on periodontal diseases. A special diet was prepared on the basis of the minimum inhibitory concentration (MIC: 0.8 mg/ml) of JGTE to several canine Porphyrmonas species. Growth of all Porphyromonas isolates was inhibited at this concentration. After 2 mths, the percentage of canine Porphyromonas significantly decreased in the plaque microbiota. Concurrently with the observed decrease in percentage of these bacteria, gingival inflammation was inhibited. However. no change in the calculus index was recorded during the observation period. Levels of oral malodour varied among the dogs and diet with JGTE was effective in the inhibition of oral malodour. We concluded that JGTE was effective in the inhibition of canine periodontal diseases. Keywords: green tea extract; canine Porphyromonas : periodontal disease

Quantitative optimization and assessments of supplemented tea polyphenols in dry dog food considering palatability, levels of serum oxidative stress biomarkers and fecal pathogenic bacteria

Article

Jan 2016

The objective of this study was to investigate the effects of supplementation of tea polyphenols (TP) in dry dog food on the palatability of dry dog food, serum oxidative stress biomarkers, and fecal pathogenic bacteria in adult dogs. Four different concentrations of TP (0.25%, 0.50%, 0.75% and 1.0%) were added to the basal dog food before or after extrusion. TP retention rate before extrusion was more than 80% and significantly higher than after extrusion (< 60%). First-choice ratios of palatability were 72%, 68% and 70% for TP concentrations of 0.50%, 0.75% and 1.0%, respectively, resulting in significant increases compared to the palatability for the control of 28%, 32% and 30%. The intake ratio (one-pan test) and consume ratio (two-pan test) of the 0.50% TP experimental dog food were 73% and 74%, respectively, significantly higher than the other three TP supplemented foods. The serum total antioxidant capacity, superoxide dismutase activities and glutathione peroxidase activities determined in the dogs’ food of 0.50% TP group increased by 19.30%, 7.72% and 4.64%, as compared to the control group after12 weeks, respectively. Serum malondialdehyde concentration was reduced by 15.05%. Fecal aerobic plate count and Coliform bacteria MPN (most probable number) of 0.50% TP group decreased by 2 logs and 1 log, respectively, compared with the control group after 12 weeks. The findings of this study have demonstrated that a concentration of 0.50% TP added to the dry dog food can significantly increase the palatability, antioxidant capacity and antibacterial activity of dry dog food in the canine model.

Subchronic oral toxicity of green tea polyphenols in rat and dogs

Article

Jan 1999
TOXICOL SCI

Effect of catechin diet on gingivitis in cats

Article

Jan 2008
INT J APPL RES VET M

We examined the effect of catechin diet on gingivitis in cats. Gingival inflammation, oral malodor, and percentage of Porphy-romonas were decreased after feeding of diet with catechin compounds. We sug-gest that feline gingivitis can be controlled by phytomedical activities of catechin in pet food. Twenty nine cats affected with gingivitis were fed either a catechin diet of 0.8 mg/g or 0.4 mg/g of catechin or a control diet and assessed for gingival inflamma-tion, oral malodor, and percentage of the genus Porphyromonas present. The catechin diet showed an anti-inflammatory effect, a deodorant effect, and a decrease in Porphy-romonas compared with the control diet. This suggests that the catechin in diet has the potential to reduce gingivitis resulting from the bacterial growth and virulence factors in cats.

Inhibition of starch digestion by the green tea polyphenol, (−)-epigallocatechin-3-gallate

Article

Nov 2012
MOL NUTR FOOD RES

Green tea has been shown to ameliorate symptoms of metabolic syndrome in vivo. The effects could be due, in part, to modulation of postprandial blood glucose levels. We examined the effect of coadministration of (-)-epigallocatechin-3-gallate (EGCG, 100 mg/kg, i.g.) on blood glucose levels following oral administration of common corn starch (CCS), maltose, sucrose, or glucose to fasted CF-1 mice. We found that cotreatment with EGCG significantly reduced postprandial blood glucose levels after administration of CCS compared to control mice (50 and 20% reduction in peak blood glucose levels and blood glucose area under the curve, respectively). EGCG had no effect on postprandial blood glucose following administration of maltose or glucose, suggesting that EGCG may modulate amylase-mediated starch digestion. In vitro, EGCG noncompetitively inhibited pancreatic amylase activity by 34% at 20 μM. No significant change was induced in the expression of two small intestinal glucose transporters (GLUT2 and SGLT1). Our results suggest that EGCG acutely reduces postprandial blood glucose levels in mice when coadministered with CCS and this may be due in part to inhibition of α-amylase. The relatively low effective dose of EGCG makes a compelling case for studies in human subjects.

Green Tea Extract-Induced Lethal Toxicity in Fasted but Not in Nonfasted Dogs

Article

Nov 2010
INT J TOXICOL

Recent chronic toxicity studies performed on green tea extracts in fasted dogs have revealed some unique dose-limiting lethal liver, gastrointestinal, and renal toxicities. Key findings included necrosis of hepatic cells, gastrointestinal epithelia and renal tubules, atrophy of reproductive organs, atrophy and necrosis of hematopoietic tissues, and associated hematological changes. The polyphenol cachetins (a mixture of primarily epigallocatechin gallate [≥55%]; plus up to 10% each of epigallocatechin, epicatechin, and epigallocatechin gallate) appeared to be the causative agents for the observed toxicities because they are the active ingredients of green tea extract studied. Conduct of the study in nonfasted dogs under the same testing conditions and dose levels showed unremarkable results. Assuming both studies were valid, at the identified no observed adverse effect levels (NOAEL) of each study, systemic exposures (based on area under the curve [AUC]) were actually lower in fasted than nonfasted dogs, suggesting that fasting may have rendered the target organ systems potentially more vulnerable to the effects of green tea extract. The toxicity mechanisms that produced lethality are not known, but the results are scientifically intriguing. Because tea drinking has become more popular in the United States and abroad, the mode of action and site of action of green tea extract-induced lethal toxicities during fasting and the role of other phytochemical components of Folia Camellia sinensis (including nonpolyphenol fractions, which are often consumed when whole-leaf products are presented) warrant further investigation.

Plant Polyphenol Intake Alters Gene Expression in Canine Leukocytes

Article

Feb 2009

Polyphenol compounds may explain most of the health-related beneficial effects of plants and vegetables, mainly through their antioxidant properties. The aim of the study was to assess the main changes on leukocyte gene expression of dogs caused by intake of three natural polyphenol-rich extracts and to compare them with caloric restriction. 20 female dogs were divided into 5 groups: control fed ad libitum (C), caloric-restricted to 30% less than control (CR), and 3 groups fed ad libitum supplemented with citrus extract (CE), green tea extract (GTE) or grape seed extract (GSE). Leukocytes gene expression was analyzed in a specially designed microarray. CE treatment mainly downregulated genes related to inflammative (IL-8, VLA-4) and cytotoxic response (GRP 58) as well as proliferation of leukocytes. GTE induced gene expression related to leukocyte proliferation and signaling (GNAQ, PKC-B). GSE upregulated some of the genes increased by CE treatment. CR downregulated genes related with energy metabolism (ATP5A1, COX7C) and inflammatory markers (VLA-4). A chronic ingestion of citric, grape seed and green tea polyphenols is able to modulate canine leukocyte functions through changes in gene expression. CE ingestion reduces expression of some genes also diminished by a 30% caloric restriction.

Green-tea extract in petfood

Abstract

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