Groene thee: De menselijke in vivo onderzoeken tot nu toe!!!

Big'r · 2 nov 2005

Voor deze post heb ik alle menselijke in vivo studies verzameld die ik kon vinden. Zowel positieve als negatieve studies werden verzameld om zo tot een relevant overzicht te komen.
Er is een waarschijnlijk verschil in werking tussen "normale" thee en groene thee.
Aangezien er zo'n grote hoeveelheid in vivo studies is in mensen, geloof ik dat de dier- en in vitro studies absoluut niet relevant meer zijn, behalve misschien voor gebieden waarop nog geen menselijke in vivo studies zijn gedaan!
Stuur me aub een pm wanneer je een interessante studie hebt gevonden om toe te voegen, zodat ik hem in het overzicht kan integreren.

ONDERWERPEN:
1 Effect op cholesterol
2 Effect op hart
3 Groene thee en kanker
4 Effect op lichaamsvet
5 Antioxidante eigenschappen
6 Biologische beschikbaarheid
7 Bijwerkingen
Overige mogelijke interessante eigenschappen[/b]

1 EFFECT OP CHOLESTEROL

Groene thee lijkt LDL(slecht)-cholesterol te verlagen.

240 adults, on a low-fat diet, with mild to moderate hypercholesterolaemia were randomly assigned to receive a daily capsule containing theaflavin-enriched green tea extract (375 mg) or placebo for 12 weeks.
After 12 weeks, total cholesterol and LDL-cholesterol were reduced by 11 per cent and 16 per cent respectively in the tea extract group. HDL-cholesterol and triglyceride levels were up 2.3 per cent and 2.6 per cent respectively (E105).

300 mg polyphenols supplementation for 2 weeks to 22 men did not change plasma concentrations of lipids, ascorbate, alpha-tocopherol, and lipid peroxides but beta-carotene was higher in the tea group.
LDL (0.1 mg/mL) was incubated with 5 microM Cu(2+) and the oxidation was measured by absorbance at 234 nm. These results suggest that daily consumption of seven to eight cups (approximately 100 mL each cup) of green tea may increase resistance of LDL to in vivo oxidation, leading to reduction in the risk of cardiovascular diseases (E106).

For 1,306 men serum total cholesterol levels were found to be inversely related to the consumption of green tea while no association was noted with serum triglycerides and high-density lipoprotein cholesterol. Adjusted mean concentrations of total cholesterol were 8 mg/dl lower in men drinking nine cups or more per day than in those consuming zero to two cups per day. Serum cholesterol levels were inversely associated with traditional Japanese dietary habits (intake of rice and soy bean paste soup) and positively associated with Westernized habits (E107).

2 EFFECT OP HART

Tot nu toe laten alle studies een significant positieve werking van groene thee op het hart zien.

1,900 people, mainly in their 60s, who had suffered a heart attack were followed up almost four years later, by which time 313 had died, mainly from heart disease. The researchers found that the less tea the patients drank the more likely they were to have died during the period.
Those who consumed less than 15 cups a week had a 28 per cent lower rate of dying. And those who drank more than 14 cups of tea a day had a 44 per cent lower death rate than non-tea drinkers (E204).

Researchers from the University of Arizona in the US and King Saud University in Saudi Arabia interviewed 3,430 Saudis aged from 30 to 70.those who drank more than six cups of tea daily (about 20 per cent of those interviewed) had a 50 per cent lower risk of heart disease than those who did not drink tea (E205).

18 healthy men ingested 254 mg of total catechins/subject.
The plasma phosphatidylcholine hydroperoxide (PCOOH) levels attenuated from 73.7 pmol/mL in the control to 44.6 pmol/mL in catechin-treated subjects, being correlated inversely with the increase in plasma EGCg level. The results suggested that drinking green tea contributes to prevent cardiovascular disease by increasing plasma antioxidant capacity in humans (E206).

Despite antioxidant efficacy in vitro, black tea does not protect plasma from lipid peroxidation in vivo. The striking discrepancy between the in vitro and ex vivo data is most likely explained by the insufficient bioavailability of tea polyphenols in humans (E207).

Polyphenols are the most abundant antioxidants in the diet and are widespread constituents of fruits, vegetables, cereals, dry legumes, chocolate, and beverages, such as tea, coffee, or wine.
Epidemiological studies have repeatedly shown an inverse association between the risk of myocardial infarction and the consumption of tea and wine or the intake level of some particular flavonoids, but no clear associations have been found between cancer risk and polyphenol consumption (E208).

Flavonoids are polyphenolic antioxidants naturally present in vegetables, fruits, and beverages such as tea and wine.
Flavonoid intake (analysed in tertiles) was significantly inversely associated with mortality from coronary heart disease (p for trend = 0.015) and showed an inverse relation with incidence of myocardial infarction, which was of borderline significance (p for trend = 0.08). The relative risk of coronary heart disease mortality in the highest versus the lowest tertile of flavonoid intake was 0.42 (95% CI 0.20-0.88).
Intakes of tea, onions, and apples were also inversely related to coronary heart disease mortality, but these associations were weaker (E209).

Green tea consumption was significantly higher in patients without coronary artery disease (CAD) than in those with CAD (5.9+/-0.5 vs 3.5+/-0.3 cups/day; p<0.001). An inverse relationship between the intake of green tea and the incidence of CAD was observed (p<0.001) (E210).

Epidemiologic studies indicated that tea consumption slightly reduces blood pressure.
Both black and green tea polyphenols attenuate blood pressure increases through their antioxidant properties in stroke-prone spontaneously hypertensive rats. Furthermore, because the amounts of polyphenols used in this experiment correspond to those in ~1 L of tea, the regular consumption of black and green tea may also provide some protection against hypertension in humans (E211).

3 GROENE THEE EN KANKER

A)Studies die geen relatie tussen thee en kanker laten zien
Studies (E758), (E773), (E779) en (E780) waren waarschijnlijk niet groene thee specifiek.

In a green tea study of 42 patients with advanced androgen-independent prostate cancer, only one patient showed a short-term drop in his prostate-specific antigen (PSA) levels (a marker for prostate cancer) (E755).

We computed flavonol intakes from dietary data collected by validated food frequency questionnaires in 1991 and 1995 from 90,630 women in the Nurses Health Study II. We evaluated the association of flavonol intake with breast cancer risk in women who were premenopausal and aged between 26 and 46 years at baseline in 1991. During 8 years of follow-up, we documented 710 cases of invasive breast cancer.
There were no associations seen between individual flavonols such as kaempferol, quercetin and myricetin and breast cancer risk. Among the major food sources of flavonols, we found a significant inverse association with intake of beans or lentils but not with tea, onions, apples, string beans, broccoli, green pepper and blueberries (E758).

In a pooled analysis of two prospective studies with 35004 Japanese women, green-tea intake was not associated with a lower risk of breast cancer (222 cases), the multivariate relative risk for women drinking >or=5 cups compared with <1 cup per day being 0.84 (95% confidence interval 0.57-1.24, Trend P=0.69) (E769).

In 59,036 swedish women (40-76 y) drinking 4 or more cups of coffee/day had a covariate-adjusted hazard ratio of breast cancer of 0.94 [95% confidence interval (CI) 0.75-1.28] compared to women who reported drinking 1 cup a week or less. The corresponding hazard ratio for tea consumption was 1.13 (95% CI 0.91-1.40). In this large cohort of Swedish women, consumption of coffee, tea, and caffeine was not associated with breast cancer incidence (E773).

Possible relationships of dietary factors to risk of breast cancer in men were assessed.
No trends in risk were observed with increasing intakes of specific foods, except for an increase in risk with citrus fruits. No increase in risk with increasing amounts of specific fats, vitamins, or minerals or with amounts of protein, fiber, carbohydrate, starches, nitrites, or alcohol consumed was observed, except for an increase in risk with dietary vitamin C consumption. A decreasing trend in risk with dietary niacin and with coffee and an increasing trend in risk with tea consumption were observed. No associations were found with use of any dietary supplements, including vitamin C (E779).

Cases were 5,984 women, below age 75, with histologically confirmed breast cancer, and controls were 5,504 women.
No relationship was observed between coffee intake and the risk of breast cancer. Tea consumption was also not associated with the risk of breast cancer (OR 0.94, 95% CI 0.85-1.03) (E780).

B)Studies die een positieve relatie laten zien tussen thee en kanker

Polyphenolic compounds account for 30% of the dry weight of the leaves.
Epidemiological studies revealed that the incidences of stomach and prostate cancers are the lowest in the world among a population that consumes green tea on a regular basis. It has also been reported that the quantity of green tea consumed, plays an important role in reducing cancer risk and in delaying cancer outbreak and recurrence (E752).

After a year's oral administration of green tea catechins (GTCs), only one man in a group of 32 at high risk for prostate cancer developed the disease, compared to nine out of 30 in a control. The 600 mg-per-day dosage of caffeine-free, total catechins (50 percent of which is EGCG) given to participants in the study was one or two times the amount of green tea consumed daily in China, where 10 to 20 cups a day is normal, said the scientists (E754).

The effects of green tea consumption on incidence of breast cancer and recurrence of breast cancer: a systematic review and meta-analysis.
To date, the epidemiological data indicates that consumption of 5 or more cups of green tea a day shows a non-statistically significant trend towards the prevention of breast cancer development. Evidence indicates that green tea consumption may possibly help prevent breast cancer recurrence in early stage (I and II) cancers (E757).

A case-control study on breast cancer patients revealed that high daily consumption of green tea was associated with a lower recurrence rate among Stages I and II patients (E760).

Cancer onset of patients who had consumed over 10 cups of green tea per day was 8.7 years later among females and 3.0 years later among males, compared with patients who had consumed under three cups per day (E761).

Recently, and epidemiologic study showed a lower risk of gastrointestinal carcinogenesis in green tea drinkers. It was determined that 1 g per day of GTE might be an effective dose. GTE was not toxic and no harmful effect was found during its clinical use (E762).

In Japan, an epidemiological study showed an inverse relationship between habitual green tea drinking and the standardized mortality rates for cancer. Some cohort studies on Chanoyu (Japanese tea ceremony) women teachers also showed that their mortality ratio including deaths caused by malignant neoplasms were surprisingly low (E764).

Increased consumption of green tea was closely associated with decreased numbers of axillary lymph node metastases among premenopausal patients with stage I and II breast cancer and with increased expression of progesterone receptor (PgR) and estrogen receptor (ER) among postmenopausal ones.
increased consumption of green tea was correlated with decreased recurrence of stage I and II breast cancer (P < 0.05 for crude disease-free survival); the recurrence rate was 16.7 or 24.3% among those consuming > or = 5 cups or < or = 4 cups per day, respectively, in a seven-year follow-up of stage I and II breast cancer, and the relative risk of recurrence was 0.564 (95% confidence interval, 0.350-0.911) after adjustment for other lifestyle factors. However, no improvement in prognosis was observed in stage III breast cancer (E765).

Among the promising bioactive food components being investigated at the National Cancer Institute in prevention clinical trials to reduce breast cancer risk are indole-3-carbinol, sulforaphanes, phytoestrogen isoflavones, perillyl alcohol, and green tea polyphenols. Prostate cancer prevention trials have focused on hormone modulation with the 5-alpha-reductase inhibitor finasteride and bioactive food components such as selenium and vitamin E. Soy isoflavones, green tea polyphenols, and doxercalciferol also are being investigated for prostate cancer prevention (E768).

A case-control study was conducted on 213 cases with histopathological diagnosis and 430 matched controls, using conditional logistic regression analysis. 28 factors were associated with breast cancer risk in one-way variance model.
Factors as later menarche, lactate longer, soybean food, fruit, drink tea habit were protective factors for breast cancer. Further breakdown of data showed some difference between premenopausal and postmenopausal women. Risks in premenopausal women were associated with history of benign breast disease, age of menarche, soybean food intake, whereas risks in postmenopausal women were related to age of menopausal, BMI, waist-hip ratio and fruit intake (E770).

epidemiologic data obtained from mainly Western populations are not supportive of a protective role of tea, mainly black tea, in the etiology of breast cancer. Much less is known about the relationship between green tea and breast cancer risk. During 1995-1998, we conducted a population-based, case-control study of breast cancer among Chinese, Japanese and Filipino women in Los Angeles County and successfully interviewed 501 breast cancer patients and 594 control subjects.
Risk of breast cancer was not related to black tea consumption. In contrast, green tea drinkers showed a significantly reduced risk of breast cancer, and this was maintained after adjusting for age, specific Asian ethnicity, birthplace, age at menarche, parity, menopausal status, use of menopausal hormones, body size and intake of total calories and black tea. Compared to women who did not drink green tea regularly (i.e., less than once a month), there was a significant trend of decreasing risk with increasing amount of green tea intake, adjusted odds ratios being 1.00, 0.71 (95% confidence interval [CI] 0.51-0.99) and 0.53 (95% CI 0.35-0.78), respectively, in association with no, 0-85.7 and >85.7 ml of green tea per day.
Both green tea and soy intake had significant, independent protective effects on breast cancer risk (E772).

A decreased HR (hazard ration) for recurrence adjusted for stage was observed with consumption of three or more daily cups of green tea (HR=0.69, 95% confidence interval (95%CI)=0.47-1.00). Particularly in stage I, the HR was decreased statistically significantly (HR=0.43, 95%CI=0.22-0.84). A similar tendency was observed for stage II subjects, but was not present among more advanced stages (E774).

Phytoestrogens have been linked to a risk of breast cancer. The main phytoestrogens in the Finnish diet are lignans, and enterolactone is quantitatively the most important circulating lignan.
This analysis concerns 194 breast cancer cases (68 premenopausal and 126 postmenopausal) who entered the study before diagnosis and 208 community-based controls.
The odds ratio in the highest quintile of enterolactone values adjusted for all of the known risk factors for breast cancer was 0.38 (95% confidence interval,0.18-0.77; P for trend, 0.03). High enterolactone level was associated with higher consumption of rye products and tea and higher intake of dietary fiber and vitamin E compared with those with low serum enterolactone values (E775).

A total of 198 women with BC, aged 21-79 years, were individually age matched to an identical number of women with no breast disease.
The adjusted odds ratio for the consumption of more than one slice of onion per day and BC was 0.27 (95% confidence interval = 0.16-0.47), with a statistically significant trend (p < 0.001). Among premenopausal women, there was also a protective and significant effect due to the intake of lettuce and spinach and nonsignificant protective effects for the consumption of apples and herbal tea (E777).

a prospective cohort study with over 8000 individuals in Saitama Prefecture revealed that the daily consumption of at least ten Japanese-size cups of green tea resulted in delayed cancer onset, and a follow-up study of breast cancer patients conducted at our Hospital found that stages I and II breast cancer patients consuming over five cups per day experienced a lower recurrence rate and longer disease-free period than those consuming fewer than four cups per day (E778).

Studies around the world were reviewed to evaluate whether there is a consensus of epidemiologic evidence on the relation of tea drinking to cancer overall or to specific cancers. Ecological data suggest at most a modest benefit.
More relevant case-control and cohort studies show mixed results.
Nevertheless, several investigations point to the possibility of lowered risks of digestive tract cancers among tea drinkers, especially those consuming green tea (E781).

C)Mogelijk effect van groene thee op kanker is misschien erfelijk bepaald

A nested case-control study involving 297 incident breast cancer cases and 665 control subjects within the Singapore Chinese Health Study showed no association between intake frequencies of green tea and risk of breast cancer among all women or those with low-activity ACE genotype.
Among women with high-activity ACE genotype, however, intake frequency of green tea was associated with a statistically significant decrease in risk of breast cancer (P for trend=0.039); the odds ratio (95% confidence interval) was 0.33 (0.13-0.82) for women drinking green tea at least monthly and 0.29 (0.10-0.79) for those drinking green tea at least weekly compared with non-drinkers.
Black tea intake was unrelated to breast cancer risk irrespective of the ACE genotype (E756).

In a case-control study conducted among Asian-American women in Los Angeles County, we reported a significant inverse relationship between intake of green tea and risk of breast cancer. We examined the interrelationships between tea intake, COMT genotype, and breast cancer risk in 589 incident cases and 563 population-based controls in Chinese-, Japanese-, and Filipino-American women.
Risk of breast cancer was influenced significantly by intake of tea, particularly green tea intake. However, the inverse association between tea intake and breast cancer risk was observed only among individuals who possessed at least one low-activity COMT allele.This risk reduction was observed in relation to both green tea and black tea intake (E759).

DE VOLGENDE STUDIES ZIJN DIER- OF IN VITRO STUDIES, MAAR LATEN ENKELE MOGELIJK INTERESSANTE SYNERGETISCHE EFFECTEN ZIEN WANNEER (MEESTAL NATUURLIJKE) SUBSTANTIES WORDEN GECOMBINEERD

Only a few drugs have been used to date in the clinic with any success, and these include non-steroidal anti-inflammatory drugs for colon, finasteride for prostate and tamoxifen or raloxifene for breast tumours. Indole-3-carbinol (I3C), epigallocatechin gallate (EGCG), curcumin and resveratrol, all have a number of different molecular targets, impinging on several signalling pathways (E730).

Low concentrations of catechins are cytotoxic to ERalpha- human breast cancer cells, and the combination of EGCG and tamoxifen elicits synergistic cytotoxicity in MDA-MB-231 cells (E737).

Seven phytoestrogens were screened for estrogen receptor binding and growth inhibition of androgen-insensitive (PC-3) and androgen-sensitive (LNCaP) human prostate tumor cells.
Quercetin, baicalein, genistein, epigallocatechin gallate (EGCG), and curcumin displaced > 85% of estradiol binding, whereas apigenin and resveratrol displaced > 40%. From growth inhibition studies in LNCaP cells, apigenin and curcumin were the most potent inhibitors of cell growth, and EGCG and baicalein were the least potent. In PC-3 cells, curcumin was the most potent inhibitor of cell growth, and EGCG was the least potent. In both cell lines, significant arrest of the cell cycle in S phase was induced by resveratrol and EGCG and in G2M phase by quercetin, baicalein, apigenin, genistein, and curcumin. Induction of apoptosis was induced by all of the 7 compounds in the 2 cell lines. Androgen responsiveness of the cell lines did not correlate with cellular response to the phytoestrogens. In conclusion, these 7 phytoestrogens, through different mechanisms, are effective inhibitors of prostate tumor cell growth (E747).

The combination of EGCG and ascorbic acid can strongly suppress the proliferation and metastasis of liver cancer cells. A mixture of EGCG and ascorbic acid exhibited 73.2% inhibition of SMMC-7721 cell proliferation in, which was much higher than EGCG (40.4%) or ascorbic acid (12.4%) alone. In the cell migration assay, the mixture also significantly suppressed the migration of SMMC-7721 cells by 65.9% while EGCG and/or ascorbic acid did by 28.9% and 18.7%, respectively (E748).

Similar to silymarin, genistein and EGCG also inhibit mitogenic signaling pathway(s) and alter cell cycle regulators, albeit at different levels, leading to growth inhibition and death of advanced and androgen-independent prostate carcinoma cells (E753).

A mix of lysine, proline, arginine, ascorbic acid, and EGCG significantly suppressed tumor growth of breast cancer cells in female athymic nude mice and significantly inhibited MMP expression, angiogenesis, and invasion in breast cancer cells, in vitro (E767).

Green Tea (GT) infusion at 1.5 g tealeaf/100 mL water produced significant (p < 0.05) reductions of 56% in final tumor weight of androgen-dependent human breast tumor in female SCID mice. GT plus Soy Phytochemical Concentrate (SPC) at 0.1% of the diet further reduced final tumor weight by 72% (p < 0.005). Analysis of serum and tumor biomarkers showed that the combined effects of SPC and GT inhibited tumor angiogenesis, and reduced estrogen receptor (ER)-alpha and serum levels of insulin-like growth factor (IGF)-I (E771).

EGCG has been shown to increase the endotoxin-induced production of proinflammatory mediators such as prostaglandin E(2) and tumor necrosis factor-alpha in RAW264.7 macrophages, whereas the soybean isoflavonoid genistein compensated for these inverse properties of EGCG, leading to marked suppression in combination (E813).

4 EFFECT OP LICHAAMSVET

690 mg catechins for healthy japanes men for 12 weeks decreases body weight, BMI, waist circumference, body fat mass, and subcutaneous fat area. Changes in the concentrations of malondialdehyde-modified LDL were positively associated with changes in body fat mass and total fat area (E108).

A mixture of green tea (90, 200, 300 or 400 mg) and guarana extracts (200 mg caffeine) 3 x/day 30 min. before meal increases 24 h energy expenditure by 750 kJ. No effect of the EGCG-caffeine mixture was observed for lipid oxidation. Systolic and diastolic blood pressure increased by about 7 and 5 mmHg (E528).

The green tea extract AR25 is an 80% ethanolic dry extract standardized at 25% catechins expressed as EGCG. In an open study, the effects of extract AR25 were evaluated in moderately obese patients. After 3 months, body weight was decreased by 4.6% and waist circumference by 4.48%. These results suggest the green tea extract AR25 to be a natural product for the treatment of obesity, which exerts its activity by several ways: inhibition of lipases and stimulation of thermogenesis (E529).

5 ANTIOXIDANTE EIGENSCHAPPEN

Human volunteers were supplemented with single doses of green tea catechins in free (Greenselect) or phospholipid complex form (Greenselect Phytosome) equivalent to 400 mg epigallocatechingallate (EGCg).
Green tea catechins were absorbed more extensively when administered as phospholipid complex rather than as free catechins. Single dose intake of both forms of catechins produced a transient decrease (10-20%) of plasma ascorbate and total glutathione and an increase of plasma TRAP (16-19%). These variations were consistent with the plasmatic levels of EGCg, ascorbate and total glutathione (E533).

Consuming red tea for 14 obese women revealed alteration in reactive oxygen species generation; the relative decrease of RFT was greater after 5 months than that after 1 month of treatment. A decrease in ROS generation after red tea consumption was accompanied by the decrease of ROS in response to tested compounds in normal cells. EGCG and TF (theaflavins) showed similar potency in antioxidative activities. Tea polyphenols were not found to modulate CRP level in obese women. Tea may thus represent an important source of dietary antioxidants (E534).

Adding 2 cups of green tea to a controlled diet of healthy volunteers for 42 days caused a significant increase in plasma total antioxidant activity [from 1.79 to 1.98 mumol Trolox equivalent (TE)/ml, P<.001], significant decreases in plasma peroxides level (from 412 to 288 Carr U, P<.05) and induced DNA oxidative damage in lymphocytes (from 14.2% to 10.1% of DNA in tail, P<.05), a moderate although significant decrease in LDL cholesterol (from 119.9 to 106.6 mg/dL, P<.05) with respect to control (E535).

Catechin intake had no effect on the basal level of endogenous antioxidants (alpha-tocopherol, beta-carotene, and lycopene) or of lipids in plasma.
These results suggested that drinking green tea daily would contribute to maintain plasma catechin levels sufficient to exert antioxidant activity against oxidative modification of lipoproteins in blood circulation systems (E824).

6 BIOLOGISCHE BESCHIKBAARHEID

EGCG was administered topically to human skin achieved high concentrations in skin but negligible systemic availability (E763).

Orally administered EGCG is rapidly absorbed from the gut. After repeated dosing (day 10) dose linearity was applied between the 200 mg and 400 mg group. Dose escalation to 800 mg was more than dose-proportional in rate and extent, and statistically different from the 200 mg and 400 mg group. An increase in elimination half-life (t1/2.z) and in the accumulation factor (R) in the 800 mg dosage group indicates dose-dependent saturation of capacity-limited excretion routes or an increase of hepato-duodenal re-circulation (E805).

The epimerisation reaction occurring in manufacturing canned and bottled tea drinks would not significantly affect antioxidant activity and bioavailability of total tea polyphenols (E807).

EGCG) can reach the brain following oral intake and could thus act as an anti-tumoral agent targeting several key steps of brain cancer cells invasive activity (E814).

200, 400 or 800 mg EGCG/day for 10 days in 36 healthy men is rapidly absorbed from the gut.
Dose linearity was applied for single-dose application (day 1). After repeated dosing (day 10) dose linearity was applied between the 200 mg and 400 mg group. Dose escalation to 800 mg was more than dose-proportional in rate and extent, and statistically different from the 200 mg and 400 mg group. An increase in elimination half-life (t1/2.z) and in the accumulation factor (R) in the 800 mg dosage group indicates dose-dependent saturation of capacity-limited excretion routes or an increase of hepato-duodenal re-circulation (E817)

The pharmacokinetic parameters of EGCG), EGC, and EC were analyzed after administration of a single oral dose of green tea or decaffeinated green tea (20 mg tea solids/kg) or EGCG (2 mg/kg) to eight subjects.
The time needed to reach the peak concentrations was in the range of 1.3-1.6 h. The elimination half-lives were 3.4 +/- 0.3, 1.7 +/- 0.4, and 2.0 +/- 0.4 h, respectively (E819).

1. Ten healthy volunteers ingested 1.5 mmole ECg, EGC or EGCg.
2. The catechin levels in plasma after ingestion were significantly different: EGC rose quickly with a short elimination half-life (t1/2 elim = 1.7 h), ECg was intermediate in rise but slowest in decline (t1/2 elim = 6.9h), EGCg was slowest in rise but intermediate in decline (t1/2 elim = 3.9h). At 24h, EGC and EGCg had returned to base levels, but ECg was still elevated.
3. Very limited interconversion (ECg-->epicatechin, EGCg-->EGC) occurred indicating that degallation is not required for uptake.
5. EGC and ECg produced an increase in antioxidant activity in plasma, but with EGCg, no statistically significant effect was found (E820).

Following a black tea preparation plasma concentrations of EGC, EC and EGCG increased significantly relative to baseline (P < 0.05). Plasma EGC, EC and EGCG peaked after 5 h, whereas ECG peaked at 24 h.
Approximately 1.68% of ingested catechins were present in the plasma, urine and feces, and the apparent bioavailability of the gallated catechins was lower than the nongallated forms. Thus, catechins were bioavailable. However, unless they are rapidly metabolized or sequestered, the catechins appeared to be absorbed in amounts that were small relative to intake (E821).

20 healthy subjects were assigned to one of the dose levels (200, 400, 600, and 800 mg based on EGCG content). The AUC and maximum plasma concentration (Cmax) of EGCG after the 800-mg dose of EGCG were found to be significantly higher than those after the 200- and 400-mg dose. The AUC and Cmax of EGCG after the 800-mg dose of Polyphenon E were significantly higher than those after the three lower doses. We conclude that the two catechin formulations resulted in similar plasma EGCG levels (E822).

225, 375 and 525 mg EGCG + 7.5, 12.5, and 17.5 mg EGC significantly and dose-dependently increases plasma levels (E824).

150 or 300 mg EGCG for 8 days in 30 healthy women showed a relative nonhaem iron absorption reduction of 14% with 150mg EGCG and 27% for 300mg EGCG treatment compared to placebo.
In this study the magnitude of the inhibitory action of EGCG on nonhaem iron absorption was found to be much lower than that reported in the literature for black tea and similar compounds (E825).

The oral bioavailability of the major green tea constituents, green tea catechins, is low, resulting in systemic catechin levels in humans many fold less than the effective concentrations determined in in vitro systems.
After an onvernight fast 30 healthy volunteers took a single dose of Polhyphenon E with or without breakfast. Greater oral bioavailability of free catechins can be achieved by taking the Polyphenon E capsules on an empty stomach after an overnight fast. Polyphenon E up to a dose that contains 800 mg epigallocatechin gallate is well-tolerated when taken under the fasting condition (E826).

Sorry, maar ik wilde toch even deze dierstudie toevoegen:

Piperine (an alkaloid derived from black pepper), enhanced the bioavailability of EGCG in mice by 1.3-fold compared to mice treated with EGCG only. EGCG appearance in the colon and the feces of piperine-cotreated mice was slower than in mice treated with EGCG alone. Coadministration of piperine and curcumin to humans and rats enhanced the bioavailability of curcumin by 2000% and 154%, respectively (E810).

7 BIJWERKINGEN

The doses of EGCG in supplements, which will be lower than those used in this study, are not expected to have any health relevant effects on iron absorption in subjects with normal iron stores (E804).

10 days' repeated administration of oral doses of EGCG of up to 800 mg per day to healthy men were found to be safe and very well tolerated (E805).

40 healthy subjects with Fitzpatric skin type II or III supplemented for 4 weeks with: 800 mg EGCG once/day, 400 mg EGCG twice/day, 800 mg EGCG as Polyphenon E once/day, 400 mg EGCG as Polyphenon E twice/day, or a placebo once/day (8 subjects/group).
Adverse events reported during the 4-week treatment period include excess gas, upset stomach, nausea, heartburn, stomach ache, abdominal pain, dizziness, headache, and muscle pain. All of the reported events were rated as mild events. For most events, the incidence reported in the polyphenol-treated groups was not more than that reported in the placebo group.
No significant changes were observed in blood counts and blood chemistry profiles after repeated administration of green tea polyphenol products.
There was no protection against UV-induced erythema.
it is safe for healthy individuals to take green tea polyphenol products in amounts equivalent to the EGCG content in 8-16 cups of green tea once a day or in divided doses twice a day for 4 weeks. There is a >60% increase in the systemic availability of free EGCG after chronic green tea polyphenol administration at a high daily bolus dose (800 mg EGCG or Polyphenon E once daily) (E816).

Ten days' repeated administration of oral doses of EGCG of up to 800 mg per day were found to be safe and very well tolerated (E817).

Single supplementation of 50-1600 mg EGCG under fasting conditions in 60 healthy men was safe and very well tolerated (E818).]

OVERIGE MOGELIJKE INTERESSANTE EIGENSCHAPPEN

200 mg poly E or EGCG/day for 12 weeks in 51 subjects effectively treated human papilloma virus (HPV) infected cervical lesions in 69% (35/51) (E525).

200 mg L-theanine (an amino acid found in green tea) 1 h before bedtime was supplemented for 6 days to 22 young men. All subjects reported a significant absence of feeling exhausted and a reduced need for sleep when administered with the L-theanine, compared to the placebo.
Seven of the 10 students had improved sleep efficiency and these same subjects reported a superior mental state prior to sleep and a decreased occurrence of nightmares. Total sleeping time did not alter between the two groups (E526).

Areas of skin of normal volunteers were treated with an extract of green tea or one of its constituents. Thirty minutes later, the treated sites were exposed to a 2 minimal erythema dose solar simulated radiation.
Polyphenolic extracts of green tea are effective chemopreventive agents for many of the adverse effects of sunlight on human health and may thus serve as natural alternatives for photoprotection (E530).

In this study we have investigated the effects of topical application of EGCG, the major polyphenol present in green tea, to human skin before UV irradiation on UV-induced markers of oxidative stress and antioxidant enzymes.
Pretreatment with EGCG was found to restore the UV-induced decrease in GSH level and afforded protection to the antioxidant enzyme GPx (E531).

The relationship between tea intake, and plasma estrogen and androstenedione levels in 130 healthy postmenopausal women showed 13% lower plasma estrone levels in regular green tea drinkers, and 19% higher in regular black tea drinkers. A similar pattern of differences between tea intake, and plasma levels of estradiol (P = 0.08) and androstenedione (P = 0.14) were found (E906).

wazzup · 2 nov 2005

Zo he, verveelde je je ?

Dier en in vitro studies geven een aanwijzing van hoe iets in vivo MISSCHIEN ZOUDEN KUNNEN ZIJN... een hele grote MISSCHIEN dus, maar zeker geen bewijs ergens van. Echt nuttig zijn ze inderdaad ook niet, althans niet zo nuttig als veel mensen willen doen geloven... het extrapoleren van theorieen uit in vitro of dierstudies is wetenschappelijk onverantwoord.. leuk voor in het cafe, maar meer ook niet.

Maar groene thee lijkt "da shizznit" te zijn ! ergogenics staat er ook vol mee:
http://search.freefind.com/find.html?id=38869215&pageid=r&mode=ALL&n=0&query=groene+thee al staat er ook eentje tussen die iets minder positief is: http://www.ergogenics.org/groenethee.html

PS: edit trouwens je post even en klik onderaan op "Smilies in tekst uitzetten", dan komen referenties als 8) in tekst over in plaats van als smilie [Afbeelding niet meer beschikbaar].

RawBas · 2 nov 2005

Met Groene thee is het net zo als met veel andere stoffen: het werkt pas vanaf een bepaalde concentratie.
Wat veel handige fabrikanten doen is een spoortje Groene thee toevoegen aan hun product en dan lopen pochen over de heilzame en vetverbrandende werking.

Ik weet niet precies welke dosering nodig is voordat de positieve effecten tot hun recht komen, maar laat je dus niet misleiden door kruidensnoepjes met Groene thee extract en dat soort dingen.

bigtony · 2 nov 2005

Ben voorzichtig:

Antioxidants may hamper cancer therapies

22/09/2005 - Antioxidants are widely believed to help reduce the risk of certain cancers, but if taken by cancer patients undergoing cytotoxic therapy they may have a detrimental effect, according to a commentary in the Cancer Journal for Clinicians.

Antioxidants,, such as vitamins A, C and E and carotenoids like beta-carotene, are believed to exert a protective effect on cells. They scavenge toxic molecules called free-radicals, which cause oxidative stress and can lead to DNA cell damage.
Gabriella D'Andrea, assistant clinical member of the Memorial Sloan-Kettering Cancer Center's department of medicine, wrote in the journal that oncologists are frequently asked what patients can do to reduce the toxicity of treatments. Surveys have shown that as many as 50 percent of cancer patients use dietary supplements.

But she warns that that there are some indications that antioxidants can actually be harmful for patients being treated with chemotherapy or radiotherapy, since they may be unable to differentiate between normal cells and cancer cells. This may mean that treatment is rendered less effective.

There is also some preclinical evidence (Vera et al; J Biol Chem 1995; 270:23706-23712) suggesting that vitamin C might have an even greater protective effect on tumors than on normal cells.

Some evidence that antioxidants may protect cells against treatment-related toxicities does exist (eg Pace et al, J Clin Oncol 2003; 21:927-931), but D'Andrea wrote that it is “promising, although not unequivocal”.

As for clinical trials, despite a small number of studies seeming to indicate that antioxidants can be detrimental when patients are receiving conventional therapies, no randomized human trial has been mounted on a scale large enough to guide clinical practice.

“The harmful effects of antioxidants might be important even if they were small; a reduction of only a few percentage points in the efficacy of chemotherapy might lead to hundreds or thousands of deaths every year,” she wrote.

D'Andrea holds that, until contrasting evidence from extensive human studies is available, patients should be advised against taking antioxidants during cytotoxic therapy.

D'Andrea's comments reinforce the message that patients should tell their doctor about supplements they are taking, in order to avoid potentially dangerous side effects.

In a recent survey of older Americans, 36 percent of respondents said they combine dietary supplements with prescription drugs – almost a quarter of whom did so without medical supervision.

Nor is this the first time that concerns have been raised over herbals and supplements' potential to interfere with the effects of cancer treatments. A study published in the April issue of Breast Cancer Research and Treatment found that black cohosh, a herbal with a long history of use to alleviate menopause symptoms and used by some breast cancer patients for the menopause-like side effects of cancer therapies, may interfere with some drugs.

Black cohosh was seen to increase cytotoxicity (cell killing) by two of the drugs, doxorubicin and docetaxel. It decreased the cytotoxicity of cisplatin.

No change in effect was seen in a fourth drug, 4-hydroperoxycyclophosphamide (4-HC), nor in radiation therapy.

Blijft moeilijk. Wel respect voor je graafwerk.

roxxe · 2 nov 2005

is alle groene thee "gelijk" ? zoals lipton en zo?

AnaboliC · 2 nov 2005

nee, daar zit veel suiker en zooi in.

Ik drink per dag 1,5 liter groene thee (van 3 theezakjes)

Big'r · 2 nov 2005

wazzup zei:
Maar groene thee lijkt "da shizznit" te zijn ! ergogenics staat er ook vol mee:
http://search.freefind.com/find.html?id=38869215&pageid=r&mode=ALL&n=0&query=groene+thee al staat er ook eentje tussen die iets minder positief is: http://www.ergogenics.org/groenethee.html

Had hem wel al doorgelezen, maar moet hem nog even grondig bekijken op de variabelen. Het schijnt de combinatie met caffeine te zijn, en niet zozeer de groene thee alleen.

wazzup zei:
PS: edit trouwens je post even en klik onderaan op "Smilies in tekst uitzetten", dan komen referenties als 8) in tekst over in plaats van als smilie [Afbeelding niet meer beschikbaar].

Onderzoek 52"smilie" staat onderin bij de referenties ook als 52"smilie" , dus je kunt ze niet door de war halen

Sportfood.nl zei:
Ik weet niet precies welke dosering nodig is voordat de positieve effecten tot hun recht komen, maar laat je dus niet misleiden door kruidensnoepjes met Groene thee extract en dat soort dingen.

Inderdaad hebben kleine hoeveelheden geen significant effect. Het gaat hier om 400 mg EGCG (kopje of 10 groene thee)/dag.

bigtony zei:
Gabriella D'Andrea, assistant clinical member of the Memorial Sloan-Kettering Cancer Center's department of medicine, wrote in the journal that oncologists are frequently asked what patients can do to reduce the toxicity of treatments. Surveys have shown that as many as 50 percent of cancer patients use dietary supplements.

Use of complementary/alternative medicine by breast cancer survivors in Ontario: prevalence and perceptions.

PURPOSE: To determine the prevalence of use of complementary/alternative medicine (CAM) by breast cancer survivors in Ontario, Canada, and to compare the characteristics of CAM users and CAM nonusers. PATIENTS AND METHODS: A questionnaire was mailed to a random sample of Ontario women diagnosed with breast cancer in 1994 or 1995. RESULTS: The response rate was 76.3%. Overall, 66.7% of the respondents reported using CAM, most often in an attempt to boost the immune system. CAM practitioners (most commonly chiropractors, herbalists, acupuncturists, traditional Chinese medicine practitioners, and/or naturopathic practitioners) were visited by 39.4% of the respondents. In addition, 62.0% reported use of CAM products (most frequently vitamins/minerals, herbal medicines, green tea, special foods, and essiac). Almost one half of the respondents informed their physicians of their use of CAM. Multiple logistic regression analysis determined that support group attendance was the only factor significantly associated with CAM use. CONCLUSION: CAM use is common among Canadian breast cancer survivors, many of whom are discussing CAM therapy options with their physicians. Knowledge of CAM therapies is necessary for physicians and other health care practitioners to help patients make informed choices. CAM use may play a role in the positive benefits associated with support group attendance.

bigtony zei:
But she warns that that there are some indications that antioxidants can actually be harmful for patients being treated with chemotherapy or radiotherapy, since they may be unable to differentiate between normal cells and cancer cells. This may mean that treatment is rendered less effective.

Dit geldt in ieder geval niet voor groene thee, wat juist in de onderzoeken wel een duidelijk verschil maakt tussen gezonde cellen en kankercellen.

bigtony zei:
There is also some preclinical evidence (Vera et al; J Biol Chem 1995; 270:23706-23712) suggesting that vitamin C might have an even greater protective effect on tumors than on normal cells.
Some evidence that antioxidants may protect cells against treatment-related toxicities does exist (eg Pace et al, J Clin Oncol 2003; 21:927-931), but D'Andrea wrote that it is “promising, although not unequivocal”.
As for clinical trials, despite a small number of studies seeming to indicate that antioxidants can be detrimental when patients are receiving conventional therapies, no randomized human trial has been mounted on a scale large enough to guide clinical practice.
“The harmful effects of antioxidants might be important even if they were small; a reduction of only a few percentage points in the efficacy of chemotherapy might lead to hundreds or thousands of deaths every year,” she wrote.
D'Andrea holds that, until contrasting evidence from extensive human studies is available, patients should be advised against taking antioxidants during cytotoxic therapy.

Dit geldt alleen voor de periode tijdens chemotherapie/bestraling. Artsen raden dan aan om er geen supplementen bij te nemen. Dit geldt niet voor de periode voor/na chemo/bestraling.
De synergetische werking van stoffen is alleen bekeken in vitro, niet in vivo, en is zo beperkt dat je er geen conclusies uit kunt trekken. Je kunt niet aanraden de combinaties wel te gebruiken, maar de hoeveelheid onderzoeken waarbij gekeken wordt naar synergie geeft vaker een positief effect bij synergie dan negatief.

De studies die ik gebruik geven of geen relatie aan tussen kanker en groene thee (dus dan maakt het niet uit of je het gebruikt), of een positieve relatie. Er zit geen onderzoek tussen waaruit je zou kunnen concluderen het niet te gebruiken.

AnaboliC · 7 nov 2005

In groene thee zit toch sowieso caffeine??

Groene thee: De menselijke in vivo onderzoeken tot nu toe!!!

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