Green Tea Extract Articles
Green Tea Extract Slashes
Stomach Cancer by 75%
Green Tea Linked With Lower Oral Cancer Risk
German Scientists Slow Incurable Disease
Green Tea Possible Breakthrough
For Alzheimers and Cancer
UK Research suggests tea benefits memory & Alzheimer’s Disease
Green Tea beneficial vs. Cancer 4 research papers offer new
evidence
Green Tea EGCG inhibits growth
and induces regression of human prostate and breast cancers in athymic mice.
Green Tea
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Green Tea Extract Slashes Stomach Cancer by 75%
There are 800,000 new cases of stomach cancer every year, according to the European School of Oncology. It is the fourth most frequent cancer in the world and it is Japan's most common type of cancer.
In this month's issue of the journal Cancer Epidemiology, Biomarkers & Prevention, the lead researcher in this study, Shizuka Sasazuki, highlights the differences between men and women and the effect that Green Tea may play in this disease.
Green tea contains between 30 and 40 per cent of water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between 3 and 10 per cent.
The four primary polyphenols found in fresh tealeaves are epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), and epicatechin (EC).
In this study, among the 36,745 subjects who answered the baseline questionnaire and provided blood samples, 494 gastric cancer cases matched to 494 controls were used in the analysis. Blood samples were taken and polyphenol levels measured using high-performance liquid chromatography (HPLC).
The researchers state that blood levels of ECG between 0.32 and 9.2 ng/mL were not associated with any change in gastric cancer risk among women. However, blood levels of 9.3 ng/mL were associated with a 75 per cent reduction in risk in women, compared to women with blood levels below the detectable limit.
On the other hand, "for men, a high plasma level of (-)-epigallocatechin was associated with an increased risk of gastric cancer," said Sasazuki .
This study adds to an ever-growing body of science supporting potential health benefits of green tea and its polyphenols, previously linked to a lower risk of certain cancers, weight loss, heart health, and protection against Alzheimer's. However, it is clear that more research is needed to examine why ECG appears to give beneficial effects in women but may increase risk in men and it also points out that when under-taking scientific studies, there is a need to consider the sexes separately.
Source: Cancer Epidemiology, Biomarkers & Prevention
1st February 2008, Volume 17, Number 2, Pages 343-351, doi: 10.1158/1055-9965.EPI-07-0428
"Plasma Tea Polyphenols and Gastric Cancer Risk: A Case-Control Study Nested in a Large Population-Based Prospective Study in Japan"
Authors: S. Sasazuki, M. Inoue, T. Miura, M. Iwasaki, S. Tsugane for the Japan Public Health Center-based Prospective Study Group
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2/12/2008
Green Tea Linked With Lower Oral Cancer Risk
A new study from Japan suggests that a woman's risk of mouth cancer decreases after consuming five or more cups of green tea per day. Men do not have similar results according to the study published in the Annals of Epidemiology.
They followed almost 50,000 men and women and found that increasing consumption of the green tea among women decreased the risk of developing oral cancer, a disease with a higher proportion of deaths per number of cases than breast, skin, or cervical cancer, with a mortality rate of about 50% due to late detection.
These results, while not conclusive, add to an ever-growing body of science linking green tea to a wide range of health benefits. Green tea has been found to lower risk of certain cancers, improve heart health, and protect against Alzheimer's. Green tea contains between 30 and 40 per cent of water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between 3 and 10 per cent. The four primary polyphenols found in fresh tealeaves are epigallocatechin gallate (EGCG), epigallocatechin, epicatechin gallate, and epicatechin.
The Japan Collaborative Cohort (JACC) Study Group, sponsored by the Ministry of Education, Science, Sports and Culture of Japan, analyzed tea consumption using a comprehensive self-administered questionnaire amongst 20,550 men and 29,671 women (average age 57) in 24 areas of Japan.
During a mean follow-up period of 10.3 years, 37 oral cancer cases were documented by the researchers. Of this total, 20 patients had died: 13 from oral cancer and seven from other causes.
The researchers adjusted for potentially confounding factors, such as age, sex, smoking, and the consumption of alcohol, green and yellow vegetables, salty foods, fruit and coffee. Reiko Ide, the leading author of this study, and his colleagues stated that women who drank five or more cups of green tea per day had an associated risk reduction of 70%, compared to women who consumed between one and two cups per day. However, due to the small number of oral cancer cases in the study group, this reduction was not classed as statistically significant.
For men, they concluded that there was no tendency for protection against oral cancer.
The researchers said the study had noteworthy limitations and that no measures were made of the polyphenol content of the tea consumed, and no mechanistic study was performed to identify the active component or components of the beverages. They also said the questionnaires were only completed at baseline which raised questions about whether dietary habits changed over the course of the study.
"The Japanese population is unique in its long tradition of high consumption of green tea. Additional epidemiologic studies are needed to evaluate the association between green tea consumption and oral cancer in Japan," concluded the researchers.
Source: Annals of Epidemiology (Elsevier) doi: 10.1016/j.annepidem.2007.04.003
"Prospective Study of Green Tea Consumption and Oral Cancer Incidence in Japan"
Authors: R. Ide, Y. Fujino, Y. Hoshiyama, T. Mizoue, T. Kubo, T.-M. Pham, K. Shirane, N. Tokui, K. Sakata, A. Tamakoshi, T. Yoshimura, and for the JACC Study Group
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September 8, 2007
German Scientists Slow Incurable Disease
The accumulation of proteins that cause Huntington's Disease is slowed by Green Tea Extract, epigallocatechin gallate (EGCG), German scientists have reported.
This news adds to a growing body of science on the health benefits of green tea, with consumption linked to a lower risk of certain cancers, increased weight loss, and protection against Alzheimer's.
Huntington's disease, along with Alzheimer's and Parkinson's, belong to the family of neurodegenerative diseases caused by protein misfolding. The incurable disease is hereditary and has a prevalence of 1 in every 15,000 people. In Germany, about 8,000 cases are currently known, in the UK the figure is reported to be about 5,000, and in the US the figure is about 30,000.
The disease is characterized by jerky, uncontrolled movements, an unsteady gait and grimaces leading to its original common name of Huntington's chorea (from the ancient Greek for "dance").
In 1993, scientists discovered the gene that encodes the mutant protein, the so-called huntingtin protein. A mutation in this protein results in elongation of parts of the protein called polyglutamine chains, which cause the overall huntingtin protein to lose its normal structure. These mutant proteins can not be disposed of by the body and accumulate in the brain of sufferers, eventually being toxic to the nerve cells in the brain.
Professor Erich Wanker from the Max Delbrück Center for Molecular Medicine Berlin-Buch (MDC), led the research and looked at the effect on EGCG on the aggregation of these mutant proteins in vitro, and found that the green tea extract could interfere with the very early events of this process.
Lead author, Dagmar Ehrnhoefer wrote, "We demonstrate that the green tea polyphenol epigallocatechin-3-gallate (EGCG) potently inhibits the aggregation of mutant huntingtin protein in a dose-dependent manner."
Professor Wanker's group used laboratory-based experiments to show that the green tea extract inhibited misfolding of the huntingtin protein in vitro, as well as using fruit flies genetically modified to over-express the mutant protein. The latter experiments showed that the degeneration of the flies' photoreceptor and motor function improved.
"These results indicate that modulators of huntingtin misfolding … like EGCG are likely to reduce polyglutamine -mediated toxicity in vivo," concluded Ehrnhoefer.
Green tea is said to contain over four times the concentration of antioxidant catechins than black tea (green tea leaves that have been oxidized by fermentation), about 70 mg catechins per 100 mL compared to 15 mg per 100 mL for black tea.
Human Molecular Genetics, September 2006 (Vol. 15, pp. 2743-2751), Dagmar Ehrnhoefer
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9/8/2006
Green Tea Possible Breakthrough For Alzheimers and Cancer
Scientists investigating the effects of green tea antioxidant EGCG on mice's brains believe their positive results may signal its use as a preventative or treatment of Alzheimer's disease in humans.
EGCG (epigallocatechin-3-gallate) is the most potent antioxidant polyphenol in green tea and has been repeatedly studies in labs for its purported anti-cancer effect.
In the Journal of Neuroscience, the researchers say that the effects they observed in their study may not be brought about by drinking green tea, but that pure EGCG extract may be required.
Daily EGCG injections (20mg/kg) were given to a group of five mice that were specially bred to be Alzheimer's prone over a period of 60 days, beginning when they were 12 months old. Another five-strong group of mice was injected with a control substance in place of the EGCG.
When the mice's brains were studied, those that had received the EGCG had greatly reduced build up of beta-amyloid - in some cases as much as 54 percent - compared to the control mice. When it causes plaque in the brain, this protein can lead to nerve damage and memory loss typical of the progressive, neurodegenerative disorder Alzheimer's disease.
These results confirmed earlier observations when mice's brains were treated with EGCG and studied in vitro.
"The findings suggest that a concentrated component of green tea can decrease brain beta-amyloid plaque formation," said senior study author Dr Jun Tan.
"If beta-amyloid pathology in this Alzheimer's mouse model is representative of Alzheimer's disease pathology in humans, EGCG dietary supplementation may be effective in preventing and treating the disease."
For humans, 1500 to 1600mg of EGCG a day would be the equivalent to the injection dosage seen to benefit the Alzheimer's mice.
But before consumers dash out to stock up on green tea, the researchers warn that other flavonoids present in the beverage could counter EGCG's beneficial effect.
The team plans to extend its investigation by administering oral doses of EGCG to mice and assessing whether they can improve memory loss as well as reducing plaque.
If this investigation delivers positive results the authors said they "believe clinical trials of EGCG to treat Alzheimer's disease would be warranted".
In another development, The American Institute of Cancer Research (AICR), Washington DC., presented evidence at an international conference on diet and cancer that a major component in green tea (ECGC) may short circuit the cancer process in a way scientists had not forseen.
Dr. Thomas Gasiewicz, a Professor of Environmental Medicine at the University of Rochester Medical Center has said, "We have determined that a unique quirk of biochemistry allows green tea's protective effects to extend to many different kinds of cells. In fact, the active substance in green tea substance, ECGC, seems to target one protein that is particularly common throughout our bodies, and it does so with a precision that cancer drugs still aren't able to match."
The protein in question is called HSP90, which is present at higher levels in many cancer cells. According to AICR, scientistis believe that in some circumstances HSP90 helps to trigger the cascade of events that eventually leads to cancer and when ECGC binds this protein it helps prevent these events from happening.
Nutraceuticals World
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September 2005
UK Research suggests tea benefits memory & Alzheimer’s Disease
Drinking tea could help improve memory and may also slow the development of Alzheimer's disease, suggests new research from the UK.
Laboratory tests by a team at the University of Newcastle found that tea, and particularly green tea, inhibits the activity of the same enzymes in the brain currently targeted by drugs for Alzheimer's disease.
The researchers are hoping to develop a medicinal tea as an alternative treatment to slow memory loss in Alzheimer's sufferers, estimated to include around 10 million people worldwide, and rising.
Lead researcher Dr Ed Okello said: "Although there is no cure for Alzheimer's, tea could potentially be another weapon in the armory which is used to treat this disease and slow down its development." Our findings are particularly exciting as tea is already a very popular drink, it is inexpensive, and there do not seem to be any adverse side effects when it is consumed. Still, we expect it will be several years until we are able to produce anything marketable."
Dr Okello added that the findings suggested tea could boost the memory of everyday drinkers too.
The researchers from Newcastle University's Medicinal Plant Research Centre found both green and black tea inhibited the activity of the enzyme acetylcholinesterase (AChE), which breaks down the chemical messenger or neurotransmitter, acetylcholine. Alzheimer's is characterized by a drop in acetylcholine.
Green tea and black tea also hinder the activity of the enzyme butyrylcholinesterase (BuChE), which has been discovered in protein deposits found on the brain of patients with Alzheimer's.
Green tea went one step further in that it obstructed the activity of beta-secretase, which plays a role in the production of protein deposits in the brain that are associated with Alzheimer's disease. Scientists also found that it continued to have its inhibitive effect for a week, whereas black tea's enzyme-inhibiting properties lasted for only one day.
Incidence of Alzheimer's disease is expected to rise fast with ageing populations but there is currently no cure. Drugs are available to slow the development of the disease by hindering the activity of AchE and others are being developed which scientists hope will inhibit the activity of BuChE and beta-secretase. But many of those currently available, such as donepezil, have unpleasant side effects and the medical profession is keen to find alternatives.
Professor Clive Ballard, director of research at the UK-based Alzheimer's Society, noted that the research builds on previous evidence that suggests that green tea may be beneficial due to antioxidant properties.
"Certainly the effect on the cholinesterase enzyme (the target of current anti-dementia drugs such as Aricept) and beta-secretase (an enzyme which is important in the build up of plaques) is very exciting and requires further investigation," he said.
The findings, published in the journal Phytotherapy Research (18, pp624-627), are the latest in a long line of results pointing to tea's disease-fighting potential. It is also being widely researched for its anti-cancer activity and benefits for heart health.
The Newcastle researchers are seeking funding to carry out further tests on green tea. They need to find out exactly which components of green tea inhibit the activity of the enzymes AChE, BuChE and beta-secretase.
Abstract
The primary target of licensed drugs for the treatment of Alzheimer's disease is the inhibition of the enzyme acetylcholinesterase, although preventing -amyloidosis is a prime target for drugs in development. The in vitro dual anti-cholinesterase and -secretase activities of Camellia sinensis L. extract (tea) is reported. Green and black tea inhibited human acetylcholinesterase (AChE) with IC50 values of 0.03 mg/mL and 0.06 mg/mL respectively, and human butyrylcholinesterase (BuChE) with IC50 values 0.05 mg/mL. Green tea at a final assay concentration of 0.03 mg/mL inhibited -secretase by 38%. These novel findings suggest that tea infusions contain biologically active principles, perhaps acting synergistically, that may be used to retard the progression of the disease assuming that these principles, yet to be identified, reach the brain.
Journal of Phytotherapy Research, (18, pp624-627)
Green Tea beneficial vs. Cancer
4 research papers offer new evidence
The debate brewing over the benefits of green tea heated up Tuesday with the release of new research supporting the cancer-fighting properties of the earthy beverage.
Four research papers presented at the American Association for Cancer Research conference in Phoenix suggest green tea is useful in fighting certain types of cancer, in addition to lowering cholesterol, preventing heart disease, boosting oral hygiene and possibly aiding in weight loss.
Drinking just two cups, but probably more like four cups, a day of green tea may retard the growth of certain tumor cells, researchers agreed.
Iman Hakim, a researcher at the University of Arizona Cancer Center, showed that cigarette smokers who drank four cups a day of decaffeinated green tea for four months cut the cellular damage caused by cigarettes.
"What we found was significant," she said, referring to tests done on the urine of the 118 smokers in the study.
The research stopped short of finding that genes damaged from smoking can be repaired by green tea. That is the subject of new research her colleagues are now doing.
Other research presented Tuesday by Jia-Sheng Wang, from Texas Tech University, showed green tea can prevent liver cancer, the third-leading cause of cancer deaths in the world. And Nurulain Zaveri, a researcher at SRI International in Menlo Park, Calif., found that green tea may not only prevent cancer but may become a treatment for those with the disease.
But researchers reminded cancer patients to consult with their doctors before consuming large quantities of the tea because it could interact with other treatments or chemotherapy.
"If you like it, you (probably) can continue to drink it," said Chung Shu Yang, chair of the chemical biology department at Rutgers University, which has been studying the therapeutic effects of green tea for a dozen years.
Green tea has been shown to be effective against lung, prostate, liver and esophageal cancer, among others.
"So, the biology actually is there and that's very exciting," Yang said. "But the disappointing part is we really don't know how it works."
Yang said anyone who drinks hot beverages, green tea included, should avoid drinking them too hot because of the association with oral and esophageal cancers.
The Arizona Republic
Oct. 29, 2003 12:00 AM
Green Tea EGCG inhibits growth and induces regression of human prostate and breast cancers in athymic mice.
Long-term consumption of tea catechins has been shown to have anti-tumor effects in animals. The same tea catechins are consumed commonly in China and Japan possibly explaining why the mortality of prostate cancer and breast cancer is lower in Asian countries than in Western countries. In this study the authors investigated the effect of intra-peritoneal injections of different catechins on the growth of human prostate cancer cell lines PC-3 and LnCaP and the human breast cancer cell line MCF-7 grown in nude mice. As shown in the figure below, the injection of EGCG slowed the growth of tumor when administered to the control mice on day 14 while the growth of tumor accelerated when EGCG was stopped in the PC-3 line on day 14. Inhibition of PC-3 growth was EGCG specific; it was not seen with EC, EGC or ECG. The galloyl group of EGCG appears to be necessary for tumor growth inhibition since EGC is not active. EGCG accounts for ~ 50% of the solid matter in the hot water extract of green tea consumed as a beverage. The frequency of the latent, localized type of prostate cancer does not vary significantly between Eastern and Western cultures, but the clinical incidence of metastatic prostate cancer is generally low in Japan and other Asian countries in contrast to the common occurrence of metastatic disease in Europe and the United States. One possible explanation is that EGCG in consumed green tea in Asian countries prevents the progression and metastasis of prostate cancer cells. (Liao S, Umekita Y, Guo J et al. Growth inhibition and regression of human prostate and breast tumors in athymic mice by tea epigallocatechin gallate.
Cancer Letters 96:239-243,1995).
Green Tea
Description
Green tea is the second-most consumed beverage in the world (water is the first) and has been used medicinally for centuries in India and China. A number of beneficial health effects are attributed to regular consumption of green tea and dried/powdered extracts of green tea are available as dietary supplements
Green tea is prepared by picking, lightly steaming and allowing the leaves to dry. Black tea, the most popular type of tea in the U.S., is made by allowing the leaves to ferment before drying. Due to differences in the fermentation process, a portion of the active compounds are destroyed in black tea, but remain active in green tea. The active constituents in green tea are a family of polyphenols (catechins) and flavonols which possess potent antioxidant activity. Tannins, large polyphenol molecules, form the bulk of the active compounds in green tea, with catechins comprising nearly 90%. Several catechins are present in significant quantities; epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG) and epigallocatechin gallate (EGCG). EGCG makes up about 10-50% of the total catechin content and appears to be the most powerful of the catechins - with antioxidant activity about 25-100 times more potent than vitamins C and E. A cup of green tea may provide 10-40mg of polyphenols and has antioxidant activity greater than a serving of broccoli, spinach, carrots or strawberries. A number of commercial green tea extracts are standardized to total polyphenol content and/or EGCG content.
Claims
1. Anti-atherogenic / Reduces cholesterol & triglycerides
2. Reduces blood clotting
3. Enhances immune function
4. Enhances weight loss
5. Anti-cancer
Theory
Because the active compounds, the catechins, found in green tea are known to possess potent antioxidant activity, they may provide beneficial health effects by protecting the body from the damaging effects of oxidative damage from free radicals. A number of chronic disease states have been associated with free radical induced oxidative damage, including cancer, heart disease, suppressed immune function and accelerated aging.
Scientific Support
Although numerous laboratory investigations have shown the powerful antioxidant activity of green tea and green tea extracts, prospective clinical studies in humans are few. From the laboratory findings, it is clear that green tea is an effective antioxidant, that is provides clear protection from experimentally induced DNA damage and that it can slow or halt the initiation and progression of cancerous tumor growth. There is also evidence from some studies that green tea provides significant immunoprotective qualities, particularly in the case of cancer patients undergoing radiation or chemotherapy. White blood cell count appears to be maintained more effectively in cancer patients consuming green tea compared to non-supplemented patients
Several epidemiological studies show an association between consumption of total flavonoids in the diet and the risk for cancer and heart disease. Men with the highest consumption of flavonoids (from fruits and vegetables) have approximately half the risk of heart disease and cancer compared with those with the lowest intake. The primary catechin in green tea, EGCG, appears to inhibit the growth of cancer cells as well as play a role in stimulating apoptosis (programmed cell death), both of which are crucial aspects for cancer prevention.
In terms of heart disease protection, the potent antioxidant properties of polyphenols would be expected to reduce free radical damage to cells and prevent the oxidation of LDL cholesterol - both of which would be expected to inhibit the formation of atherosclerotic plaques.
Aside from the clear benefits of green tea as an antioxidant, recent studies have suggested a role catechins in promoting weight loss. In one animal study, the anti-obesity effect of green tea was evaluated by feeding different levels of green tea (1-4% in their diets) to female mice for 4 months. The study found that the mice receiving the green tea in their diets had a significant suppression of food intake, body weight gain and fat tissue accumulation. In addition, levels of cholesterol and triglycerides were lower in mice receiving the green tea diet. Perhaps the most interesting finding from this study was that Leptin levels in serum showed a decrease with green tea treatments - indicating that green tea may have a direct effect on the regulation of body weight (downward).
In some studies, green tea is associated with a mild increase in thermogenesis (increased caloric expenditure) - which is generally attributed to its caffeine content. At least one study has shown that green tea extract stimulates thermogenesis to an extent that is much greater than can be attributed to its caffeine content per se - meaning that the thermogenic properties of green tea may be due to an interaction between its high content of catechin-polyphenols along with caffeine. A probable theory for the thermogenic effect of green tea is an increase in levels of norepinephrine - because catechin-polyphenols are known to inhibit catechol-O-methyl-transferase (the enzyme that degrades norepinephrine). One study examined this theory, and the effect of green tea extract on 24-hour energy expenditure, in 10 healthy men - who each consumed 3 treatments of green tea extract (50mg caffeine and 90mg epigallocatechin gallate), caffeine (50 mg), and placebo (at breakfast, lunch, and dinner). The results of the study showed that, relative to placebo, the green tea extract resulted in a significant (4%) increase in 24-hour energy expenditure (approximately 800 calories per day) and a significant increase in the body's use of fat as an energy source (24-h Respiratory Quotient). In addition, the 24-hour urinary norepinephrine excretion was 40% higher during treatment with the green tea extract than with the placebo. It is interesting to note that treatment with caffeine in amounts equivalent to those found in the green tea extract (50mg) had no effect on energy expenditure of fat oxidation - suggesting that the thermogenic properties of green tea it due to compounds other than its caffeine content alone.
Safety
Green tea consumption of as much as 20 cups per day has not been associated with any significant side effects. In high doses, teas that contain caffeine may lead to restlessness, insomnia, and tachycardia. Decaffeinated versions of green tea and green tea extracts are available - but due to differences in caffeine extraction methods, the amounts of phenolic/catechin compounds can vary between extracts. Be sure to choose an extract that is decaffeinated as well as standardized for total polyphenol content and/or catechin concentrations. In addition, individuals taking aspirin or other anticoagulant medications (including vitamin E and ginkgo biloba) on a daily basis should be aware of the possible inhibition of platelet aggregation (blood clotting) associated with green tea (in some cases, green tea may prolong bleeding times).
Value
Especially beneficial to individuals at high risk for cancer (e.g. family history) or those undergoing chemotherapy or radiation treatment. Also beneficial as a general protective measure and dietary "insurance" of adequate polyphenol intake. Recent data provides strong evidence that green tea may be effective in stimulating thermogenesis, increasing caloric expenditure, promoting fat oxidation and controlling body weight.
References
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16. Tanaka H, Hirose M, Kawabe M, Sano M, Takesada Y, Hagiwara A, Shirai T. Post-initiation inhibitory effects of green tea catechins on 7,12-dimethylbenz[a]anthracene-induced mammary gland carcinogenesis in female Sprague-Dawley rats. Cancer Lett. 1997 Jun 3;116(1):47-52.
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18. Weisburger JH, Rivenson A, Aliaga C, Reinhardt J, Kelloff GJ, Boone CW, Steele VE, Balentine DA, Pittman B, Zang E. Effect of tea extracts, polyphenols, and epigallocatechin gallate on azoxymethane-induced colon cancer. Proc Soc Exp Biol Med. 1998 Jan;217(1):104-8.
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