Showing posts with label green tea. Show all posts
Showing posts with label green tea. Show all posts

Thursday, April 19, 2018

European Food Safety Authority Warns Green Tea Extracts May Be Associated With Liver Damage

According to new research from the European Food Safety Authority (EFSA) consuming more than 800mg of green tea catechins per day may lead to higher health risks, including liver damage.

Scientific opinion on the safety of green tea catechins EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS)
Maged Younes Peter Aggett Fernando Aguilar Riccardo Crebelli Birgit Dusemund Metka Filipič Maria Jose Frutos Pierre Galtier David Gott Ursula Gundert‐Remy Claude Lambré Jean‐Charles Leblanc Inger Therese Lillegaard Peter Moldeus Alicja Mortensen Agneta Oskarsson Ivan Stankovic Ine Waalkens‐Berendsen Rudolf Antonius Woutersen Raul J Andrade Cristina Fortes Pasquale Mosesso Patrizia Restani Davide Arcella Fabiola Pizzo Camilla Smeraldi Matthew Wright

First published: 18 April 2018


The EFSA ANS Panel was asked to provide a scientific opinion on the safety of green tea catechins from dietary sources including preparations such as food supplements and infusions. Green tea is produced from the leaves of Camellia sinensis (L.) Kuntze, without fermentation, which prevents the oxidation of polyphenolic components. Most of the polyphenols in green tea are catechins. The Panel considered the possible association between the consumption of (‐)‐epigallocatechin‐3‐gallate (EGCG), the most relevant catechin in green tea, and hepatotoxicity. This scientific opinion is based on published scientific literature, including interventional studies, monographs and reports by national and international authorities and data received following a public ‘Call for data’. The mean daily intake of EGCG resulting from the consumption of green tea infusions ranges from 90 to 300 mg/day while exposure by high‐level consumers is estimated to be up to 866 mg EGCG/day, in the adult population in the EU. Food supplements containing green tea catechins provide a daily dose of EGCG in the range of 5–1,000 mg/day, for adult population. The Panel concluded that catechins from green tea infusion, prepared in a traditional way, and reconstituted drinks with an equivalent composition to traditional green tea infusions, are in general considered to be safe according to the presumption of safety approach provided the intake corresponds to reported intakes in European Member States. However, rare cases of liver injury have been reported after consumption of green tea infusions, most probably due to an idiosyncratic reaction. Based on the available data on the potential adverse effects of green tea catechins on the liver, the Panel concluded that there is evidence from interventional clinical trials that intake of doses equal or above 800 mg EGCG/day taken as a food supplement has been shown to induce a statistically significant increase of serum transaminases in treated subjects compared to control.

In The Media
Green tea supplements may cause liver damage, warns EU watchdog
The European Food Safety Authority assessed the safety of the supplements
More than 800mg of green tea catechins each day may pose health concerns
Officials at the EU funded organisation were unable to confirm a safe dose
It today called for further scientific trials into the effect of green tea catechins

Sunday, February 9, 2014

Tea Benefits: A Research Wrap-Up - Skip green tea supplements

Tea Benefits: A Research Wrap-Up

by Berkeley Wellness | February 07, 2014
Okay tea drinkers, your turn. A few months ago we explored the latest research about coffee, almost all of it positive. Scientists have uncovered a similar array of potential health benefits for tea—the world’s most popular beverage, after water. Green tea has gotten the most buzz, but black may be just as healthful. Should you drink a cup—or two or three—a day?

In December a dozen review papers from the Fifth International Scientific Symposium on Tea and Human Health were published in the American Journal of Clinical Nutrition. These drew largely on the more than 2,000 studies done on tea in the past few years. Here’s a wrap-up of this and other tea research.

Tea types and components
Tea comes from Camellia sinensis, an evergreen shrub native to East and South Asia. (“Herbal teas” are made from other plants and are not true tea.) Tea has been consumed for thousands of years in Asia, where it is an important part of many cultures and has long been associated with health benefits. In China and Japan, in particular, its preparation and presentation have been taken to the level of an art form.

Green tea, popular in Asia, is minimally processed—the leaves are steamed, rolled and dried. Black tea is withered, rolled or crushed, and then “fermented” (in this case meaning oxidized, or exposed to oxygen) before being dried, which makes it black and stronger in taste. Oolong tea is partly fermented. White tea is harvested in early spring; the young leaves and silvery white buds are just steamed and dried.

Like coffee, cocoa and many plant foods, tea contains hundreds of biologically active chemicals, notably a wide range of flavonoids and other polyphenols, which can be absorbed and used by the body to varying degrees. Accounting for about one-third of the weight of dried tea leaves, polyphenols have antioxidant and other potentially beneficial properties.

The chemical composition of tea depends on the specific botanical variety, how and where it is grown, and how it is processed. Green tea, for example, is rich in catechins, including the potent antioxidant EGCG. In black tea, the catechins convert into other compounds during fermentation. Oolong tea falls between black and green teas in composition. Various polyphenols have different effects in the body.

Other factors affecting tea’s chemistry include its age and how it’s stored, brewed and served. Longer steeping time results in more polyphenols being released, though steeping for more than three minutes or so usually doesn’t increase these compounds significantly. Decaffeinating tea reduces its catechins. Instant and bottled teas generally have lower levels of polyphenols. Some research suggests that adding milk to tea binds catechins and reduces their effects somewhat. Lemon, in contrast, may enhance the body’s absorption of catechins.

Unless it has been decaffeinated, tea averages about 40 milligrams of caffeine per six-ounce cup (versus 100 milligrams in coffee, on average), depending on the type, brewing time, and other factors. Black tea tends to have more caffeine than green

Teasing apart tea benefits
So can drinking tea actually improve your health? Studies have yielded inconsistent, though mostly positive, results (be prepared to hear this again). Complicating matters is the fact that the constituents of tea vary, as do the cultural and dietary contexts in which it is consumed, which may also have effects on health. That may help explain, for instance, why Asian studies sometimes find certain benefits while Western ones do not, or vice versa. Your genes and even your colonic microflora (the bacteria living in your large intestine) may also help determine what effects tea has in your body.

Here’s a look at some of the research:

  • Cardiovascular health. Of all the potential benefits of tea, those involving cardiovascular disease are “the most promising,” according to Jeffrey Blumberg, Ph.D., professor of nutrition science at Tufts University and chairman of the tea symposium. Many (but not all) observational studies have found that people who consume moderate or high amounts of green or black tea (or flavonoids from all dietary sources) have a reduced risk of cardiovascular disease and, especially, stroke—usually with higher consumption linked to greater benefit. Furthermore, most research has shown that tea can slightly lower LDL (“bad”) cholesterol and blood pressure, as well as improve blood vessel functioning, reduce inflammation, inhibit blood clotting and have other cardiovascular effects. In 2013 a British review of 11 clinical trials concluded that tea seems to improve blood pressure and cholesterol levels, but that longer, better studies are needed to confirm tea’s benefits in terms of cardiovascular disease prevention.
  • Cancer. In lab studies, green tea extracts and tea polyphenols have been shown to inhibit a wide variety of cancers; black tea has been less studied. There are many theories as to how tea polyphenols may have anti-cancer effects—for instance, by inducing cell suicide in cancer cells and by inhibiting insulin growth factor (a protein involved with cell proliferation). However, the many human studies looking at the association between tea consumption and various types of cancer—such as breast, colon, prostate, oral, liver, ovarian and lung cancer— have had conflicting results. So farm there is insufficient support for claims that tea can help prevent or treat any cancer.
  • Diabetes. Most research has linked green or black tea or compounds in tea (such as catechins) to improved blood sugar control or reduced risk of type 2 diabetes. For instance, a 2012 study in BMJ Open looked at data from 50 countries and found that high consumption of black tea was strongly associated with a reduced diabetes risk. And a 2013 Chinese meta-analysis of clinical trials suggested that green tea helps reduce blood sugar.
  • Weight control. There’s some evidence that tea, especially green tea, has a modest weight-loss effect. It’s theorized that tea catechins and caffeine help boost fat burning, at least slightly and temporarily. A 2013 analysis of data from the large National Health and Nutrition Examination Survey linked tea consumption with lower weight and smaller waist size; this was not true of iced tea. But not all studies have found an effect on weight. One reason for the inconsistent findings is that the stimulant effect of caffeine depends largely on whether people are used to it or not; if they consume it regularly, they quickly build up a tolerance. What about concentrated green tea extracts, which are often marketed as diet supplements? A 2012 Cochrane review of 14 clinical trials concluded that they do not cause weight loss in overweight or obese people.
  • Brain health and mood. Lab studies support the potential role of tea in improving cognitive function. Studies in people are limited, though. For instance, in a study in Japan in 2006 and one in China in 2008, older people who regularly drank green tea were found to have a reduced risk of cognitive impairment compared to nondrinkers. Tea can increase alertness, thanks largely to its caffeine. It may also help enhance concentration and learning ability because of its theanine (an amino acid), which at the same time promotes relaxation. Of course, the experience of drinking a hot aromatic beverage, along with the associations that come with it, can contribute to the calming effect.
  • Parkinson’s disease. A 2008 study in the American Journal of Epidemiology found that people who drank the most black tea—but not green tea—had a much lower risk of Parkinson’s disease than nondrinkers. According to a paper in the Annual Review of Nutrition in 2013, human and lab studies suggest that tea or constituents in it may help protect against Parkinson’s and other neurodegenerative diseases. Coffee seems to be similarly protective.
  • Bone health. Lab studies show that tea polyphenols have beneficial effects on factors affecting bone mass and bone strength and thus may help protect against osteoporosis. Bones may also benefit from the fluoride in tea. Most studies of postmenopausal women have linked long-term consumption of tea (usually green and often high intakes) or tea extracts with greater bone density, but there are discrepancies among the results. “More basic research and human studies are warranted,” the researchers at the symposium concluded.
  • Dental health. Researchers have found that tea has antibacterial effects and thus may reduce levels of bacteria that cause cavities and contribute to gum disease. Like bones, teeth may benefit from the fluoride in tea. At least two Japanese studies have linked green tea consumption with a reduced risk of tooth loss.
Tea: drinks or supplements?
Tea’s effects in the body are still not fully understood, but don’t expect it to prevent heart disease, cancer or any other conditions on its own. Moreover, it is just one source of flavonoids and other polyphenols—fruits and vegetables, wine, coffee and cocoa are others. Nevertheless, tea can be a healthy addition to your daily diet, especially if it takes the place of high-calorie beverages. All types of tea have something to offer, including small amounts of minerals such as potassium. Without added sugar, tea has negligible calories. Check the labels on bottled and instant teas, however, since some are as sugary as soda.

Skip green tea supplements
It’s not known if they have any benefits or, more importantly, are safe. In any case, they vary widely in composition— found a 15-fold difference in catechin levels in products it tested in 2012. Supplements containing high levels of catechins may interact with medications, and there are continuing concerns about potential liver damage. Some, particularly those marketed for weight loss, may contain very high doses of caffeine.

Hepatitis C New Drug Research And Liver Health
A collection of research articles specific to the beneficial effects of coffee on liver disease

Monday, February 6, 2012

Green tea could be secret to healthy old age

Green tea could be secret to healthy old age, study suggests

Elderly adults who regularly drink green tea may stay more agile and independent than their peers over time, according to a Japanese study that covered thousands of people.

For the new study, published in the American Journal of Clinical Nutrition, researchers decided to examine the question of whether green tea drinkers have a lower risk of frailty and disability as they grow older.

Yasutake Tomata of the Tohoku University Graduate School of Medicine and his colleagues followed nearly 14,000 adults aged 65 or older for three years.

They found those who drank the most green tea were the least likely to develop "functional disability," or problems with daily activities or basic needs, such as dressing or bathing.

Specifically, almost 13 percent of adults who drank less than a cup of green tea per day became functionally disabled, compared with just over 7 percent of people who drank at least five cups a day.

"Green tea consumption is significantly associated with a lower risk of incident functional disability, even after adjustment for possible confounding factors," Tomata and his colleagues wrote.

The study did not prove that green tea alone kept people spry as they grew older.

Green-tea lovers generally had healthier diets, including more fish, vegetables and fruit, as well as more education, lower smoking rates, fewer heart attacks and strokes, and greater mental sharpness.

They also tended to be more socially active and have more friends and family to rely on.

But even with those factors accounted for, green tea itself was tied to a lower disability risk, the researchers said.

People who drank at least five cups a day were one-third less likely to develop disabilities than those who had less than a cup per day. Those people who averaged three or four cups a day had a 25 percent lower risk.

Although it's not clear how green tea might offer a buffer against disability, Tomata's team did note that one recent study found green tea extracts seem to boost leg muscle strength in older women.

While green tea and its extracts are considered safe in small amounts, they do contain caffeine and small amounts of vitamin K, which means it could interfere with drugs that prevent blood clotting.


Green tea consumption and the risk of incident functional disability in elderly Japanese: the Ohsaki Cohort 2006 Study1,2,3

Yasutake Tomata, Masako Kakizaki, Naoki Nakaya, Toru Tsuboya, Toshimasa Sone, Shinichi Kuriyama, Atsushi Hozawa, and Ichiro Tsuji

© 2012 American Society for Nutrition

Background: Previous studies have reported that green tea consumption is associated with a lower risk of diseases that cause functional disability, such as stroke, cognitive impairment, and osteoporosis. Although it is expected that green tea consumption would lower the risk of incident functional disability, this has never been investigated directly.

Objective: The objective was to determine the association between green tea consumption and incident functional disability in elderly individuals.

Design: We conducted a prospective cohort study in 13,988 Japanese individuals aged ≥65 y. Information on daily green tea consumption and other lifestyle factors was collected via questionnaire in 2006. Data on functional disability were retrieved from the public Long-term Care Insurance database, in which subjects were followed up for 3 y. We used Cox proportional hazards regression analysis to investigate the association between green tea consumption and functional disability.

Results: The 3-y incidence of functional disability was 9.4% (1316 cases). The multiple-adjusted HR (95% CI) of incident functional disability was 0.90 (0.77, 1.06) among respondents who consumed 1–2 cups green tea/d, 0.75 (0.64, 0.88) for those who consumed 3–4 cups/d, and 0.67 (0.57, 0.79) for those who consumed ≥5 cups/d in comparison with those who consumed <1 cup/d (P-trend < 0.001).

Conclusion: Green tea consumption is significantly associated with a lower risk of incident functional disability, even after adjustment for possible confounding factors.

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Tea is the most frequently consumed beverage in theworld. Three billion kilograms of tea are produced worldwide annually. Because of the high rates of tea consumption in the global population, even small effects on an individual could have a large impact on public health.

The health effects of green tea have been extensively investigated by prospective cohort studies. We have found that green tea consumption is significantly associated with a lower risk of mortality due to stroke (1) and pneumonia (2) and a lower risk of cognitive impairment (3), depression (4), and psychological distress (5).

These results have been confirmed by other researchers (6–9). In addition, other epidemiologic studies have indicated that green tea consumption is associated with a lower risk of osteoporosis (10, 11), and randomized controlled trials have indicated that green tea is effective for cardiovascular risk factors (12, 13).

Because all of the above conditions are major causes of functional disability (14–16), it is expected that green tea consumption would contribute to disability prevention. To our knowledge, however, no study has yet investigated the relation between green tea consumption and the incident risk of functional disability.

We therefore conducted the present analysis to test the hypothesis that green tea consumption is associated with a lower risk of developing functional disability.

Study cohort
The design of the Ohsaki Cohort 2006 Study has been described in detail elsewhere (17). In brief, the source population for the baseline survey comprised 31,694men and women aged 65 y who were living in Ohsaki City, northeastern Japan, on 1 December 2006.

The baseline survey was conducted between 1 December and 15 December 2006. A questionnaire was distributed by the heads of individual administrative districts to individual households and then collected by mail.

In this analysis, 23,091 persons who provided valid responses formed the study cohort (Figure 1). We excluded 6333 persons who did not provide written consent for review of their Long-term Care Insurance (LTCI) information, 1979 persons who had already been certified as having disability by the LTCI at the time of the baseline survey, 5 persons who had died or moved out of the district during the period of the baseline 1 From the Division of Epidemiology, Department of Public Health and Forensic Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan (YT, MK, NN, TT, TS, SK, AH, and IT); the Department of Nutrition and Dietetics, Faculty of Family and Consumer Sciences, Kamakura Women’s University, Kamakura, Japan (NN); and the Department of Public Health, Yamagata University Graduate School of Medical Science, Yamagata, Japan (AH).

2 Supported by Health Sciences Research grants (nos. H21-Choju-Ippan-001 and H22-Choju-Ippan-001) from the Ministry of Health, Labor, and Welfare of Japan.

3 Address reprint requests and correspondence to Y Tomata, Division of Epidemiology, Department of Public Health and Forensic Medicine, Tohoku University Graduate School of Medicine 2-1, Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan. E-mail:
Received July 12, 2011. Accepted for publication December 22, 2011. doi: 10.3945/ajcn.111.023200.

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Thursday, February 24, 2011

Green Tea and the Risk of Gastric Cancer in Japan

Original Article

Green Tea and the Risk of Gastric Cancer in Japan

Yoshitaka Tsubono, M.D., Yoshikazu Nishino, M.D., Shoko Komatsu, M.D., Chung-Cheng Hsieh, Sc.D., Seiki Kanemura, M.D., Ichiro Tsuji, M.D., Haruo Nakatsuka, Ph.D., Akira Fukao, M.D., Hiroshi Satoh, M.D., and Shigeru Hisamichi, M.D.
N Engl J Med 2001; 344:632-636
March 1, 2001

Although laboratory experiments and case–control studies have suggested that the consumption of green tea provides protection against gastric cancer, few prospective studies have been performed.

In January 1984, a total of 26,311 residents in three municipalities of Miyagi Prefecture, in northern Japan (11,902 men and 14,409 women 40 years of age or older), completed a self-administered questionnaire that included questions about the frequency of consumption of green tea. During 199,748 person-years of follow-up, through December 1992, we identified 419 cases of gastric cancer (in 296 men and 123 women). We used Cox regression to estimate the relative risk of gastric cancer according to the consumption of green tea.

Green-tea consumption was not associated with the risk of gastric cancer. After adjustment for sex, age, presence or absence of a history of peptic ulcer, smoking status, alcohol consumption, other dietary elements, and type of health insurance, the relative risks associated with drinking one or two, three or four, and five or more cups of green tea per day, as compared with less than one cup per day, were 1.1 (95 percent confidence interval, 0.8 to 1.6), 1.0 (95 percent confidence interval, 0.7 to 1.4), and 1.2 (95 percent confidence interval, 0.9 to 1.6), respectively (P for trend=0.13). The results were similar after the 117 cases of gastric cancer that were diagnosed in the first three years of follow-up had been excluded, with respective relative risks of 1.2 (95 percent confidence interval, 0.8 to 1.8), 1.0 (95 percent confidence interval, 0.7 to 1.5), and 1.4 (95 percent confidence interval, 1.0 to 1.9) (P for trend=0.07).

Full Text of Background...


Our study had several methodologic advantages over prior studies of green tea and the risk of gastric cancer. We recruited subjects from the general population, and there was a large variation in green-tea consumption among our subjects. In addition, we assessed the consumption of green tea and other variables before cases of gastric cancer and other diseases were diagnosed, thus avoiding recall bias. The questionnaire used to measure green-tea consumption had a reasonably high level of validity and reproducibility. A large number of cases of gastric cancer were identified, because the incidence rate in the study region was high and the period of follow-up was reasonably long.

Our study had some limitations. Our food-frequency questionnaire included only a limited number of items and could not be used to calculate the consumption of total energy and other nutrients. Although we adjusted for the consumption of dietary items other than green tea as much as possible, we could not exclude the possibility of residual confounding by other dietary characteristics.

We did not obtain information on the presence or absence of a history of infection with Helicobacter pylori, a strong risk factor for gastric cancer.16 The prevalence of H. pylori seropositivity (determined by the presence of IgG antibodies) among subjects 55 to 64 years of age in the study area was 88 percent in men and 87 percent in women.17 The subjects with chronic gastritis caused by H. pylori infection might have limited their consumption of foods and beverages, including green tea. Some studies have suggested an antibacterial effect of green tea,18,19 which may apply to H. pylori. In either case, the prevalence of infection would have been lower in the subjects with higher intakes of green tea. Thus, we believe it is unlikely that the failure to account for H. pylori infection masked an inverse association between the risk of gastric cancer and the consumption of green tea.

Another concern is that 16 percent of the participants were lost to follow-up. Nevertheless, the proportion did not differ according to the category of green-tea consumption. Therefore, we believe that loss to follow-up did not have a substantial effect on the observed associations between the consumption of green tea and the risk of gastric cancer.
Our findings are in general agreement with those of a prospective study of Japanese persons in Hawaii, which found no inverse association between green-tea consumption and gastric cancer.12 Although in that study there was a nonsignificant increase in the risk of gastric cancer among subjects with higher levels of green-tea consumption, the number of cases of gastric cancer was relatively small (108).

Our results contradict those of most case–control studies, which show an inverse association between the risk of gastric cancer and the consumption of green tea.5-10 In these retrospective investigations, some patients with gastric cancer might have decreased their consumption of green tea before the diagnosis because of their abdominal symptoms. This change in practice might have biased their recall of past intake in such a way that they underestimated their true consumption, resulting in spurious inverse associations. Epidemiologic studies have found that patients with gastric cancer decrease their consumption of tea two years before the diagnosis20 and that the accuracy of the recall of an earlier diet is strongly influenced by the recent diet.21 This bias would partly explain the difference in the findings between prospective and case–control studies.

We also found that there was no association between the risk of gastric cancer and the consumption of black tea or coffee. These results are consistent with the findings of a review conducted by the World Cancer Research Fund, which concluded that probably neither beverage is associated with a decreased or increased risk of gastric cancer.22
In conclusion, in a prospective cohort study, we found no association — inverse or otherwise — between the consumption of green tea and the risk of gastric cancer in Japan.
Supported in part by grants from the Japanese Ministry of Health and Welfare and the Japanese Ministry of Education, Science, and Culture.

Source Information
From the Divisions of Epidemiology (Y.T., Y.N., S. Kanemura, I.T., S.H.) and Environmental Health Sciences (H.S.), Department of Public Health and Forensic Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan; the Department of Nutrition, Harvard School of Public Health, Boston (Y.T.); the Faculty of Physical Education, Sendai College, Miyagi, Japan (S. Komatsu); the Division of Biostatistics and Epidemiology, Cancer Center, University of Massachusetts Medical Center, Worcester (C.-C.H.); Miyagi University School of Nursing, Sendai, Japan (H.N.); and the Department of Public Health, Yamagata University School of Medicine, Yamagata, Japan (A.F.).

Address reprint requests to Dr. Tsubono at the Division of Epidemiology, Department of Public Health and Forensic Medicine, Tohoku University Graduate School of Medicine, Sendai 980-8575, Japan, or at .

Full Text of Background...