Image is courtesy of Sentra Informasi IPTEK
Who are in this world who do not know tea? Tea is popular beverages consumed around the world. Black tea is the most common tea beverage consumed in the world, about 75% of the world's tea consumption.
When I think about tea, I remember to my friend, lets called him Andy, who once made a crossword puzzle game, which in Bahasa Indonesia is known as
teka teki silang, or TTS. But, he changed the TTS to
tanya tanya saja, which means in English as
just asking, a humour crossword puzzle game.
Andy made a question which had an answer of five empty boxes, or five letters answer. The question was, when translated in English as: What is the traditional drink of Indonesian people? My other friends, including me were so hard to find the answer. All of my friends answers were claimed by Andy as the wrong answer.
You know what? Andy said that the correct answer is five letters word (which actually the combination of two words) of
esteh. The ridiculous answer that made everybody laugh including me, es teh, which in English means tea ice, is not only a common drink for most Indonesian people, but also for all the people around the world.
The data from the Indonesian Ministry of Health is mentioned that, cancer prevalence in Indonesia, in 2012, has reached 4.3 in every 1,000 people. If the Indonesian population is 251,160,124 (CIA Factbook, July 2013 est.), it means that there are more than 1,079,988 cancer patients, in Indonesia, in 2013.
Tea (Camellia sinensis [L.] Kuntze), is known by many common names, such as, enteh (Sundanese), pu erh cha (Chinese), theler(France), teestrauch (German), te (Italy), cha da India (Portugal). Tea is believed to be originated from the north of India (Camellia sinensis var. assamica), and South China (Camellia sinensis var. sinensis).
The varieties of tea, such as, black tea, green tea, oolong tea, white tea, and etc, are all harvested from the species of Camellia sinensis [L.] Kuntze, but are processed in different levels of oxidation. Black tea is produced when tea leaves are wilted, bruised, rolled, and fully oxidized. Green tea is made from unwilted leaves that are not oxidized. Oolong tea is made from wilted, bruised, and partially oxidized leaves, creating an intermediate kind of tea. White tea is made from young leaves, or growth buds that have undergone minimal oxidation.
Tea and Cancer Prevention
Tea contains polyphenol compounds, particularly catechins, which are antioxidants and whose biological activities may be relevant to cancer prevention. Catechins are thought to be responsible for the health benefits, that have traditionally been attributed to tea, especially green tea. That is why most studies of tea and cancer prevention have focused on green tea. Black tea, although not as well studied as green tea, has also shown cancer preventive effects, in laboratory models.
Polyphenols in green tea include, Epigallocatechin-3-gallate (EGCG), Epigallocatechin (EGC), Epicatechin-3-gallate (ECG), and Epicatechin (EC). But, the most active, and abundant catechin, in green tea is EGCG. Meanwhile, EGCG and ECG have substantial free radical scavenging activity, and may protect cells from DNA damage, caused by reactive oxygen species. Researchers also believe that, polyphenols help kill cancerous cells, and stop them from growing.
Black tea contains much lower concentrations of catechins than green tea. Oolong tea contains a mixture of simple polyphenols, such as catechins, and complex polyphenols. White and green tea contain similar amounts of EGCG, but different amounts of other polyphenols.
Most animal studies on tea have been found to inhibit tumorigenesis at different organ sites, including the skin, lung, oral cavity, esophagus, stomach, small intestine, colon, liver, pancreas, and mammary gland. But, the results of human studies, both epidemiologic, and clinical studies have been inconclusive.
The inconsistencies in study findings regarding, tea and cancer risk, may be due to variability in tea preparation, tea consumption, the bioavailability of tea compounds (the amounts that can be absorbed by the body), lifestyle differences, and individual genetic differences. That is why, the National Cancer Institute does not recommend for, or against the use of tea, to reduce the risk of any type of cancer.
Several Human Clinical Studies on Cancer
A pooled analysis of two prospective cohort studies among 35,004 Japanese women, found that green tea intake was not associated with a lower risk of breast cancer. (Suzuki Y, et al. 2004)
Recent cross sectional study among 191 healthy Japanese American women, suggested that intake of green tea may modify estrogen metabolism, and reduce the risk of breast cancer. Polyphenols in green tea can influence enzymes that metabolize estrogens, known causal factors in breast cancer etiology. (Fuhrman BJ, et al. 2013)
A prospective cohort study among 58,279 men, and 62,573 women aged 55-69 years, in Netherlands, failed to reveal a protective effect of tea consumption, on the risk of three cancer types studied (colorectal, lung, and breast cancers). (Goldbohm RA, et al. 1996)
A cohort study among 69,710 Chinese women, aged 40 to 70 years, which followed up six years later, suggested that regular consumption of green tea may reduce colorectal cancer risk in women. (Yang G, et al. 2007)
A prospective cohort study of diet and cancer involving more than 60,000 men and women, in Singapore, found that the intake of black tea was not associated with risk of colorectal cancer. (Sun CL, et al. 2007)
Digestive Tract Cancer
A comparative case referent study of 21,128 people aged 40 years and over, in Nagoya, Japan, suggested the potential for protective effect against site specific digestive tract cancer, by consumption of green tea and coffee. (Inoue M, et al. 1998)
A large population based prospective cohort study among 69,310 women, and 1,255 cases of digestive system cancers (stomach, esophagus, colorectal, liver, pancreas, and gallbladder/bile duct cancers) were followed up for 11 years since 2000 until 2011. The study found that regular tea intake, mostly green tea, was associated with reduced risk of all digestive system cancers combined, and women who consumed ≥150 g tea/month (2-3 cups/day) had a 21% reduced risk of digestive system cancers combined. The study concluded that tea consumption was associated with reduced risk of colorectal, stomach, and esophageal cancers, in Chinese women. (Nechuta S, et al. 2012)
A population based, prospective cohort study among 11,902 men, and 14,409 women, aged 40 years or older, in Miyagi Prefecture, in northern Japan, found no association between green tea consumption, and the risk of gastric cancer. (Tsubono Y, et al. 2001)
Follow up study from a pooled analysis of six cohort studies, among 219,080 subjects, in 3,577 cases of gastric cancer, found that green tea may decrease the risk of distal gastric cancer in women. Compared with those drinking less than 1 cup/day, no significant risk reduction for gastric cancer was observed, with increased green tea consumption in men. However, in women, a significantly decreased risk was observed, for those with consumption of 5 cups, or more in a day. (Inoue M, et al. 2009)
An Australian population based, case control study (1,368 cases and 1,416 controls), found that women who drink green tea, have a lower risk of ovarian cancer, and the study supported for the hypothesis that, tea consumption reduces the risk of ovarian cancer. (Nagle CM, et al. 2010)
A study based on 157 incident cases, and 285 people aged 40-79 years, found no inverse association between green tea consumption and the risk of stomach cancer. (Hoshiyama Y, et al. 2004)
Despite of the National Cancer Institute recommendation, drinking different types of tea beverages will have different effects in any person. My living grandfather, who aged 89 years old, is always drinking black tea without sugar, twice a day, in the morning and afternoon.
The main reason why I wrote this article, is because couple of days ago, an anonymous spammer wrote comments (twice) with a link promotion, which lead to an article about green tea. The article claimed a fact that,
...people in green tea consuming countries mainly Japan, and China have very low rates of cancer.....
But, I disagree with the article, because based on Globocan 2008 data, Japan was in the top 46 of the highest cancer rate in men, with the ASR of 247.3 per 100,000 people. China was not listed in the top 50 of Globocan 2008 data. But, report from Chen W, et al. 2013, the crude incidence rate, in Chinese cancer registration areas, in 2009, was 285.91 per 100,000 people. Meanwhile, a news in August 2010, Chen Zhu, minister of China's Ministry of Health said that, there were about 2.6 million people in China, who suffered cancer annually, in which 1.8 million patients died.
Tea and Cancer Prevention
National Cancer Institute
University of Maryland Medical Center