Green Tea - Health Benefits

Green tea is a beverage made from the Camelia sinensis plant, a shrub native to Southern China that has been used through time for its many attributed benefits ^[1]. It is of major cultural importance in Asia where it is known as China’s National Drink. Both India and China have incorporated green tea in their complementary medicine practices for supporting digestion, cardiovascular and mental health among others ^[1]. In the last decade alone, there have been numerous studies that have endorsed green tea’s diverse applications in promoting health. These studies have also ushered in a newfound appreciation for green tea in the West.

The production of green tea differs from black tea in that there is little or no oxidation and inactivation of polyphenols such as catechins, proanthocyanidin and Epigallocatechin gallate (EGCG). These polyphenols are therefore present in large quantities in green tea, with the highest concentration being Epigallocatechin gallate (EGCG) ^[2]. ECGC is a powerful antioxidant-a substance that negates harmful free radicals in the body. This compound has been researched and used for a variety of conditions from the treatment and prevention of different types of cancer- gastric, colorectal, breast, lung, prostate, liver, leukemia- and weight loss to the improvement of mental alertness and athletic endurance ^{[3, 4]} . Topically, it has shown promising results in the management of acne, and cervical cancer as well as the progression of skin aging ^[4]. As a botanical therapy, green tea can be used as a hot beverage a few times a day or as a supplement that is standardised to polyphenols. One cup of green tea, in addition to polyphenols, also contains alkaloids such as caffeine although not in as large amounts as in coffee ^[2]. Although it is safe when consumed regularly, the presence of caffeine in green tea can create side effects if it is over-consumed ^[2]. It is interesting to note that the Chinese originally consumed green tea as a powder (matcha) and with time, transitioned into steeping the loose leaves. Its evolution of use in recent times has paralleled some exciting scientific findings. This article will discuss the applications of green tea therapeutically in weight loss and as an adjunctive treatment for cancer.

Weight Loss

Green Tea is undoubtedly one of the most commonly consumed teas in North America to date. Despite being a popular alternative to coffee, this caffeinated beverage is well known for its strong antioxidant properties and more recently, its ability to aid in weight reduction. Is it possible that a magic natural supplement weight-loss pill exists on the market? More importantly, does it work? As mentioned, green tea contains a potent active constituent known as EGCG, epigallocatechin-3-gallate, one of many catechins found in green tea leaves. EGCG is purported to be the main active ingredient enabling weight-loss and research suggests it is effective in certain populations. In 2015, one double-blind randomized placebo controlled clinical trial of 115 women with central obesity, who had taken 857mg of EGCG for 12 weeks had significant weight loss, a decrease in BMI and reduced waist circumference ^[5]. Blood work also showed a decrease in total cholesterol and in LDL (low-density lipoproteins). There were no side effects or adverse events. The positive results of the study may be due to EGCG’s effect on reducing the levels of the hormone ghrelin in the body ^[5]. Ghrelin is referred to as the “hunger hormone” as it is responsible for regulating energy expenditure and more importantly, appetite and hunger. EGCG was also found to increase adiponectin levels; adiponectin is involved in glucose regulation and the breakdown of fatty acids (fats) in the body. The participants in the placebo group of the study did not have these results. An early double-blind randomized placebo-controlled clinical trial in 2014 with 83 obese women who were pre-menopausal examined EGCG’s role in changing body composition and metabolism ^[6]. This group had consumed 300mg of EGCG for 12 weeks and the results of the study showed that EGCG did not have any change on body fat composition or on energy expenditure and no effect on overall weight loss ^[6]. Though many do wish for the existence of a magic, harm-free, weight-loss pill, with the limited research available, and the variances in research results, it cannot be conclusively stated that EGCG is the magic pill for weight reduction. However, given the right dose, in the right population, EGCG may show promise. As more research is underway, eating a diet full of fruits and vegetables, maintaining a steady exercise regime and the occasional cup of green tea may be a great start to keeping a healthy mind and body.

Oncology

Green tea has been reported to be protective against several types of cancers, including osteosarcoma, leukemia, skin, breast, prostate, esophageal, stomach, colorectal, pancreatic, lung, cervical and bladder cancer ^[7]. Green tea is composed of catechins, which are polyphenolic flavonoid-derived compounds that have been found to inhibit cancer growth ^[8]. Some of the major catechins found in green tea include epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG), and epigallocatechin-3-gallate (EGCG) ^[7]. Green tea is stated to have anti-inflammatory, antioxidant, and anti-carcinogenic properties due to its polyphenol contents ^[8]. Some of the antioxidant and anti-carcinogenic mechanisms of green tea include free radical scavenging, stimulation of phase I and II detoxification systems, inhibition of tumour promoters, and prevention of mutagenicity and genotoxicity ^[7]. Additionally, in vivo studies have found that green tea polyphenols prevent UV radiation-induced carcinogenesis by decreasing oxidative stress, reducing oxidation of proteins, preventing immune system suppression and stimulating DNA repair enzymes ^[9]. Green tea consumption has been reported to decrease metastases and recurrence of stage I and II breast cancer, likely by preventing the binding of estrogen to its receptors ^[7]. Another study found that green tea consumption lowered the risk of metastasis of breast cancer to lymph nodes and provided an overall reduction of breast cancer incidence in those who drank 10 cups or more a day ^[10]. Green tea consumption has also been found to decrease the risk of women developing esophageal cancer, with a 50% risk reduction in the participants who were assigned to drink the most tea compared to the other groups, while another study reported that consumption of green tea reduced the risk of developing esophageal cancer by 60% ^[10]. Additionally, smokers who consumed green tea had a reduced risk of lung cells and lymphocytes mutations, however its consumption was also found to reduce the risk of lung cancer in non-smokers ^[10].

EGCG, one of the polyphenols found in green tea has been reported to be protective against the development of cancerous tumours. It is a potent antioxidant, and has been shown to slow tumour development by inhibiting the factors that promote cancer cell growth ^[7]. EGCG has been suggested to stop the growth of cancer cells while leaving healthy cells intact ^[7]. Furthermore, studies have also found it to inhibit the release of tumour necrosis factor-alpha, and suppress tumour promotion and progression of both premalignant and initiated cells ^[10]. Researchers have found that EGCG inhibits the growth of cancer cells by apoptotic cell death in prostate cancer. EGCG was also reported to reduce the proliferation of human breast cancer cells in vitro, and decreased the severity of the initial diagnosis and likelihood of recurrence ^[10]. Additionally, EGCG was stated to inhibit cervical cancer cell growth through programmed cell death and cell cycle arrest ^[10].

The recommended therapeutic dose of green tea consumption is 4 to 10 cups a day, which would be equivalent to 500mg of green tea polyphenols three to four times a day, and its high safety profile makes it safe to be consumed on a regular basis. Research studies have concluded that green tea has potent antioxidant and anti-carcinogenic properties and may be effective in preventing the development of different types of cancers ^[10]. However, we always suggest seeking the advice of your Naturopathic Doctor prior to making any modifications regarding your health, as every individual is unique. For some, a supplement extract may the best way to go, while for others the incorporation of a couple of cups of green tea per day would be more appropriate.