The properties of green tea are being used as a medicine in China for thousands of years but only in the last 25 years it has been the subject of study according to the paradigms of modern science because of its properties highly beneficial to health. Green tea is made exclusively from leaves of Camellia Sinensis which undergo roasting immediately after harvest. The leaves that undergo partial fermentation before being dried give black tea.
Among these, the main include weight reduction, reduction of the metabolic syndrome, the prevention of cardiovascular disease, cancer and neurodegeneration.
The tea is rich in polyphenolic compounds known as catechins of which the most important is the bioactive and epigallocatechin gallate which has shown excellent antitumor activity both in vitro and in vivo.
The anticancer potential of this substance have collected so many experimental evidence that in the last three years there have been presented numerous patent applications in the United States for both epigallocatechin gallate both its derivatives synthesized by Big Pharma.
In fact, a characteristic disadvantage of the polyphenolic catechin of green tea is to be poorly bioavailable in the oral intake in vivo, probably due to their inability to cross the intestinal whole mucosa . For this, analogs derivatives of epigallocatechin were synthetized and pro drugs designed in order to be more stable and absorbable to increase its effectiveness.
In “Expert Opinion Therapeutic patens” in 2013 we find that there are patents covering the use of single Epigallocatechin gallate (EGCG), patents for EGCG associated with a chemotherapeutic agent such as 5-fluorouracil and some others concerning the association of EGCG in combination with a DNA vaccine for the so-called immunotherapy. All this serves to understand the amount of work and scientific and economic interests that revolve around this ancient plant.
As regards the use of green tea in the treatment and prevention of cancer, there are studies done on both animal models and humans. In a paper published in “Pharmacological Research” 2011, there were induced lung tumors in mice treated with carcinogenic substances extracted from the cigarette smoke; tumors were developed in 15-20 weeks.
If during the “intoxication”, a group of mice was made to take water with green tea extracts and other group plain water, you could see that the group treated with green tea developed a number of tumors significantly below that treaty with plain water. In animal models it is now proven that the tea and its major components inhibit the genesis of tumors in various organs such as for cancers of the digestive system, skin, prostate, bladder, pancreas.
Even for human beings, there are studies that have tried the beneficial effects of the plant to prevent the development of cancer. Here we have to emphasize the important clinical trial appearance on “Cancer Research” in 2006, made by Dr. Bettuzzi Parma that, at least among the insiders, it is known all around the world and is still-quoted.
The study was performed on a selected population of 60 volunteers biopsy positive for high-grade prostatic intraepithelial neoplasia (PIN HG) which is a pre-cancerous lesion with a risk of about 30% of developing invasive prostate cancer within a year from diagnosis. There are no preventive therapies but only controls biopsy.
A group of 30 patients were treated for the twelve following months after the diagnosis with 600 mg/day of extracts of green tea catechins, the other group took only placebo. And everything is double-blind.
After a year of treatment, only a cancer was diagnosed among the 30 men who took green tea catechins with a final impact of 3%, while in the group that received placebo nine tumors are diagnosed with a final impact of 30%, a figure which was presumed by traditional clinical prognosis. In particular in the placebo group , 6 tumors are diagnosed after 6 months from the start of the trial and other third to the twelfth month. In the group treated with green tea the only tumor is found in the twelfth month. The results give us an efficacy of chemo prevention of catechins in men at high risk for prostate cancer around 90%; for the statistical analysis this is a highly significant result!
Another study, this time Japanese, published in “Cancer Epidemiology Biomarkers and Prevention” in 2008, studied the preventive properties of green tea extract on colon cancer. This work was conducted to evaluate whether supplementation with 1.5 grams per day of green tea (three 500 mg tablets) in addition to the normal use of the Japanese about 6 cups a day, inhibited the regrowth of colon rectal adenomas after endoscopic resection .
125 patients were enrolled and were divided into two groups. One was treated with the supplement of 1.5 grams of tea (of 10 or more cups a day) whereas the control group did not receive any extra but continued to take the classic six cups of tea a day in common use in Japan . It was not given placebo.
After one year of treatment in the control group (who had received no supplement) colonoscopy is diagnosed at least one adenoma in 31% of subjects, exactly 20 of 65. In the group with a supplement of 1.5 grams, the recurrence of adenomas was decreased significantly and was located in 15% of patients, 9 to 60. Furthermore, the size of adenomas in this group were smaller than in the control. So supplementation had halved relapses and this study confirmed the full results of dr. Bettazzi on the prevention of prostate cancer.
In a paper published in the “European Journal of Cancer Prevention” in 2003, it has been studied the clinical efficacy of green tea extracts in the form of ointment or capsules, in patients positive for infection with human papillomavirus (HPV) and cervical lesions . Among the subjects treated with extracts of green tea there was a response rate of 69% (35 of 51 patients responded treated), whereas among patients treated there was a response rate of 10% (they 4 of 39 treated patients responded).
The data collected show that the tea in the form of an ointment or capsules is effective for the treatment of injury to the cervix.
The mechanisms of action by which the plant interferes with the metabolic pathways of cancer cells are numerous and still under study, but the antioxidant effect and stimulation of programmed cell death (apoptosis), were confirmed by several researchers.
Improving the metabolic syndrome and weight reduction
The metabolic syndrome is a complex of symptoms which include in the same individual: elevated waist circumference, elevated triglyceride levels, blood glycemia and blood pressure and reduced concentration of high-density cholesterol. It’s jumped to the news because at a vascular level it creates and maintains a chronic and silent inflammatory state which in the long leads to a net increase of cardiovascular and cerebrovascular events. The fight against Metabolic Syndrome through a controlled diet, smoking cessation and changes in lifestyle is in place throughout the West because of the given high incidence of diseases it causes.
In this context, the positive effects of green tea on decreased body weight and metabolic syndrome have been extensively documented in an extensive experimental case in which there has been a daily intake of four or more cups of tea or 600-900 mg of tea polyphenols.
On “Pharmacogical Research” 2011, it is reported a study in which mice are fed with a high-fat diet (60% of total calories) and treated with extracts of epigallocatechin for 16 weeks at a concentration of 3.6 grams per pound of food assumed ; mice had shown a significant reduction in weight of the fatty tissue, as well as the levels of blood sugar and insulin. All this had led to a greater sensitivity of the organs to insulin itself. This means that low concentrations of the hormone were sufficient to reduce the levels of glucose in the blood.
Tea catechins have been shown to reduce the infarction of the liver (fatty liver) and to protect rodents from ethanol toxicity and other toxic substances.
The metabolic effects on adipose tissue and the body weight of human being have been the subject of numerous studies, most of which has documented a decrease of weight and a slight loss of adipose tissue with a consumption of tea than four cups per day equal to 600-900 mg of polyphenols.
In a Chinese study randomized and placebo-controlled study published in “Obesity“, 2010, in groups of patients was administered for 90 days a beverage with increasing concentrations of catechins and caffeine 30 mg catechin + 10 mg caffeine (a low content drink ) up to 886 mg catechins + 198 mg caffeine per day (drink with a high content).
In the latter group of intensive treatment was observed a loss of 1.9 cm in waist circumference, a weight loss of 1.2 kg and a significant loss of intra-abdominal fat which led to the conclusion that these doses led to visible improvements in body composition.
A paper published in the “Journal American College Nutrition” in 2010, confirms that taking at least four cups of tea a day for eight weeks, due to a significant loss of weight (2 to 3 kg) compared with placebo, and a modest reduction of cholesterol contributes naturally to counter the effects of the metabolic syndrome in obese patients.
Also in the “Journal American College Nutrition” in 2005, it was studied the relationship of green tea against the risk of developing type 2 diabetes (non-insulin dependent diabetes) and it is concluded that the consumption of tea (3-6 cups a day ) is associated with a reduced risk of developing this disease.
For thermogenesis we are referring to a metabolic process that leads to the production of heat by the organism, especially in adipose tissue and muscle. In the field of the dietician and food supplements for thermogenic effect is meant the recruitment of products which tend, at rest, to stimulate or accelerate the metabolism increasing energy expenditure in the form of heat and preventing the storage of alimentary energy in the form of fat. In other words, the dream is to lose weight by not doing either physical activity or submitting to a balanced diet.
It Is thus studied the thermogenic action of green tea, ie the ability to increase the metabolism and consequently the energy consumption even in conditions of rest. In the important study by Abdul Dulloo published in “American Journal of Clinical Nutrition” in 1999, it is proven that the intake of tea increases energy expenditure in the 24 hours of 4%.
A very interesting result of this study is that the effects of green tea on the energy expenditure could not be explained only on the basis of its caffeine content, because the treatment with a dose equivalent to that of caffeine contained in tea, was not able to increase energy expenditure. The inference to be drawn is that the metabolic effects of tea are due to substances other than caffeine and typical of the plant. Furthermore it is seen that the tea causes a peculiar increase of fat oxidation (consumption of fat deposits) whereas massive recruitment of caffeine equal to 1,000 mg/day have no significant effect on this parameter.
Last important consideration is that the stimulation of thermogenesis and fat oxidation with green tea is not accompanied by an increased heart rate typical of high doses of caffeine.
Cardiovascular disease prevention
There are many human studies in taking tea against cardiovascular disease. The most convincing evidence to document a reduction in cardiovascular risk with tea consumption comes from large studies done in Japan. With the study published in “JAMA” in 2006, taking two cups to five cups a day was associated with a significant decrease in mortality from cardiovascular disease.
In another Japanese study published in the “Journal Epidemiology Community Health” in 2011, consuming more than six cups of tea a day confirmed the reduction of mortality in tea drinkers.
A meta-analysis published in “American Journal Clinical Nutrition” in 2011, compared the effects of black tea against the green tea in regard to the prevention of the events of diseases of the coronary arteries of the heart. The results, very interesting, showed that consumption of green tea, but not black tea, was associated with a decreased risk of coronary heart disease by 10%. No data were emerged that supported the protective role of black tea.
Recent researches and meta-analyzes have found that drinking tea can slightly reduce the risk of Parkinson’s disease and epidemiological studies have suggested that drinking tea is associated with an improvement of cognitive function.
The theanine, an amino acid found in tea, can easily penetrate into the brain where it carries out a neuro protective. In addition, several studies show that this substance can improve memory and attention in individuals with mild cognitive impairment.
The antioxidant action of tea polyphenols is certainly important in the prevention of cancer, cardiovascular disease and in the reduction of inflammation in obesity and metabolic syndrome.
Many results were obtained with green tea and not with the black one as the polyphenols of the latter are practically not bioavailable, also not absorbed polyphenols exert their effect on the gastrointestinal tract by reducing the absorption of lipids and proteins and facilitating the growth of microbial strains useful to wellness.
It has been documented hepatotoxicity in consumers of dietary supplements containing high doses of green tea extracts used for weight loss.
Caution should be exercised and it is not uncommon that drunk on an empty stomach can create gastric irritation. In these cases the association with ginger can significantly reduce this problem.
The intake of four or five cups a day is associated with the protection against some chronic diseases with a very few side effects, which undoubtedly led green tea to a fit and useful beverage to health.
Translated by Ms Jeanne Marie Arcaini