Green tea is one of the healthiest beverages available to us. It originated in China more than 4000 years ago, and has been used in traditional Chinese medicine for a wide variety of health benefits.
As the use of green tea has become more popular and widespread, so has the research invested into it. There are now several proven health benefits of green tea, mainly due to the antioxidants it contains, as well as a number of benefits claimed that have yet to be researched fully. The abundance of benefits green tea provides has made it a very popular supplement for all round good health, as well as to tackle specific health issues.
Whilst much of the scientific research into green tea is relatively new and needs further study, the fact that it has been used for so many centuries and has produced positive effects for many people across the world suggests that it is as powerful as it is claimed to be. The research that has been conducted so far shows results that point to it being beneficial for many aspects of our health.
What is Green Tea?
Green tea comes from the Camellia sinensis plant. This is the same plant which produces black tea, white tea, oolong tea, and several other tea varieties. The same plant is able to produce all these teas through the different processing methods we can use.
Green tea is made by harvesting the plant leaves, withering them, and then steaming them. This means that it goes through minimal oxidation during processing, which preserves the powerful antioxidants that are stored within the plant. Black tea, however, is oxidized, which causes the antioxidants it contains to form into different, more complex compounds. Whilst black tea still has benefits for our health, the oxidization means that some of the most powerful antioxidants are no longer present.
The powerful antioxidant compounds in green tea are called polyphenols. These compounds are originally produced by the plant for defence. The most significant type of polyphenols contained in green tea are called catechins, and these make up over 90% of the polyphenols in tea. There are several types of catechins contained in green tea, but by far the most abundant and significant is epigallocatechin gallate, more commonly known as EGCG.
Many of the beneficial effects tea has for our health can be contributed towards EGCG, and recent studies into the benefits of green tea have mainly focused around this catechin. Out of all the teas, green tea contains the highest concentration of EGCG (on average, approximately 10% of dried green tea leaves is EGCG). This is a large part of the reason as to why it is considered amongst the healthiest of teas available.
In order to maximize the beneficial effects of green tea and the EGCG it contains, it can be recommended that several cups a day should be consumed. For this reason, some people choose to take additional supplements in the form of pills.
EGCG is known to be a very powerful antioxidant. In fact, it has been shown to be a more powerful antioxidant than both Vitamins C and E. This is because it helps to rid the body of free radicals. Free radicals are atoms that are unstable, and can be formed in the body through several ways. The most common way free radicals are formed in humans is when oxygen interacts with certain molecules, but environmental factors such as pollution and smoking can also lead to their formation. Free radicals can be dangerous to our health, as they attack healthy, stable molecules in order to stabilize themselves, which can lead to quickened ageing and several different illnesses.
By fighting off free radicals and protecting healthy cells, green tea helps to keep the body strong and can protect it from all sorts of conditions.
Many studies have shown that green tea can help to reduce the risk of different heart diseases. This is due to the fact that green tea can have a beneficial effect on some of the factors which lead to heart disease in the first place.
Green tea has been shown to lower the levels of bad cholesterol (low-density lipoprotein) in the blood and to improve the ratio of good cholesterol (high-density lipoprotein). This is significant for protecting us against heart disease, as too much bad cholesterol in the system will start to build up in the walls of the arteries, and this can cause atherosclerosis and other heart conditions.
Green tea also has a positive effect on LDL cholesterol through protecting it from oxidation. Oxidation of LDL cholesterol causes inflammation to the arteries, which can cause heart problems.
One of the most promising results from research conducted into green tea and heart health was from the Ohsaki National Health Insurance Cohort Study in Japan, one of the largest population studies ever done. Results showed that adults were 26% less at risk of heart disease, as well as being 16% more likely to live longer, when they drank at least 5 cups of green tea per day.
Recent research has shown green tea to have a positive effect on the brain. The key findings showed that green tea enhances the working memory by increasing connectivity in parts of the brain associated with memory.
As a result of this, it has been suggested that green tea could be promising in treating conditions associated with memory loss.
Although scientific research into this area is still new, there has been promising evidence for how green tea can help to promote weight loss. Research has shown that EGCG increases the rate of the metabolism, which can help to burn fat quicker. A study in the American Journal of Clinical Nutrition showed that when green tea was consumed three times a day, metabolic rate increased by 4% in 24 hours.
Green tea can help promote relaxation and avoid anxiety. This is due to the active chemical it contains called theanine. Studies have shown that theanine can have calming effects because it acts as a neurotransmitter, increasing alpha waves in the brain; alpha waves have been strongly associated with relaxation. Furthermore, the studies showed that the calming effects of theanine were without drowsiness, meaning that it could also help in improving focus.
Other aspects of our health that green tea has been linked to include:
- Benzie IF, Szeto YT, Strain JJ, Tomlinson B. “Consumption of green tea causes rapid increase in plasma antioxidant power in humans.” Nutr Cancer. 1999; 34(1):83-7.
- Dulloo AG, Duret C, Rohrer D, Girardier L, Mensi N, Fathi M, Chantre P, Vandermander J. “Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans.” Am J Clin Nutr. 1999 Dec; 70(6):1040-5.
- Graham HN. “Green tea composition, consumption, and polyphenol chemistry.” Prev Med. 1992 May; 21(3):334-50.
- Harold N, Graham PD. “Green tea composition, consumption and polyphenol chemistry. Journal of preventive medicine and hygiene.” 1992 May; 21(3):334-50.
- Lambert JD, Yang CS. “Mechanisms of cancer prevention by tea constituents.” Journal of Nutrition. 2003; 133(10):3262S–3267
- Lekh R. Juneja, Mahendra P. Kapoor, Tsutomu Okubo, Theertham Rao. “Green Tea Polyphenols: Nutraceuticals of Modern Life.” 2013.