Green Tea Science Part 1: Polyphenols, Catechins, and EGCG - 15 Commonly Asked Questions and How You Can Benefit
Although the popularity of green tea in the Western world is a fairly recent phenomenon, the highly beneficial nutritional value has enjoyed a favorable reputation throughout many parts of Asia for thousands of years. Only recently is scientific research beginning to understand green tea's health benefits in relation to its high concentration of phytochemicals, known as polyphenols, which include subclasses of tannins and gallic acid.
In this article, I will address commonly asked questions about polyphenols, catechins, epigallocatechin-3-gallate (EGCG), tannin, gallic acid and caffeine.
Because this article ended up being quite long, I have broken the articles into multiple parts. Here is a list of questions and topics I cover in this entire series so that you can skip to the question you want to read.
Polyphenols and Green Tea - 8 Answers to Commonly Asked Questions and How You Can Benefit
1. What are polyphenols?
Polyphenols are antioxidants or substances that combat free radicals, which can damage DNA and alter or even kill cells in the body.
Also known as phenolics, they are chemical compounds that occur in plants. They have over one phenol unit or building block in every molecule. They give plants their color and help protect them from insects. Foods or drinks containing polyphenols will have an astringent bite to their flavor.
There are 8,000 types of polyphenols that have been found in edible plants, and half of them belong to a group called the flavonoids that is further subdivided into six categories. Back To Top
2. Green tea has so many health elements. What is the difference between catechins, tannins and polyphenols in green tea?
Catechins, also called flavanols, and tannins are actually types of polyphenols. The leaves of the tea plant produce more catechins than any other plant. The fermentation and oxidation process is believed to strip black and oolong tea of some antioxidants, so green tea has more catechins than the other types. EGCG is the most abundant catechin in tea.
One difference between a catechin and tannin is size: Tannins are larger. A catechin with over 20 or more hydroxyl groups (-OH) is classed as a tannin.
Coffee and tea are the main source of tannins in the human diet. Tannins help give coffee and tea their flavor. Back To Top
3. How many polyphenols are in green tea?
Determining the amount of polyphenols in green tea is not a straightforward process, as some brands have more than others. A 2003 study of different green and black teas, for example, found that the amount of EGCG in green tea could range from 22 mg per 100 ml to nearly 100 mg per 100 ml. Similarly, the amount of catechins ranged from 52 mg per 100 ml to 216 mg per 100 ml.
EGCG, however, is the most abundant catechin in all of the teas. Epicatechin gallate (ECG) is the second most abundant, with numbers ranging from 22 mg per 100 ml to nearly 80 mg per 100 ml. Back To Top
4. Compared to other teas, how many polyphenols are in green tea?
Green tea has far more catechins than black tea. The 2003 study showed that the amount of catechins in black tea ranged from none at all to 81.6 per ml, with the lowest numbers being in iced teas. While decaffeinated black teas had some catechins, they had no EGCG or ECG. The amount of EGCG in other black teas ranged from nearly 4 mg per 100 ml to around 74.5 mg per 100 ml, with a Darjeeling tea having by far the most. The amount of ECG ranged from approximately 1.4 mg per 100 ml to around 21.3 mg per 100 ml.
Conversely, black tea contains a family of polyphenols called theaflavins that does not occur in green tea. Back To Top
5. Who should take polyphenols?
Many people can use polyphenols, and they can be taken in supplement form. They also come in a variety of foods and drinks, many of which are quite tasty and enjoyable. (Who doesn’t like dark chocolate or green tea?) Back To Top
6. What are polyphenols good for?
Polyphenols are antioxidants and can therefore fight and even prevent disease. Some of the catechins found in tea may prevent the development of diabetes. Researchers suspect the catechins impede the gut’s absorption of glucose.
Polyphenols may help fight some types of cancer by reducing the size and/or number of tumors. Researchers are studying some polyphenols, like quercetin and resveratrol, to learn about their anti-aging and cancer-fighting properties.
The polyphenols found in green tea have been linked to a reduced risk of Parkinson’s disease. Other polyphenols found in vegetables and fruits may slow down the development of Alzheimer’s disease.
Polyphenols help prevent low-density lipoprotein (LDL) cholesterol from reacting with free radicals, thus slowing the development of atherosclerosis. Scientists have found that a diet based on plant foods reduces the likelihood of developing cardiovascular disease.
Researchers believe that polyphenols might prevent osteoporosis and some lung diseases, such as asthma. More studies need to be done, however. Back To Top
7. Are there side effects associated with polyphenols?
There are no known side effects caused by the polyphenols themselves. Some of their plant sources may cause allergic reactions, however.
Green tea, however, can cause drug interactions. People taking anti-depressants, birth control pills, blood-thinners, some heart medications, and some antibiotics should talk to their doctor before drinking green tea or taking supplements made from green tea. Back To Top
8. What is the most effective way to take polyphenols?
Polyphenols can be eaten or drunk. In 2010, a group of French scientists ranked foods by their polyphenol and listed them by concentration or serving. The former can be misleading; some foods, like many herbs, have high concentrations of polyphenols but are eaten in such small amounts that they don’t contribute much to a meal. Cloves, for example, have the highest concentration of polyphenols of all, with over 15,000 mg per 100 grams, but they are eaten in such small amounts that they don’t even make the “Most Polyphenols per Serving List.”
By contrast, green tea like Issaku Green Tea, one of the premium green teas from Japan, is an excellent source of polyphenols. Other excellent sources of polyphenols include berries, coffee, black tea, dark chocolate, red wine and artichoke.
Catechins and Green Tea - 8 Answers to Commonly Asked Questions and How You Can Benefit
1. What are catechins?
Catechins are types of antioxidants that belong to the flavonoid family. Flavonoids are plant pigments that help give plants their color and have health-giving properties when those plants are ingested. Catechins in particular are abundant in the leaves of the tea plant, or camellia sinensis. The name comes from catechu, which is a juice derived from the Mimosa catechu plant that is then boiled. Catechins are also tannins and give tea its pleasing astringency.
Botanists believe that catechins are used by the plant to protect them against other plants growing too near and competing for nutrients in the soil. Back To Top
2.What is the difference between catechins, ECG, and EGCC?
ECG and EGCG are both forms of catechins. They are both polyphenols, plant chemicals found in tea. They are both flavonoids and belong in the subfamily of galloylated catechins. ECG and EGCG are only two of many types of catechins found in green tea.
EGCG in particular is a strong antioxidant. Scientists believe it is 25 to 100 times more powerful than the antioxidants vitamins C or E. Antioxidants are substances that protect the cells against being damaged by free radical molecules. These molecules lack electrons and grab them from other molecules, including DNA. This causes damage that can lead to disease. EGCG has been seen to inhibit the growth of breast, lung, liver, and colon tumors. It kills cancer cells outright and supports brain function by helping the brain create more nerve cells, or neurons, in the hippocampus, which is responsible for memory. This was seen in mice but holds promise for human beings. EGCG also helps in weight loss and prevents cardiovascular disease.
EGCG is the main catechin found in green tea. Scientists believe that catechins work because they bind to proteins and keep bacteria and viruses from clinging to cells and attacking them. Catechins also fight the poisons produced by bacteria as well as toxic metals, such as lead and mercury. Back To Top
3.How Much catechins are in green tea and other teas?
Catechins are especially plentiful in green tea because green tea leaves do not go through the same fermentation process as black or oolong teas. The catechin level in green tea is between 59.3 and 103.2 milligrams per gram. It is 21.2 to 68.3 mg/g in black tea, which has a lower overall level of flavonols overall due to the fermentation process. Flavonols are chemicals related to flavonoids. Decaffeinated tea, both black and green, has even fewer flavonols. Iced tea has fewer flavonols than warm tea because it is more diluted, and the levels of flavonols are different for different brands of tea.
The amount of catechins in green tea depend on when the tea was picked and the age of the leaf. Tea picked in the spring has 12 to 13 percent of catechins, while summer-picked tea has 13 to 14 percent. This higher level also explains why summer-picked tea has a more astringent taste. Younger leaves also have more catechins than older leaves.
A very high quality type of Japanese green tea called Issaku is rich in catechins. It also has a uniquely sweet taste because it is fertilized with sugar cane. Back To Top
4.Who should take catechins?
People who are interested in a natural way to guard against cardiovascular disease and certain cancers should take catechins in the form of green tea. Patients who are enduring cancer treatment should take catechins, because they support the immune system. They do this by boosting the levels of white blood cells, which destroy pathogens that enter the body.
Catechins are digested through the gastrointestinal tract, specifically through the first part of the small intestine, or jejunum and the liver. Back To Top
5.What diseases are catechins good for?
Catechins are good at preventing heart disease because they appear to cause blood vessels to dilate. This promotes good blood circulation. The catechins found in green tea have been seen to lower high blood pressure, though researchers don’t quite know how. The antioxidants in tea, especially green tea, can help lower bad, or LDL, cholesterol and can help protect a woman against breast or ovarian cancer. Back To Top
6.Are there side effects of catechins?
Catechins are well tolerated by most people, though if they are taken in great doses they can cause anemia or even kidney failure. This happens because the catechins tendency to bind to proteins. In very large doses, catechins bind to the user’s red blood cells. This was why a catechin-based drug used to treat hepatitis was taken off the market in Europe. Back To Top
7.What is the most effective way to take Catechins?
The most effective way to consume the catechins found in green tea is to brew it and drink it. Experts recommend brewing two teaspoons of Issaku tea in 8 ounces of fresh water at 175 degrees Fahrenheit for two minutes. The one caveat is that green tea should not be steeped too long because this brings out the tannins. Though this is harmless, it can make the tea too bitter to enjoy. Though the drinker can add milk to the tea, the proteins in milk form chemicals that make the catechins indigestible, at least temporarily. However, when the chemicals are digested, the green tea is able to be digested through the small intestine as usual.
When it comes to teapots, many connoisseurs prefer glass when it comes to brewing green tea. Glass lets the drinker see the color and clarity of the tea, and watch the tea leaves unfurl in the hot water. Green tea tastes better in a smaller teapot, gives the drinker more control over the temperature and the time the leaves steep and lets them resteep the leaves.
Catechins provide health benefits for nearly ever system in the body. They support the functioning of the nervous system, help in weight loss and reduce the risk of obesity. They offer some protection against certain forms of cancer, and lower the risk of Type 2 diabetes. They support the health of the liver, the organ in the body responsible for removing toxins and dilate the blood vessels. This allows for an improved flow of blood and therefore nutrients throughout the body.
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Author : Kei Nishida
Kei Nishida is a writer, a Japanese Green Tea enthusiast, and the founder and CEO of Japanese Green Tea In. You can find his published work in Fresh Cup Magazine, Yoga Digest Magazine, T-Ching and more. He is also the author of three published books. Read more about Kei Nishida