EGCG, Catechins and Polyphenols
FAQ Guide

What are EGCG, catechins and polyphenols, and their health benefits and side effects? Pros and cons of green tea, matcha and extract supplement.

1. What are tea polyphenols?

Polyphenols is a much abused term. Strictly speaking, it refers to a class of micronutrients that is presents in most vegetables and fruits. In recent years, they have attracted much scientific scrutiny due to their antioxidant properties and health benefits.

There are many types of polyphenols, of which the most well-researched are flavonoids. Flavonoids themselves are further divided into six sub-classes:

  • Flavanols
  • Flavonols
  • Flavones
  • Isoflavones
  • Flavanones
  • Anthocyanidins.

Flavonoid is a fascinating subject. To learn more about it and which is the richest source of food for flavonoids, read

Green Tea Catechins and Flavanoids Explained

Tea contains lots of polyphenols but it also contains other compounds. Confusingly, tea seller tends to use the word polyphenols interchangably with green tea extract, which can be misleading, as you shall learn later.

What's In Polyphenols?

According to a 1992 study by Harold Graham, one third of dried tea extract is flavanols such as catechins. Another 10-14% are flavonols such as kaempferol, quercetin, and myricetin. This is explained further in the article below:

Green Tea Ingredients and Chemistry Explained

2. What are catechins?

When buying a green tea extract, inteads of looking at polyphenols, you should focus on how much catechins it contains.

Catechins are what make green tea special. They make up the bulk of green tea's antioxidants and its healing potential.

Let's say you come across an exciting product that says "300 milligrams of polyphenols". You may be led to believe it contains 300 milligrams of catechins. You could be wrong.

A standardized green tea extract contains only about 30% catechins. So 300 milligrams of polyphenols may only contain 90 milligrams of antioxidants, not the 300 milligrams that you expect

Green Tea Versus Black Tea

Catechins are unoxidized. When black tea is made, catechins oxidize to form more complex compounds called thearubigins and theaflavins. Between the two, only theaflavins contain significant antioxidant potential.

Green tea contains about 30% catechins, whereas black tea contains only 4% of theaflavins. Both are powerful antioxidants. But green tea has far more in quantity, which explains why it is associated with more health benefits.

3. What is EGCG?

Okay, now you understand what catechins are, the rest is easy.

Green tea contains six types of catechins: EGCG, EGC, ECG, EC, GC and C. Among the six, there is some evidence that EGCG and ECG are the most potent.

However, what makes these catechins so interesting is not their potency, but their abundance. About half of the catechin content of tea is EGCG. Just a small quantity of tea leaves will steep many cups of tea.

It is this relative abundance that makes green tea special. No other food or beverage contain this much antioxidants!

EGCG is the focus of almost every scientific study, and has been associated with most of the newly discovered green tea benefits!

4. What are the health benefits?

The health benefits of EGCG are deep and wide ranging, literally covering every part of your body. The following article covers this in some details feel free to scan through it:

Green Tea Health Benefits -16 Things That Make Miracles Possible

The Ohsaki National Health Insurance Cohort Study is one of the largest population studies ever conducted - 40,530 Japanese adults were questioned over the course of 11 years.

Researchers found those who drank 5 or more cups of green tea a day were 16% more likely to live longer than those who drank less than one cup a day.

Heavy green tea drinkers are also 26% less likely to die from heart disease.

EGCG Health Benefits - 6 Discoveries You Can't Ignore

5. Can it help me lose weight?

The weight loss effects of green tea are slow but significant, and there is real scientific evidence to justify its inclusion as one of the top ingredients in many reputable weight loss products.

It can help you lose weight safely and effectively in three ways:

  • Increase metabolism

  • Burn fat

  • Reduce fat storage

Many scientific studies have indicated that it can have some big benefits to overall health, especially because it can help you lose weight.

Weight Loss - Green Tea 3-Way Magic

6. Does it have any side effects?

Green tea has few side effects.

After all, the Chinese people have been drinking tea for thousands of years. It has been officially proven by study that green tea is the second most consumed beverage in the world after water.

It is water-soluble, which means if you overdose, it is unlikely to build up. The excess simply gets flushed out of your body.

There is only one caveat: Be careful when you are pregnant or consuming lots of sub-quality processed products (such as tea powder or dietary supplement).

Side Effects - Green Tea Extract Consumers Beware!

7. How much should I consume daily?

When considering how much to consume daily, you want to consider two things:

  • What is the manufacturer's recommendation? You don't want to exceed the maximum as it can be dangerous. This is explained in the Green Tea Supplement Side Effects article, where three studies have found green tea extract to be toxic at high doses.

  • You don't want to consume too little or else you will lose out on the health benefits. In the Green Tea Extract Weight Loss article, we examine four scientific studies, which found that you need to consume somewhere between 300 to 700 milligrams of catechins or EGCG a day to have any weight loss effect.

How to Maximize Benefits

8. Which foods and beverages contain the highest levels of this compound?

When choosing the healthiest tea beverage to drink, always go for the least processed option.

A 2007 report published by the US Department of Agriculture (USDA) analyzes nearly 400 foods for their EGCG content. It shows that regular green tea contains the highest concentration of antioxidants.

It is followed by decaffeinated green tea, flavored green tea and instant or bottled tea.

EGCG Content in Green Tea - USDA Study

The same study shows why green tea is probably the best way to ingest antioxidants.

One gram of green tea steeped in 100 milliliters of water yields 127 milligrams of catechins.

In comparison, 100 grams of dark chocolate contains 54 milligrams, blueberries 52 milligrams and black grapes only 22 milligrams!

Green Tea Catechins - Best Food and Beverage Sources

9. So green tea contains the highest concentration of EGCG. Should I take a green tea extract supplement or drink green tea?

This is an open-ended question, much depends on the quality of the green tea or supplement product you are comparing.

I personally prefer to drink green tea consisting entirely of young tea buds plucked from the top of the tea bush in the first three days of spring. I think these high grade green teas offer the best value in term of taste, nutrition and avoidance of side effects.

The problem with tea supplement is that it demands you to trust the brand you are buying from. For me, this is a big ask, as the highest quality tea farms make high grade green tea for drinking, whereas the low quality tea farms make tea extract.

You can tell a cup of green tea is high quality by looking at it and tasting it. You can't do the same for a green tea extract supplement.

Also, scientific study has shown that the potency of a supplement is often over-stated. For further analysis, please read the following article:

Green Tea Supplements Vs Drinking - Pros and Cons

10. How about matcha green tea powder?

For a tea lover, I love matcha for its emerald green, rich flavors and ceremonial grace. However, if you are considering matcha as a health food, and as a replacement for a cup of high quality tea, I think you should go in with a more realistic expectation.

Just like green tea, there are many grades of matcha tea powder.

A high grade tea powder is made from young tea buds plucked in the early spring, just like a high grade green tea. However, additional labour is needed to grind the tea buds into powder form, which means a high grade matcha is more expensive than the tea itself.

It is nice to add low grade tea powder to smoothie or instant iced tea. However, one should only buy the tea powder from reputable sources as much of Japanese tea powder is sourced from China, where only low quality tea farm caters for this market.

This is further explained in Matcha Powder Health Benefits Vs Green Tea Leaves.

11. How does it affect the taste of a cup of tea?

The level of EGCG present in tea leaves decreases with leaf age. Its concentration is the highest in tea buds. These tender sprouts are reserved for making the highest grade tea.

Although catechins taste astringent (the dry-mouth feeling of a banana skin), tea buds taste rich, fresh and even sweet.

Tea appreciation is an holistic experience. (Green tea contains more than 200 bioactive compounds.) High grade tea contains high levels of astringent antioxidants, and even higher levels of theanine.

The presence of EGCG by itself does not guarantee a quality cup of tea. Having too much can make a cup of tea undrinkable.

Scientists have repeatedly observed that the health benefits of tea are maximized when EGCG is acting in combination with the other tea compounds.

12. Which dietary supplement do you recommend?

While drinking a tea infusion is the tried-and-tested way for consuming green tea antioxidants, you may prefer to use a dietary supplement because of convenience or you want something that is caffeine free.


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Harold N, Graham PD (1992). Green tea composition, consumption and polyphenol chemistry. Journal of preventive medicine and hygiene. 1992 May;21(3):334-50.

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