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Japanese Green Tea Can Be Negative For Your Health?: Three Ingredients In Green Tea You Should Know About

What can green tea work negatively on your health Food & Recipes

How many cups of green tea do you drink a day?

Or, do you like to know the appropriate amount of consuming green tea per day?

I talk about the powerful health benefits of Japanese green tea by focusing on the main ingredients in this post.

Then, recent studies have shown that continuously taking a certain amount of green tea, which brings you various health benefits.

Contrary does green tea has dark sides when we talk about it as a daily healthy drink? Today, let’s talk about the over-drinking of Japanese green tea.

Beware of caffeine

Japanese green tea contains caffeine.

What Does The Caffeine Affect Your Body

Caffeine has various positive effects such as improving concentration and memory, promoting lipolysis, improving athletic ability, and recovering from fatigue.

If you intake a high amount of caffeine or continue to take it for a long period, it can cause nervousness, sleep disorders, and gastrointestinal symptoms.

The WHO (World Health Organization) limits the daily intake of caffeine to 300 mg.

The amount of caffeine in green tea is about 20 mg per 100 g (1 cup of hot water), so it can be said that there is no particular problem if it is about 10 cups a day.

Beware Of Tannin

Tannin is an astringent ingredient that is abundant in seeds and is a polymer of many catechins. A type of polyphenol, also called proanthocyanidin, is an astringent ingredient of tea.

Catechin is already well known for many benefits such as antioxidant activity, immunity enhancement, and weight loss that I explain in this post.

Additionally, it is known for its prevention of dementia and lifestyle-related diseases, intestinal regulation, and skin lightning effect.

There are no critical side effects of over-intaking, but what you should be aware of is the effect of hindering the absorption of iron.

So how much tannin does tea contain?
Take a look at the Standard Tables of Food Composition in Japan by the Ministry of Education, Culture, Sports, Science, and Technology.

Types of teaTannin levelThe amount of tea leavesWater temperatureThe amount of waterThe steeping time
Gyokuro230mg10 g60°C60 ml2.5 minutes
Matcha200mg2 g80°C60 ml
Sencha70mg10 g90°C430 ml1 minute
Hojicha40mg15 g90°C650 ml30 seconds
Genmaicha10mg15 g90°C650 ml30 seconds
Bancha30mg15 g90°C650 ml30 seconds
Oolong tea30mg15 g90°C650 ml30 seconds
Black tea100mg5 gpiping hot360 ml1.5 – 4 minutes
Coffee250mgInstant coffee 10 gpiping hot 150 ml

Does Tannin Reduce Iron Absortion?

The effects of green tea and black tea tannins on iron absorption have been studied at overseas and Japanese research institutes.

Researchers indicate that the direct effect of tea-based beverages on iron nutrition is extremely small. It seems You don’t have to be nervous while having a balanced diet and drinking a moderate amount of tea.

If You Still Consider About “Tannins”

If you are still worried about “tannins” but like to enjoy tea, change the brewing method, type of tea, or time of drinking tea.

Drink Genmaicha, Hojicha that contains fewer tannins, or tannin-free barley tea with your meal.

About Sencha, apply cold-brewing which the amount of tannin and caffeine extracted can be reduced make a regular sencha tea.

If you like to drink hot sencha or matcha, wait at least 1 hour after meals.

Instead, consider having your tea between meals.

If you are anemic, be careful not to consume too much tannin-containing beverages and foods. Also, it seems to cause constipation.

Use An Iron Kettle To Intake Iron

Iron is dissolved in the hot water boiled in an iron kettle, it is recommended to use an iron kettle that makes it easier to take in iron.

Moreover, the water boiled in an iron kettle becomes round and mellow so it is good for making delicious and sweet Japanese green tea, in this reason, many tea specialty stores using iron kettles (or teapots.)

If you hesitate to purchase an iron kettle just for it, we recommend putting the “cooking iron ball” in the kettle you normally use.

Also, it is ideal to use an Iron Kyusu teapot instead of an iron kettle. Note that you can’t boil the water with an iron Kyusu teapot.

Tea tannin (catechin) has many health benefits. Enjoy tea well while devising how to drink.

If you are being treated for iron deficiency, be sure to follow your doctor’s instructions.

Beware Of Oxalic Acid

Green tea contains oxalic acid, which causes urethral stones. It is found in most foods, not in extraordinary amounts in green tea.

Popular foods that are high in oxalic acid; bananas, nuts, cacao powder, coffee, beet greens, rhubarb, beets, swiss chard, endive, kale, and spinach.

In 2015, an American who was transported by drinking too much-iced tea had kidney failure due to oxalic acid. It’s one of the unusual cases, but avoid eating or drinking unbalanced as it can cause terrible illnesses such as urethral stones and renal failure.

Intake Sufficient Calcium

Also, to prevent urolithiasis caused by urinary oxalic acid, reduce the amount of oxalic acid in the diet as much as possible. When oxalic acid is ingested, intake sufficient calcium to the digestive system which forms calcium oxalate in the body and reduces the absorption of oxalic acid.

From the point of preventing the urinary stones by calcium oxalate, the research indicates a result that Matcha had the most lack of calcium level (10.23 mg.) Then, black tea 5.26 mg, Gyokuro 2.21 mg,
Sencha 1.87 mg and Bancha 0.81 mg are followed.

Beverages high in oxalic acid are green tea especially Gyokuro and Matcha, oolong tea, and black tea. If you consume a lot of liquid, mineral water, barley tea, Hojicha tea are preferable.


Today, I told you about the downside of drinking “too much” green tea, but the conclusion is that if you are in healthy condition, up to 8-10 cups of Japanese green tea per day will affect your health positively rather than work negatively.

However, daily health care cannot be measured by the amount of green tea alone, and it really depends on your health conditions.

Even 3 cups of green tea a day cause some people to have stomach and other unhealthy conditions.

Continuing to drink green tea on a regular basis will definitely have a positive effect on your health, but please keep in mind a “moderate amount” and a “common sense amount”.

Health Benefits Of Japanese Green Tea

The Types Of Japanese Green Tea


The Impact of Tannin Consumption on Iron Bioavailability and Status: A Narrative Review

Man’s kidney failure caused by drinking 16 cups of iced tea a day

Oxalate, magnesium and calcium content in selected kinds of tea: impact on human health

Oxalic Acid and Calcium Contents in Tea [In Japanese]

Oxalate, magnesium and calcium content in selected kinds of tea: impact on human health

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