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Caffeine levels in various tea types

Posted by CTH Blog 11/12/2019 07:45:34 Healthy Tea 0 Comments

All real teas have caffeine—even the decaf ones. In decaf teas levels will be very low, less than 2-5 mg per cup. If you are a healthy grown-up with no serious health condition, enjoying a few cups of caffeinated tea per day shouldn’t pose a danger. Safe daily intake should not exceed 500 mg. But, does 500 mg per day equals 2 or 20 cups of tea? What are the caffeine levels in various tea types?

Caffeine levels in loose leaf tea

Interestingly, despite the common belief, green tea can have less caffeine than white tea, and white tea can have more caffeine than black tea. A study published in the Journal of Analytical Toxicology concluded that the “caffeine concentrations in white, green, and black teas ranged from 14 to 61 mg per serving with no observable trend in caffeine concentration due to the variety of tea.”[1] Meaning, every tea is different, and it’s impossible to make general assumptions based on the type only.

The total amount of caffeine in your cup of tea will depend on dozens of factors. From tea varietal, processing methods, brewing technique and even the type of fertilizer used for growing tea. Using fertilizers, especially nitrogen, has an influence on the total caffeine content in tea as well. Nitrogen is used to increase the yield, but it also increases the amounts of caffeine by 14%[2]. Therefore, same tea type from two different producers may have different caffeine levels.

(Source: Nipapun Jiranukul )

White Tea

Most white teas come from China, Fujian and Yunnan. Fujian white teas are made from Camellia sinensis var. sinensis and Yunnanese from Camellia sinensis var. assamica. Although not a general rule, assamica tea plants are more likely to have higher caffeine content.[3] These same plants are used for making strong black Assam tea as well.

A recent study in Poland examined nutritional values of dried tea leaves and infusions specifically in Chinese teas. Results showed that Silver Needle has around 34.07 mg of caffeine, White Peony around 38.33 mg and White Pearl 28.86 mg. On the other hand, Anji Bai Cha, a very light green tea, has much less – only 19.46 mg, and Bi Luo Chun 24.14 mg.[4] Infusions were made with 100 ml of boiling water and 1 gram of tea. In another study from Brazil, all white tea samples had more caffeine than some black teas[5]. Therefore, brewing Silver Needle with 90 degrees Celsius and 5 grams of tea might give a quite strong infusion, stronger than making a cup of delicate green tea with 75 degrees and 3 grams of leaves.

Green Tea

Green tea generally has between 20 and 60 mg of caffeine per cup. However, there are some types that may have even less. Roasted green teas with mature leaves like Japanese kyobancha or hojicha will very likely have less than 10 mg of caffeine per cup. Fresh spring harvest green teas with young leaves and buds will have the most. Gyokuro is a great example of a tea with a very high level of caffeine. A cup might easily reach well above 100 mg. This depends on the brewing technique too. Gyokuro is usually made with much more leaves than regular green tea. Matcha is made from similar leaves as gyokuro, but one serving will have only around 60 mg of caffeine. Why? Because one serving of matcha equals 2 grams of tea powder, while one gyokuro brewing session might require even up to 10 grams of loose leaf tea. Pan-fired tea like Long Jing will have less caffeine than steamed teas, and so will teas made of stems—like kukicha.

Black Tea

A cup of black tea might have anywhere from 30 to more than 100 mg of caffeine per cup. Black tea is usually made with 2-3 grams per 200 ml of water. Brewing leaves with almost boiling water will increase the caffeine extraction. The strongest black teas usually come from Assam, are usually broken and made from Assamica tea plant. A comparative study of Indian black teas showed that Assam tea dust had the highest levels of caffeine, almost double the amount of Darjeeling and Nilgiri leaf and 3 times more than unbroken Assam leaf[6]. Interestingly, the amount of caffeine in Assam tea dust corresponds to Gyokuro green tea.

In the previously mentioned study from Poland, black teas had an average of 34.997 mg of caffeine per 100 ml, green teas 26.445 mg and white teas 28.584 mg per 100 ml. All infusions were made with only a gram of tea, infused for 5 minutes at 100 °C. [7] To put things into perspective, think that you are usually making black tea with very hot water and 2-3 grams of leaves, very likely increasing the caffeine content 2-3 times. For green tea, you might use the same or higher amount of leaves, but water will be much cooler, reducing extraction of caffeine.

Oolong Tea

Oolong tea is the most versatile category of teas. Regardless versatility, all oolong teas are usually made from more mature leaves and may even contain full branches. Most of them are roasted or baked. In general, a cup of oolong tea will probably have not more than 50 mg of caffeine.

Tea Blends

Tea blends contain less caffeine than pure tea because they are usually mixed with other ingredients like flowers, dried fruits and spices making the ratio of actual tea leaves lower. For example, 3 grams of flavored green tea might have only 1 gram of pure tea, lowering caffeine content significantly.

Herbal Tea

With a few exceptions, almost all herbal teas are caffeine free. Rooibos, chamomile, mint, and all fruit tea have zero caffeine. The most popular herbal tea with caffeine is south American Yerba Mate. However, even yerba mate might have 50% less caffeine than regular green tea[8].

When is caffeine released?

Caffeine is best extracted at 100 °C, which is a temperature rarely used for brewing any other tea type except black. The best water temperature for brewing white tea is from 80 to 95 degrees Celsius, 60-85 for green, and 85-95 for black. The brewing time will have a big impact on the total level of caffeine in a cup of white tea too. 5 minutes steeping will extract almost double the amount of caffeine than a 1 minutes steeping[9]. Re-steeping of tea leaves will lower caffeine content in each additional cup, white still offering a great flavor. However, simply washing out the tea leaves with hot water will not make your tea decaf. If you brew your tea using western technique, refrain from washing the leaves, unless you want to end up with a flavorless dull cup of tea.

Flavor-wise, caffeine is bitter. However, it’s not influencing the bitterness of tea like catechins do. Most of bitterness in tea won’t come from caffeine, making bitterness an unreliable factor for judging the total caffeine content of your cup. You can’t use color for guessing caffeine levels either. White color of white tea and red color of black tea have nothing to do with caffeine content.

Is caffeine bad for you?

Caffeine is not necessarily bad. Unless you are strictly forbidden to take any caffeine or are over-sensitive, there may be some caffeine benefits in your cup of real tea. Small doses of caffeine (20-200mg) per day may be beneficial in treating depression, headaches, prevent caries and increase focus[10]. Research showed that drinking green tea containing both caffeine and catechins increased energy expenditure compared to the caffeine alone[11].

Pregnant and breastfeeding women need to pay extra attention and limit their intake to max 300 mg or less per day. That means, sometimes even up to 10 cups of tea per day would be acceptable for a healthy grown-up. The best suggestion would be to try with one cup at a time and add more tea to your diet if there are no side-effect. Keep in mind that everyone is different and reaction to caffeine and other tea compounds will be different in every person. Consult your doctor if you have any serious conditions or worry about safety of tea and caffeine intake.