A Closer Look: Brewing vs. Caffeine

Can YOU affect the CAFFEINE in your Cup of Tea? 

YES, you can! In general, articles or blog posts about this topic only talk about the amount of caffeine contained in a cup of tea.1 What is not often addressed is how caffeine level can VARY GREATLY depending on how you brew the tea.

Brewing conditions include tea leaf to water ratio, water temperature, brewing time, number of brews, etc. The effect of tea leaf to water ratio is obvious – the more tea leaves used, the more caffeine in your cup of tea. 

Water temperature can make a huge difference! The dissolution rate of caffeine increases as water temperature increases. So caffeine dissolves readily in hot water. According to a study conducted by Taiwan’s tea research agency2, for all types of teas tested, the amount of caffeine in a cup of tea brewed at 100oC (212oF) was at least double the amount when brewed at 80oC (176oF).  

Longer brewing time also allows for more caffeine to dissolve into tea.  

For multiple brews using the same tea leaves, the caffeine level decreased but caffeine continued to dissolve into the tea. In the study, green tea (every brew was 5 minutes) was used as an example. The caffeine amount in the second brew was 75% of the first brew; the third brew was 30% and by the fourth brew, it was only 9%.  

In contrast, cold-brew3 tea contained low levels of caffeine. In the study, green tea was cold-brewed for 2 and 4 hours respectively. For both these cold-brewed teas, the combined amount of caffeine for the first three brew was lower than the amount in the first brew tea using hot water. 

Many tea drinkers in the U.S. are concerned about the caffeine in their cup of tea. Based on these results, if you are concerned about caffeine intake from tea4, you can use lower water temperature to brew your tea or switch to the cold brew method. Another option would be to consume less from the first few steeping of tea brewed with hot water. 

Please remember, however, there is a flip side to these methods. Caffeine is not the only solid that dissolves in hot water. Using lower water temperature may significantly weaken a tea’s flavor profile. As always, experiment a little to find the right balance for yourself.

If you are interested in another closer look at caffeine, stay tuned to our next post: Factors affecting Caffeine in Tea Leaves.  



* 1: According to Mayo Clinic, there are 25-48 mg caffeine in 8oz of brewed black tea, and 25-29 mg in the same size of brewed green tea.

*2: The research agency’s name is TRES [Tea Research and Extension Station]. For the study, the standard brewing method was used (3 grams tea to 150 ml water, steeped for 5~6 minutes) and applied to all major categories of tea sold in Taiwan.  

*3: Cold-brew tea – tea brewed by infusing tea leaves with room temperature water, then placing it in refrigeration. Depending on the recommended brew time, the tea leaf to water ratio can be 1:50 to 1:100. The cold-brew method is an especially wonderful way to make refreshing drinks during hot summer days! 

*4: According to U.S. FDA recommendations, healthy adults can consume up to 400 mg of caffeine daily without negative effects on health. [Taiwan’s FDA recommends 300 mg of caffeine.] That is about 3.5 cups of coffee. Tea has less than half of coffee’s caffeine. Furthermore, the amino acid theanine in tea acts synergistically with caffeine to create a calming-alert state of mind. However, if you consume both coffee and tea, or if you enjoy strong and heavily-brewed tea, it would be advisable to watch your daily caffeine intake.