How much caffeine is in black tea?

By Nathan Pulley

How much caffeine is in black tea?  Or better yet, how much caffeine is in tea in general? What are seemingly simple question is quite complicated with no quick and easy answer.

We’ve all heard the saying that black tea has the most caffeine, followed by oolong teas, green teas and then white teas with the least amount of caffeine.  This is a general rule by loose definition that does has some merit, but it really is more myth than fact. While some of the processes that create the different styles of tea do contribute to the amount of caffeine released from the tea leaf, and the brewing variations between tea styles as well, there are many more physical and biological factors that contribute to the final amount of caffeine that ends up in the cup.

The first thing we should look at to answer this question are the three factors that determine the physical and chemical characteristics of the finished leaf. They are the plant variety or cultivar, the terroir (influence on the leaf by the location the tea is grown) and the way the tea leaf is manufactured.

There are over 700 chemical constituents that are found in the tea leaf with caffeine being just one. Each variety and cultivar have a different combination of chemical ingredients within their leaves. According to The Tea Enthusiast’s Handbook there are over 20,000 types of tea, so right from the start our conversation has become complicated. Camellia sinensis assamica produces more caffeine than Camellia sinensis sinensis, and that’s just the tip of the iceberg. You can also factor in the age of the plant and the leaf; the older the tea bush, the greater the amount of caffeine, and the younger the tea leaf, the greater the amount of caffeine.

Let’s move on to terrior, or the influence that the location of cultivation has on the plant. The region the tea is grown, the elevation, time of year, weather patterns, moisture, temperature, soil composition and shade all play a part in the tea leaf. One example of this is that caffeine is bitter and is a natural insecticide, and teas grown in a region that has more insects will produce more caffeine. Also, teas grown in soil with more nitrogen have more caffeine, and teas grown with more shade or less sunshine have more caffeine as well. The Laboratory for Germplasm, Breeding and Molecular Biology at the Tea Research Institute Chinese Academy of Agricultural Sciences is continually studying the variations of the main chemical components in the tea leaf. They have found that in teas grown in China, the average caffeine content was 4.2%, varying from 1.2 to 5.9%. Yunnan province has plentiful high caffeine genetic resource with Fujian province following in second.

The next determining factor is the processing and manufacturing of the tea leaves and how it influences the physical and chemical components of the finished tea leaf.  This is where our long-held beliefs regarding the type of tea come in to play. Tea is made up of compounds that influence the aroma, flavor, and taste of tea, including polyphenols, amino acids, methylxanthines (caffeine), and volatile organic compounds. These are all contained within the waxy surface of the tea leaf and are chemically altered and released during processing. The rolling and cutting of the tea leaf, withering and firing all have an impact of the final chemical composition of what goes in to our cup. The less that a leaf is adulterated, the less caffeine that is drawn. The final size and shape of the leaf has an effect too. The smaller the leaf size, the greater amount of caffeine can be extracted due to larger surface area-to-mass ratio. In the same vein, the more tightly rolled the leaf, the lower the extraction rate since the water has more difficulty penetrating the leaf.

The final factor contributing to the amount of caffeine in your cup is the brewing method. Different teas require varying water temperatures and time to achieve the optimum brew. The hotter the water used in brewing and longer the extraction time both contribute to more caffeine being drawn from the leaf. We again generalize that black teas require both greater temperature and time in brewing compared to oolong, green and white teas, but there is a breadth of variation within each style of tea. For example, some green teas might have a longer brewing time than a first flush darjeeling black tea.

Obviously, the question of how much caffeine do the various types of tea have has a very complicated answer, and the tried-and-true associations to tea types are not what we once believed. We can trust that tea typically has half the caffeine as coffee, and the body metabolizes the caffeine in tea differently than coffee; the process is more measured and over a longer period of time. Ultimately, we should trust our body, and if it tells us we’ve had too much caffeine, then we need to alter the amount or type of tea we’re enjoying.

*This article was guided by content learned through courses from the World Tea Academy. They are experts in the field of tea, and we highly recommend their courses of study.