Tea 101
What Is In Tea? – Pt. 1 Caffeine, Antioxidants, & More

What Is In Tea? – Pt. 1 Caffeine, Antioxidants, & More

Tea is a fascinating beverage. We all know & love our favorite teas for the flavor, but tea is so much more than just a tasty cuppa, it is a full on body experience!

I personally got into tea because of what was in it versus the actual flavor. Back in high school I was up early for practice & stayed after school for practice, all while trying to maintain my focus in class. I wanted a small boost of for my day but knew I wanted to avoid coffee. After talking with a few family members & looking into it myself, I found that green tea seemed to fit my desires! It not only met my energy desires, but kick started a lifelong passion!

Before jumping into the nitty gritty, it is important to note that whenever you brew a cup or pot of tea you are performing a small chemistry experiment. This means that time, temperature, type, amount, etc. all make a difference on what will ultimately be in your cup. All tea comes from the same plant. That plant is known as Camellia sinensis. This is important to note because whether you drink green, black, oolong, or white tea you will be getting the same compounds, but different quantities. Tea truly is a science!

This article will provide a general idea of what tea contains & will help layout the answers to the question, “What is in tea?”. It will discuss the commonly known constituents, while also diving deeper into the less common compounds!

This is part 1 of a 2 part series!


You may be saying, “Woah…I thought we were talking about common compounds???”, well this is! This is actually the group that caffeine belongs in! Methylxanthines include caffeine, theophylline, & theobromine.

Tea contains all three of these compounds with theophylline being the highest in quantity. Theophylline does not act as a high stimulant like caffeine does. This was why tea was perfect for me, someone looking for a small boost of energy!

Caffeine is one of the most misunderstood compounds in tea. A common myth is that in order of LEAST caffeine to MOST caffeine it goes white, green, oolong, black. In reality however there is a lot that goes into just how much caffeine will be in your cup, like time & temperature. Although the quantities may vary, caffeine will be present!

These compounds provide stimulation to the mind & body & may be the reason tea has been tied to boosting metabolism. They also give tea the slightly bitter taste it has. Roughly 2% to 5% of the dried leaves composition is made up of methylxanthines.


Love our cuppa polyphenols!

You may have heard about all the wonderful health benefits found in tea. You can thank this wonderful group for that! Polyphenols make up about 30% to 40% of the dried leaves composition. They are responsible for the astringent taste that may leave your mouth feeling dry. They are actually produced by the tea leaves as a defense against insects & animals!

In tea, we can find around 30,000 different types of polyphenols…wow! While that is a lot, the most important one to focus on are flavonoids. This group of polyphenols is responsible for all the claimed yummy healthiness of tea. Specific types of flavonoids found in tea that you may have heard of are catechins & EGCG. EGCG is the most active & studied flavanol.

When the tea leaves are oxidized to make the different types of teas, the flavonoids undergo a chemical conversion & form into theaflavins & thearubigins. These create those robust & deep flavors & colors in black & pu’erh teas.


Oxidation is the process of subjecting tea leaves to oxygen & thus providing a chemical alteration within the leaves. Depending on how long the leaves are subjected to oxygen will depend on how great of a change occurs. The reason this oxidation occurs so quickly is due to enzymes, more specifically polyphenol oxidase & peroxidase.

These two enzymes are the reason tea leaves brown! You may also know them for the browning of your fruits & veggies. Have you ever baked apples & notice they do not brown? Well that is because you can denature these enzymes with heat & therefore halt the browning process! This is the same process with green tea & why those leaves remain green. Ultimately, the two ways to denature these enzymes is via heat addition (>150 degrees F) or by eliminating moisture in the process.

Polyphenol oxidase & peroxidase are important for the unique variety found in tea!

Amino Acids

L-Theanine, the powerful tea amino acid!

Tea plants are a unique vegetable that contain a high amount of specific amino acids. The reason being is that many teas are shaded near the end of their growing season for 7 to 22 days. Sunlight converts amino acids to polyphenols. By shading the plants, this boosts the amino acid content by up to 4 times the amount as compared to non-shaded plants!

The amino acids found in tea provide some awesome benefits, but also give tea a unique flavor profile. Green tea contains the most amount of amino acids. This provides a sweet brothiness to it also known as umami.

One of the most prominent amino acids is known as L-Theanine. Most commonly found in green tea, especially matcha. Caffeine in combo with L-Theanine gives you a feeling of “calm focus“. The caffeine boosts energy, while the L-Theanine relaxes the mind.

Want to learn more about L-Theanine? Check out the Fresh Steeps post on this amino acid here!


There is a bunch going on in your cup of tea! Each cup or pot that you brew is like its own chemistry experiment! You can change what happens by altering how long you steep, or how hot you heat the water, what type of tea you use or how much of it. Either way, you will be brewing your favorite cup!

So…what is in tea? Well hopefully this has answered a little of that question! A lot is happening, but it is all necessary for that delicious cup of tea.

This article is part 1 of a 2 part series! Yes, there is more in your tea!!! Want to discover more about what is in tea? Check out part 2 here!

Let me know in the comments what your favorite tea compound is & why!


  1. Tea Compounds
  2. Chemistry of Tea
  3. Tea Nutrition

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