Antioxidants in Tea

It's commonly known that tea is good for us, but most of us don’t really know why.  One of the primary reasons is antioxidants, and these form the basis for a great deal of ongoing research about tea's health benefits.

Some of the questions we'd like to find answers to include:

  • What are antioxidants and why do we need them? 
  • Do all teas contain antioxidants? 
  • Are some types of tea better for you than others? 
  • Which teas have the highest levels of antioxidants?

Antioxidants and Free Radicals

A discussion of antioxidants requires a basic understanding of free radicals; these require some understanding of chemistry's building blocks. Bear with me—I'll keep it simple so you won’t need to take out your old chemistry textbook to understand it. 

Our bodies are made up of cells that, in turn, are made up of smaller particles called molecules.  Molecules are made up of atoms that are composed of a nucleus, protons, neutrons, and electrons.  Electrons bind atoms together—they are also key to the antioxidant/free radical discussion.

Electrons orbit around the nucleus in even numbers (they like to travel in pairs) in shells.  A shell accommodates a specific number of electrons.  When that number is achieved, the atom is considered stable and is not prone to chemical reactions.  Atoms prefer stability, so they will gain, lose, or share electrons in their outer shell to achieve a stable state.

Sometimes a molecule is left with an unpaired electron.  A free radical is the result of this unstable condition.  Because atoms seek stability, the molecule with the unpaired electron immediately seeks nearby available electrons.  When they steal an electron in order to achieve stability, another free radical is created.  This sets up a domino effect of unstable molecules seeking stability.  Left unchecked, free radicals proliferate, and eventually they begin to negatively impact the functioning of cells.

What causes free radicals in the first place?  Factors as varied as air pollution, exposure to dangerous chemicals, eating processed foods, excessive alcohol consumption, smoking, and overexposure to the sun can all cause free radicals.  Sometimes the cells in our body even initiate the formation of free radicals in order to combat bacteria and viruses. 

We can tolerate a certain level of free radicals in our bodies, but at some point cellular damage occurs.  And this eventually leads to the potential for disease. 

Antioxidants are the solution to the free radical problem.  They are unique in that they are stable regardless of the number of electrons they contain, so they can donate electrons to unstable molecules and stop the free radical cycle.

Increasing the Antioxidants
in our bodies

The plant world provides us a rich smorgasbord of antioxidants with the polyphenols they contain.  Tea is one rich source.  Other foods with an abundance of polyphenols include berries, grapes/wine, olive oil, cocoa, coffee, nuts, legumes, fruits, and vegetables.

Providing our bodies with enough antioxidants reduces the potential for free radical damage.  This is a major reason why scientists and nutritionists encourage us to eat several servings of fruits and vegetables every day.  Vitamin supplements are another common way to add these substances. 

Drinking tea every day can also be an important and enjoyable way to increase the antioxidants in our bodies. 

The Antioxidants in Tea

The antioxidants/polyphenols in tea are also referred to as tannins.  The young shoots of tea plants are composed of about 30 percent polyphenols, and as a result all tea contains some level of antioxidants.  During its processing, tea's polyphenols are either fixed or transformed depending upon the processing method, so different kinds of tea contain varying levels of antioxidant compounds.  Additionally, some growing methods and even types of tea plants can also influence the levels of polyphenols in tea leaves long before processing.

Polyphenols (tannins) are released when we brew tea.  The temperature of the water and the water itself encourage these substances to diffuse into the liquid in our finished cup. 

The polyphenols in tea are called flavonoids.  Flavonoids help determine a tea's color, flavor, and body.  There are two types of flavonoids in tea—flavanol and flavonol.  About 75 percent of the flavonoids in tea are flavanols. 

Within tea's flavanols are substances called catechins.  As much as research can tell us at this point, catechins are considered key antioxidant compounds in fighting free radicals.

Which Tea Has the Most Antioxidants?

Well, that depends… 

Let's stress upfront that research is ongoing to investigate antioxidants in tea.  Part of the difficulty is that we don't know specifically how individual antioxidants behave or benefit us.  Further, tea presents so many variables that replicating experiments and drawing conclusions is difficult.  At this point it's impossible to make any blanket claims about one tea being better than another.  Here's some things we know.

We know that the buds and first leaves of the tea plant are higher in polyphenols than other parts of the plant.  So a case could be made that, from this standpoint, white teas made solely from buds have the antioxidant advantage. 

We also know that more catechins are left intact with the minimal processing that both white and green teas undergo, so a claim could be made that these are the best to drink. 

Are all green teas the same?  Most Japanese green teas are grown from a particular cultivar of Camellia sinensis.  While this plant is higher than others in its amino acid content, it's lower in polyphenols.  Additionally, some Japanese tea is grown in the shade.  This causes an increase in both chlorophyll and amino acid levels but a reduction in polyphenols.  But please, don't dismiss Japanese green teas because of this.  They are most always steamed early in their processing, and this seems to be the best way to retain the leaves' vitamin content.  Surely vitamins count for something! 

We can also make a case for oolongs and black teas being the healthiest.  Both of these undergo a process called oxidation during their manufacture.  Essentially, the same enzymes that are fixed when producing green tea (and usually in white tea) are exposed to oxygen and transformed, first into theaflavins and later during oxidation into thearubigins.  Both of these are also antioxidants.  Theaflavins play a major role in the astringency and briskness of a cup of tea; thearubigins mellow out the taste.

Black teas are fully oxidized, and if done slowly they are high in thearubigins.  Chinese black teas fall into this category while teas with more briskness (including most black teabags) are higher in theaflavins.  Oolongs present an additional challenge in trying to quantify since their levels of oxidation vary widely—some are barely oxidized and are quite similar to green teas while others are much closer to black teas on the scale of oxidation.

Both theaflavins and thearubigins are being researched for their beneficial effects.  Thearubigins, in particular, are thought to have their own advantages over green tea in preventing disease.  Claims are also made that they might even have anti-inflammatory properties.

Other Factors in the Equation

Thoroughly confused?  Many other factors aid and abet in the difficulty of reliably measuring antioxidants in tea. 

Consider that polyphenol content is highest in leaves harvested earliest in the spring, and levels generally decrease later in the season.  Do you know when your tea was harvested?  I rarely do. 

Other factors affecting antioxidant levels that are completely out of our control include where the tea was grown, the weather during the year the tea was produced, which leaves were harvested, or even how the tea plant was pruned.

Factors we do have some control over include the amount of tea we use for brewing, water temperature, and the length of time we steep it.  This is reason enough to heed the brewing instructions on tea packaging (see Water Temperature for Tea) since these optimize the release of the tannins.  

These variables makes conclusive studies difficult since batches of tea have different polyphenol levels during different parts of the growing season and are certainly different from year to year.  And that doesn't take into account differences introduced from variations in brewing.

To make matters even more difficult, humans don't metabolize nutrients in the same way as one another.  So depending upon factors like age, gender, diet, or ethnic background, you may get different benefits from tea than your neighbor.

Final Words about Tea's Antioxidants

Someday we'll have solid answers for the questions about tea's antioxidants and their benefits to us.  In the meantime, I'm quite content knowing that all teas have at least some antioxidants in addition to a variety of other health benefits—some of which already are being studied and those we have yet to imagine.  So to cover all the bases, I'll continue to drink a variety of teas based on my mood, the season, the weather, or sometimes even the day of the week.

We know that tea is good for us—let’s just enjoy drinking it.

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