Caffeine and Tea

Monday, Apr 30, 2007

Perhaps it’s 10 PM and you really want a pot of your new Russian Caravan black tea . . . sans caffeine. Or maybe you got some amazingly fresh Organic Darjeeling Makaibari from a friend who visited India . . . right before you found out you’re pregnant. Or it could be that you love teas that are not decaf or naturally caffeine-free but can’t take the caffeine without your stomach hating you, your neuroses running wild or your muscles tensing up like a rubber band about to snap. For whatever reason, you want little or no caffeine. Read on, my friend.

How Much Caffeine is in Coffee, Tea, Cola & Other Drinks (on my other site, About.com Coffee/Tea)
Factors Influencing Caffeine in Tea (also on About Coffee/Tea)
Caffeine 101
Caffeine in Tea: How It Works
Caffeine Contents in Tea
Caffeine-Free vs. Decaf
Making Decaf
Tisanes (Herbal Teas)
Recent Technological Innovations in Caffeine


Caffeine 101

Caffeine is a naturally occurring chemical compound that can be found in 60 plants from around the world. The best-known of these plants are camellia sinensis (the tea plant), coffee, yerba mate, cocoa, and kola nut. It is often extracted from coffee and tea to produce "decaf" versions of the beverages. The byproduct from this process, extracted caffeine, is used in most caffeinated sodas.

Caffeine is a stimulant that is quickly absorbed into the bloodstream and assimilated into the system. It causes an increase in alertness and energy levels for a short period of time. Its chemical structure is similar to adenosine, which triggers a decrease in cell activity, or a feeing of tiredness. It blocks the brain’s adenosine receptors, tricking them into speeding up activity rather than slowing it down. (They don’t recognize the caffeine itself, but react to the LACK of adenosine.) Also, where adenosine would dilate blood vessels, caffeine causes them to constrict. When cell activity speeds up rapidly, the pituitary gland interprets the neural firings as an emergency and releases epinephrine (a.k.a. adrenaline). Adrenaline, in turn, increases your heart rate, blood pressure and blood sugar levels while dilating your pupils and breathing tubes and tensing your muscles. The result? You feel excited, alert, and ready to go . . . but not for long. Your body responds to the increase in blood sugar by releasing insulin. If your blood sugar levels were rising rapidly (as they tend to do with the rapid absorption of caffeine), then the body tends to overreact. It sends out too much insulin, resulting in LOWER blood sugar levels than BEFORE you consumed the caffeine, as well as the craving for MORE caffeine.

Caffeine also alters the body’s response to dopamine, a neurotransmitter that activates the pleasure centers in the brain, by increasing its content, then slowing its rate of up re-uptake. (That means you feel happy at the time, but it’s harder to reproduce that feeling later without taking more and more caffeine to get it.)

Together, these factors mean that caffeine is (according to Johns Hopkins University, anyway) addictive and dangerous. Duke University has also published studies on its dangers to blood pressure and stress levels.

For more information on the effects of caffeine, read How Stuff Works’ take on it and the University of Texas’ blurb on caffeine and the brain, or watch this entertaining BBC video about caffeine and mental performance (scroll to the bottom).


Caffeine in Tea: How It Works

So, it sounds like caffeine is a terrible thing and everyone should avoid it, right? Strangely enough, it is widely reported that drinkers of tea experience a different effect than drinkers of other caffeine-containing beverages. Tea drinkers describe an energy "plateau" that has a gradual increase, sustained high, second energy boost, and gradual return to a "normal" energy level. Coffee and soda drinkers, on the other hand, describe an energy "spike" and subsequent "crash" resulting in a lower energy level than they originally had. Hippie talk? Maybe. Easily explained by the fact that coffee (usually) has more caffeine than tea? Not really. Not enough research has been done for us to fully understand (or agree on) why this is, but my thoughts on the matter are this: In freshly brewed tea, the caffeine binds to the tannins (a.k.a. catechins, a type of polyphenol) and L-theanine when it is brewed. The bond requires more time to metabolize than unbound caffeine, so the absorption of caffeine into the bloodstream is slower and more gradual than it is with coffee and caffeinated sodas. (L-theanine also has some other really cool benefits, like stimulating alpha wave production and GABA formation to induce an alert yet euphoric state.) Meanwhile, the body is absorbing L-theophylline, a naturally occurring substance in tea that produces similar effects to those of caffeine, but with a slower absorption rate. After absorption, caffeine’s effects last about 4 hours, L-theophylline, about 8 hours, and the L-theanine, 8-10 hours. This means that you are left with a calm, gentle return to your original energy level. Coffee is different from tea in that its caffeine is quickly absorbed, causing an increase in adrenaline (and stress) levels and resulting in a icky feeling when it wears off (often referred to as a "crash"). For more information about the chemistry behind caffeine, read this article.


Caffeine Contents in Tea

Generally speaking, herbal teas have no caffeine, white tea has a little caffeine (about 15 mg per 8 oz), green tea has more than white (20-40 mg), oolong has more than green (about 30) and black has the most (40-70). (Coffee has about 80 mg per 8 oz., and we already know that those 80 mg may be processed VERY differently from the caffeine in your tea.) There are many factors in a tea’s caffeine content, so this is a very loose guide. The main stages to consider can be separated into three major areas: growing, processing and brewing.

Growing

A number of factors involving the growing of your tea will influence its caffeine content. You must consider the type of plant that is being grown and the growing conditions.

All true teas (white, yellow, green, red, oolong, black and puer) come from the same plant, camellia sinensis. There are different varieties of this plant, each one with a different caffeine level. The more prevalent Chinese variety (C. sinensis var. sinensis) contains the least caffeine (1-3% dry weight) and the Indian Assam variety (C. sinensis var. assamica or C. assamica) contains the most (3-5% dry weight). In between the two is the unusual Cambodian variety (C. sinensis var. parvifolia), which is considered to be a hybrid between the other two varieties. The fact that the Assamica variety is most often used for black tea helps to explain why black tea usually has more caffeine than the other teas. It is also worth noting that Assam teas (usually grown in India, South America and Africa) are lower in the tannins that retard the absorption of caffeine (see above).

Other "teas" (such as chamomile, lavender and rooibos) are actually tisanes, a.k.a. herbal teas.

Growing conditions also play a major role in determining caffeine content. A prime example of this is the highly prized Japanese gyokuro green tea. Several weeks prior to harvesting, screens are placed over the tea to block out the majority of the sunlight. The leaves are accustomed to more sunlight and increase their chlorophyll content significantly to offset the imbalance they are experiencing. The increase in chlorophyll then alters the levels of the plant’s sugars, amino acids and, of course caffeine. Other environmental factors that may influence caffeine are rainfall, mineral content in the soil and water, temperature and exposure to the sun (in terms of time and intensity).


Processing

The part of the plant that is being harvested makes a difference, too. Very young leaves are higher in caffeine than older growths on the plant. In dry weight, the bud and the two leaves closest to it contain about 5% caffeine, compared to 3.5% in the next set of leaves, 2.5% in the upper stem, and 1.4% in the lower stem. Since white tea is usually picked from the youngest leaves, some white teas may be higher in caffeine than some green teas.

Many also say that broken tea leaves (the kind most often used in tea bags) release more caffeine than their whole leaf counterparts. It’s not that, per se. It’s really that broken tealeaves have an increased surface area, which causes them to lose flavor rapidly. Tea baggers compensate by using more leaves per serving, thus increasing the caffeine content.


Brewing

This is the factor you can control the most. Your brewing conditions can cause the same tealeaves to release more or less caffeine. Higher heat, longer brew times, more leaves and less water will all increase your caffeine content. The opposite conditions will decrease your brewed tea’s caffeine levels. Earlier infusions have significantly higher caffeine contents than later ones. You can use this fact to decaffeinate your tea.


Caffeine-Free vs. Decaf

Although people commonly use "caffeine-free" and "decaf" as synonyms, they are NOT the same thing. Likewise, there’s a difference between something that is "caffeinated" and something that "naturally contains caffeine."

"Caffeine-free" means the product does not contain any plants that naturally contain caffeine and no caffeine has been added to it. It never had any caffeine in it before and it does not now.

"Decaf" means that most, but not all of the tea’s caffeine has removed. In many countries, there are legal limits on the remaining caffeine content in "decaf" products, though there has been some controversy over whether or not these laws are adhered to, particularly with regard to instant (bagged) tea. (Bagged teas usually contain broken leaves and tea dust, which release more caffeine than whole leaves. In other words, if you have a teaspoon of broken leaf tea and a teaspoon of whole leaf tea with the same caffeine content, they will brew cups of tea with different caffeine content.)

So, if you’re fine with a little caffeine, decaf is OK for you. If you want a truly caffeine-free tea, stick with tisanes (herbal teas).


Making Decaf

UPDATE: The paragraph below is a very common claim in the world of tea. However, it has been disproven. Please do not heed the caffeine advice below!

It is possible to reduce your tea’s caffeine content by about 80% on your own. Just warm an extra cup of water to your brewing temperature or slightly higher, then brew the leaves for 1 minute. Pour out the water, and then start brewing all over again with fresh hot water. Most of the caffeine is removed in the first minute, so your brew will get only part of the remainder. A small amount (about 5%) of the essential oils and polyphenols are removed, but if you don’t want the caffeine, it’s probably worth it.

Tisanes (Herbal Teas)

Tisanes, commonly known in the U.S. as herbal teas, encompass a wide range of types and parts of plants. Common tisanes include chamomile, peppermint, verveine, lavender, ginger and rooibos. There are 60 caffeine-containing plants in the world. All tisanes are naturally caffeine-free unless they contain one of those 60 plants. The most common of these plants, as they relate to tisanes, are yerba mate (which may be blended with other tisanes or served on its own) and cocoa (which is sometimes used to flavor teas and tisanes).


Recent Technological Innovations in Caffeine

Here’s an abstract for a new (and improved!) caffeine extraction method for tea. Here’s Wired Magazine’s blurb on Japanese scientists’ isolation of the caffeine synthase gene, which is what causes caffeine production in coffee, tea and the other 58 plants that naturally contain caffeine. They think it can be suppressed to make naturally caffeine-free coffee and tea with the full flavor associated with the real thing. Cool!


Enjoy your tea (or tisane)!