Tea is one of common source of caffeine, different from coffee; its effect on human body tends to be more milder and gradual. At a given weight, tea contains more caffeine than coffee, but this doesn’t mean that a usual portion of tea contains more caffeine than coffee because tea is usually brewed in a weak way.
Some kinds of tea, such as oolong and black tea, contain higher level of caffeine than most other teas. Among six basic teas (green, black, yellow, white, oolong, dark), green tea contains less caffeine than black tea and white tea contains less than green tea. But many studies found that the caffeine content varies more among individual teas than it does among broad categories. Generally, the levels of caffeine content in different parts of one tea plant can vary much. Because caffeine is a natural substance the younger leaves have more caffeine than the more elder tea leaves.
Different parts of tea parts have different levels of caffeine content, tender leaves and buds contain more caffeine than elder leaves and stems
Taste of caffeine
One outstanding feature of caffeine lies in its intolerable bitter taste. This is the reason why there are hints of bitterness lingering inside your oral cavity when drinking teas or coffee. The amino acid and tea polyphenol included in tea leaves can decrease the bitterness to some extent. So for a certain kind of tea, Longjing tea as an example, its younger leaves taste more fresh even though they are higher in caffeine when compared with mature elder leaves low in caffeine.
Similar to Amino acid and tea polyphenol, the distribution of caffeine are decided by several factors such as environmental conditions, proceeding methods, temperature, etc.
Below are some information goes more into detail and can help you to get a better understanding of them.
1. Teas made form tender young leaves or buds tend to have more caffeine content, in other words, more mature leaves are low in caffeine.
2. It was investigated that tree species also make a big difference. Large leaves teas accumulate more caffeine when they grow.
3. Temperature: Tea plants grow fast in hot summer days and accumulate a large amount of caffeine. So it is no surprise that teas harvested in summer have a bitter and astringent taste somewhat like bitter coffee. When at 178℃, pure caffeine( white odorless power) can turn into gas and volatilize into open air. Some Chinese green teas processed by traditional methods have lesser caffeine content (here kill-green is done by moderately heating tea leaves).
The Effects of Caffeine on Body
Caffeine is probably the most widely used drug. It affects our central nervous system and makes us awake. It is rapidly absorbed through the stomach lining, and reaches the bloodstream in within 30-45 minutes. It becomes equally distributed throughout the water of the body, later being metabolized in the liver and expelled via the kidneys.
Caffeine, a mild stimulant, also provides benefits: It's been linked to lower risks of Alzheimer's disease, for example. But when it comes to caffeine, there really can be too much of a good thing. Those who study caffeine's lesser-known effects point to studies that indicate it can be worrisome for people with high blood pressure, diabetes and osteoporosis. Plus, caffeine can interact poorly with some common medications, and it can worsen insomnia, anxiety and heartburn.
Other effects of too much caffeine:
It increases anxiety and disrupts sleep patterns, leading to a vicious cycle of restless sleep, relying on caffeine to help with daytime fatigue, followed by more insomnia.
Caffeine interacts with some medications, including thyroid medication, psychiatric and depression drugs, the antibiotic Cipro and the heartburn drug Tagamet.
It increases blood sugar levels, making it harder for those with type 2 diabetes to manage their insulin, according to a number of studies; it also can slightly raise blood pressure. If you have difficulty controlling either your blood pressure or diabetes, switching to decaf may help.
It is also known that caffeine content in tea metabolizes differently in the body than the caffeine in coffee. This is mainly explained by the fact that tea contains a large amount of tannins that slow the absorption of caffeine. Especially green tea contains large amounts of catechin tannins (10-25%). A cup of tea contains lesser amounts of caffeine than coffee, but the tannin content is much higher. Tannins are known to have anticancer and carcinogenic properties and decrease the digestibility of proteins.