Green tea is a beverage made from the leaves of the Camellia sinensis plant. Unlike black tea, which is allowed to oxidize during the production process, turning the leaves black, green tea is produced by heating the leaves (by steaming or pan-firing them), thus preserving the green color of the leaf and imparting a unique flavor and aroma, which is often described as being grassy.
Green tea is often promoted as a healthy beverage; potential benefits include protection against cancer, benefits for the digestive system, lowering of cholesterol and lowering of the risk of heart disease, and positive effects on the immune system among other benefits. Not all of these benefits have been thoroughly explored scientifically, and it may be that some of the preliminary results are not supported after further study. However, there is a growing body of evidence confirming some of these benefits–particularly the effect of lowering the risk of heart disease.
Does green tea have any side effects?
Although tea has health benefits and medicinal uses, it is consumed primarily as a beverage. Tea, including both green and other types (black, oolong, white, etc.) is generally recognized as safe by the U.S. Food and Drug Administration. Green tea has a notable absence of serious side effects, which is good news for tea drinkers.
However, too much of anything can have downsides and pose health risks, and tea is no exception. All tea naturally contains caffeine, a central nervous system stimulant. Although the amount of caffeine in tea is generally less than that of coffee, the caffeine content varies greatly among different teas, and also depends on how the tea is brewed. The amount of leaf used and the length of time that the leaves are steeped greatly influences the caffeine content of the brewed cup or pot. The caffeine content per 8oz cup generally varies between 15mg and 75mg, but can be higher or lower depending on brewing strength and other factors.
Side effects of Caffeine:
Caffeine is known to have a number of side effects, especially when large doses are involved. The Mayo Clinic recommends avoiding consuming more than 500mg of caffeine daily in order to avoid side effects such as insomnia, nervousness, restlessness, irritability, headaches and anxiety. Very large amounts can also result in gastrointestinal problems, fast or irregular heartbeat, and muscle tremors. Lastly, regular caffeine use can result in dependence (addiction), with mild withdrawal symptoms when discontinued.
It is unlikely that green tea drinkers would consume more than 500mg of caffeine unless they were consuming huge amounts of tea, brewing it very strongly, or consuming it in addition to other sources of caffeine. However, it is important to note that the sensitivity to the side effects of caffeine vary greatly from one person to the next. A few particularly sensitive individuals may find that even a single strong cup of tea makes them jittery.
Other Side Effects of Green Tea:
Side effects can be associated with improper brewing. Unlike black tea, most green tea is best brewed with water that is well below boiling point (160-180 degrees Fahrenheit). Especially in the U.S. and other countries that do not have strong traditions of drinking green tea, people often make this mistake. In many cases, using water that is too hot will result in a cup that is acidic, astringent, or contains unpleasant “off” aromas. Drinking such a cup can contribute to acid reflux (heartburn) and an upset stomach.
Other side effects of green tea are subtle. Tea, especially when made from larger, mature leaves, can contain high concentrations of fluoride. High doses of fluoride can be problematic for health because they can inhibit calcium absorption. There have been a few studies that have explored other side effects but most of the rest of the evidence is conflicting or inconclusive.
Green tea is safe for most people to consume as a beverage; it shows evidence of a number of health benefits, and a noticeable absence of serious side effects. The most serious side effects are due to the presence of caffeine, and are easily avoided by moderate use.