Green tea is a drink made from leaves or tea bags and has been consumed since ancient times in Asia. This popular beverage has many health benefits, such as lowering cholesterol and blood pressure levels, improving skin health, fighting free radical damage, and protecting against heart disease. Green tea is also known for its anti-aging properties, helping with weight loss, and increasing endurance. Some studies suggest that it may reduce the risk of cancer, although results are mixed.
Most people who drink green tea experience few or no negative side effects. However, those who are sensitive to caffeine or tannins should be careful about the amount they consume. Caffeine can cause dizziness, nausea, or tinnitus (ringing in the ears). Some people who are taking medications for high blood pressure, such as ACE inhibitors, should not drink green tea because it can lower blood pressure too much.
Green tea can improve working memory, thanks to theanine, a chemical that enhances attention and performance. A 2014 study published in Psychopharmacology showed that subjects who drank green tea extract performed better on tests of working memory than those who drank a placebo. Theanine also enhanced brain connectivity, allowing the different parts of the brain to communicate more effectively.
A growing body of research suggests that green tea can reduce the risk of some types of cancer, including esophageal, breast, colon, and lung cancer. The protective effect of green tea seems to be mainly due to its polyphenols, which inhibit the growth of cancer cells in test tubes and in animals. However, population-based studies have produced conflicting results.
One such study found that people who drank more green tea had a lower risk of esophageal cancer, but another report found that frequent tea drinking was linked to an increased risk. The protective effect of green tea may depend on other factors, such as diet and smoking habits.
Green tea can protect against liver disease and help with digestion, thanks to its caffeine content. In addition to stimulating the metabolism, it has a natural diuretic effect, which helps to flush out excess water and salt from the body. It can be helpful for people with type 2 diabetes, as it can lower blood glucose and triglyceride levels. One study found that the catechins in green tea can improve glucose metabolism in healthy volunteers and diabetic db+/db mice. It can also decrease plasma triglyceride levels in Zucker rats fed a sucrose-rich diet. However, more research is needed to confirm these effects in humans. Moreover, some studies have found that caffeine can increase the occurrence of seizures in people with epilepsy. It is therefore recommended that those with this condition avoid green tea and other beverages containing caffeine. Nevertheless, this shouldn’t prevent them from enjoying the many other health benefits of this drink.