Green Tea: Health Effects

Green Tea:  Health Effects

Green tea contains salubrious polyphenos, particularly catechins, the most abundant of which epigallocatechin gallate, which is a potent antioxidant and therapeutic for cancer.  Green tea also contains carotenoids, tocopherols, ascorbic acid (vitamin C), minerals such as chromium, manganese, selenium or zinc, and certain phytochemical compounds.  It is a more potent antioxidant than black tea, although black tea has substances which green tea does not such as theaflavin.

In vitro, animal, preliminary observational, and clinical human studies suggest that green tea can reduce the risk of cardiovascular disease, dental cavities, kidney stones, and cancer, while improving bone density and cognitive function. 

Green tea consumption is associated with reduced heart disease in epidemiological studies.  Animal studies have found that it can reduce cholesterol.  However, brief human trials have found that tea consumption did not reduce cholesterol in humans.  In 2003, a randomized clinical trial found that a green tea extract with added theaflavin from black tea reduced cholesterol.

A study performed at Birmingham University, showed that average fat oxidation rates were 17% higher after ingestion of green tea extract than after ingestion of a placebo.  Similarly, the contribution of fat oxidation to total energy expenditure was also significantly higher by a similar percentage following ingestion of green tea extract.  This implies that ingestion of green tea extract can not only increase oxidation during moderately intensive exercise but also improve insulin sensitivity and glucose tolerance in healthy young men.  Green tea is also effective in preventing glaucoma or systolic and diastolic blood pressure.