Caffeine

Green teas have about a third the caffeine content, by liquid volume, of coffee. Green teas contain two caffeine metabolites (caffeine-like substances): theophylline, which is stronger than caffeine, and theobromine, which is slightly weaker than caffeine.

Potential effects of green tea on health

Green tea consumption is reportedly associated with various health-promoting properties. For example, it has been shown to promote fat oxidation in humans at rest and to prevent obesity and improve insulin sensitivity in mice.

In a recent study performed at Birmingham (UK) University by Michelle C Venables, Carl J Hulston, Hannah R Cox and Asker E Jeukendrup, it was shown 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 proves that ingestion of Green Tea Extract can not only increase fat oxidation during moderately intensive exercise but also improve insulin sensitivity and glucose tolerance in healthy young men.