We've heard of the benefits of green tea but what about the evidence. The scientific community has shown strong interest in uncovering just what the benefits might be. Some have been cautious and say that there is limited long term evidence that green tea can combat certain diseases (1).
However, a recent study (reported on the ScienceDaily site) has found green tea improves the risk factors involved in heart disease (2). Drinking green tea improves the way cells in the lining of the circulatory system work. These cells are called endothelial and if they are not working well, then atherosclerosis may take hold. So the function of the endothelial cells are an indicator of cardiovascular risk.
A team of researchers at the Athens Medical School (Greece) led by Dr. Nikolaos Alexopoulos conducted a trail where volunteers had their brachial artery measured after consuming green tea, caffeine and hot water. The brachial artery was measured for the amount it had dilated. Dilation occurs when there is an increase in blood flow, and increased blood flow is good news.
Dilation was significant after drinking green tea, while it wasn't after drinking hot water or caffeine. It is known that black tea also impacts positively on endothelial function, but green tea is likely to have stronger antioxidants as it undergoes less oxidisation during processing.
What is positive for us is that antioxidants reverse the effect of oxidisation in the human body. This has to be good for many diseases. In fact another study mentioned in the ScienceDaily report (ibid) showed that damage to the endothelial cells caused by smoking can be reversed by green tea. Overall tea drinking is linked to reduced cardiovascular problems and mortality rates.
Another study, whose researchers were motivated by the value of green tea in oral hygiene, has looked at antibacterial activity in inhibiting bacteria (2). A bacteria called DNA gyrase locates a site or binds itself to a location. Drugs cannot be used to remove the bacteria because of serious side effects.
A team of researchers at the National Institute of Chemistry in Ljubljana (Slovenia) found that green tea catechins, in particular one known as EGCG (short for epigallocatechin), are able to target the DNA gyrase. The benefit of green tea, according to the lead researcher Roman Jerala, is its safety record as opposed to toxicity associated with drugs (3).
Further related research has found that green tea helps overcome the resistance of certain bacteria to antibiotics. Dr. Mervat Kassem from the Faculty of Pharmacy at Alexandria University in Egypt found that drinking green tea at the same time as taking the antibiotics improved the efficiency of the drugs to kill the bacteria including the strain of superbugs (4).
The antioxidant levels of green tea is reported to be a hundred times that of vitamin C and 25 times that of vitamin E. It is the catechins that are the most effective antioxidants in the tea. If these have the potency to reverse damage to cells, what other effects does green tea have? The cautions showed by some are valid; but they are a little behind given the conclusions of the recent research which has positive news about the benefits of green tea.