Health Benefits of Drinking Green Tea: The Science
In Asian, and especially Chinese cultures, legends abound of the health properties of green tea. Some varieties have the reputation of curing all illness, others of sharpening the mind, others of focus and concentration. There are legends of some types of green tea being served to scholars and wise men who visited towns and villages in ancient times; and in the present, some varieties of tea have a protected status and to earn their name they must originate from trees growing in certain areas.
With thousands of years of claims, myths and legends behind it, it’s not surprising that the fame of green tea has spread from the Asian countries where it is grown, to Western countries where it is being embraced with enthusiasm.
But is green tea all myths and legends? Is it simply a drink like any other, for hydration and enjoyment? Or does it really have those outstanding benefits for health and happiness? Here is a round-up of some of the many claims of green tea that are backed up by hard scientific research as well as thousands of years of tradition. There are links at the end of each section that will take you to abstracts of original research that has investigated the properties of green tea scientifically.
Babesia is a parasitic infection of the blood that often occurs in conjunction with tick-borne diseases in humans. Scientists at Obihiro University in Japan conducted an experiment on both cows and rodents whereby creatures infected with Babesia were given an extract of green tea, a substance called EGCG. The researchers found that the parasites were gone completely by the 16th day of treatment with the green tea extract.
The amount of EGCG given to the animals was equivalent to that found in about 4 cups of green tea for people of around average body weight.
Although no human trials have been done, green tea has been shown to be safe even if much higher amounts are drunk.
Researchers at The University of Western Australia found that both black and green tea protect to some degree against cardiovascular disease. Although the researchers were not able to pinpoint the reason why tea exerts this protective effect, they identified various potential areas where tea improves how the immune system works against disease, and how green tea helps our bodies function at their best.
The findings of the research are backed up by very large scale 'population studies' which show that people who consume black or green tea regularly are up to 20% less likely to suffer cardiovascular disease than people in the same population who do not drink tea.
In cases of stroke, and possibly other conditions that attack the brain, green tea has been found to exert a neuroprotective effect. Recovery from stroke has also been found to be faster and more complete in those already drinking green tea before the stroke occurs.
There are many hundreds of studies which show that green tea may prevent some cancers, and may aid recovery from others. The research is at an early stage as yet, and the reasons why green tea might help are still not fully understood, but much of the research in this area focuses on amounts of green tea extracts that are equivalent to drinking a few cups of green tea per day, and many have proposed that it is possibly due to tea’s anti-oxidant and anti-inflammatory effect.
There is growing evidence from research that green tea has a great beneficial effect on lung health, not least on those who either smoke or who are subjected to second-hand smoke, because it helps the body ‘clean up’ and neutralise free radicals – molecules that can wreak toxic damage in our bodies. Interestingly, since green tea has this antioxidant property, it may also help to provide some relief from symptoms of many different conditions that are thought to be worsened by the same mechanism, such as Alzheimer’s, Parkinson’s, Schizophrenia and many more.
At the Karolinska Institutet in Stockholm, researchers found that in an animal model of diabetes, mice fed with an extract of green tea had enhanced glucose tolerance, so green tea may thus offer a dietary method of improving the condition in diabetics. Like most of the research into green tea, research on diabetes is still at an early stage, but the results look promising for the future.
Aiding Modern Medicine
Researchers in Egypt needed to investigate how green tea might affect antibiotics because it is such a popular drink there, and it has quite a wide range of possible effects. The researchers found that antibiotics worked much better at fighting disease in those who regularly drank green tea, and it even made some antibiotic-resistant diseases susceptible again. To my knowledge, there has been no further research yet on this area, although similar results were found by researchers at the Showa University School of Medicine in Tokyo where low doses of antibiotics in combination with green tea were shown to combat H. Pylori – the bacteria responsible for stomach ulcers.
Happiness and Well-Being
Anxiety, Mood enhancement, Focus and Concentration
One of the most important beneficial substances in green tea is called l-theanine (often called simply ‘theanine'). Theanine has been shown to promote relaxation, focus and learning, and has also been linked to other benefits associated more generally with green tea, such as improving the immune system and preventing chronic disease. Whilst theanine as an extract has been studied, it is also thought by many that some of the fabulous effects of theanine in reducing anxiety and enhancing mood, focus and concentration, are due to the combination of theanine with some of the other substances a cup of green tea naturally contains, like EGCG, antioxidants, and low levels of caffeine.
The sun’s rays, in particular UVB and UVA, are responsible for both long-term skin damage – that is, damage that can develop over time into skin cancer – and damage to the eyes that can contribute to macular degeneration, which is one of the leading causes of blindness in older people. EGCG found in green tea has been found in a number of research studies to halt the damage to skin and eyes caused by the sun. Since sun exposure also causes aging of the skin, this protective effect from the sun’s rays may go some way to explaining why green tea also keeps us looking young.
One of the reasons why memory gets worse as we age is because of a build up of toxins and metals in the brain over long periods of time. Green tea is not only excellent at flushing out toxins through its abundance of antioxidants, but it also ‘binds’ to molecules of damaging metals and sweeps them away. Researchers have found that to get – and maintain – this memory-enhancing effect, you need to drink a few cups every day.
A study in Tokyo, at the Health Care Food Research Laboratories of the Kao Corporation, showed that over a three-month period, people who drank green tea high in catechins (the ‘good stuff’ that’s found in large amounts in fresh loose-leaf green tea) lost markedly more weight than people who did not. An additional benefit was found in that those drinking green tea also had decreased ‘bad’ cholesterol levels as well as losing weight.
Osteopenia and Osteoporosis
In women, bone density decreases as we age, and after the menopause we’re at risk of conditions like osteopenia and osteoporosis, conditions that can lead to very fragile bones that break easily. There has been a lot of research on how exercise can help to prevent these conditions, and in particular Tai Chi has been found to help. What is more surprising is that research has also found that the polyphenols in green tea also caused a marked improvement in bone renewal in women with osteopenia over just a one-month period. In a comparison study, Tai Chi on its own improved the rate of bone renewal over a three-month period; green tea improved bone renewal over a one-month period; and further improvement was seen over longer periods. Muscle strength was also improved by both Tai Chi and green tea. The amount of green tea polyphenols given to the women in the study was equivalent to about 4-6 cups of green tea per day.