The truth about green tea
That lovely hot beverage, tea, is one of the most popular liquids regularly consumed by humans. It can give you a “lift”, without the edginess that sometimes accompanies a cup of coffee.
There’s one specific variety of tea called “green tea”, for which many marvelous claims are made. But not all green tea is what it’s cracked up to be and in some cases, it can harm you.
Green teas makes up most of the rest of the tea that’s enjoyed, and it’s widely drunk in almost around the globe. The difference between green and black tea is firstly that they tend to come from different varieties of the tea plant, Camelia sinesis, and secondly, how they are processed.
The green tea leaves do not go through an oxidising process, so the leaves contain so-called “non-oxidised phenolic compounds”, such as catechins, and the teas are lighter in colour. However, the black teas do go through an oxidising process, and so they contain “oxidised phenolic compounds” such as theaflavins and thearubigins, and the final liquid is darker in colour.
So the dried leaves of each contain roughly the same levels of proteins and amino acids (about 19 per cent by weight), fibre and other carbohydrates (33 per cent), fats (7 per cent), pigments (2 per cent) and minerals (5 per cent). The difference is that green tea has no oxidised phenolic compounds, while black tea has about 25 per cent.
You’ve heard of caffeine in coffee an average cup has about 100 milligrams. Black tea has about 55 mg of caffeine, while green tea has about 20 milligrams. But it’s mostly the phenolic compounds that are claimed to be the basis of all those amazing health effects a treatment for headaches, various body aches and pains, and depression, as well as a protector again cancers of the stomach, colon, breast, ovary, bladder and prostate. And just to round things off, green tea is also claimed to protect against osteoporosis and dental caries.
Now about 80 per cent of the green tea is produced in China. A study in 2006 measured lead levels in Chinese green teas. It found that some of them were 50 times the maximum permitted level. This lead contamination is due to China’s massive industrialisation. The lead is absorbed from the soil via the roots, or lands on the leaves from the local environment.
Now some of the chemicals in green tea are quite powerful. So looking not at liquid green tea, but rather at the green tea extract pills sold in health food shops, there are many cases of these pills causing liver damage and visible jaundice requiring hospitalisation.
Americans drink about 10 billion servings of green tea each year in various forms. In 2013, an independent tester of health products of all kinds, ComsumerLab.com, tested green teas.
The pre-prepared bottled green tea beverages were mostly loaded with sugar and extra caffeine and usually didn’t carry the advertised quantities of good green tea chemicals as claimed on the label. The chemical analyses of the loose leaf and tea bag versions of green tea were similar to the prepared beverages but without the added sugar. The surprise was that some of the tea bags delivered 2.5 micrograms of lead per serving.
Now green tea was apparently first brewed way back some 28 centuries before Christ, in the reign of the Chinese Emperor Chen Nung so it has a long history.