With cancer rates set to double by the year 2020, it makes sense to do anything we can to reduce our risk. The World Health Organisation has declared that perhaps 70 p.c. of cancers are diet-related. Over the last decade there has been growing interest in the cancer-protective properties of certain foods and drinks. One foodstuff which has been the subject of particular interest in this respect is green tea ” a popular beverage in both China and Japan. Research published in this month’s edition of the International Journal of Cancer shows that drinking green tea helps reduce inflammation in the stomach (gastritis) which may, in turn, protect against development of cancer here. This latest research supports already existing evidence for green tea’s cancer-protective effects. In addition, other studies suggest drinking green tea may protect against conditions such as heart and liver disease too. The balance of evidence does appear to show that significant health benefits may be had by incorporating green tea in the diet.
Green tea is prepared by drying leaves harvested from tea plants (Camellia sinensis). Green tea differs from black tea ” the variety predominantly drunk in Britain ” in that it is not fermented prior to drying. Green tea is popular in the East, where it has been used medicinally for more than 5,000 years. Green tea is rich in a class of substances known as polyphenols. These polyphenols have ‘antioxidant’ action in the body, and therefore help to quench damaging molecules known as ‘free radicals’ which are believed to promote illnesses such as cancer and heart disease. The antioxidant potential of green tea’s constituents have been shown to be up to five times more powerful than better-known antioxidants such as vitamin C and E. The fermenting process which converts green tea into black tea appears to reduce polyphenol content by up to 90 p.c., which is why green tea may offer significant health benefits over black tea.
Green tea’s chief antioxidant is believed to be a compound known as epigallocatechin gallate (EGCG). EGCG appears to have ability to suppress many different elements of the cancer-forming process. Work published in the medical journal Mutation Research in 1998 found that drinking more than 10 cups of green tea a day significantly delayed the development of cancer compared to drinking less than three cups a day. In women, cancer onset was delayed more than seven years. Men saw a more modest but still significant delay in cancer development of more than three years.
To date, there have been more than 30 studies which have examined the effect of consuming green tea on cancer risk. As with many areas of science, not all of these studies have been positive. However, the balance of evidence does suggest that green tea can help protect against several different forms of cancer including those of the colon, stomach, oesophagus (gullet), bladder and pancreas.
Green tea drinking is also associated with changes in the blood which might help protect against heart disease. In a study published in the British Medical Journal in 1995, individuals who consumed the most green tea were found to have lower levels of cholesterol and other unhealthy blood fats known as triglycerides. Importantly, green tea consumption also seemed to raise the level of high-density lipoprotein (HDL) cholesterol ” the ‘good’ cholesterol which is associated with a reduced risk of heart disease and stroke. Research published in the Journal of Nutritional Biochemistry last year, green tea extract was found to protect cholesterol from biochemical changes (oxidation) which are believed to contribute to it’s potential to promote heart disease.
Another organ which green tea consumption may benefit is the liver. When assessing liver function, doctors generally order blood tests which evaluate the level of substances called liver enzymes. These enzymes are commonly be elevated in liver disease. There is some research that green tea consumption reduces the level of liver enzymes, which suggests that green tea may have some liver-supporting properties.
Green tea contains stimulants such as caffeine and theobromine, and these may have side effects if taken in excess. Common problems associated with the excessive consumption of these stimulants include digestive discomfort and insomnia. While it does appear that green tea offers significant health-giving properties, it is also prudent to keep in mind these potential hazards. Anyone experiencing such symptoms would do well to reduce their consumption of green tea