Green tea comes from the same plant, Camellia sinensis, as black tea does. The difference is in the way the two teas are processed. While black tea is fermented, green tea is not. Green tea is made from a variety of tea plants called Camellia sinensis sinensis that is native to China.. It is either consumed as a decoction after steeping or as a supplement.
Several studies have tried to elucidate the effects of green tea on obesity and type 2 diabetes. One study observed 25 communities across Japan, a country known for its high green tea consumption. It concluded that consumption of green tea was associated with a reduced risk of type 2 diabetes.
Another cross-sectional survey of 1210 people found an inverse relationship between green tea consumption and body fat percentage/ body fat distribution.
A 2006 cohort study performed on around 40,500 Japanese individuals aged 40 to 79 years concluded that green tea consumption was associated with reduced mortality because of all causes including cardiovascular disease.
The 2013 study published in Diabetes and Metabolism Journal suggested that that green tea extract may be a useful tool for preventing both obesity and obesity-induced type 2 diabetes.
A meta analysis published in the American Journal of Clinical Nutrition, that comprised of a total of 17 trials totaling 1133 individuals, found that green tea decreased fasting glucose and HBA1c concentrations.
Tea is rich in a number of bioactive compounds, the most active being catechins. Epigallocatechin gallate (EGCG) is the most abundant of all catechins in tea and is believed to be the most active compound showing the beneficial effects of green tea.
EGCG is a potent antioxidant and helps in decreasing oxidative stress, especially oxidative DNA damage. Another study found that the insulin resistance decreasing effects of green tea were due to its ability to increase the expression of specific receptors called glucose transporters. This decrease of glucose transporters was vital to amelioration of insulin resistance.
Another study found that EGCG was able to suppress pancreatic beta cell damage. In type 2 diabetes mellitus, the immune system overproduces chemicals called cytokines which are implicated in the destruction of insulin producing beta cells in the pancreas. EGCG prevented this damage from occurring and is a promising therapeutic agent for preventing the progression of type 2 diabetes.
Green tea extract pills are prepared by extracting the active compounds of green tea leaves and concentrating them either in liquid or powder form.
If you like consuming green tea as a decoction tea, you should drink at least 3 – 5 cups daily or around 1200 ml. This will give you around 250 mg per day of catechins. For diabetes, a dosage of 84 to 386 mg per day of EGCG was found to be effective. You should choose a supplement that provides you with this dose of EGCG. For effective weight loss, you need from 270 to 800 mg of EGCG.
When green tea is consumed as a drink in moderate amounts, it is safe for most adults. If high amounts of green tea are consumed for a longer term, it is possibly unsafe due to the consumption of large amounts of caffeine.
In small amounts (2 cups a day), green tea is safe for pregnant and breastfeeding women. Drinking more than 2 cups a day is possibly unsafe. High consumption of green tea during pregnancy may increase the risk of miscarriage due to high caffeine intake.
Most of the side effects of green tea are experienced due to overconsumption and can be attributed to caffeine.
Green tea has a host of beneficial effects on the overall health of an individual. Studies on the population of South East Asian countries like Japan, Korea, etc. have shown an overall positive public health due to their culture of consuming green tea. In moderation, green tea is an elixir that reduces mortality from various causes, especially obesity and diabetes.
Type 2 diabetes is a dietary disorder and most of its symptoms are due to oxidative stress. These health complications are exacerbated by the consumption of anti-diabetic medication. Dietary supplements such as green tea extract help reduce the oxidative stress as well as the cardinal causes of diabetes.
A holistic diet and an active lifestyle are key to reversing diabetes. Add to it a positive outlook, meditation and yoga and you have a comprehensive regimen to reverse this chronic disease and get back to a healthier self.
1. Effect of green tea on glucose control and insulin sensitivity: a meta-analysis of 17 randomized controlled trials; Liu K1, Zhou R, Wang B, Chen K, Shi LY, Zhu JD, Mi MT., American Journal of Medical Nutrition, August 2013