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Green tea: Health benefits, side effects, and research
Green tea, native to China and India, has been consumed andhailed for its health benefits for centuries globally, but has only recently gained popularity in the United States.
Tea is the most consumed beverage in the world behind water. However, 78 percent of the tea consumed worldwide is black and only about 20 percent is green.
All types of tea, except herbal tea, are brewed from the dried leaves of the Camellia sinensis bush. The level of oxidation of the leaves determines the type of tea.
Green tea is made from unoxidized leaves and is one of the less processed types of tea. It therefore contains the most antioxidants and beneficial polyphenols.
Fast facts on green tea
Here are some key points about green tea
- green tea has been used in traditional Indian and Chinese medicine
- there are many different types of green tea available
- green tea may help prevent a range of ailments including cancer
- more research is needed to prove many of the health claims surrounding green tea
Green tea health benefits
Recent studies have shown green tea can potentially have positive effects on everything from weight loss to liver disorders, type 2 diabetes, and Alzheimer's disease.
Green tea and cancer prevention
According to the National Cancer Institute, the polyphenols in tea have been shown to decrease tumor growth in laboratory and animal studies and may protect against damage caused by ultraviolet UVB radiation.
In countries where green tea consumption is high, cancer rates tend to be lower, but it is impossible to know for sure whether it is the green tea that prevents cancer in these particular populations or other lifestyle factors.
Some studies have also shown the positive impacts of green tea on the following types of cancer:
- breast
- bladder
- ovarian
- colorectal (bowel)
- esophageal (throat)
- lung
- prostate
- skin
- stomach
Researchers believe that it is the high level of polyphenols in tea that helps kill cancerous cells and stop them from growing. However, the exact mechanisms by which tea interacts with cancerous cells is unknown.
However, other studies have not found that tea can reduce cancer risk. The amount of tea required for cancer-preventive effects also varies widely in studies - from 2-10 cups per day.
In 2005, the Food and Drug Administration (FDA) stated, "there is no credible evidence to support qualified health claims for green tea consumption and a reduced risk of gastric, lung, colon/rectal, esophageal, pancreatic, ovarian, and combined cancers."