What Is The Effect Of Drinking Too Much Green Tea To Our Human Body?

Tea is a favorite beverage for hundreds of millions of people around the world, says the University of Maryland Medical Center. Only water is more widely consumed than tea. Green tea, made from fresh leaves from the Camellia sinensis plant that are steamed and dried, has been shown to have health benefits, but it may also have some negative effects if you drink too much.

Caffeine

Like all teas, green tea contains caffeine unless it is decaffeinated during processing. According to the Linus Pauling Institute, an 8-oz. cup of tea has between 9 and 50 mg of caffeine; for comparison purposes, coffee has 72 to 130 mg per 8-oz. cup. A stimulant, caffeine can cause anxiety, insomnia and agitation, as well as gastrointestinal problems. Higher caffeine intakes have also been linked to increased risk of low birth weight babies and miscarriage.

Kidney Stones

While high fluid intake is commonly recommended in people who have a history of kidney stones, tea has been found to increase the oxalate levels in the urine. Calcium oxalate stones are one of the more common types of kidney stones. There are concerns among some health care professionals that drinking tea can increase the risk of stone development.

Medication Interactions

Green tea can interact with a number of medications or supplements. Among the most important of these, green tea may inhibit the action of adenosine, a heart medication; reduce the sedative effects of benzodiazepines; increase blood pressure in people who take propanolol and metoprolol, and reduce the effects of lithium and clozapine, which are taken for mental illness. Green tea may cause a severe increase in blood pressure in people who take monoamine oxidase inhibitors, which are used to treat depression. Green tea in high amounts can interfere with the anticoagulant Coumadin, making it less effective. According to the Linus Pauling Institute, tea can also interfere with the absorption of iron from plant substances and supplements; a cup of tea can decrease the amount of iron absorbed by about 70 percent.

Cancer

When it comes to cancer, green tea has pluses and minuses. Although green tea shows some promise in various studies on cancer prevention, the University of Maryland notes that at least one large study indicated it may increase the risk of esophageal cancer, and that the stronger and hotter the tea, the higher the risk. Green tea also has mixed results in chemotherapy. The combination of green tea with doxorubicin and tamoxifen showed the drugs were more effective in laboratory tests. But green tea extract can stimulate a gene in prostate cancer cells that may decrease sensitivity to chemotherapy drugs, and the University of Maryland recommends that men receiving chemotherapy for prostate cancer should not drink green tea.

Considerations and Warnings

While the Linus Pauling Institute states that green tea is generally considered to be a safe beverage, there are special circumstances when you should limit your intake or forgo it entirely. If you have specific questions about your medical condition and green tea, it would be wise to consult with a health care professional.