Green Tea: Would it cause any harm?

Question

I've recently started to drink green tea and I enjoy it a lot. I drink about 3 cups daily but I feel like being kind of addicted to it. I've got an oddly strong desire to drink more like 7 or 8 cups. Is that harmful? Could it hurt me?

Answer 1

Aside from its wonderful taste, green tea (obtained from the plant Cammelia sinensis, (L.) Kuntze, Theaceae) contains caffeine, and this might be the reason for your possible addiction. Studies have shown that caffeine withdrawal symptoms exist and that their intensity is correlated to the amount of caffeine that was being used previously, and the frequency of use. That being said, tea contains other ingredients: catechins, flavonoids, caffeic acid derivatives etc. While tea has been proven to have many beneficial effects (there have been extensive clinical studies in China and Japan, which have proven that tea consumption is correlated with decreased risk of some types of cancer)

7 - 8 cups of tea per day is way too much!

Why? There are two main reasons:

Caffeine

Aside from being addictive, too much caffeine can cause an overdose. Possible symptoms are: restlessness, tremor and elevated reflex excitability. An overdose can also cause headaches or dizziness, abnormal hearth rhythms, dehydration or sleep problems. According to PDR overdose occurs in doses corresponding to 300 mg of caffeine (approximately 5 cups of tea as a beverage). Even in "regular" amounts, caffeine can affect blood pressure, so people with these problems ought to be careful. Tea is, of course, not the only source of caffeine, so when deciding on the daily amount of tea, all sources of caffeine should be taken into account.

Possible anemia

Tannines in tea precipitate iron. If this happens in your digestive system it means that iron becomes insoluble, and cannot be absorbed. This decreases the effective uptake by your body, while regular loss via excretion and desquamation remains the same, so over time you start having less and less iron at your body's disposal, which can lead to anemia. There were several studies that have proven this effect - many were epidemiological and observational. There was a clinical trial involving patients with haemochromatosis which also proved that drinking tea reduced iron absorption from the GIT.

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Possible solutions:

Drinking decaf tea might solve the first problem, but won't solve the second. Moderation is the key. Also, drinking tea with or right after meals (especially those which are the greatest source of iron) should be avoided most of the times. Drinking tea is an indulgent ritual for many, so perhaps switching one or two cups a day for a herbal tea might help.

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An interesting aside: PDR cites studies which have proven that tea mouthwashes can reduce growth of some cavity-associated bacteria and reduce formation of plaque (the 2nd goes for oolong). But tanines can deposit on your teeth causing them to turn yellow, so rinsing your teeth with tea is a double-edged sword.

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References:

1. Caffeine - Medline Plus
2. Caffeine withdrawal - Johns Hopkins Medicine
3. Impact of tea drinking on iron status in the UK: a review.
4. Clinical trial on the effect of regular tea drinking on iron accumulation in genetic haemochromatosis
5. PHYSICIAN'S DESK REFERENCE (PDR) FOR HERBAL MEDICINES, 2nd Edition, Medical Economics Company, 2000