Three cups of green or black tea are very beneficial to your health. It is not very obvious how these teas are interchangeable, but health experts are very confident about their recent discoveries. According to the Health Council of the Netherlands, drinking three or four cups of tea (green or black) might prevent conditions such as heart diseases, diabetes, cancer, dementia and depression.
Drinking tea actually has similar effect to eating high quantities of wild fruits, which are rich in antioxidants. Similar to the proven fact that eating blueberries daily will lower your blood pressure, green or black tea will also lower your systolic pressure by 2mmHG on an average, simultaneously preventing cholesterol from clotting the arteries.
Another aspect worth in mentioning is the effect of black tea on preventing diabetes. It seems that consuming 4 cups of black tea on a daily basis might prevent the risk of developing diabetes by 15%, based on results gathered over 10 years of study.
Black tea is a very strong stimulant, similar to coffee, sometimes containing an even larger amount of caffeine, which absorbs very fast into the organism. This is why, for people who are sensitive to the effects of caffeine, drinking 4 or 5 cups might trigger unwanted adverse effects.
A cup of black tea typically contains 70 mgs of caffeine, so drinking 4 cups every day would amount to 280-300 mgs of caffeine, which may lead to anxiety states, or even panic attacks.
The other studies focusing on black and green tea consumption, were not very conclusive of whether or not drinking black or green tea would actually prevent cancer, or would slow down its development.