Black tea is a beverage that is made from brewing the dried leaves of the Camellia sinesis plant in boiling water. This tea, enjoyed hot or cold, contains a considerable amount of caffeine, which is likely effective for improving mental alertness, even for people who are considerably sleep deprived. Black tea is different from herbal teas, which are brewed from other plants, or green tea, which is brewed from the fresh leaves of the Camellia sinesis plant.
Black Tea Consumption
Dr Barry Popkin, PhD, a professor at the University of North Caroline at Chapel Hill, initiated the Beverage Guidance Panel to investigate various features of beverages that Americans regularly drink, including calorie and caffeine content. This panel found that the three most commonly consumed teas are green tea, black tea and oolong tea. Some people drink black tea to treat certain ailments, although the scientific evidence to support the effectiveness of treating health conditions with black tea is not yet conclusive. Black tea is consumed to treat headache, low blood pressure, type 2 diabetes, and gastrointestinal problems, including diarrhea and vomiting. People also drink it as a diuretic, which increases the amount of urine excreted by the kidneys.
Caffeine Content of Black Tea
The Beverage Guidance Panel reports that one cup, or 8 fluid oz., of brewed black tea contains about 43 mg of caffeine. However, this may be a low estimate, as the Linus Pauling Institute at Oregon State University reports that one 8 oz cup of black tea contains between 42 and 72 mg of caffeine. Additionally, MedlinePlus puts the estimate between 40 and 120 mg of caffeine in an 8-oz. cup of black tea. It is important to note that the amount of caffeine in a cup of black tea may vary widely according to time the tea is allowed to brew and the amount of tea used to brew an 8-oz. cup.
Recommendations
The caffeine in black tea is safe when you consume moderate amounts of this type of tea. The Beverage Guidance Panel reports that up to 400 mg of caffeine each day is safe for most people. If it is estimated that a cup of black tea contains 80 g of caffeine in one 8-oz. cup, which is the median estimated value of the range reported by MedlinePlus, then it is safe for you to drink 5 or less cups of black tea a day.
Consequences of Consuming Too Much Black Tea
Consuming too much caffeine may cause certain side effects, some of which are the same as the ones that some people use black tea to treat. For example, more than 5 cups of black tea a day may cause headache, vomiting and/or diarrhea. Additionally, an excess of black tea can cause ringing in the ears, confusion, dizziness and irritability, convulsions, heartburn and tremor.
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