Caffeine is a natural stimulant found in a wide range of foods and drinks including coffee, tea, soda and chocolate. While tea and soda do not contain as much caffeine as coffee, they still have enough to cause physiological effects on the body. Moderate consumption of caffeinated beverages appears to be harmless, but excess caffeine may cause health problems.
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Many people drink beverages with caffeine, including tea and soda, because they boost energy, at least for a short while. Caffeine can help you stay awake, although too much of it may keep you awake past the point at which you are ready to finally get to sleep. Another effect of caffeine is that it acts as a diuretic, causing the kidneys to release more water and making you urinate more frequently. Caffeine also causes your fatty tissue to release free fatty acids into the bloodstream.
Amounts in Tea
Regular black tea contains 40 to 120 mg of caffeine in 8 oz of tea, while decaffeinated black tea has only 2 to 10 mg per 8-oz cup. A 6-oz cup of hot green tea contains about 26 mg of caffeine. One tbsp of generic mix to make iced tea contains 27 mg of caffeine, while the decaffeinated version has only 1 mg. Commercial bottled iced teas contain 15 to 27 mg of caffeine in a 12 or 16-oz can or bottle.
Amounts in Soda
The caffeine content in colas ranges between 35 to 38 mg per 12-oz can. Lemon-lime sodas are typically free of caffeine. Some diet sodas contain up to 47 mg per 12-oz can. A 12-oz can of some specialty sodas may contain up to 71 mg.
People who consume more than 500 to 600 mg of caffeine a day may experience symptoms of nervousness, insomnia, irritability, restlessness, nausea, muscle tremors, headaches, anxiety and a racing heart. If you often drink beverages containing high levels of caffeine, you may experience withdrawal symptoms, especially headaches, when you try to cut back or stop. Withdrawal symptoms typically begin within 12 to 24 hours after the last time you consumed caffeine.
Women who are pregnant or planning on becoming pregnant should limit caffeine intake to under 200 mg per day. More caffeine than this may increase the risk of miscarriage and may cause fertility problems. A single cup of tea or soda will generally be far below this limit. Children should consume no more than 85 mg of caffeine each day. Some people are more susceptible to the effects of caffeine than others and may need to limit their consumption even more.