Caffeine, a naturally occurring stimulant, can be found in many foods and drinks, from coffee to tea, to chocolate and soda. Research in the past focused predominantly on the negative impacts of the amount of caffeine a person consumes, but recent studies suggest that there are positive health benefits as well. While too much caffeine can be dangerous, doctors and nutritionists agree that the average healthy adult can consume 300 to 400 milligrams (mg) daily, or the equivalent of the amount of caffeine in two to three cups of coffee.
Caffeine levels vary between products and even within a single product. For example, an 8-ounce cup of coffee can contain anywhere from 60 to 120mg of caffeine, depending on the type of bean and how it was brewed. An 8-ounce (about 236 ml) cup of tea usually contains 20 to 90mg of caffeine, while an 8-ounce soda has about 20 to 40mg. Remember, of course, that most beverages these days are supersized; a large coffee at a retail coffee shop typically is 16 ounces (roughly 473 ml) of coffee—almost the suggested intake limit for the day.
The effects of caffeine vary greatly depending on the individual. The appropriate amount of caffeine changes based on how it affects each person. For some people, drinking caffeine makes them more alert, while for others it causes insomnia or anxiety.
Recently there has been a great deal of research into the positive health benefits of coffee. Some studies suggest that caffeine consumption can help protect against Parkinson’s disease, gallstones, and cardiovascular problems. Caffeine has also been shown to improve mood, physical and mental performance, and alertness. Caffeine can help relieve headaches as well and is one of the primary ingredients in migraine medications.
Pregnant women usually can safely consume up to 300 mg of caffeine a day. Some studies have shown, however, that a large amount of caffeine may contribute to miscarriages and other birth complications. As such, many women choose to cut out caffeine entirely during pregnancy.
Given all the health benefits, it's important to note there are some health risks to caffeine as well. There are some indications, for example, that even moderate caffeine consumption can increase the risk of osteoporosis. There also are more health risks associated with people who consume more than 1,000 mg per day, including heartburn, bowel irritation, sleep deprivation, and anxiety. Side effects also can occur when consumption is less than the 400 mg-per-day recommended limit; if symptoms such as irritability, shakiness or insomnia occur, it's likely a sign that too much caffeine was consumed.
If coffee or other caffeinated beverages are consumed daily, caffeine addiction also can occur. Research indicates that the level of addiction is minor compared to drug and tobacco addictions, however. The symptoms of caffeine withdrawal can vary and may include headaches, nausea, drowsiness, and irritability. The symptoms may take anywhere from a day to a week to subside after consumption ceases.