Caffeine stimulates your central nervous system, and is a common ingredient in coffee, tea, chocolate, soft drinks, kola nuts and some medications. For example, medications designed to fight off drowsiness often have caffeine, which is how they increase alertness and boost your energy. Eighty percent of adults in the U.S. consume caffeine every day, according to the U.S. Food and Drug Administration.
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Moderate amounts of caffeine have no negative health effects, according to the American Medical Association Council on Scientific Affairs. A moderate amount of caffeine is roughly 250 milligrams per day, which is about the amount you would get from three 8-ounce cups of coffee. In contrast, an excessive amount would be 10 8-ounce cups of coffee a day. If you consume excessive amounts of caffeine, you might experience some negative side effects, including an increased heart rate, excessive urination, nausea, restlessness, vomiting, anxiety, tremors, depression and sleeping problems.
Caffeine can cause an uneven heart rhythm, increased heart rate and temporarily raise your blood pressure. How much your blood pressure increases depends on your current health condition and your sensitivity to caffeine. For example, you can build up a tolerance to caffeine if you drink it regularly for a long time, which means your heart rate might not go up as much as it would for someone who has never had caffeine before.
Caffeine may cause a rise in your blood pressure, particularly if you are prone to hypertension, according to a study in the medical journal "Polski Merkuriusz Lekarski." According to the study, healthy subjects did not see a significant rise in blood pressure, but those who were prone to hypertension did. For now, experts typically suggest that people with heart-related problems limit or avoid caffeine to prevent sharp, dramatic increases in heart rate. For example, the FDA recommends that people with heart, anxiety or panic problems avoid caffeine completely. The FDA points out that caffeine makes your heart work harder, so people with these conditions might overstimulate their hearts and put themselves at risk.
After you ingest caffeine, it reaches its peak level within an hour, so that’s when you might experience the greatest effects, which typically taper off after four to six hours. If you don’t have any existing health conditions that prohibit you from ingesting caffeine, stay within the recommended amounts to avoid the negative effects. If you do have heart-related problems, such as high blood pressure or coronary heart disease, avoid products with caffeine unless your doctor approves.