Killer Coffee? How much caffeine is safe?


A recent story made coffee lovers jittery. According to experts, they need not worry, as long as they are not going overboard on caffeine consumption.

Earlier this year a teenager died after drinking a large diet Mountain Dew soda, a café latte and an energy drink in two hours. A “caffeine-induced cardiac event causing a probable arrhythmia” was the cause of death, according to the county coroner.

Caffeine is a stimulant that acts on the central nervous system and also increases the heart rate and blood pressure. The symptoms of a caffeine overdose include tachycardia, hypertension, headaches, muscle tremors, dizziness and insomnia. The elevated blood pressure leads to more frequent urination, and there are subjective feelings of anxiety and restlessness.

The American Academy of Pediatrics (AAP) warns that children and teenagers should not consume energy drinks, because they typically contain as much caffeine as is found in three cups of coffee, along with as much as four teaspoons of sugar. In fact, children should watch any kind of caffeine consumption.

So how much caffeine is safe for adults? Clearly, it varies, according to experts.

“Most people can safely take in about 400 milligrams of caffeine daily or about four cups of coffee,” says Robert Glatter, M.D., an emergency room physician at Lenox Hill Hospital in New York City. Glatter warns against mixing caffeine and alcohol: “Mixing caffeine with alcohol is a dangerous practice, because it may lead to higher levels of alcohol consumption as the person often believes and feels that he or she is more alert. The risk of alcohol poisoning increases as people consume more alcohol, because they feel that the caffeine will keep them awake and alert.”

Glatter related that it would take a lot of coffee to cause side effects. As he says, “It would likely take anywhere from 50 to 100 cups of coffee to result in a lethal dose of caffeine. That said, pure powdered caffeine can be lethal if a teaspoon of it is consumed at once. The recommended dose of powdered caffeine in this form is just 1/16 of a teaspoon.”

Another medical opinion was similar: “For adults it would be uncommon to experience effects of caffeine intoxication at less than 250 milligrams of caffeine (2.5 cups of coffee). It would typically be more than 12 ounces, but much more common to have the negative effects with greater than 500 milligrams of caffeine. It highly varies from person to person as to how much caffeine can affect them. It can be due to the speed in which our bodies process or how caffeine leaves the body, a metabolic difference,” says Maggie Sweeney, postdoctoral research fellow at Johns Hopkins University Medical School.

Even if it sounds like an oxymoron, coffee lovers can relax – about the effects of normal amounts of coffee, that is. The key is moderation, and it helps to be aware of one’s own limitations.


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