How Much Caffeine is in That Cup of Coffee?

Caffeine content of coffee varied significantly depending on source.


A cup of java is a cup of java. When it comes to caffeine content, that could be another matter entirely.

Data from the Center for Science in the Public Self Interest and the website indicate caffeine content per ounce of coffee can vary widely.

According to a March article in The Huffington Post, coffee from McDonald's could have as little as 9.1 milligrams per fluid ounce. Deathwish brand coffee, however, contains 54.2 milligrams per ounce.

Starbucks was the second highest, at 20.6 milligrams per fluid ounce. Seattle's Best, Bigby, Dunkin' Donuts and Dutch Bothers coffees were on the low side, with caffeine content of 12.8 milligrams per fluid ounce.

Caffeine content matters for several reasons.

First, caffeine is a nervous system stimulant, according to the National Institute of Medicine (NIM). Too much can lead to a racing pulse, elevated blood pressure, jittery feeling and insomnia. Too much caffeine can also cause gastrointestinal issues.

People can become habituated to caffeine, and suddenly stopping your regular coffee habit can lead to withdrawal. Headaches, sleepiness, irritability and nausea can occur if coffee drinkers quit without tapering off.

The NIM notes that caffeine in large amounts has been linked to thinning bones (osteoporosis), increased risk of miscarriage and lumpy, painful breasts (fibrocystic disease).

On the other hand, coffee has been shown to have health benefits, according to pediatrician Aaron E. Carroll, MD, a professor of pediatrics at Indiana University School of Medicine.

Writing in The New York Times, Dr. Carroll noted that people who drank three to five cups of coffee a day had the lowest risk of heart disease compared to those who drank more or none. Research findings on stroke risk and heart failure were similar to those on heart disease.

People who have liver disease benefited from daily coffee consumption, according to Dr. Carroll. He noted that with the exception of lung cancer, coffee consumption has not been linked to an increased risk of cancer. The higher risk for lung cancers who drank coffee showed up among those who also smoked.

Finally, Dr. Carroll notes there's a difference between the health effects of caffeine and the health effects of coffee. He also commented that the sugar and fat in many caffeinated drinks can have negative health effects.

As with many things, the issue is probably quantity.

The NIM recommends pregnant women limit their coffee intake to two cups a day. Dr. Carroll and the NIM both noted that children shouldn't drink coffee or other caffeinated beverages.

Four eight-ounce cups of coffee is considered moderate intake, according to the NIM, while 10 eight ounce cups a day is excessive. Within that range, people should pay attention to their health. If caffeinated coffee causes anxiety, insomnia or a fast pulse, consider switching to decaf.

Taper your intake to avoid withdrawal symptoms.