Bean jumpy?

Coffee is perhaps the best known source of caffeine, but the amount of caffeine in energy drinks usually surpasses that in coffee. Photo: eyeore2710

An estimated 90 percent of North American adults consume caffeine. Increased caffeine intake can cause irritability, jumpiness and, more seriously, heart rhythm disturbances.

Although consuming too much coffee can lead to unhealthy caffeine levels, coffee isn’t the only culprit. Drugs such as Luvox, used to treat depression, or quinolone antibiotics, used to treat infection, amplify caffeine blood levels five-fold by tying up an enzyme pathway shared with caffeine.

Then there are energy drinks. These typically contain larger amounts of caffeine does coffee. Ingredients that contribute caffeine are yerba mate, guarana and ilex guayusa plants. Mateine and guaranine, which may also be among the ingredients in your pick-me-up beverage, are just caffeine derived from their respective plants. Energy drinks reported caffeine levels ranging from 80 to 300 mg per 16-ounce serving; a similar serving of coffee contains between 70 and 200 mg.

More may not be better if your goal is to be more alert. Although causality could not be established, a military study noted a paradoxical association of intake of three or more energy drinks with daytime sleepiness among respondents drinking that amount and reporting less than four hours of sleep.

Getting to high caffeine levels quickly is also dangerous. There are now caffeine dispensing strips, powders and gums that deliver the caffeine they contain directly through the mouth membranes. This results in near-instant absorption, as contrasted with the 45-minute delay measured in caffeinated beverages.

Then there are the dangers of “mixers.” Alcohol, a depressant, offsets the stimulant properties of an energy drink. Alcohol in combination with an energy drink can lead to an underestimation of both alcohol and caffeine intake. The Substance Abuse and Mental Health Services Administration tracks emergency room visits attributed to different drugs. It saw an increase in energy-drink-related admissions from 1,128 to 13,114 per year between 2005 and 2009—a 10-fold increase!

A lethal dose is estimated to be the equivalent of 80 to 100 cups of coffee for an adult. However if your liver is not healthy or is tied up by medications, the lethal amount is less.

The FDA is investigating a number of deaths that occurred in a four-year period tied to two different energy drinks. Although currently regulated as a food supplement, these drinks can cause adverse health effects if taken in combination with certain medications, with alcohol or in rapid succession.

Brian Svazas, M.D., M.P.H.