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Caffeine: How much is too much?

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Posted: Monday, March 18, 2013 4:30 am

SANTA ANA, Calif. — Led by strong coffee sales and an explosion in the popularity of energy drinks, our addiction to caffeine has intensified. It is estimated that 90 percent of Americans consume caffeine daily, with more than half of us drinking down at least 300 milligrams of it. Although a safe limit for caffeine consumption has never been determined, some medical experts said 400 mg should be roughly the limit for adults.

Caffeine is safe for the vast majority of people who consume it, and those who overindulge usually endure symptoms no worse than jitteriness or sleeplessness. But ignoring the caffeine content in certain products, or not knowing about it at all, can bring trouble. Over the past few months, there have been several reports illustrating the dangers of overconsumption of caffeine, for young people and adults. In October, the FDA said it knew about five deaths in the previous three years that were possibly linked to Monster Energy drinks; less than a month later, the agency said it had received reports of 13 deaths possibly linked to 5-Hour Energy shots.

At the heart of this nationwide caffeine jolt is the pursuit of an elusive, prized commodity called “energy.” As we juggle home and work schedules, trying desperately to hold on to a job or pass a final exam, we’re open to just about any product that will keep us alert just a little longer.

There are hundreds of products that give us our daily (or hourly) fix, from those ubiquitous beverages to candies, mints, beer and even inhalants.

“The weird thing about all of this is, you’ve got to listen to your body: If you’re really that tired, go to sleep,” said Matthew Ganio, an assistant professor at the University of Arkansas who has conducted research on the physiological effects of caffeine. “Unfortunately, our lives don’t usually lend themselves to doing that. That’s why we turn to caffeine.”

Benefits and drawbacks

The reason we use caffeine is that it works: It boosts alertness and improves cognitive and physical performance, for a period of time, which can vary widely, depending on the individual. Ganio has studied the influence of caffeine on athletes, and he said just the right dosage — 3-6 mg per kilogram of body mass, or 245-490 mg for a 180-pound person — can improve endurance. Which is one of the reasons runners love those packets of energy gel: Some contain from 25 mg to 100 mg.

The way caffeine works its magic is this, Ganio said: A molecule called adenosine attaches to receptors in the brain, causing a reaction that leads, over time, to fatigue and drowsiness. Caffeine “actually blocks that receptor, and does not allow drowsiness to occur,” Ganio said.

It gets complicated after that, because after the dosage reaches its peak, about an hour after consumption, the level in the blood begins to go downhill.

After five hours, the level is down 50 percent from the peak, Ganio said. And so the body can start to crave it again, leading to withdrawal symptoms.

For habitual users, not feeding the habit can bring weariness and headaches, which is why many need that midafternoon fix to keep from crash-landing.

There are other negative effects from this push-and-pull between a caffeine buzz and withdrawal: Our sleep patterns get disrupted (caffeine lingers in the bloodstream for several hours); it can cause stomach problems and elevate blood pressure.

Defending products

In December, Consumer Reports magazine put 27 energy drinks and shots through its lab analysis. Eleven of them didn’t list the caffeine content on the label. Of the 16 that did, five had more than 20 percent above the labeled amount of caffeine.

After the FDA reports of deaths possibly linked to Monster and 5-Hour Energy, those companies defended their products, insisting they are safe and not responsible for the deaths. The reports themselves did not prove that the drinks caused the deaths.

Critics of energy drinks are pushing for clearer labeling that includes caffeine levels.

“I personally think that the more disclosure the better,” Ganio said, “so consumers can know how much caffeine they’re taking in.”

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