Caffeine: How much is too much?

A safe limit for caffeine consumption has never been determined, but some medical experts say 400 mg should be roughly the daily limit for adults. Here’s a sampling of the caffeine dosage in five popular products.

AEROSHOT caffeine inhalant: 100 mg per cartridge, good for 4-6 puffs.

STARBUCKS coffee: 330 mg in a Grande cup (16 oz.) of medium roast, like Pike’s Place

5-HOUR ENERGY shot: 215 mg per shot (1.93 oz.)

RED BULL energy drink: 164 mg per can (16 oz.)

MONSTER ENERGY drink: 184 mg per can (16 oz.)

Source: Consumer Reports

SANTA ANA, Calif. — Sitting in a booth at the La Palma Chicken Pie Shop in Anaheim, Calif., takes you back to a time long before Starbucks.

As you scan the interior to admire the macramé hanging planters, the waitress fills your coffee mug, smiling and calling you “dear.” The coffee they serve at the pie shop — which opened in 1955, the same year as Disneyland — is Farmer Brothers of Torrance, Calif., a tough, no-nonsense brew that costs $1.20 for a bottomless cup.

“We’ve been using that coffee all along,” says Otto Hasselbarth, who has owned and operated the restaurant with his wife, Antje, since 1972. “People sure like it, and that’s the reason we’ve never switched.”

We’re no longer happy with that simple cup of joe, or even four of them.

Led by strong coffee sales and an explosion in the popularity of energy drinks, our addiction to caffeine has intensified. It’s 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 say 400 mg should be roughly the limit for adults. That 6-ounce mug at La Palma probably has about 80 milligrams of caffeine. A Venti-sized cup of Starbucks’ signature blend, Pike Place, has 415 mg.

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 says 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 says: 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 says. 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.

Regulation needed?

Each energy drink has its own proprietary recipes, with ingredients that include taurine, an acid, and ginseng, a plant root. “We don’t know what those do to the body,” Ganio said.

Beverage-makers aren’t required to list caffeine content. Some labels warn that the products aren’t recommended for children, pregnant women or people sensitive to caffeine.

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 incident 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.

Anais Fournier, a 14-year-old Maryland girl who died in December 2011 after drinking two 24-ounce cans of Monster, officially died of “cardiac arrhythmia due to caffeine toxicity,” but she also had a genetic disorder that caused one of her heart valves to leak. Her family has sued Monster Beverage.

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.”