St. Mark's Hospital - March 12, 2019

Coffee, tea, cola or energy drinks — for most of us there’s nothing quite like the day’s first jolt of caffeine. It lifts the fog from our brains, eases stiff muscles and joints, and makes us ready to face the world.

Caffeine is the world’s most widely used drug. The Food and Drug Administration estimates that about 80 percent of Americans consume some form of caffeine every day. Though most of our caffeine comes from beverages and chocolate, caffeine also is in some medications and in products like energy bars and even beef jerky, whimsically named Perky Jerky.

Given caffeine’s near-universal consumption and the expanding market for energy drinks, there’s growing concern about how much caffeine is safe to consume.

Here’s a quick shot: While some people should minimize or avoid caffeine for health reasons, studies say moderate amounts are generally safe for adult use. The FDA says most healthy adults can handle up to 400 mg of caffeine a day without ill effects — about the equivalent of two 10-oz. mugs of coffee or five servings of tea or regular cola. However, less is known about how much caffeine is safe for children and teens, who are a large part of the market for caffeinated energy drinks.

Recently, heavily caffeinated energy drinks have come under close scrutiny by the FDA after being linked to more than a dozen deaths. Data from the Drug Abuse Warning Network show that emergency room visits connected to energy drinks doubled from 10,068 in 2007 to 20,783 in 2011, with the largest increase among people 40 and older.

Caffeine 101

Caffeine is found in about 60 plants, including coffee beans, tea leaves, cocoa beans, kola nuts, yerba maté (a popular South American beverage) and guarana berries (often used in energy drinks).

In plants, caffeine acts as a kind of natural pesticide that protects against insect predators. In people, caffeine is a mild stimulant that affects the brain and central nervous system, says Tracy McDowd, PharmD., director of clinical and quality services for H2U.

Caffeine works by blocking the effects of adenosine — a body chemical that is a natural sedative, McDowd says. This tricks our bodies into producing chemicals that rev up the brain so we feel alert and energized.

Caffeine also can help relieve minor aches and pains and constricts blood vessels in the brain that widen when you have a headache. This is why caffeine is used in headache remedies like Anacin and Excedrin.

Athletes often drink coffee or tea shortly before exercising to get a performance boost. The caffeine helps runners and other endurance athletes burn fat instead of just stored carbohydrates in the muscles, according to Nutrition Action Newsletter. This keeps them from tiring as quickly.

It takes only a few minutes for caffeine to enter your bloodstream. Its peak effects can last for several hours, but are largely gone after about eight to 10 hours.

How much is in your drinks?

The average American consumes about 300 mg of caffeine per day, according to the FDA, which defines moderate caffeine use as 100–200 mg per day, and heavy use as exceeding 500 mg per day.

Since the FDA doesn’t require nutrition labels to list caffeine amounts, you may need to hunt to find out how much your favorite drink contains. You may be surprised — even decaffeinated beverages have a few milligrams.

Some companies provide this information. Starbucks, for example, lists caffeine data on its website, but cautions that caffeine levels in brewed beverages can vary widely, depending on the variety of coffee or tea and brewing methods. For example, a Starbucks grande (16 oz.) coffee packs around 330mg of caffeine, but a 16-oz. McDonald’s coffee has only about 133 mg. And Starbuck’s grande Earl Grey tea has 115 mg, while a grande Tazo Awake tea has 135 mg.

If you’re a soft drink fan, a 12-oz. Pepsi Max has 69 mg of caffeine, while a 12-oz. Coca-Cola has only 35 mg, according to the Center for Science in the Public Interest. (Much of cola’s energy boost comes from its high sugar content.)

As for energy drinks, even when the caffeine amount is listed on the label, it may not be spot on. A Consumer Reports test published last December found that in 16 products that listed caffeine amounts on the label, seven actually had at least 20 percent more caffeine per serving than the label indicated.

Some drinks also contain multiple servings, which means you can consume more caffeine than expected if you don’t read the label carefully.

Good or bad for you?

“Studies show that moderate caffeine intake probably isn’t harmful,” McDowd says. “But heavy caffeine use can trigger insomnia, irritability, anxiety, upset stomach, jitters, tremors or more serious effects, including increased heart rate or cardiac arrhythmia.”

Caffeine’s effects vary depending on genetics, age, sex and even medications you take, McDowd says. In people who are sensitive to caffeine or who rarely consume it, even small amounts can cause insomnia or jitters. On the other hand, regular caffeine users can develop a tolerance to its stimulating effects and may need more to feel alert. Though caffeine isn’t addictive in the same way that, say, painkillers are, daily use can lead to dependence. So quitting abruptly can cause withdrawal symptoms.

Meanwhile, research — and debate — continues into the health impact of caffeinated beverages. A Harvard review of two long-running studies of health professionals found that coffee drinkers did not have a higher risk of dying from cancer, heart disease or other factors. In fact, research suggests that the antioxidants in coffee and tea provide some protection from certain cancers, heart disease, Parkinson’s and other age-related diseases.

Still, some people should limit or avoid caffeine altogether, McDowd points out.

People who have cardiac arrhythmias or heart disease should ask their doctor how much caffeine is safe to use. Although large studies have not established a direct link between caffeine and cardiovascular events, there is concern that too much caffeine can be risky for some people.

Daily caffeine use can increase the risk of chronic migraines and rebound headaches in people prone to headache disorders.

In people with a history of panic and anxiety disorders, caffeine can increase feelings of anxiety.

Some medications can slow the breakdown of caffeine in the body, thus prolonging its effects. These include antibiotics such as ciprofloxacin (Cipro) and anti-depressants such as fluvoxamine (Luvox). Also, people using theophylline, a bronchodilator, should discuss appropriate use of caffeine with their doctor.

Pregnant women should limit caffeine intake to less than 200 mg/day or quit completely while pregnant. Caffeine crosses the placenta to the fetus, and while studies on how it affects a fetus are inconclusive, it’s best to be cautious.

Caffeine and kids

As children, many of us heard that coffee would stunt our growth. McDowd says this is a myth that may have originated with early studies that indicated caffeine might reduce bone density. Subsequent research disproved this theory. But this doesn’t mean it’s okay for children and adolescents to use caffeine.

For one thing, kids’ bodies can’t handle as much caffeine as grownups, so they’re more likely to feel side effects. Also, the empty calories in sodas and energy drinks fill them up, so kids who consume lots of sodas and energy drinks may not get enough important nutrients from food. Sugary drinks also can damage young teeth and lead to weight problems.

The American Academy of Pediatrics (AAP) recommends no more than 100 mg of caffeine a day for adolescents. Younger children shouldn’t have caffeinated beverages on a regular basis. And the AAP says children and teens should never have energy drinks.

The last drop

Unless you have any of the health concerns mentioned above, keep on enjoying your daily dose of caffeine. If you experience side effects of over-consumption, or are worried about being dependent, cut back or gradually wean yourself off caffeine. (See box below.)

Cutting back on caffeine

The best way to tell if you’re dependent on caffeine is to avoid it for a day or two and see if you experience withdrawal symptoms such as headache, fatigue, anxiety, irritability, depressed mood or difficulty concentrating.

If so, you may want to minimize your caffeine dependence with these steps:

Identify your caffeine sources and why you like them. Is it the mental jolt or the taste (sugar, whipped cream, caramel, etc.)? Look for satisfying substitutes for caffeine-containing products.

Use a little less caffeine each day to minimize withdrawal symptoms:

  • Switch to less-caffeinated drinks or types of coffee or tea.
  • Use a smaller cup or glass.
  • Increase the time between consuming caffeinated beverages.
  • Mix your regular drink with decaf and gradually increase the decaf portion.

(Note: “Decaf” beverages have traces of caffeine.)