“Don’t talk to me until I’ve had my coffee.”

Sound familiar?

“I can’t survive without caffeine.”

Maybe it’s just a case of the Mondays, or maybe you’re unaware of exactly how much caffeine you’re guzzling on a daily basis. Time for a reality check: When you’re feeling that afternoon lull, do you reach for a cup of energy-boosting java or chug a Coke? How do you know if and when it’s time to switch to decaf … or water?

“Having caffeine later in the day can delay our inner circadian clock,” says Dr. Mark Hyman, director of the Cleveland Clinic Center for Functional Medicine.

The mild stimulant – yes, it’s defined as a drug – can disrupt sleep and promote anxiety and depression. “We all know someone who tends to be tired, wired and over-caffeinated,” Hyman says.

The Institute for Scientific Information on Coffee suggests​ adults consume no more than 400 milligrams of caffeine per day. Pregnant women should hit the brakes around 200 mg ​ – or two to three cups – a day, says Roger Cook​, science manager at the ISIC, a nonprofit dedicated to the study of coffee’s effects on health. For measure, a single cup of coffee packs roughly 95 to 200 mg of caffeine. “As with many elements of our diet, too much can be harmful,” Cook says, adding that even too much water can make you ill. “Most consumers self-regulate – that is, they consume a level of caffeine they are comfortable with.”

In 2014, researchers published a paper ​in the journal Pediatrics reporting that although caffeine is considered a safe substance by the U.S. Food and Drug Administration, its potential adverse effects on children and adolescents aren’t certain. That’s why the American Academy of Pediatrics​ recommends no caffeine for kids. Yet the Centers for Disease Control and Prevention estimates 73 percent of Americans ages 2 to 22 consume caffeine on any given day. ​

According to the National Institutes of Health, caffeine has no nutritional value. It’s found naturally in the leaves, seeds and fruits of more than 60 plants, including tea leaves, kola nuts, coffee beans and cocoa beans. It’s also found in processed foods such as instant coffee​, tea, chocolate, most colas, candies, energy drinks​​, snacks and gum. And it’s an ingredient in many ​over-the-counter medications,​ such as pain relievers, diet pills and cold remedies.

Benefits of Caffeine

In moderation, caffeine provides mental and physical performance benefits, Cook explains: “Caffeine can be beneficial at improving alertness, particularly when the circadian clock is low after lunch or in the middle of a night shift,” he says. For instance, a caffeinated beverage and a short nap can help reduce driver fatigue among those who spend long hours on the road.

There’s no harm in enjoying a caffeinated drink for a pre-workout boost, according to the Academy of Nutrition and Dietetics​. The group suggests a low-fat latte, which typically delivers about 120 calories, 10 grams of protein and 75 milligrams of caffeine.

Coffee, in particular, has taken the spotlight in recent research. In May, the ISIC presented a report at the European Association for Cardiovascular Prevention and Rehabilitation’s annual meeting, detailing multiple studies that have linked drinking coffee to improved heart health​. One such study, published in the American Journal of Epidemiology​, found that drinking three to five cups of coffee each day could reduce the risk of dying from cardiovascular disease by up to 21 percent.

In July, an analysis published in the Journal of Alzheimer’s Disease revealed that the risk for mild cognitive impairment – or MCI, a stage between the normal aging process and dementia – may be influenced by how often coffee is consumed. The study examined drinking habits and cognitive function among a group of 1,445 people from the Italian Longitudinal Study on Aging. Adults with normal cognitive functioning who also drank one to two cups of coffee each day, the researchers found, ​had a reduced risk​ for developing MCI compared with those who never or rarely drank coffee. It’s worth noting that the findings didn’t extend to heavy coffee drinkers who downed more than four cups a day – moderate amounts appeared to bring the greatest benefit.

Your Body on Caffeine

Caffeine affects various parts of the body in different ways, Hyman says. For some people with diabetes, just one or two 8-ounce cups of black, brewed coffee can increase or decrease blood sugar levels, according to the Mayo Clinic​. Since it’s absorbed from the stomach, caffeine can reach ​the highest levels in the bloodstream within one or two hours, increasing blood pressure for a short period of time. That’s why it’s important for people with diabetes and high blood pressure​ to ask their doctor if caffeinated drinks are safe.

When you drink caffeinated beverages such as tea, soda or coffee, greater levels of serotonin – an important neurotransmitter that helps regulate mood and appetite – are released, which is why you feel that jolt of energy. Caffeine can also increase cortisol, the hormone responsible for stress control. But once the stimulation of caffeine has worn off, the fluctuation of hormones can actually leave you feeling more irritable and anxious.​

Although caffeine may perk up your mood or make you feel more focused, it can’t make a drunk person sober, according to the FDA. ​ And too much can lead to headaches, the jitters and irritability. ​

How Much Is​ Too Much?

Consider limiting​ your caffeine intake​ if you’re pregnant or you find that you’re having side effects​ from the stimulant.

People taking certain medications and supplements should also be cautious, according to the Mayo Clinic. The antibiotics Cipro and Noroxin, for instance, can increase the amount of time caffeine stays in the bloodstream, increasing the likelihood of negative side effects, such as insomnia, nervousness, restlessness, stomach upset, irritability, fast heartbeat and muscle tremors. And caffeine can increase the potency of the respiratory illness drug theophylline, which can lead to nausea, vomiting and heart palpitations. If you’re taking the herbal supplement echinacea, note that it can​ increase the amount of caffeine in your bloodstream, leading to caffeine-related side effects.

In 2013, the American Psychiatric ​Association recognized caffeine withdrawal as a syndrome in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders. ​To fit the criteria for diagnosis, you need to have had more than 250 mg of caffeine and experience five or more of the following symptoms: restlessness, nervousness, excitement, insomnia, flushed face, diuresis, gastrointestinal disturbance, muscle twitching, rambling speech, tachycardia or cardiac arrhythmia, periods of inexhaustibility or psychomotor agitation.

So You’ve Decided to Cut Back – Here’s How

Pay attention. Figuring out how much caffeine is in your drink, food or medication might be tricky since, for example, there isn’t a nutritional chart affixed to your mug. It’s up to you to do your research. You’ll learn that one shot of espresso has about 75 mg of caffeine, while energy drinks can range from 47 to 163 mg of caffeine per 8 ounces, according to the Academy of Nutrition and Dietetics. Chocolate contains caffeine, too, so don’t overlook the labels on your Hershey bar. And check over-the-counter pain relievers to determine just how much caffeine is in a single dose. For example, two tablets of Excedrin Migraine – which is the recommended dosage – contain 130 mg of caffeine.

Cut back gradually. If you’re afraid you’ll get a headache or feel tired if you go cold turkey, try decreasing your intake over a few days or more. Cook says that cautiously decreasing the amount of caffeine you consume may prevent you from developing the withdrawal-like symptoms described in the DSM-V.

Consider other options. While decaf might sound blasphemous to coffee chuggers, one 8-ounce cup contains a much milder amount of caffeine: 2 to 12 mg. If you’re still craving the bitter stuff, try a single shot of espresso, which packs 47 to 75 mg of caffeine. Tea can also​ help lower caffeine consumption. One 8-ounce cup of black tea holds 14 to 70 mg of caffeine, and an 8-ounce bottle of ice tea ranges from 5 to 40 mg. Most ​clear sodas, such as ginger ales and lemon-lime flavors, are 100 percent caffeine-free. It depends on the brand, though, so make sure to check the label on your favorite fizzy drink. If you’re trying to cure a headache and don’t want any more caffeine than you’ve already had, try ​​regular ibuprofen, aspirin or Tylenol – as opposed to those with additional medications for multiple symptoms. ​

Your Body On Caffeine: When Enough Is Enough was originally published on U.S. News & World Report.

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