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One Major Side Effect of Drinking Too Much Coffee, Says Science

Before you take another sip, discover what you're really getting in that cup.
FACT CHECKED BY Olivia Tarantino

For many people, drinking a cup of coffee in the morning is an essential part of their day. And while the occasional cup of coffee may boost your energy level, focus, or even your mood, you can definitely have too much of a good thing when it comes to your coffee intake.

While the U.S. Food & Drug Administration (FDA) says that most healthy adults can safely consume up to 400 milligrams of caffeine each day—the amount you'd get in approximately four to five cups of coffee—individual tolerance can vary greatly based on weight, metabolic rate, health conditions, and a number of other factors, and drinking too much coffee can have serious effects on not only your physical health, but also your mental wellbeing, as the caffeinated drink can be addictive.

Anika Christ, RD, CPT, a registered dietitian, and director of client optimization at Life Time, explains that people can build up a tolerance to caffeine in just a few days, noting that she personally recommends that her clients consume just one to two cups of coffee a day to limit their reliance on it. However, even among moderate coffee drinkers, the caffeine contained in the beverage can trigger serious feelings of restlessness and anxiety.

Amid the pandemic in particular, "People are stressed out, not sleeping as well, so they're in dire need of more caffeine," says Christ. "That's fueling that same fire over and over and over again because then we can't fall asleep and get into a heavy sleep.''

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Even if you're not drinking coffee close to when you plan on hitting the hay, your coffee intake can have a profound effect on how well you sleep. A 2013 study published in the Journal of Clinical Sleep Medicine found that even when consumed six hours prior to bedtime, a 400-milligram dose of caffeine was associated with pronounced sleep disturbances. Furthermore, a 2010 study published in the Journal of Behavioral Therapy and Experimental Psychiatry found that sleeplessness itself can exacerbate anxiety symptoms, thus creating a self-perpetuating cycle of insufficient rest and subsequent anxiety.

Fortunately, giving up coffee—or at least strictly limiting your intake—can make a major difference when it comes to combatting anxiety and sleeplessness.

"Coffee can increase the jitters and anxiety, thanks to its boosting of lactic acid in your bloodstream, but cutting coffee out of your routine reduces lactic acid and also reduces stimulation of your nervous system, potentially helping you feel calmer and less anxious throughout your day," explains Lauren Minchen, MPH, RDN, CDN, nutrition consultant for Freshbit, the AI-driven visual diet diary app.

So if you find yourself feeling sluggish in the morning or anxious throughout the day, scaling back your coffee intake—even by just a cup or two—may provide some serious relief.

RELATED: Surprising Side Effects of Not Drinking Coffee, Say Dietitians



Sarah Crow
Sarah Crow is a senior editor at Eat This, Not That!, where she focuses on celebrity news and health coverage. Read more about Sarah
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