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One Surprising Side Effect of Drinking Coffee, According to Science

Is it really the pick-me-up you think it is?
FACT CHECKED BY Cheyenne Buckingham
woman holding coffee pot and mug

During a week of sabotaged sleep due to Netflix binges and social scrolling, are you doomed to brain fog and constant distraction? A recent study in the journal Progress in Neuro-Psychopharmacology & Biological Psychiatry offers a potential hack: Have some coffee.

Researchers in Germany looked at 26 participants who agreed to five nights of sleep restriction—getting just five hours of sleep—and daytime testing of their alertness, reaction times, memory, and accuracy on tasks. Half of the group had a cup of coffee at breakfast and another after lunch, while the other half had decaffeinated coffee.

Those with the caffeinated beverages showed significantly better performance on the daytime tests, especially in terms of sustained attention, compared to those drinking decaf. However, both groups reported feeling sleepiness during the day, which means that even the coffee couldn't provide a physical energy boost. (Related: 15 Underrated Weight Loss Tips That Actually Work).

Although coffee can give you a temporary mental lift, it's important to realize it's not a long-term replacement for quality sleep, says W. Chris Winter, MD, president of Charlottesville Neurology and Sleep Medicine, and author of "The Sleep Solution."

"Unfortunately, it doesn't take long for sleep disruption to begin causing issues with your health, including reduced immune system function, daytime sleepiness, and even weight gain," he says. "That includes sleeping too little, and even sleeping too much."

For example, a study in the journal Sleep found that both short and long sleeping times predict an increased risk of not just weight gain, but also fat gain in otherwise healthy adults.

Even in the recent study, the effects of caffeinated coffee didn't last. Despite feeling refreshed by the beverage for three or four days during a week of restricted sleep, participants started to tank by the fifth day. At that point, there was no difference in attention or cognitive function compared to those who had the decaffeinated coffee.

That means if you've had a night or two of bad sleep and need to rally some brainpower for work or school, coffee can help. But in addition to that temporary fix, Winter suggests putting more effort into developing solid sleep habits like going to bed and waking up at the same times every day, not having caffeine in the evening, and limiting screen time before sleep.

"The more you focus on getting good sleep, the healthier you'll be overall," says Winter. "Plus, solid sleep tends to sync up with other great habits like exercising regularly, getting fresh air, and eating healthy foods."

For more tips, be sure to read 20 Foods More Energizing Than a Cup of Coffee and 8 Ways to Support a Healthy Immune System, According to Harvard.

Elizabeth Millard
Elizabeth Millard is a freelance writer specializing in health, fitness, and nutrition. Read more
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