According to a new study, coffee increases the number of calories people burn during the day, but it robs them of vital sleep at night.
The results suggested that people who regularly drink coffee walk 1,000 more steps each day than non-drinkers, but miss about 30 minutes of sleep at night.
Lead author of the study Dr. Gregory Marcus, a cardiologist at the University of California, San Francisco, said: “The reality is that coffee isn’t all good or all bad — it has different effects.”
His study, published today in the New England Journal of Medicine, followed 100 adult men and women for two weeks. Their exercise and sleep patterns were tracked on days when they did or did not drink coffee.
Coffee helps someone walk more during the day but harms their sleep, a study suggests (stock image)
The graphs above show the amount of sleep someone got while drinking coffee (orange) and not drinking coffee (blue) and stepping both on and after coffee
Coffee is arguably the most widely consumed beverage in America, consumed daily by up to three-quarters of adults.
Some research has suggested that the drink may improve heart health and lower the risk of conditions such as diabetes. It can even improve performance in the gym.
These effects appear to be driven by caffeine, which works by blocking receptors in the brain that signal exhaustion, helping a person stay alert longer. It also helps to increase the heart rate.
But caffeine can also be harmful because it takes up to 10 hours for the caffeine — a stimulant that makes it harder to sleep and puts stress on the nervous system — to be flushed out of the body.
According to the Centers for Disease Control and Prevention (CDC), everyone needs at least seven hours of sleep per night. But a third of Americans fail to do so.
Not getting enough sleep has been linked to numerous health problems, including difficulty concentrating, memory problems, and a higher risk of diseases, including Alzheimer’s disease and obesity.
Some research has suggested that it’s possible to get many of the health benefits of coffee by drinking the decaffeinated version.
“Overall, this study suggests that coffee consumption is almost certainly generally safe,” Dr Marcus added.
“But people need to recognize that there are real and measurable physiological effects that — depending on the individual and their goals of care — could be harmful or helpful.”
In the study, researchers recruited 100 healthy men and women in San Francisco who drink coffee. They were about 39 years old.
They were all equipped with a FitBit to track their steps and sleep, as well as an electrocardiogram to monitor their heart rate and blood glucose meters.
Then they followed a strict schedule for two weeks.
For two days, they were allowed to drink as much caffeinated coffee as they wanted and were reimbursed for the costs by the scientists. But for the next two they had to abstain. This cycle was put on repeat.
On the days they were allowed to drink coffee, participants drank an average of one to three coffees per day, although some drank as many as six cups.
The results indicated that they took 1,000 extra steps per day while drinking coffee, with the number of steps increasing from an average of 9,665 to 10,646 per day.
The researchers said this was most likely due to the energy and motivation boosts caffeine provides.
On the other hand, however, they also found that participants’ sleep was affected while drinking coffee.
When they didn’t drink coffee, they slept an average of seven hours and twelve minutes a night. But when they did, it dropped to six hours and 37 minutes, or by 35 minutes.
Coffee blocks hormones that make people sleepy.
Since caffeine takes up to 10 hours to break down in the brain, this means that the effects of a 2 p.m. cup of coffee may not wear off until midnight.
The study also looked at the impact caffeine had on people’s hearts.
They found that on days when they had more caffeine, they were 50 percent more likely to have premature ventricular contractions — when the ventricles, or lower heart chambers, beat early — and nine percent more likely to have premature atrial contractions — when the atria, or upper heart chambers, , hit early.
Experts said this is not dangerous in a healthy person, but could pose a risk in someone with a heart problem.
Dr. Amit Khera, a cardiologist at the University of Texas who was not involved in the study, told the Washington Post: ‘In healthy people with normal hearts it is what I would call a quality of life issue, not a life threatening issue.
“If you feel your heart skip a beat and it bothers you, then, based on these research results, stopping coffee may reduce those symptoms.”