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Why does coffee tire me sometimes?


Caffeine, the main active ingredient in coffee, has a good reputation for being an energy booster. But caffeine is also a drug, which means it can affect each of us differently, depending on our drinking habits and our genes.

“The paradox of caffeine is that in the short term, it helps with attention and alertness. It helps with certain cognitive tasks and it helps with energy levels, ”said Mark Stein, a professor in the Department of Psychiatry and Behavioral Sciences at the University of Washington, who has studied the impact of caffeine on people with ADHD. the effect – or the long-term impact – has the opposite effect.

Part of the paradoxical effects of caffeine results from its effects on what researchers call “sleep pressure,” which fuels our drowsiness as the day progresses. As soon as we wake up, our body has a biological clock that prompts us to go back to sleep later in the day.

Seth Blackshaw, a Johns Hopkins University neuroscientist who studies sleep, said researchers are still learning how sleep pressure builds up in the body, but over the course of the day our cells and tissues use up. and burn for energy in the form of a molecule called adenosine triphosphate, or ATP. As this ATP is spent – as we think, exercise, run errands, or attend conference calls – our cells generate a chemical called adenosine as a byproduct. This adenosine binds to receptors in the brain, making us more drowsy.

Chemically, caffeine is sufficiently similar to adenosine at the molecular level where it occupies these binding sites, preventing adenosine from binding to these brain receptors. As a result, caffeine works to temporarily suppress sleep pressure, making us feel more awake. During this time, adenosine continues to build up in the body.

“Once the caffeine wears off you get a really high level of sleep pressure and you have to pay it back,” Dr. Bradshaw said. In fact, the only way to relieve and reset a high level of sleep pressure is to sleep.

The problem is compounded by the fact that the more caffeine we drink, the more we develop our body’s tolerance to it. Our liver adapts by making proteins that break down caffeine faster, and adenosine receptors in our brains multiply, so they can continue to be sensitive to adenosine levels to regulate our sleep cycle.

Ultimately, continued or increased consumption of caffeine has a negative impact on sleep, which will also make us more tired, Dr. Stein said.

“If you sleep less and are stressed out and rely on caffeine to improve it, it’s just a perfect storm for a short-term fix that’s going to make things worse in the long run,” he said. declared. “You’re going to add more shots to your espresso, but the negative impact on your sleep will continue, and it’s cumulative.”

Caffeine can also cause spikes in blood sugar or lead to dehydration, which can make us more tired, said Christina Pierpaoli Parker, a clinical researcher who studies sleep at the University of Alabama in Birmingham.

If you feel bad the afternoon even after a cup of coffee, the solution may be to consume less, say scientists. Don’t drink it every day or worry about it for a few days so that your body can flush the caffeine out of your system and then gradually add it to your routine. Ideally, drinking coffee “should be fun and useful, and really give you a boost when you need it,” said Dr Bradshaw.

In the meantime, if you feel like caffeine is not giving you more energy, experts recommend taking a nap, exercising, or sitting outside and exposure to natural light, which can add a boost of energy – naturally.

“Monitor your sleep and make sure you sleep well,” Dr. Stein said. “Adequate sleep and physical activity are the first-line interventions for attention problems and drowsiness. Caffeine is a helpful supplement, but you don’t want to become addicted to it.

Wudan Yan is a freelance journalist in Seattle, covering science and society.


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