If you’re like 85% of U.S. adults, caffeine starts your morning, powers you through the workday and gives you the fortitude to face situations you’d rather avoid.
According to some news stories and opinions, that’s good news for your brain, as caffeine boosts your mood and reduces your risk of Alzheimer’s, Parkinson’s and other brain diseases, especially when consumed in tea or coffee.
However, you’ve perhaps also seen media coverage that says the opposite — warning that caffeine shrinks brain volume and increases the risk of dementia.
You may rightly wonder: Which is it? Does caffeine protect your brain? Or harm it?
The answer doesn’t neatly fall into “yes” or “no” categories. Whether caffeine’s cognitive benefits outweigh the risks depends on many factors, including how much you consume, how you consume it and how you metabolize it, says Donald D. Hensrud, M.D., M.S., an associate professor of nutrition and preventive medicine at Mayo Clinic College of Medicine.
What happens when you consume caffeine
It takes about an hour for caffeine to make its way down your throat, into your stomach, through your intestines, and eventually into your bloodstream and brain. As it circulates in the body, caffeine triggers wide-ranging effects.
These include the following:
- Production of stomach acid goes up.
- The muscular walls of the colon contract, which can trigger the urge to defecate.
- Blood vessels constrict.
- Urine production increases.
What does caffeine do to your brain?
Once in your brain, caffeine impersonates adenosine, a neurotransmitter that depresses the nervous system.
You might remember adenosine triphosphate (ATP) from high school or college biology. As you go about your day, cells break down ATP to create energy, releasing adenosine molecules in the process. In your brain, these adenosine molecules function like keys that fit into specialized locks called A1 and A2A receptors. Once enough adenosine keys open enough A1 and A2A locks, your muscles relax, motivation plummets, and an “I can’t keep my eyes open” sensation kicks in.
Then, as you sleep, your brain reassembles ATP, clearing adenosine and allowing you to wake feeling refreshed.
As it turns out, caffeine’s chemical structure looks a lot like adenosine’s. This allows caffeine to attach to the same A1 and A2A receptors, blocking adenosine’s “sleepy” signal from getting through. You feel more awake, motivated and alert. Reaction time improves, and you process information, make decisions and solve problems more quickly, says Dr. Hensrud.
Several hours after ingestion, however, adenosine receptors clear the caffeine. This allows adenosine to reach its destination, causing an afternoon slump in some people.
Can caffeine and coffee prevent dementia and other cognitive problems?
If you’ve searched for information about caffeine and brain health, you’ve likely come across research that linked caffeine consumption to increased dementia risk and smaller brain volumes. For example, one study analyzed MRI results from 17,702 people, determining that study participants who consumed more than six cups of coffee a day had smaller brain volumes and a 53% higher risk of being diagnosed with dementia than did people who drank one or two daily cups.
Then again, you also may have come across research that reported the opposite finding. For example, a recent review pooled the data from 141 meta-analysis studies concerning more than 70 health outcomes and hundreds of thousands of participants. Much more powerful than a single study, these pooled results found that coffee consumption was associated with a reduced risk of cognitive disorders such as Alzheimer’s disease and Parkinson’s disease.
When conflicting findings like the ones above get released, media outlets generally jump on the results, printing headlines like “Caffeine increases dementia!” and “Coffee reduces the risk of Alzheimer’s disease!”
Though such headlines accurately describe the specific studies in question, they miss the much more nuanced big picture.
The nuances of caffeine and brain health
“It’s hard to look at just one aspect of diet and connect it to a health condition because so many other factors could play a role,” says Dr. Hensrud.
For example, heavy coffee drinkers also tend to use tobacco and be sedentary, both of which can raise dementia risk.
In addition, as the adage goes, the dose makes the poison. It’s likely that caffeine protects the brain when consumed moderately but potentially harms it when consumed excessively, says Dr. Hensrud.
Finally, most people don’t consume straight shots of caffeine. Instead, the chemical comes embedded in a food or beverage, including cola, energy drinks, coffee, tea and chocolate. Other components of these foods or beverages could offset or accentuate caffeine’s healing properties.
For example, coffee and tea contain an abundance of health-protective substances like flavonoids that are thought to protect cells from damage as well as keep inflammation in check.
However, sweetened soft drinks and energy drinks come loaded with added sugar and few, if any, nutrients. Still other drinks combine the health-promoting substances from coffee or tea with hefty amounts of added sugar and fat. Some of these blended coffees and teas contain more calories, sugar and fat than most frosted and cream-filled donuts.
Caffeine vs. phytochemicals: Which protects the brain?
As mentioned above, caffeine isn’t the only beneficial ingredient in coffee and tea.
Coffee, for example, contains more than 1,000 compounds, including protective plant chemicals like flavonoids, mentioned earlier. Similarly, tea also contains flavonoids and L-theanine, an amino acid thought to be involved in attention and cognitive health.
“Some effects of these beverages are due to caffeine, and other effects are due to other components in the beverage,” says Dr. Hensrud. “Regarding dementia, caffeinated coffee is protective, and caffeine seems to account for most of the protective effect because decaffeinated coffee has much less protective effect.”
The health upsides of caffeine and coffee
In addition to reducing risk of Alzheimer’s, Parkinson’s and other degenerative brain diseases, caffeine consumption is associated with several other benefits, says Dr. Hensrud. By altering levels of brain chemicals involved in mood, caffeine consumption may reduce risk of depression. In research that examined the health records of more than 200,000 men and women, risk of suicide was 45% lower in people who consumed two to three daily cups of coffee compared with people who drank no coffee.
Other health benefits include a decreased risk of the following:
- Liver disease
- Liver cancer
- Type 2 diabetes
- Gallstones
- Kidney stones
- Gout
- Some cancers
- Possibly overall mortality
The downsides of caffeine
If you consume caffeine regularly, you’re likely familiar with some of the drawbacks. The increased urine output can lead to urgency and bladder incontinence in susceptible people. More gut motility can do more than relieve constipation. In some people, it triggers diarrhea.
Depending on your disposition and how much caffeine you consume, you also may feel anxious and stressed, says Dr. Hensrud. It can disturb sleep, which leads to a vicious circle. You drink more caffeine to stay awake during the day, which keeps you wide awake at night, and the cycle continues.
Other potential downsides include:
- Heartburn and stomach upset.
- Difficulty conceiving, miscarriage and poor pregnancy outcomes like low birth weight and preterm birth.
- Caffeine is mildly addictive and can lead to withdrawal headaches if you abruptly decrease your consumption.
Whether you experience these downsides will depend on your health, individual physiology and how you metabolize caffeine.
“Caffeine is metabolized on a genetic basis,” says Dr. Hensrud.
Some people are fast metabolizers and can go to sleep soon after drinking coffee, Dr. Hensrud says. Other people metabolize it more slowly and struggle to sleep if they consume it late morning or early afternoon.
In addition to your genetics, your age can affect how you metabolize caffeine. In people age 65 and older, it may take 33% longer for the brain to clear caffeine. Some steroids, oral contraceptives, antidepressants, heart medicines and antibiotics also can slow caffeine metabolism.
How to weigh the pros and cons
Overall, the positive effects of consuming caffeine from unsweetened coffee and tea appear to outweigh the drawbacks. To decide if caffeine is right for you, consider the following questions:
Do you enjoy coffee and tea? If you do, there’s little reason to stop, assuming you drink it moderately, says Dr. Hensrud. However, if you don’t enjoy coffee or tea, there’s no reason to force yourself to consume these beverages.
Does caffeine lead to problems? If you experience side effects, limit your consumption. If coffee or tea makes you feel anxious, gives you heartburn or keeps you up at night, you might want to cut back, says Dr. Hensrud.
Do you consume caffeine moderately? Assuming you’re not experiencing side effects like anxiety or stomach upset, up to five or six cups of coffee (about 600 milligrams of caffeine) is safe and potentially beneficial for most healthy adults. Keep in mind that the actual caffeine content in beverages varies widely.
Are you pregnant or trying to conceive? If so, the American College of Obstetricians and Gynecologists (ACOG) recommends limiting caffeine intake to 200 daily milligrams or less.
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