The Science Behind Caffeine and Your Body

Caffeine. It’s the punchline of every cheesy office joke and exasperated adult eye roll. You purse your lips and take a sweet, sweet sip of salvation, but did you ever stop to think what gives that pick-me-up its pep?

According to the Food and Drug Administration, caffeine is both a drug and a food additive, and it’s being consumed in massive amounts nationally. In fact, according to a recent FDA study, 80 percent of adults consume about 300 milligrams of caffeine every day, which is the equivalent of two 8-ounce cups of coffee or five sodas. Apart from soda containing high amounts of sugar and fancy coffee creamers sneaking in empty calories, there’s a whole lot more going on in your body.

According to Nicole Robertson, MD, a family physician with ProMedica Physicians, the effects of caffeine kick in about an hour after consumption, and has a half life of three to seven hours. That means your morning cup of joe will be half as potent in your system right around lunch time.


Your Brain on Caffeine

Your brain is made up of all kinds of tissues, cells and hormones working together to tell our bodies what to do. One of the most important players is the neurotransmitter, which are chemicals that relay information between nerve signals to regulate body processes. When caffeine makes its way up to our brains, it forms a strange relationship with the chemical processes already taking place, especially the process that regulates sleepiness. Adenosine is one such chemical that when accumulated, will tell your body it’s time to rest. Adenosine is received by adenosine receptors in the brain, and since caffeine looks deceivingly like adenosine, it can easily sneak in and block up the receptors. Without adenosine, other neurotransmitters can get to work. “Caffeine is a central nervous system stimulant,” says Dr. Robertson. “It causes us to be more alert, awake and increases concentration.” When caffeine finally wears off, it allows the adenosine—that’s been accumulating all this time—to come rushing back in. This is why we feel our bodies crash after a jolt of caffeine.

While your brain is having the time of its life under caffeine’s effects, your cardiovascular system is working overtime. Your heart begins pumping harder and faster, and can even raise your blood pressure by about 10mmHg.

Caffeine and Your Other Organs

Down in your gastrointestinal system, caffeine can raise the amount of acid produced by the stomach, causing reflux. It can also increase cholecystokinin which is a hormone that can increase gallbladder contraction. Why is gallbladder contraction a bad thing?

“If a person already has gallstones or gallbladder disease and the gallbladder contraction increases, this can worsen symptoms of gallstones or gallbladder disease,” explains Dr. Robertson. “It’s like making a dysfunctional organ work harder even though it is not working well as it is.”

Another organ working hard is your kidneys, which help your body by filtering out all the substances it can’t use. And while some studies suggest coffee isn’t as dehydrating as once thought, in large amounts, caffeine speeds up this filtration process while inhibiting your body from reabsorbing sodium. All that sodium has to go somewhere, and while it’s exiting your body, it’s pulling water with it. This particular side effect is why you find yourself running to the bathroom more frequently.

When to Avoid Caffeine

Women don’t often think about caffeine impacting their reproductive health, but it’s one more area to consider. Expectant moms know to avoid foods like sushi and soft cheeses, but some also choose to avoid caffeine. “Because caffeine passes through to the placenta, it can cause fetal symptoms similar to adults in large amounts,” says Dr. Robertson. “It can also exacerbate fibrocystic changes in breasts.” The tissue in breasts may change over time, feeling lumpy or ropey to the touch. This change can sometimes increase breast pain or tenderness during menstruation.

When caffeine cruises through our bloodstream, it has the ability to touch virtually every organ in our bodies. Since we’re now aware of how the substance affects some of our most major organs, someone with a chronic condition associated with one or more of these body systems could really see adverse effects.

“Caffeine should be avoided or consumed in moderation with those who have uncontrolled acid reflux, uncontrolled hypertension, cardiac arrhythmias or other heart conditions,” says Dr. Robertson. “Also, caffeine in higher doses can precipitate headaches, migraines, insomnia and anxiety.”

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The news about caffeine’s impact on organs and body systems isn’t all bad. Recent research suggests the benefits may outweigh the risks in a healthy adult. “Caffeine has actually been found to decrease overall mortality and may also have protective qualities against Parkinson’s, type 2 diabetes, and cognitive function,” says Dr. Robertson. There have also been some interesting developments for asthma patients.

“Caffeine acts similar to theophylline which is a bronchodilator,” says Dr. Robertson. “It has been studied that caffeine can improve lung function for a few hours.”