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Surprising Side Effects Coffee Has on Your Immune System, Says Science

Your favorite cup of java impacts your body quite a bit.
FACT CHECKED BY Kiersten Hickman

You may already know that a cup of coffee can reduce your risk of certain chronic diseases, boost your cognitive health, and help you lose weight—all while fueling you through those morning meetings. But what side effects does coffee have on your immune system? You may be surprised to find out that there are both benefits and potential drawbacks to your daily pick-me-up when it comes to warding off illness.

Of course, the impact that coffee has on your immune system depends largely on the nature of your habit. Drinking anything caffeinated in excess, coffee included, can cause some seriously unpleasant effects, like anxiety, fatigue, and disrupted sleep.

According to the FDA, a maximum of four cups per day is generally a safe amount to drink in order to reap the rewards without the possible risks. With that in mind, here are some of the ways your favorite caffeinated beverage can impact your immune health. And for even more healthy tips, read up on our list of The 7 Healthiest Foods to Eat Right Now.

It can raise your blood pressure.

pour black coffee

According to Mayo Clinic, coffee can raise your blood pressure (blame it on the caffeine content).

That's bad news, considering that high blood pressure is associated with a weaker immune system.

Keep in mind that this increase in blood pressure is temporary, so it may not prove problematic unless you're consuming coffee in excess on a regular basis—or if you already have (or are at risk for) hypertension.

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It can impact your sleep.

coffee cups

It's no secret that caffeine can totally sabotage your sleep—especially when you consume it later in the day. In fact, studies have shown that sleep deprivation essentially puts your body into a state of chronic stress, which negatively impacts immune functions. More specifically, researchers have determined that consistently not getting enough sleep puts you at a higher risk for immunodeficiency and thus, higher susceptibility to certain infections and diseases, as a result of persistent systemic inflammation as well as a reduced immune response to vaccination.

Not only that, but a lack of sleep can also impact how quickly you recover from illness, according to Mayo Clinic. This is because your immune system releases cytokines, a type of protein essential to fighting inflammation and infection, while you sleep. So, when you're not catching plenty of Zs, the production of these protective proteins (along with other important antibodies) is reduced.

The bottom line is that consuming lots of caffeine can sabotage your ability to get the rest that you need to ward off infectious diseases. The solution? Consider cutting back on your caffeine consumption, avoiding it at least six hours before bedtime, or even switching to decaf. Here's This One Trick Will Help You Cut Down On Caffeine For Good.

It may decrease your body's ability to fight off infections due to cortisol.

black coffee

Did you know that caffeine increases cortisol secretion? While cortisol is known as a stress hormone, it can actually help to keep inflammation and stress at bay in normal doses. However, numerous studies have shown that when there's too much of it, your body responds by ramping up the production of inflammatory substances that impair the immune response.

This may explain why a small 1990 study determined that drinking coffee may hinder the immune system's ability to fend off infections. Essentially, researchers found that coffee restricts your white blood cells' ability to divide—which is essential for reacting to potential pathogens.

It's packed with antioxidants.


Coffee lovers, rejoice! Your beloved morning beverage is packed with a multitude of antioxidants, like phenolic acid. It should come as no surprise, then, that a 2017 study suggested coffee can improve the body's immune system. However, there is a caveat: these benefits were only observed when two cups were consumed without the addition of milk or sugar. So, your best bet is to drink it black. Here's What Happens To Your Body When You Drink Black Coffee.

It can decrease inflammation in the body.

cup of coffee

Some studies have suggested that coffee (in moderate doses) can have an anti-inflammatory effect. That might explain why research has demonstrated that coffee drinkers tend to have lower circulating levels of inflammatory markers.

But before you down that second cup of joe, consider this. Other research has suggested that coffee can have the opposite effect in certain individuals, promoting inflammation.

Confusing, right? Researchers concluded that whether coffee has an inflammatory or anti-inflammatory effect may depend on the individual's genetics. If you suspect that coffee is actually triggering or worsening inflammation for you, try reducing your intake to see if your symptoms improve. Not sure how much coffee you should have? Here's How Much Coffee You Can Have in a Day, According to the Mayo Clinic

Rebecca Strong
Rebecca Strong is a Boston-based freelance health/wellness, lifestyle, and travel writer. Read more about Rebecca
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