Exactly How Caffeine Affects Your Digestive System

Caffeine has the potential to wake up both your mind and your digestive system. But are the effects of caffeine bad for digestion? It depends on a few factors. If you do consume caffeine, stick to an upper limit of 400 milligrams daily — about two to four cups of coffee.

You probably know caffeine can do a good job of keeping you alert and awake, but it affects your body in several other ways as well, according to the U.S. National Library of Medicine (NLM). Caffeine can:

• Help your body get rid of extra salt and water (it's a diuretic)
• Stimulate your central nervous system
• Increase the release of acid in your stomach
• Increase your blood pressure

Simply put, caffeine stimulate your digestion, says Shanthi Appelö, RD, registered dietitian and health and wellness spokesperson with Blue Cross Blue Shield of Michigan in Detroit.

Caffeine stimulates muscle contractions in the colon connected with having a bowel movement, so it's common to need to poop after your cup of joe.

Another way caffeine affects digestion is by increasing the stress hormones cortisol and epinephrine, Appelö says. These hormones can increase the secretion of stomach acids and cause indigestion.

Drinking caffeine may also lead to an upset stomach or heartburn due to its effects on the release of stomach acid, according to the NLM.

With all the ways caffeine can affect digestion, where does that leave us with our beloved coffee? It depends. On one hand, coffee can absolutely help empty the bowels, even within just a few minutes, Appelö says. Both caffeinated and decaf coffee can cause this effect, although it's more pronounced with caffeinated coffee.

If you're mildly constipated, the stimulation coffee provides may be a welcome relief. Certain people should limit or avoid too much caffeine or coffee though, Appelö says, such as people with:

• Crohn's disease
• Ulcerative colitis
• Irritable bowel syndrome

If you have any of the conditions above, or if you have heart disease, high blood pressure or have had a heart attack, you should talk to your doctor about how much is safe for you.

For most people, up to 400 milligrams a day of caffeine is safe, according to the NLM. That ends up being about two to four cups of coffee a day, depending on the strength of your brew, because an 8-ounce cup of coffee has 95 to 200 milligrams of caffeine.

Keep in mind decaf coffee still contains about 2 to 15 milligrams of caffeine despite its name, according to the U.S. Food & Drug Administration.

Caffeine is also found in teas, sodas, energy drinks, chocolate and some medications, like cold medicine, according to the NLM. So take into account any and all caffeine sources you might consume during your day.

If you're pregnant or breastfeeding, your doctor may ask you to limit your intake to 200 milligrams a day, Appelö says. Teens should limit caffeine to no more than 100 milligrams a day and avoid energy drinks, according to the Centers for Disease Control and Prevention. Children should avoid caffeine altogether, according to the American Academy of Family Physicians.

If you do get too much caffeine, it could cause some problems, like insomnia, dizziness, dehydration, anxiety or an abnormal heart rhythm, per the NLM.

Digestive issues may not be specifically related to getting too much caffeine, but it can increase the amount of stomach acid, leading to heartburn. It also may affect your body's absorption of calcium, per the NLM.