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It’s common knowledge that coffee can help get you going in more way than one before a competition. But it wasn’t until recently, that we (sort of) discovered why. Courtesy of this recent video post from the American Chemical Society, here's the latest biological explanation for why your favorite morning beverage helps you poop.

Why Coffee Might Make You Go

Coffee is acidic which causes the stomach to secrete heightened levels of gastric acid—a fluid that helps break down protein. It also contains chlorogenic acid which helps the stomach dump food into the intestines.

As the video explains: "It has been proven that coffee affects the movement of the large intestine within four minutes of ingestion, similar to the way a large meal does.” Once food reaches the intestines, scientists believe that coffee somehow triggers a "digestive call to arms" by increasing levels of two hormones, gastrin and cholecystokinin which cause the release of digestive enzymes and bile, and activate peristalsis—the waves of muscle contractions that help move waste through, and ultimately out of the body.

What they still don't know is which of the nearly 1,000 compounds in coffee is responsible for this interesting side effect—but they know it's not caffeine, at least not by itself; otherwise, people would have similar experiences while drinking soda and energy drinks (which they don't), but not decaf coffee (which they do).

What You Drink Matters

Not everyone is prone to bowel movments after drinking coffee. But researcher Joseph Rivera, founder of CoffeeChemistry.com and a scientific consultant for the ACS video, says that java's bowel-moving effects are really quite universal.

"Individuals vary significantly, and most of us just experience it to a lesser extent," he says. People who don't have to go No. 2 immediately after their morning cup "maybe just aren't drinking enough—or the right kind of coffee—to have this effect."

The kind that's most likely to make you run to the bathroom? Instant coffee crystals and cheap gas-station brews which tend to be made with lower-quality robusta beans, and have higher concentrations of chlorogenic acid.

Pre-Workout, Timing Is Everything

So should you drink coffee—and then hit the bathroom—before a long run or a strenuous workout? Absolutely, says Rivera. Apart from its role in helping to emptying your tank, coffee triggers other physiological reactions that are optimal for exercise.

"Caffeine has a thermogenic, or heat-causing, effect on our metabolism, and increases overall energy expenditure," says Rivera. "It also causes the release of short-chain fatty acids to be released from our cells, which enter our bloodstream and make them available for use." In other words, it makes it easier for the body to burn fat—an important skill when you've depleted all your glycogen stores during aerobic exercise.

But keep in mind, too much caffeine can backfire and cause stomach problems, making it difficult for you to focus during and after your workout.

So if you need to speed things up, try this trick: "Having an apple in conjunction with a cup of coffee should, theoretically assist in a bowel movement," Rivera says. The fruit contains a high concentration of chlorogenic acid, he explains, and should have the right stimulating effect.