What Causes Constipation? 8 Reasons Why You Can't Poop, According to Doctors

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Constipation, or trouble using the bathroom, happens to just about everyone at some point or another. Unfortunately, because it’s such a universal affliction with so many sources, it can be surprisingly difficult to figure out which constipation causes apply to any given person. (The fact that it makes for an awkward dinner conversation doesn’t help with self-diagnosis, either.)

Living with constipation, whether occasional or chronic, can be anywhere from a severe annoyance to frequently debilitating. It leads to bloating, gassiness, abdominal pain, and a litany of other side effects, and if it goes on long enough, constipation can wind up impacting the bowels and doing serious damage to the stuffed-up sufferer.

Related: Get Constipation Relief Naturally With These 31 Home Remedies That Work Quickly

Constipation can be caused by a wide range of issues, so a self-assessment (or one with a doctor) must be taken before any treatment should be pursued.

“I always ask questions: Did you start any new medications? Because a lot of medications can cause constipation,” says Dr. Raj Devarajan, MD, a gastroenterologist and the head of the Massachusetts Gastroenterology Association. “If that’s not the case, then how's your diet? Are you drinking water? Do you have a family history of this? Because one of the theories is that it’s genetic. You ask these questions and then do the risk-benefit ratio in regards to how aggressive we have to be.”

With the help of a number of leading doctors and medical professionals, we’ve tracked down the most common culprits and causes of constipation and provided some antidotes and habits that could help clear up the build-up sooner rather than later.

What Causes Constipation?

1. Lack of fiber

The modern Western diet leads to several very common causes of constipation. Among the most prominent is a lack of fiber. There are several different kinds of fiber, though you’ll largely see them categorized into soluble and insoluble. According to Dr. Valencia Porter, a board-certified doctor and the author of the book “Resilient Health: How To Thrive in Our Toxic World,” the two kinds each play important roles. Soluble fiber helps you absorb nutrients but may slow digestion, while insoluble fiber is key for helping avoid constipation.

“Insoluble fiber that doesn't dissolve in water and generally attracts water into the stool. This includes plant cellulose & hemicellulose,” Dr. Porter says. “This type generally adds bulk to the stools and helps move things along.”

Foods with high levels of insoluble fibers include wheat bran, vegetables, whole grains, quinoa, beans, nuts, and brown rice, according to Amanda A. Kostro Miller, a registered dietician in Chicago. Most experts suggest increasing fiber intake to 25-35 grams per day, though it has to be gradual and paired with other measures.

“Don’t drastically increase your fiber all at once,” Miller says. “Water should be increased if you are increasing your fiber intake. If you eat more fiber without drinking more water, then you can become constipated!”

Related: A Little Backed up? Here Are 14 Ways to Poop Fast and Make Constipation a Distant Memory 

2. Dehydration

That brings us to a second very common cause of constipation: Dehydration. The issue can be caused by a number of different physical challenges and lifestyle choices, but the most direct way to handle it is to ensure enough water intake.

“Not drinking enough water and fluid: Fluid helps move things along in the digestive tract and gives your gut enough ‘juice’ to create healthy stool,” Miller explains. “Fluid helps to make stool softer and easier to pass.”

Water is key to alleviating dehydration, but there are other factors to consider as well. Dehydration can also be caused by drinking too much coffee and soda, taking certain medications, or frequent and profuse sweating.

Related: Backed Up? You Might Be Dealing With Keto Constipation

3. Not eating enough healthy fats

Eating a lot of fiber and drinking plenty of water can leave you feeling pretty full, which may, ironically, lead to other causes of constipation. Any diet that does not include enough good fats is liable to lead to trouble with the entire digestive system.

“Intentionally eating three types of healthy fats—polyunsaturated, monounsaturated, and Omega-3s—has been linked to anti-inflammatory benefits for the digestive tract, especially the small intestine,” says John Fawkes, a Level 1 Precision Nutrition-certified nutritional counselor and managing editor of The Unwinder. “These fats also ensure your body absorbs nutrients properly, leading to more regular bowel movements to pass digestive leftovers.”

These fats also help lubricate your digestive system, which makes it easier for stool to travel and pass. A lack of healthy fat doesn’t necessarily cause constipation, but introducing more of them into the diet can help alleviate the problem.

Related: Peeing a Lot? Here Are a Few Reasons Why You Might Be Heading to the Bathroom Every Hour

4. Prescription drugs

You know how at the end of pharmaceutical commercials, the narrator rushes through a whole list of side effects that could accompany a particular drug? Constipation is amongst the most frequent of the side effects mentioned because so many different kinds of medications wind up significantly slowing down the bowels.

Many medications can cause this through a variety of mechanisms, including decreasing contractility in the gastrointestinal tract and messing with the flora balance in the gut.

“Some drugs can cause an increase in the absorption of fluid and electrolytes in the intestine, which could contribute to constipation. This can be a direct effect or a result in the slower transit time that occurs from drugs that reduce intestinal motility,” says pharmacist Aaron Emmel, a doctor of pharmacy and the founder of PharmacyTechScholar.com.

“Another possible mechanism is an alteration of the healthy bacteria in the GI tract, which may be an explanation for example of why iron can cause constipation,” he adds. “Additionally, some medications and supplements can contribute to the ‘bulkiness’ of stool, which in some cases can result in constipation. Examples here include cholestyramine and calcium supplements.”

Related: If You're Backed Up, Registered Dietitians Agree That a Popular Summer Fruit Could Help You Poop

5. Lack of magnesium 

Sure, plenty of pills can cause constipation, but there are also some natural, non-fiber supplements that can turn things around and get the digestive system moving again.

If you’re on a diet that doesn’t permit you to eat a lot of the foods we mention above, like almonds, nuts, beans, and brown rice, you’re not just forgoing important servings of fiber, you may not be getting enough magnesium. That can cause some serious backup, but a stop at the pharmacy or even most grocery stores can solve the problem.

“Consider magnesium supplement,” says Shae Leonard, a physician assistant and functional medicine clinician in private practice. “Taking magnesium citrate 400-800 mg in the evening is particularly helpful. Magnesium works by promoting the natural wave-like movement of peristalsis.”

6. Physical inactivity

If you’re eating all the right foods and taking the proper supplements, you might want to take a look at your physical activity level. It’s often hard to do much moving around in the winter and the quarantine makes it all the more difficult, but too sedentary a lifestyle can be the culprit for constipation.

“Mobility equals gut motility! Movement and exercise massage the gut and get it moving,” Miller says. “Try walking, jogging, yoga, stretching or abdominal exercises. If you feel some gas pass, then you’re making progress.”

Related: New Research Says 60 Seconds of Exercise Can Offset 14 Minutes of Sedentary Activity—Here Are 10 One-Minute Workouts to Try

7. Irritable bowel syndrome

For many people, constipation isn’t a product of any nutritional deficiency, lack of physical activity, or prescription medication. Instead, according to Dr. Devarajan, the constipation is likely caused by a functional problem, which means that it’s a matter of how the body works (or, in this case, doesn’t work). When that’s the case, it’s often a result of what’s known as Irritable Bowel Syndrome.

“The muscles in our GI tract are what we call smooth muscles, whereas the muscles we have control over are called straight muscles,” Dr. Devarajan explains. “When I'm talking, when I'm moving my hands when I’m walking, these are all volitional movements, which means I have control over them. But you cannot will your stomach to move, no matter how hard you try. You can say ‘stomach empty,’ it's not going to do it. That’s because they’re what’s known as smooth muscles.”

Smooth muscles are part of the autonomic nervous system, which powers body processes that we don’t really think about. There is no definitive treatment for IBS, though a growing number of medications can mitigate it, largely by drawing water into the colon.

8. Stress

While not technically part of IBS, stress-induced constipation is also caused by a disruption to the autonomic nervous system. When you’re stressed, it can lead to inflammation in the GI tract, which can, in turn, slow digestion and prevent evacuation. It can even happen when you aren’t aware of your own stress levels, like when you travel or you’re just tired or working hard.

Dr. Devarjan says that stress-induced gastrointestinal issues have risen during the COVID-19 pandemic. As a result, ways to relax can be helpful for constipation, as well.

Next up, learn how you can start and maintain a gut-health diet.

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