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What are the causes of diarrhea?

A dietitian discusses common causes of diarrhea and how to manage it at home.
Cropped shot of an unrecognizable woman reaching for toilet paper
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While traditional and more severe symptoms of COVID-19 include coughing and shortness of breath, about 80 percent of people experience less severe illness, which may not include respiratory symptoms but other bodily maladies. For example, one source of coronavirus distress may be a bout of diarrhea. But there are other causes of diarrhea too. Here are some of the most common causes of diarrhea, as well as some home remedies that may bring relief.

Viruses that cause diarrhea

If you’ve come into contact with someone who has had the coronavirus, or perhaps if you’re an essential worker who’s in contact with a number of people every day and diarrhea is a new occurrence, it may be a symptom of this virus. A new study (that hasn’t undergone peer-review) suggests that diarrhea related to COVID-19 may be more common among women. It may last up to two weeks, with an average duration of around 5 days. Additionally, it may or may not be accompanied by fever. Among participants in this study, abdominal pain was uncommon.

Bear in mind that even if your diarrhea is a recent occurrence, the study authors point out that other causes are more likely. Still, it’s a good idea to check in with your doctor to see if you might need to take extra quarantine precautions.

Aside from coronavirus, plenty of other viruses may cause diarrhea. The norovirus and rotavirus are some of the more common infections that lead to GI issues. These viruses spread very easily, so wash hands thoroughly and often to help prevent infection.

Food-borne causes of diarrhea

A variety of different germs and toxins can cause diarrhea if you’ve consumed a contaminated or improperly cooked food. Norovirus and salmonella are among the more common causes of food-borne illness. To prevent these types of infections, it’s important to keep raw and cooked foods separate, to store foods at the proper temperature and to cook them to the right internal temperature in order to kill the germs. In addition to following good hand-washing measures, be sure to clean surfaces, including counters and cutting boards, that come into contact with your food.

Foods that cause diarrhea

Intolerances and allergies to certain foods can also cause diarrhea. The difference between these two is that an allergy causes an immune reaction that may produce other, life-threatening symptoms. While food allergies require total avoidance of the food in question, an intolerance is typically less serious so you may be able to tolerate small amounts of the food or substance (such as a food additive) without producing symptoms.

Lactase, the natural sugar in dairy foods, like milk, is a common intolerance that can trigger diarrhea. Foods with highly fermentable short-chain carbohydrates, known as FODMAPs, are other common triggers.

Products made with sugar alcohols, like sorbitol and mannitol, which are very low calorie sweeteners, can cause diarrhea because the sugar alcohols draw water into your colon. These sweeteners are often found in chewing gum, snack bars and sugar-free sweets.

Causes of chronic diarrhea

Common GI disorders, including Crohn’s disease, ulcerative colitis, celiac disease and irritable bowel syndrome, are associated with chronic diarrhea. Some of these illnesses may be accompanied by bloating, cramping and bloody diarrhea. Report any blood or mucus in your stool to your doctor.

Diarrhea from supplements and drugs

You can get diarrhea from common prescription and over the counter drugs and supplements. For example, NSAIDs, like ibuprofen, and omeprazole (Prilosec) may induce diarrhea. Magnesium citrate is a supplement that’s often used to help you feel more relaxed so you can sleep better, but this form of magnesium is also used to treat constipation and in higher doses, can cause diarrhea. Whenever you’re taking a new medication or supplement, be sure to check the label for common side effects.

Managing diarrhea at home

Adults with diarrhea should check with a doctor if it lasts more than a couple of days, is accompanied by blood or mucus or if they have fever or severe belly pain too. Persistent diarrhea can lead to dehydration, which is another reason to call your doctor.

When you have diarrhea, certain foods may exacerbate it. While you recover, you’re best off avoiding:

  • Alcohol
  • Coffee and other caffeinated beverages
  • Dairy foods, including milk, ice cream and cottage cheese
  • Fatty food, like high-fat meats and French fries
  • Certain fruits, including those with edible skins, like apples, as well as fruits with seeds
  • Raw veggies
  • Beans
  • Spicy foods
  • Products that contain sugar alcohols, such as sorbitol, mannitol or xylitol

In addition to avoiding foods and drinks that may worsen diarrhea, it’s a good idea to consume a lot of liquids, including clear broth, decaffeinated and herbal teas — and if your diarrhea is frequent, you may want to consider an electrolyte-containing drink like coconut water or Gatorade.

Remember that diarrhea has a number of causes so there isn’t one specific remedy; however, when you have diarrhea, you may feel better eating smaller meals and more easily digestible foods. Some examples include:

  • Scrambled or boiled eggs
  • Hot cereal, like oatmeal and cream of wheat
  • Cooked, peeled veggies, such as cooked carrots and zucchini
  • Starchy foods, like peeled potatoes, white rice and soda crackers, which can be added to broth — toast is another option
  • Bananas

These types of foods are gentle on your GI system, but they don’t represent a balanced, nutritious diet. When you’re back on track and can tolerate a wider variety of foods, remember to add fruits, veggies, nuts, seeds, whole grains, beans, dairy and protein back into your diet.