Bile acid malabsorption (BAM) is a condition that occurs when your intestines can’t absorb bile acids properly. This results in extra bile acids in your intestines, which can cause watery diarrhea.

Bile is a natural fluid your body makes in the liver. It’s necessary for proper digestion. Bile contains acids, proteins, salts, and other products. The common bile duct moves it from your liver to your gallbladder, where it’s stored until you eat. When you eat, your gallbladder contracts and releases this bile into your stomach.

Once the bile is in your stomach and small intestine, the acids in the bile help break down food and nutrients so your body can absorb them efficiently. In your colon, bile acids are reabsorbed back into your bloodstream so they can be used again.

From time to time, the bile acids aren’t reabsorbed properly, leading to BAM. Too much bile acid in your colon can lead to diarrhea and watery stool, which is why BAM is sometimes called bile acid diarrhea.

The main symptom of BAM is diarrhea. Salt and water from bile acid in your colon prevent stools from properly forming, leading to diarrhea. This diarrhea might happen every day or only occasionally.

Some people with BAM also experience bloating and diarrhea urgency, which refers to suddenly needing to use the restroom as soon as possible.

In some cases, there’s no clear explanation for why the colon doesn’t fully reabsorb bile acids. When this happens, it’s called primary BAM.

In other cases, BAM results from an underlying condition. For example, it’s been estimated that about one-third of people with irritable bowel syndrome and diarrhea (IBS-D) have BAM.

BAM can also be a symptom of another condition. This is referred to as secondary BAM.

Other conditions related to secondary BAM include:

Side effects of medications can also contribute to BAM.

There are a few tests available in Europe that can help to diagnose BAM, but many aren’t available in the United States. However, according to the Mayo Clinic, two tests are now available for U.S. use, one for research purposes and the other clinical use:

  • fasting serum C4, for research use only
  • fecal bile acid test

The fecal bile acid test involves collecting stool samples over the course of 48 hours and examining them for signs of bile acid.

Keep in mind that this test still has limited availability in the United States, so your doctor may instead make a diagnosis by ruling out other conditions that might be causing your watery diarrhea, such as another type of malabsorption. They may even prescribe a medication used to treat BAM to see if it helps. If your symptoms start to improve with the medication, this may be enough to make a diagnosis.

Treatment for bile acid malabsorption usually focuses on medication and dietary changes. Most people with BAM find the best results by using a combination of the two.

In many cases of secondary BAM, treating the underlying condition can also eliminate symptoms.

Medication

The main type of medication used to treat BAM is called a bile acid binder. It binds with the bile acids in your digestive tract, which reduces their impact on your colon.

Bile acid binders are typically very effective at treating diarrhea associated with BAM. Some common bile acid binders include:

Diet

Dietary changes may also help reduce episodes of diarrhea if you have BAM. Bile is required for fat digestion. This means your body has to release more bile and bile acids when you eat a lot of foods that are high in fat.

Following a low-fat diet can reduce the amount of bile acid your body produces, causing less of it to make its way to your colon. Having lower levels of bile acids in your colon lowers your chances of having diarrhea if you have BAM.

To reduce your fat intake, try to avoid eating:

  • butter and margarine
  • mayonnaise
  • fried or breaded foods
  • baked goods, such as croissants, cookies, and pastries
  • lunch meats, hot dogs, sausage, bacon, or other processed meats
  • full-fat dairy products, such as whipping cream or sour cream

Keep in mind that your body still needs some fat to function properly. Try swapping some of the foods above for these healthier fats, such as:

  • avocados
  • fatty fish, such as salmon and sardines
  • nuts, including cashews and almonds

While these fats are better for your body, you should still try to consume them in moderation if you have BAM. Your doctor may refer you to a registered dietitian or nutrition counselor. Together, you can create a diet plan that works for your lifestyle and helps you to manage your symptoms.

Most people with bile acid malabsorption respond well to treatment and are able to prevent or manage their symptoms with medications and lifestyle changes. If you and your doctor are able to identify an underlying condition that’s causing BAM, you may be able to eliminate the condition entirely by treating the underlying issue.