Bile acid malabsorption (BAM)

Bile acid malabsorption (BAM) is a digestive condition that occurs when the intestines are unable to properly absorb bile acids produced by the liver. This leads to extra bile in the intestines, which may in turn cause watery diarrhea. Bile is a natural body fluid containing acids, proteins, salts, and other materials essential to proper digestion. Under normal circumstances, bile acids help break down food and nutrients in the stomach and intestines so that they can be efficiently absorbed into the body. Conditions like BAM interfere with this process and ultimately cause digestive problems like diarrhea. Bile acid malabsorption is also sometimes known as bile acid diarrhea (BAD) because modern research has suggested BAM may not always be the result of malabsorption. In any event, the symptoms of BAM or BAD can typically be improved with pharmaceutical treatment, changes to one's diet, or some combination of both.

Background

Bile is a thick, sticky yellow-green fluid that aids digestion by breaking down fats into fatty acids that can be absorbed into the body via the digestive tract. Bile is produced in the liver and stored in the gallbladder, which is a storage sac organ found on the underside of the liver. Bile is released from the gallbladder and liver while food is being consumed. In order for this to happen, the bile must pass through tubes known as bile ducts to the small intestine. Most gallbladder problems arise from blockages of the bile ducts.

The liver is a crucial organ without which one could not live more than about a day. It is primarily responsible for detoxification, metabolism, synthesis, and storage of different substances. One of those substances is bile. Bile is composed of an array of materials such as salts, water, copper, cholesterol, and pigments. Chief among the pigments found in bile is bilirubin, which causes a yellowish discoloration known as jaundice when it accumulates in blood and tissues. Bile stored in the gallbladder is released when food enters the duodenum, which is the first section of the small intestine. Bile pumped into the duodenum mixes with food, stomach acids, and digestive fluids from the pancreas to make it easier for the intestines to absorb nutrients into the bloodstream. Bile also helps the body to get rid of waste products like excess cholesterol and hemoglobin from destroyed red blood cells.

There are a number of potential medical conditions tied to bile. One of the most common of these is bile reflux. Bile reflux happens when bile backs up into the stomach and esophagus, which is the tube that connects the mouth to the stomach. Bile reflux often occurs alongside acid reflux, a similar condition that occurs when stomach acid backs up into the esophagus. While acid reflux can usually be resolved with dietary or lifestyle changes, bile reflux often requires pharmaceutical treatment or sometimes even surgical intervention. The delivery of bile can also be hampered by bile duct blockages caused by gallstones or gallbladder cancer or bile duct damage caused by chronic hepatitis C. BAM is another common bile-related medical condition.

Overview

BAM is a condition traditionally thought to occur when the intestines are unable to properly absorb bile acids. When bile enters the stomach and small intestines, it helps the body absorb nutrients into the bloodstream. Eventually, the bile injected into the digestive tract reaches the colon. An overabundance of bile acids in the colon caused by BAM can ultimately lead to diarrhea, watery stool, and bloating. Other possible symptoms of BAM include stomach cramps, flatulence, weight gain or loss, lethargy, difficulty concentrating, or nausea. In some cases, BAM may also cause diarrhea urgency, which is the sudden need to have a bowel movement as quickly as possible.

There are three types of BAM that are categorized according to their specific causes. Type 1 BAM typically arises following surgical removal of part of the small intestine. It can also be caused by inflammatory bowel conditions like Crohn's disease. Type 2 BAM, which is also known as primary or idiopathic BAM, has no obvious cause. Type 3 BAM, or secondary BAM, occurs as a symptom of other conditions. Some of the conditions that may result in secondary BAM include Crohn's disease, celiac disease, small intestine disease, pancreatic diseases, and small intestinal bacterial overgrowth. Radiation treatment can also cause secondary BAM. In addition, it is important to note that while BAM is traditionally viewed as a condition ultimately caused by malabsorption, modern research has revealed that may not always be the case. This is why BAM is alternatively known as BAD.

BAM can be a difficult condition to diagnose. While there are several tests used to diagnose BAM in Europe, only one, the fecal bile acid test, is available clinically in the United States. The fecal bile test requires the collection of stool samples over a 48-hour period and checking them for signs of bile. More frequently, BAM is diagnosed simply by ruling other conditions that could be causing a patient's symptoms. Even with these measures, it can take years for a patient to be officially diagnosed with BAM.

Treatment for BAM usually involves medication, dietary/lifestyle changes, or some combination of the two. Secondary BAM can also be addressed by treating the underlying condition. Medicinally, BAM is treated with a type of drug called a bile acid binder. These drugs bind with acids in the digestive tract to reduce the impact these acids have on the colon. Cholestyramine (Questran), colestipol (Colestid), and colesevelam (Welchol) are among the most commonly prescribed bile acid binders. Dietary treatment of BAM typically involves sticking to a low-fat diet so as to limit the body's production of bile acid. Those attempting to follow such a diet may need to avoid foods like butter/margarine, mayonnaise, fried/breaded foods, baked goods, processed meats, and full-fat dairy products. Because the body does need fats for healthy functioning, it is a good idea to replace problematic fats with healthier fats found in foods like avocados, salmon, sardines, and nuts. That being said, even these foods should be consumed only in moderation to mitigate their potentially negative impact on digestion in connection with BAM.

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