Bile acid diarrhea (BAD) is caused when bile salts are not absorbed properly in the small intestine and pass into the large intestine. This results in increased colonic motility and secretion that causes chronic watery diarrhea. 

Approximately 1% of the population will experience BAD. Around 25-33% of patients presenting with chronic diarrhea have BAD as an underlying contributing factor. Bile acid malabsorption occurs in approximately one-third of patients with irritable bowel syndrome with diarrhea (IBS-D), up to 50 percent of those with functional diarrhea, and 35 percent with microscopic colitis.

Bile acid diarrhea can be approached with the help of integrative medicine by under covering and addressing contributing factors like pancreatic dysfunction, bowel inflammation, dysbiosis, and cholesterol imbalances. For example, an anti-inflammatory diet incorporating fibers like resistant starch can help bind excess bile acids and rebalance the gut environment.  

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What is Bile Acid Diarrhea?

Bile is a fluid that the liver makes. The liver filters the blood, sorts waste products like excess cholesterol and bilirubin from breaking down red blood cells, potassium, sodium, copper, and other metals, and water, and combines these wastes with bile salts. The liver then sends the bile to the gallbladder, where it is concentrated and stored until it is released into the small intestine to help with digestion. In the small intestine, bile helps to break down fats for absorption. Normally, once digestion is completed, most of the bile acids pass from the end of the small intestine back into the bloodstream, returning to the liver to be recycled into bile again.

If the bile acids are not reabsorbed like this back into the bloodstream, they continue in the digestive tract and into the large bowel (colon). This triggers abnormally high levels of water and salts to be pulled into the large bowel from the blood, leading to watery diarrhea or bile acid diarrhea. 

Bile Diarrhea Acid Symptoms 

The main symptom of BAD is watery diarrhea, which may be persistent or intermittent. In addition to diarrhea, people with BAD may experience:

• increased frequency of stools
• the urgency to empty the bowels
• flatulence
• abdominal pain
• nocturnal defecation
• fecal incontinence
  

Over time, chronic diarrhea can result in dehydration, headaches, fatigue, dizziness, and weight changes. Severe bile acid malabsorption eventually leads to a deficiency of bile acids that impacts digestion and nutrition. Bile acid deficiency results in the malabsorption of fats and fat-soluble vitamins (A, D, E, and K). 

What Causes Bile Acid Diarrhea

The symptoms of BAD occur mainly due to a higher concentration of bile acids entering the colon. This can happen for several reasons. 

The causes of bile acid diarrhea can be subdivided into four major categories.

Type I Bile Acid Diarrhea

Type I occurs due to conditions like Crohn's disease, inflammation of the small intestine due to radiation treatment, and removal of parts of the ileum. These conditions prevent the reabsorption of bile acids from the terminal ileum or end of the small intestine. 

Type III Bile Acid Diarrhea

Type III is related to conditions that impact the pancreas, liver, gallbladder, and/or intestines resulting in malabsorption. For example, chronic pancreatitis, celiac disease, cholecystectomy (removal of the gallbladder), or exocrine pancreatic insufficiency can all cause malabsorption and imbalance of bile acids.

Type II and Type IV Bile Acid Diarrhea

In Type II and Type IV or primary BAD, the liver produces too many bile acids due to the interruption of the normal negative feedback loop that regulates bile acid synthesis. This results in more than typical bile acids entering the colon. High triglyceride levels or taking the medication metformin can cause this type of BAD. In some cases, the underlying cause of chronic diarrhea is unclear and is often labeled as diarrhea-predominant irritable bowel syndrome (IBS-D). 

Once these bile salts reach the colon, several impacts are thought to occur. It has been proposed that the presence of bile salts in the large intestine triggers increased secretion of sodium and water into the colon. Others have suggested that bile acids stimulate increased colonic motility and the urge to defecate with bile salts causing mucosal damage in the colon and leading to increased permeability. 

The microbes in the gut microbiome also play a role in the metabolism and regulation of lipids and bile salts, playing a role in their breakdown and recycling. Studies suggest that the higher proportion of primary fecal bile acids seen in patients with BAD may be due to decreased Bifidobacteria and Leptum species and increased Escherichia coli in their gut microbiota. Likewise, bile acids play key roles in metabolism, cell signaling, and microbiome composition. When bile acid levels are decreased in the gut, bacterial overgrowth and inflammation can occur.

Functional Medicine Labs to Test for Root Cause of Bile Acid Diarrhea

Functional medicine practitioners commonly use specialty labs to get to the root cause of bile acid diarrhea. Below are some of the most common ones:

Bile Acid Levels

Bile acids can be measured through the blood and stool. Increased total fecal bile acids are seen with chronic functional diarrhea. Higher levels of the primary bile acids cholic acid (CA) and chenodeoxycholic acid (CDCA) can occur with IBS-D.

Comprehensive Stool Testing

Comprehensive stool testing like the Gut Zoomer evaluates fat malabsorption, intestinal inflammation, and dysbiosis in the gut that frequently accompanies bile acid imbalances. This stool test evaluates microbes in the digestive tract to assess overall balance, conditions like SIBO, metabolic imbalances, and functional digestive status.

Nutrition Status

Since chronic diarrhea and bile acid, malabsorption increases the risk of malnutrition and nutritional deficiencies, testing can evaluate areas of concern to target. The NutraEval FMV measures a variety of antioxidants, vitamins, minerals, fatty acids, and other biomarkers to determine nutritional deficiencies and imbalances if fat malabsorption is suspected.

Cholesterol and Triglyceride Levels

A cholesterol panel can evaluate high or low cholesterol levels that can contribute to abnormal bile acid levels. Further evaluation with the Cholesterol Balance test can help elucidate the cause of abnormal cholesterol levels by measuring markers of endogenous synthesis and gastrointestinal absorption of cholesterol.

Liver and Gallbladder Health

A comprehensive metabolic panel (CMP) can evaluate blood sugar and liver/gallbladder function. Liver function tests evaluate liver enzymes (alanine aminotransferase (ALT) and aspartate aminotransferase (AST)), proteins, and bilirubin (a substance in bile) to assess liver dysfunction or damage. Gamma Glutamyl Transferase (GGT) is another enzyme primarily made in the liver that can reflect that the body is trying to generate greater levels of glutathione to deal with detoxification or oxidative stress.

Pancreatic Function

Blood tests can measure elevations in the levels of two digestive enzymes (amylase and lipase) produced by the pancreas to assess inflammation that would indicate pancreatitis.

Elastase is a specific marker for pancreatic function that can be measured in the stool. It can help to assess how well the pancreas is making certain digestive enzymes as a result of chronic pancreatitis or other causes.

Additional Labs to Check  

Conventional guidelines recommend a selenium homocholic acid taurine (SeHCAT) scan or measurement of 7αC4 levels to investigate whether BAD contributes to chronic diarrhea.

The SeHCAT is a nuclear medicine imaging test. It requires swallowing a capsule containing a radioactive tracer and a synthetic bile acid (SeHCAT) to track how much is absorbed in the small intestine over time.

The 7αC4 blood test is a more readily available alternative to nuclear imaging to diagnose BAD. It measures levels of 7α-hydroxy-4-cholesten-3-one in your blood, a downstream product of CYP7A1, which correlates with how many bile acids your liver is producing. Elevated 7αC4 levels (not to be confused with C4 complement levels) suggest primary BAM caused by the overproduction of bile acids or secondary BAM (types 1 and 3) if malabsorption triggers the liver to compensate by producing more bile acids. 

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Conventional Treatment for Bile Acid Diarrhea

Conventional treatments for bile acid diarrhea center around a low-fat diet and medications called bile acid binders or sequestrants. These medicines, like cholestyramine, colestipol, or colesevelam, bind to bile acids in the bowel.

Functional Medicine for Natural Treatment of Bile Acid Diarrhea

Based on intake questionnaire and lab results a personalized treatment plan is made. Below are some of the most common integrative medicine treatment modalities for bile acid diarrhea.

Best Diet for Bile Acid Diarrhea 

As an alternative to bile acid sequestrant medications, resistant starch and fiber in the diet can reduce secondary bile acids in the stool by binding to them and increasing their elimination. Resistant starch is present in various plant-based foods like lentils, peas, beans, cooked and cooled rice, whole grains, and firm/green bananas. It provides a source of fiber and prebiotics to feed healthy gut bacteria. 

Consuming a wide variety of plant foods and sources of fermentable fiber also helps to feed the good bacteria in your gut so that they can produce adequate amounts of short-chain fatty acids (SCFAs). Consuming adequate amounts of insoluble fiber promotes short-chain fatty acid production by microbes in the colon, which lowers the pH and inhibits the enzyme that normally deconjugates bile salts, reducing concentrations of bile acid breakdown products that can trigger diarrhea. 

Dietary fibers, including arabinoxylans, inulin, pectin, and fructooligosaccharides, as well as polyphenols found in plant foods and vitamin D, influence the balance of microbes in your gut and therefore impact the metabolism and levels of bile acids. A well-balanced, anti-inflammatory diet incorporating a variety of plant-based foods promotes a variety of beneficial bacteria, which helps to optimize the metabolism of bile acids and the production of SCFAs. 

Research suggests that reducing dietary fat intake can improve symptoms of BAD. When less fat is consumed, fewer bile acids are released to help digest and absorb them. Consuming high amounts of inflammatory animal products containing saturated fats is associated with elevated secondary bile acid levels that can result in watery diarrhea. On the other hand, medium-chain triglyceride (MCT) oils from coconut products do not require bile acids for digestion and may be better tolerated.

Supplements and Herbs for Bile Acid Diarrhea

Guggul regulates the transport of bile acids and also has anti-inflammatory impacts. 

Probiotics containing bacteria of the genera Lactobacillus may reduce the amount of bile acids that reach the large bowel, reducing the severity of diarrhea.

For those with inadequate digestive enzymes and/or pancreatic enzyme insufficiency, replacing digestive enzymes can help digest proteins, carbohydrates, and fat to take some of the burdens off the digestive tract.

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Summary

Bile acid diarrhea or bile acid malabsorption is a common cause of chronic diarrhea. This condition occurs when bile salts that normally help with the digestion of fats are not adequately taken back up in the small intestine for reuse and instead pass into the large intestine. This results in large amounts of water and salts being pulled into the bowel, causing watery diarrhea.

Malabsorption and/or overproduction of bile acids can occur with inflammatory conditions of the intestines like Crohn's disease, conditions which impact the pancreas, liver, gallbladder, and/or intestines resulting in malabsorption like chronic pancreatitis, celiac disease, cholecystectomy (removal of the gallbladder), or exocrine pancreatic insufficiency, and imbalances in the gut microbiome. This results in chronic watery diarrhea, abdominal bloating and pain, fatty stools, gas, and potential dehydration and malnutrition over time.

Bile acid levels can be measured in the blood and stool. In addition, functional medicine testing can evaluate the balance of the gut microbiome and the health of the digestive tract, including the function of the liver, gallbladder, and pancreas, to look for contributing factors.

Conventional treatments for BAD center around a low-fat diet and medications called bile acid binders or sequestrants. A dietary approach incorporating fiber and sources of prebiotics like resistant starch is an alternative approach to binding excess bile acids that contribute to diarrhea.