Bile acids are biosurfactants that emulsify fats and activate lipase, enabling it to cleave triglycerides. They also promote fat absorption in the small intestine. The primary bile acids are cholic acid, deoxycholic acid (DCA) and chenodeoxycholic acid (CDCA).

Normally, chemicals in your blood signal the liver to produce and send bile acids into your small intestine to help with digestion, then return to the liver to be recycled back into bile. This is called the enterohepatic circulation.

1. Improves Digestive Function

Bile Acid is the main component of bile and is secreted by the liver. Its primary components are cholic acid (3a, 7a, 12a-trihydroxy-5b-cholan-24-oic acid, CA), chenodeoxycholic acid (3a, 7a, 12-dihydroxy-5b-cholan-24-oic acids, CDCA) and subsequent C24 taurine or glycine conjugates (also known as the bile salts).

They have detergent action on fat particles in the gut that allows them to break down and emulsify the fat so it can be digested by lipases in a water-based environment. This helps to improve nutrient absorption.

Bile acid molecules also have antimicrobial properties. They can disrupt bacterial membranes, chelate polyvalent metals (such as iron and calcium) and inhibit protein synthesis. In addition, BAs have bacteriostatic effects in the small intestine and stimulate mucin secretion. However, the mechanisms by which they exert these effects remain largely unknown.

2. Reduces Cholesterol Levels

Bile acids are a major constituent of bile and play important roles in intestinal, hepatic, and cholesterol homeostasis. They promote fat digestion as a natural emulsifier and activate lipase to improve fat digestibility. They also protect the liver from damage by oxidative stress.

Bile acid synthesis begins with cholesterol in the liver, which is converted via 7a-hydroxylase and 27a-hydroxylase to the primary bile acids cholic acid (CA) and chenodeoxycholic acid (CDCA). In the intestine, they are further metabolized by bacteria and conjugated with glycine or taurine, which is secreted into the duodenum as conjugated bile salts.

The bile acids enter the small intestine and solubilize dietary lipids promoting their absorption. These actions of bile acids have long been recognized. More recently, however, it has become apparent that they are important as signaling molecules, regulating not only their own synthesis and enterohepatic circulation but triglyceride, glucose, and energy metabolism (1,2).

3. Helps Break Down Endotoxins

Endotoxins are a group of toxic substances which promote deterioration of shrimp hepatopancreas and decreases immunity ability. Bile acids can break down or combine these compounds into harmless substances, prevent absorption of endotoxins from the intestinal mucosa, and reduce hepatic damage by binding them.

The primary bile acids (cholic acid, taurocholic acid, and glycocholic acid) are important constituents of bile secreted by the liver in response to dietary fat. These bile acids create strong selective forces that shape gut microbiome composition, including increasing Firmicutes and decreasing Bacteroidetes phyla in obesity-associated gut microbial profiles.

The chemical structure of bile acid is shown in figure 1. These molecules are amphipathic, with hydrophobic and polar groups that associate with the surface of lipid droplets and interact with water to form stable emulsions of mixed micelles. These emulsions facilitate the digestion and absorption of dietary lipids. Moreover, bile acids are also involved in various other metabolic processes such as cholesterol metabolism, glucose homeostasis, and inflammation.

4. Aids in Weight Gain

Bile acids are cholesterol-derived metabolites that have well-established roles in the digestion and absorption of dietary fat. Specifically, they assist in solubilization and emulsification of fat and fat-soluble vitamins and promote the activation of lipases to improve fat digestibility. Gut microbiota can also transform primary bile acid pools through deconjugation and dehydroxylation to form secondary bile acids. The discovery that bile acid ligands act as natural agonists for nuclear farnesoid X receptor (FXR) and membrane Takeda G-protein coupled receptor 5 (TGR5) has led to a paradigm shift in knowledge of the role of bile acids in metabolic health.

Following a meal, primary bile acids are discharged from the gallbladder into the intestine. Upon entering the gut, they are conjugated to glycine and taurine, and secreted into bile, returning to the liver for re-secretion in a process known as enterohepatic circulation. The recognition that bile acid signaling through FXR and TGR5 modulates the secretion of gastrointestinal hormones such as glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), hepatic gluconeogenesis, glycogen synthesis, blood glucose metabolism, energy intake, and body weight has stimulated active research on their role in obes