Why do bile acids join with taurine or glycine before entering bile?

Bile acids are synthesized from cholesterol in the liver and must be modified before they are secreted into the bile to function effectively in the digestive system.12

Bile acids join with the amino acids taurine or glycine through a process called conjugation, where these molecules are chemically linked to a side-chain carboxyl group of the bile acid. This conjugation serves two primary purposes:12

• Increased Solubility: Linking these amino acids significantly increases the solubility of the bile acids.1
• Enhanced Digestive Effectiveness: By increasing their solubility, conjugation makes the bile acids more effective as detergents. These conjugated bile acids act as emulsifiers in the small intestine, breaking down dietary fats into small droplets that can be easily processed by digestive enzymes and facilitating the absorption of fat-soluble vitamins.132

Once conjugated, these substances are typically secreted as sodium salts, which assist in the emulsification and absorption processes essential for human nutrition.42