The bile is a bodily fluid that is greenish-yellow in colour. In humans, it is produced and secreted by the liver. The bile then passes through the bile duct towards the gallbladder where it will be stored. The gallbladder bile is comprised mainly of water (97%). Other components include bile salts, bilirubin and other bile pigments, fats (e.g. cholesterol), and inorganic salts. Bile salts aid in the digestion of fats. Adult humans produce about 400 to 800 ml of bile per day.
Digestion of a fat-containing foodstuff incites the discharge of bile from the gallbladder into the duodenum to aid in the digestion of lipids. It acts as a surfactant, emulsifying the lipids. The bile salts, in particular, aggregate around the droplets of lipids and form micelles. This prevents fat droplets from aggregating into larger fat particles.