The greenish digestive fluid produced by the liver that helps break down fats is bile.
Bile is made continuously by the liver and stored and concentrated in the gallbladder. After a meal, the gallbladder releases it into the duodenum, the first section of the small intestine. Its bile salts act like detergents: they disperse large fat droplets into tiny micelles, giving pancreatic lipase more surface area to digest triglycerides.
Bile does not itself digest fat with enzymes. Instead, it helps emulsify fats and supports absorption of fat-soluble vitamins A, D, E, and K. It also helps neutralize acidic stomach contents entering the small intestine and carries bilirubin, a pigment produced when old red blood cells are broken down.
People often confuse bile with stomach acid or digestive enzymes. Its yellow-green color comes mainly from bilirubin and biliverdin. Excess cholesterol in bile can crystallize into gallstones, while inadequate bile reaching the intestine can cause poor fat absorption and greasy stools.