Expansion
Bile salts, phospholipids, cholesterol, bilirubin and bicarbonate
Expansion
Composition
- Bile salts (conjugated with glycine or taurine), the functional component
- Phospholipids, mainly lecithin
- Cholesterol
- Bilirubin, conjugated, giving the colour
- Bicarbonate and electrolytes
- About 500 ml a day
Functions
- Emulsification of fat, increasing the surface area for lipase
- Micelle formation, solubilising fatty acids and monoglycerides so they can reach the enterocyte brush border
- Absorption of fat-soluble vitamins A, D, E and K
- Excretion of bilirubin, cholesterol, drugs and heavy metals
- Neutralisation of gastric acid
Gallstones form when the ratio of cholesterol to bile salts and lecithin exceeds the capacity for solubilisation, which is why the classic risk factors of obesity, rapid weight loss, oestrogen, and ileal disease with bile salt loss all operate on the same balance.