Produced in the liver by specialized cells called hepatocytes, bile salts comprise about 10 percent of bile. They are ionized bile acids, a form that makes them more active in fat digestion. Once they are ionized, the bile salt molecules have a side that is hydrophilic — water loving — and another that is hydrophobic — water hating. This allows the molecules to surround fat droplets in the small intestine and stop them from clumping together to form large fat globules. If there were no bile salts, fats would pass through the body largely undigested.
Once produced, these salts flow through the bile ducts in the liver to the common bile duct that connects the liver, the gallbladder and the small intestines. From here, they either flow into the intestines or are stored in the gallbladder, depending on what stage the digestive process is in. When food is present in the intestines, bile flows through a sphincter between the common bile duct and intestines to aid in the digestion of fats. If there is no food in the intestines, the bile is stored and concentrated in the gallbladder.
The primary function of bile salts is to emulsify fats in the small intestines. Acting in the same manner as detergents, bile salts break fats from foods into smaller particles. They surround each fat droplet with the hydrophobic side facing the fat particle. This action of breaking fats into small particles increases the total surface area of the fats to be digested. The fat particles are more available to the enzymes that will complete their digestion.
After the bile is used in the intestines, most of the bile salts are reabsorbed. They are returned to the liver and reprocessed into new salts. Research has shown that in addition to aiding in the digestion of fats, these salts may act as hormones. These hormones play a role in the regulation of cholesterol in the body. Another role of the salts is aiding in the proper digestion and absorption of the fat-soluble vitamins — vitamins A, D, E and K.
People who have had their gallbladder removed no longer have the site where bile is stored, concentrated and made available for digestion. The liver still secretes bile, but without the gallbladder, normal digestive processes may be disrupted. There may be an excess of intestinal bile at times or not enough at others. Bile salt supplements can be taken with meals to aid in the digestion of healthy fats; a lack of bile can cause constipation.