Answer · Bile
Bile Salts vs Bile Acids
Bile acids are the cholesterol-based molecules the liver makes, mainly cholic acid and chenodeoxycholic acid. Bile salts are those acids after the liver joins them to glycine or taurine, which lets them dissolve in water and break dietary fat into small droplets. In the intestine, the salt form does most of that emulsifying work.
By Stephen Heuer, B.S. Nutripath · 36+ years · Published · Updated
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What is a bile acid?
A bile acid is an end product of cholesterol metabolism. Hepatocytes make primary bile acids, then gut bacteria can change them into secondary bile acids. Hofmann and Hagey describe bile acids, in the form of their conjugates, as amphipathic molecules with several jobs: they help absorb lipids, they travel in an enterohepatic loop between liver and ileum, and they act as signals on nuclear receptors and G-protein-coupled receptors.
Chiang’s 2013 review makes the same split. Bile acids carry lipids and waste out in bile, and they also regulate lipid, glucose, and energy metabolism. That signaling role is separate from the detergent role people mean when they say “bile for fat digestion.”
What is a bile salt?
A bile salt is a conjugated bile acid. Before secretion into bile, the liver attaches glycine or taurine. The conjugate is an anion, paired with a counter-ion such as sodium, and that water-soluble form is what textbooks and Hofmann’s review call a bile salt.
The naming is loose in everyday writing. People say “bile acid” for the whole family. When the question is salts versus acids, the useful line is conjugation. Unconjugated acids are the parent molecules. Salts are the conjugated form that mixes with watery intestinal contents and emulsifies fat.
Why does the difference matter for fat digestion?
Fat digestion needs a detergent at the oil-water boundary. Bile salt anions do that. Hofmann and Hagey write that bile salt anions promote lipid absorption and also help trypsin cleave dietary protein. Without enough of that conjugated pool, fat and fat-soluble nutrients are harder to absorb.
A purified bile acid, such as a prescription ursodeoxycholic acid drug, is not the same object as a mixed bile-salt supplement. One is a single therapeutic acid. The other is a mixture of the conjugated salts that normally sit in bile.
Is ox bile a salt or an acid?
Ox bile supplements are dried animal bile. Bile, as secreted, is mostly the conjugated salt form, not a jar of free cholic acid. The Ox Bile 500 mg capsule in this catalog is that kind of digestive bile product. It is not a prescription bile-acid drug, and the capsule label is the dose information.
Which studies is this based on?
These two reviews are the sources for the chemistry and the signaling role. They are not studies of the Ox Bile capsule sold here.
- Hofmann AF, Hagey LR. Bile acids: chemistry, pathochemistry, biology, pathobiology, and therapeutics. Cell Mol Life Sci. 2008;65(16):2461-2483. doi:10.1007/s00018-008-7568-6
- Chiang JYL. Bile acid metabolism and signaling. Compr Physiol. 2013;3(3):1191-1212. doi:10.1002/cphy.c120023
Frequently asked questions
Are bile salts and bile acids the same thing?
No. Bile acids are the cholesterol-derived molecules. Bile salts are those acids conjugated with glycine or taurine so they dissolve in water. Everyday writing often uses the names interchangeably.
Does an ox bile capsule replace a prescription bile acid?
No. Ox bile is a mixed digestive bile product, mostly conjugated salts. Prescription bile acids such as ursodiol are single drugs used for specific medical reasons. They are not substitutes for each other.
Do bile salts only digest fat?
Emulsifying fat is the job people ask about. Reviews also describe an enterohepatic circulation and signaling through nuclear receptors and G-protein-coupled receptors. A supplement page is not a treatment for a bile-acid disorder.
Related on this site
Educational information only. These statements have not been evaluated by the Food and Drug Administration. This page does not diagnose, treat, cure, or prevent any disease.
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