What is taurine?

In one line

Taurine is an amino acid found throughout the body that is not used to build protein, and it does several jobs, such as making part of bile.

What is taurine?
The name on energy drink cans
You often see the name 'taurine' on energy drink cans and ingredient lists. Taurine is actually a substance found throughout our own bodies. This post explains, step by step, what taurine is, what it does in the body, and how much of it is in energy drinks.
In one line
An amino acid that is not used to build protein
Amino acids are usually the small pieces that make up protein. Taurine is also a kind of amino acid, but it is one of the few amino acids not used to build protein. Instead, it does various jobs throughout the body without being tied into protein.
What it looks like
An amino acid containing 'sulfur'
Taurine looks a little different from ordinary amino acids. It lacks one part that all ordinary amino acids have, and in its place it carries a part containing the element 'sulfur'.
Where is it in the body?
Especially high in the brain, eyes, heart and muscles
Taurine is found in almost every tissue of the body, including the brain, eyes, heart and muscles. In these places it is one of the most common amino acids.
Where does it come from?
The body makes it, and we also eat it in meat and seafood
The body makes taurine from other amino acids (such as cysteine), in the liver and elsewhere. But humans make only a small amount, so taurine eaten in meat, seafood and dairy also helps keep the body's level up. People who eat only plant foods get much less taurine from food.
A conditionally essential nutrient
Usually not short, but sometimes it is
Taurine is classed as a 'conditionally essential nutrient'. This means that what the body makes plus food is usually enough, but in some situations it runs short and must be supplied separately. Taurine shortage has been reported in people who cannot eat by mouth and get nutrition only through a vein.
Job in the body #1
Making part of bile
The liver makes a digestive fluid called 'bile' (gall) and sends it to the gut, where bile helps digest the fat in food. Taurine attaches to 'bile acids', the main part of bile, and becomes a raw material for 'bile salts'.
Job in the body #2
Keeping cell size steady
Cells need water to move in and out in the right amounts, or they swell up or shrivel. Taurine stays dissolved inside cells and is used to keep cell size steady.
Taurine in energy drinks
Usually about 1,000 mg per can
Energy drinks are usually made so that one 250 mL can contains about 1,000 mg of taurine. That is far more than the taurine a person who eats meat and fish gets from food in a whole day.
Common misconception
Is taurine extracted from bulls?
No. Taurine got its name because it was first found in the bile of cattle, and the name comes from the scientific name for cattle, 'Bos taurus'. The taurine added to energy drinks and supplements is made in factories by chemical reactions, not taken from animals.
Summary
Not a protein building block, but an amino acid found all over the body
Taurine is an amino acid that is plentiful throughout the body but is not used to build protein; it makes part of bile and keeps cell size steady. Its name comes from cattle bile, where it was first found, and the taurine in drinks and supplements is made in factories. Related terms: amino acids, caffeine, pre-workout.