What are amino acids?
General information only. This article explains the basics and is not medical advice. For anything about your own health, talk to a doctor or other qualified professional.
Quick answer
Amino acids are the building blocks of proteins. The human body uses 20 different amino acids to make proteins. 9 of them are essential, meaning your body can’t make them, so they must come from food.
Every protein in your body, from the keratin in your hair to the enzymes that digest food, is a chain of amino acids folded into a particular shape. Change the order of the amino acids and you get a completely different protein, much as the same 26 letters spell different words.
The three groups
| Group | What it means | Amino acids |
|---|---|---|
| Essential (9) | Must come from food | Histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine |
| Conditionally essential | Usually made by the body, but needed from food during illness or stress | Arginine, cysteine, glutamine, glycine, proline, tyrosine |
| Nonessential | The body makes enough on its own | Alanine, asparagine, aspartic acid, glutamic acid, serine |
What amino acids do
- Build and repair tissue, including muscle, skin and organs.
- Make enzymes and hormones, the molecules that run chemical reactions and send signals.
- Make neurotransmitters: tryptophan, for example, is used to make serotonin.
- Provide energy when the body needs it.
Short chains of amino acids are called peptides; long, folded chains are proteins.
Which foods have them?
A complete protein contains all nine essential amino acids in useful amounts.
- Complete: meat, fish, eggs, dairy, soy and quinoa.
- Incomplete: most beans, grains, nuts and seeds, which are low in one or more essential amino acids.
Plant-based eaters can still get everything they need by eating a variety of protein sources over the day, such as beans with rice or hummus with whole-wheat bread.
Do you need amino acid supplements?
Most people who eat enough protein from varied foods get all the amino acids they need. Supplements are sometimes used in medical care or sports, but they aren’t necessary for most healthy people, and anyone with a health condition should ask a doctor first. See how much protein you need a day.
Sources
Still curious?
Jump to a random question from the archive.