Twenty amino acids build every protein. Nine are essential — they must come from food.
How it works, step by step
Digestion frees amino acids from food protein.
They're absorbed and travel to the liver, then the body.
Ribosomes link them in the order DNA dictates.
Extras are burned for energy; nitrogen leaves as urea.
What does Amino Acids do?
Linked in chains to make enzymes, muscle, hormones, antibodies and transporters. Some also become neurotransmitters (tryptophan → serotonin; tyrosine → dopamine).
Which foods contain Amino Acids?
All protein foods. Animal foods and soy contain all nine essential amino acids in useful proportions; other plant foods are combined across the day.
How much Amino Acids do adults need?
Requirements are set for each essential amino acid by the National Academies; meeting total protein needs from varied foods usually covers them.
What is known and unknown about Amino Acids?
Essential amino acid needs are well established. Benefit of BCAA supplements beyond adequate total protein is not well supported.
Evidence & sources
Nine amino acids are essential for humans: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Evidence: established. Known: Foundational nutrition science. Unknown: — Source: National Academies (Institute of Medicine), Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (2002/2005).