Amino acids: what they do and where to find them

It means the body usually makes enough, but may not during illness, injury or rapid growth. Arginine, cysteine, glutamine, glycine, proline and tyrosine are in this group.

There is no US RDA for single amino acids. The WHO, FAO and UNU 2007 report sets adult needs per kilogram of body weight a day: leucine 39 mg, lysine 30 mg, valine 26 mg, phenylalanine with tyrosine 25 mg, isoleucine 20 mg, methionine with cysteine 15 mg, threonine 15 mg, histidine 10 mg and tryptophan 4 mg. For a 70 kg adult that is about 2.7 g of leucine a day.

Usually not. Food protein supplies all of them, and adults need about 0.8 g of protein per kilogram of body weight a day (0.83 g in EFSA's reference). Single amino acid and BCAA supplements are also a source, but they add only the amino acids on the label.

Most are low in one essential amino acid: grains in lysine, beans and lentils in methionine. Eating both across the day covers each, and soy protein is close to complete on its own.

Branched-chain amino acids: leucine, isoleucine and valine, named for the branch in their side chain. Unlike most amino acids, they are broken down mainly in muscle rather than in the liver.

Yes, but not one that builds protein. The body makes it from cysteine, meat, fish and dairy supply it, and it is added to many energy drinks.

Caltide adds up the nine essential amino acids, plus cystine and tyrosine, from the foods you log and the supplements you tick, and shows them in the Nutrition tab.