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Essential Amino Acid
Amino acid that cannot be synthesized by humans in sufficient quantity to meet metabolic demand and must be obtained from the diet: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine.
Also: EAA, Indispensable amino acid
Some amino acids are conditionally indispensable (arginine, cysteine, glutamine, glycine, proline, tyrosine) under stress, growth, or specific disease (e.g., glutamine in critical illness, tyrosine in PKU). Quality of dietary protein is increasingly assessed by DIAAS (Digestible Indispensable Amino Acid Score) rather than PDCAAS, with animal proteins generally scoring higher than plant proteins, though strategic combining closes most gaps.
How each textbook covers it
duyff-complete-food-and-nutrition-guide-5e
Modern Nutrition in Health and Disease, 12th ed. — Ch 1: Proteins and Amino Acids
Some amino acids are conditionally indispensable (arginine, cysteine, glutamine, glycine, proline, tyrosine) under stress, growth, or specific disease (e.g., glutamine in critical illness, tyrosine in PKU). Quality of dietary protein is increasingly assessed by DIAAS (Digestible Indispensable Amino Acid Score) rather than PDCAAS, with animal proteins generally scoring higher than plant proteins, though strategic combining closes most gaps.
Related terms
DIAAS, Leucine, PDCAAS, Protein