GIFSQ Tools · Module 19 — Nutrition, Labeling & Dietary Assessment · Tool 369 of 500
Score a protein's nine essential amino acids against the FAO/WHO reference pattern and find the limiting one.
Try sample values — fills the form with the worked example below.
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Limiting score (%)
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Limiting amino acid
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Mean score (%)
Equation: Amino acid score (%) = amount (mg/g protein) ÷ reference (mg/g protein) × 100, per amino acid. The limiting score is the lowest of the nine.
Method: FAO/WHO/UNU Protein and Amino Acid Requirements in Human Nutrition (2007), adult reference pattern (mg/g protein): Histidine 15, Isoleucine 30, Leucine 59, Lysine 45, Methionine+Cystine 22, Phenylalanine+Tyrosine 38, Threonine 23, Tryptophan 6, Valine 39.
Assumptions: amounts are per gram of protein as analysed; the adult pattern is used — the pattern for children differs.
Limitations: the score alone is not protein quality — digestibility must be applied (see the Protein Quality Calculator, Tool 368); methionine and cystine, and phenylalanine and tyrosine, are scored as combined pairs.
Rounding: scores to 1 decimal place; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Method: FAO/WHO/UNU Protein and Amino Acid Requirements in Human Nutrition (2007), adult reference pattern (mg/g protein): Histidine 15, Isoleucine 30, Leucine 59, Lysine 45, Methionine+Cystine 22, Phenylalanine+Tyrosine 38, Threonine 23, Tryptophan 6, Valine 39.
Assumptions: amounts are per gram of protein as analysed; the adult pattern is used — the pattern for children differs.
Limitations: the score alone is not protein quality — digestibility must be applied (see the Protein Quality Calculator, Tool 368); methionine and cystine, and phenylalanine and tyrosine, are scored as combined pairs.
Rounding: scores to 1 decimal place; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Worked example: A protein matching the reference pattern on all nine amino acids scores 100.0% on every one, limiting amino acid Histidine (first of the tied minima), mean 100.0%. With lysine at 30 mg/g instead of 45, lysine limits at 66.7%.
Enter values above to see results.
Cereal proteins are usually limited by lysine; legume proteins by methionine plus cystine. Tool 369 of 500 — GIFSQ
