Protein quality score

Not all protein is equal. This score reflects how well a food's amino acid profile matches what the human body needs.

Reference

FAO/WHO/UNU (2007). Protein and Amino Acid Requirements in Human Nutrition. WHO Technical Report Series 935. Table 7: Reference amino acid scoring pattern for adults.

How it works

We calculate how many milligrams of each essential amino acid the food provides per gram of its protein, then compare it to the FAO adult reference pattern — the ideal profile the human body requires.

Each amino acid gets a ratio: (food / reference) × 100. The protein quality score is set by the limiting amino acid — the one with the lowest ratio. This follows the Amino Acid Score (AAS) method, a simplified form of PDCAAS.

A score of 100 means every essential amino acid meets or exceeds the reference. Animal proteins typically score 100. Plant proteins often have one limiting amino acid — combining foods (rice + lentils) raises the effective score.

FAO adult reference pattern

Histidine 15 mg / g protein

Isoleucine 30 mg / g protein

Leucine 59 mg / g protein

Lysine 45 mg / g protein

Methionine + Cysteine (SAA) 22 mg / g protein

Phenylalanine + Tyrosine (AAA) 38 mg / g protein

Threonine 23 mg / g protein

Tryptophan 6 mg / g protein

Valine 39 mg / g protein

N/A score

Foods with less than 1 g of protein per 100 g receive an N/A score — there is not enough protein to meaningfully evaluate its amino acid profile.