The amino acid score is a ratio indicating how well a food protein's amino acid composition meets the body's needs. A high score suggests a complete or ideal protein, providing all essential amino acids in sufficient amounts. Conversely, a low score points to a protein lacking one or more essential amino acids, potentially leading to nutritional deficiencies.
Understanding the Calculation
The amino acid score is calculated by comparing the amount of each essential amino acid in a food protein to the amount in a reference protein, typically an ideal protein profile based on human requirements. The score is determined by the limiting amino acid: the essential amino acid present in the lowest amount relative to the reference. This limiting amino acid dictates the overall score.
- Example: If the limiting amino acid in a protein is found at 70% of the reference level, the amino acid score is 70.
The calculation is detailed in the Wikipedia entry on Amino Acid Score.
Different Scoring Methods
Several methods utilize amino acid composition to assess protein quality. These include:
-
Protein Digestibility Corrected Amino Acid Score (PDCAAS): This widely used method, adopted by the FAO/WHO, considers both amino acid composition and the protein's digestibility. Information on PDCAAS can be found on Wikipedia and in the Journal of Nutrition article. A study highlighting its advantages and limitations is available on PubMed.
-
Digestible Indispensable Amino Acid Score (DIAAS): Proposed as a replacement for PDCAAS, DIAAS focuses solely on the digestibility of indispensable (essential) amino acids. See the Wikipedia page and a Frontiers in Nutrition article for further details. A PubMed Central article here discusses its conceptual goal.
-
A simple Amino Acid Score, as noted in the Tofu Association's website, expresses the level of each amino acid as a percentage relative to a reference.
These various methods highlight the multifaceted nature of evaluating protein quality, with each offering unique perspectives and considerations.
Practical Implications
The amino acid score is a valuable tool in:
- Assessing the nutritional quality of proteins in foods.
- Formulating balanced diets and protein supplements.
- Comparing the protein value of different food sources.
A score of 100 indicates a complete protein, perfectly meeting the reference profile. Scores below 100 suggest a deficiency in one or more essential amino acids, necessitating complementary protein sources for optimal nutrition. For example, a blog post explains how a 100 score reflects good protein digestibility.
