Protein Biological Value (Protein BV) and Protein Digestibility Corrected Amino Acid Score (PDCAAS) - Protein Comparison
There are several ways for comparing quality of proteins in food. Most often, Protein Biological Value (Protein BV) and Protein Digestibility Corrected Amino Acid Score (PDCAAS) are used to compare various protein sources.
Protein Biological Value (Protein BV)
Protein Biological Value (BV) is a value that measures proportion of absorbed protein from food which body can incorporate into the organism's proteins. The higher the protein biological value is, the more nitrogen your body can use for protein synthesis.
Thus, formula for calculating protein BV would be:
BV = 'incorporated nitrogen' / 'absorbed nitrogen' * 100
This formula gives maximum value for protein BV of 100% (more than 100% would be impossible).
Since protein BV is often used for comparing different protein sources, and since eggs have the best protein BV for any natural source, eggs are given a protein BV of '100' (no more percentages) and all other foods are rated by comparing them with eggs.
Whey proteins as nitrogen source have higher protein BV when compared with eggs, because body can incorporate more nitrogen into the body's proteins from whey than from eggs.
Of course, this doesn't mean that one should eat only whey protein isolate and hope for athletically build body (or performance), but protein BV gives nice value for comparing different protein sources.
Protein Digestibility Corrected Amino Acid Score (PDCAAS)
Another method for comparing different protein sources is protein digestibility corrected amino acid score (PDCAAS). The PDCAAS method is based on human amino acid requirements - a PDCAAS of 1.00 or 100% is good quality. Anything lower and that protein source must be combined with another protein source so that their combination contain sufficient amino acids to increase the score.
Protein Biological Value and PDCAAS don't take into the account speed of digestion, so for bed time meal, casein is much better protein source than any whey. On the other hand, almost nothing beats whey around, during and after workout as protein source.
Following table shows Protein BV and PDCAAS of the foods often found on menus of people wanting to become and stay fit:
|Food||Protein Biological Value||PCDAAS|
|Whey Protein Isolate||159||1.0|
|Whey Protein Concentrate||104||1.0|
Protein Biological Value and PDCAAS are just showing us that for healthy nutrition, one needs to eat varied foods - there are no the best protein source, no the best vegetable, fruit etc ...
One another way of testing food as protein source is verifying if the food is source of complete protein - if the food contains essential amino acids in right amounts and ratios.