PDCAAS vs DIAAS Protein Quality Scoring

[SteelPhysique]

Both PDCAAS and DIAAS are ways to rate the quality of proteins, but they do not work in the same way. PDCAAS rates digestibility of protein and fecal digestibility at 1.0, which can make proteins that are very different look like they are the same. DIAAS measures how well each amino acid is absorbed at the end of your small intestine, which gives a more accurate view. It can also get a score above 1.0, which helps you tell the difference between good sites.

PDCAAS and Its Function​

The Protein Digestibility Corrected Amino Acid Score (PDCAAS) has been used for a long time by the FDA and FAO to rate the quality of proteins. It works by comparing the limiting essential amino acid of a protein to a reference amino acid pattern. Then, the overall digestibility of the protein is used to fix the score. The crucial amino acid with the shortest chain length is called the limiting amino acid, and it determines your ultimate PDCAAS number. Compared to the reference. The adjustment factor is fecal crude-protein digestibility, which means that one digestibility percentage is used for the whole protein. Because scores can only go up to 1.0, proteins that match or beat the reference pattern all get the same highest number. Because of this truncation, researchers started to wonder if PDCAAS really can tell the difference between high-quality protein sources.

Why PDCAAS Falls Short as a Protein Quality Measure​

PDCAAS was a big step forward in figuring out the quality of proteins, but it has some problems with how it's built that make it less useful. One big difference between PDCAAS and DIAS is that PDCAAS depends on fecal digestibility while DIAS depends on ileal digestibility. This difference is important because fecal readings take into account the activity of bacteria in the large intestine, which can make the amount of protein your body absorbs seem higher than it really is.
PDCAAS also only fixes one thing about the protein's digestibility at a time, instead of looking at how each amino acid is taken one at a time. PDCAAS also cuts scores off at 1.0, which means that proteins with really better amino acid profiles are squished into the same group. This ceiling effect makes it harder to tell the difference between higher-quality protein sources, which makes measuring protein quality less accurate.

How DIAAS Fixes the Flaws in PDCAAS Scoring​

Each of these problems is directly fixed by DIAAS. It doesn't use a single fecal digestibility value for the whole protein; instead, it checks at the end of the small intestine how well your body absorbs each essential amino acid separately. That's important because different amino acids in the same protein break down at various speeds.
This measurement of the ileum also leaves out bacterial activity in the large intestine, which gives you a more accurate picture of what is absorbed. Instead of stopping at 1.0, DIAAS scores can go over 100 for high-quality protein sources. This lets you tell the difference between proteins that PDCAAS would group.
This makes a more accurate measurement of protein quality that is based on real digestive physiology instead of a rough approximation that hides important differences between protein sources.

PDCAAS vs DIAAS Scores for the Most Common Protein Sources​

When you can see how things really compare, paper scores don't mean as much. Whey protein provides an excellent profile of essential amino acids and is easy to digest, as it sits near the top of both PDCAAS and DIAAS. The PDCAAS for soy protein is 1.0, but the DIAAS is usually a little lower because the digestibility numbers for each amino acid are more accurate. PDCAAS squeezes a lot of proteins into that 1.0 ceiling, but DIAAS makes it easy to tell them apart. Most of the time, plant proteins like pea and wheat score lower on DIAAS because they don't have enough lysine or methionine. When you mix plant sources that are good together, like rice and pea, the overall amino acid pattern can be improved in a meaningful way.

Which Score Should Guide Your Protein Choices?​

You shouldn't let either scoring system decide what protein you eat on its own. PDCAAS and DIAAS are both helpful ways to learn about protein quality, but they're not hard and fast rules that you have to follow. The idea behind DIAAS is that it is more accurate because it measures how well each amino acid is broken down in the small intestine. This gives you a better idea of what your body actually absorbs. Even though PDCAAS isn't as accurate, it is still useful and often used.
The most important things are how much protein you eat each day, how you divide it up between meals, and how well you meet your daily needs for essential amino acids. If you eat a variety of foods that include different types of protein, worrying about whether something gets a 0.9 or 1.0 won't make a difference in your results.

 

[jenm_88]

DIAAS scores above 100 don't mean "extra good" in a stacking sense. It just means that amino acid isn't your limiting factor, so it's more useful for comparing protein quality than for maximizing gains from a single source.