PDCAAS: What It Means, and Why Your Label Might Not Be Telling the Truth

Protein quality matters just as much as protein quantity. Learn what PDCAAS is, how digestibility affects usable protein, and how to read protein labels accurately.

Most people in the fitness community focus on hitting their daily protein target without giving much thought to the quality or digestibility of that protein.

Recognizing this, many food manufacturers and supplement companies formulate products using the cheapest protein sources available so they can advertise a high protein number in large, bold font on the label.

The problem is that not all protein is created equal.

Some protein sources are less digestible and provide fewer essential amino acids in the proportions your body needs. As a result, you may be absorbing and utilizing significantly less protein than the label suggests.

This article breaks down why protein quality matters, how protein digestibility impacts what your body actually uses, and how to tell whether the protein content on a label is overstated.

What Is Protein?

Protein plays a critical role in immune function, metabolic reactions, fluid balance, and muscle repair and growth.

Proteins are made up of chains of amino acids, often compared to beads on a necklace.

There are hundreds of amino acids found in nature, but only 20 are used to build proteins in the human body.

Of these 20 amino acids, nine are considered essential, meaning your body cannot produce them and they must be obtained through the diet.

The remaining 11 amino acids are classified as nonessential because your body can synthesize them from essential amino acids.

However, some nonessential amino acids become conditionally essential during times of increased demand, such as pregnancy, illness, injury, or recovery from physical trauma.

What Is the Protein Digestibility-Corrected Amino Acid Score (PDCAAS)?

Protein quality refers to how well your body can digest, absorb, and use a protein source to build and repair tissues.

There are several methods used to assess protein quality, but the protein digestibility-corrected amino acid score (PDCAAS) is the most widely accepted and is the official method used in the United States.

PDCAAS compares the essential amino acid profile of a protein source to human requirements and then adjusts for how digestible that protein is.

Scores range from 0.0 (very poor quality) to 1.0 (high quality).

Animal-based proteins typically score higher because they contain all essential amino acids in the correct proportions and are more easily digested and absorbed.

For this reason, animal proteins such as whey, casein, milk protein, and egg all have a PDCAAS of 1.0.

Most plant proteins score lower, typically ranging from 0.4 to 0.9, meaning only 40–90% of the protein consumed is actually available for use after digestion.

An exception is soy protein isolate, which has a PDCAAS of 1.0.

Because different plant proteins vary in their amino acid profiles, combining multiple plant sources can increase overall protein quality. For example, rice protein is low in lysine but high in methionine and cysteine, while pea protein is high in lysine but lower in methionine and cysteine.

Blending these proteins together creates a more complete amino acid profile similar to high-quality animal proteins.

Common Protein Sources and Their PDCAAS

Casein: 1.0
Milk protein concentrate: 1.0
Whey protein: 1.0
Egg: 1.0
Soy protein isolate: 1.0
Beef: 0.92
Pea protein concentrate: 0.89
Black beans: 0.75
Rice: 0.50
Wheat gluten: 0.24

Navigating Protein Content Claims

Food and supplement companies can label a product as a “good” or “excellent” source of protein.

To qualify as a “good source,” a product must provide at least 5 grams of protein, or 10% of the daily value (DV), which is set at 50 grams. To qualify as an “excellent source,” it must provide at least 10 grams of protein.

Manufacturers must substantiate these claims using the PDCAAS method.

However, many products list total protein content without adjusting for protein quality or digestibility, which can significantly overestimate how much protein your body can actually use.

In some cases, the usable protein may be overstated by 15–20% or more.

For example, a product containing 10 grams of wheat gluten protein may list 10 grams on the label. But since wheat gluten has a PDCAAS of around 0.25, only about 25% of that protein is available to your body. In reality, it should be listed closer to 3 grams of usable protein.

In contrast, a product containing 10 grams of casein protein is accurately labeled because casein has a PDCAAS of 1.0.

This issue is especially common with plant-based proteins and inexpensive protein sources.

How to Tell If Protein Content Has Been Adjusted

If a product makes a claim about protein content or health benefits, it must list the percent daily value (%DV) for protein.

The %DV is calculated using the formula:
(Protein grams ÷ 50) × 100

If a product provides 10 grams of protein and lists 20% DV, the protein has likely been adjusted properly and has a PDCAAS close to 1.0.

If that same product lists only 5% DV, you know the protein quality is much lower and the usable protein is overstated.

This simple check can help you determine whether a product’s protein content reflects what your body can actually utilize.

How Much Protein Do You Need?

The current recommended dietary allowance (RDA) for protein is 0.36 grams per pound of body weight (0.8 grams per kilogram).

For a 150-pound person, this equals about 54 grams per day.

While most people meet this minimum requirement, the RDA represents the bare minimum needed to prevent deficiency — not what is optimal for health, performance, or body composition.

Research consistently shows that higher protein intakes can benefit muscle growth, recovery, immune function, blood sugar regulation, and fat loss.

General evidence-based guidelines suggest:

Athletes: 0.63–0.9 g per lb (1.4–2.0 g per kg)
Weight loss: 1.0–1.4 g per lb (2.3–3.1 g per kg)
Blood sugar and blood pressure support: 0.45–0.55 g per lb (1.0–1.2 g per kg)
Older adults: 0.45–0.55 g per lb (1.0–1.2 g per kg)

Protein intake should ideally be distributed evenly throughout the day.

You can meet protein needs through whole foods like meat, poultry, seafood, dairy, beans, and legumes, with supplements and fortified foods serving as convenient additions.

Those following plant-based or vegan diets can still meet protein needs by consuming higher total protein and prioritizing complementary protein sources.

The Bottom Line

Protein quality matters just as much as protein quantity.

The PDCAAS is the standard method used to assess how digestible and complete a protein source is, and manufacturers are required to use it when making protein claims.

Many products list total protein without adjusting for digestibility, meaning you may be getting far less usable protein than advertised.

By checking the %DV for protein, you can quickly determine whether the protein content has been adjusted appropriately.

Alternatively, choosing transparent brands that properly account for protein quality ensures that the protein listed on the label is what your body can actually use.