Most people in the fitness community focus largely on meeting their protein targets rather than focusing on the quality or digestibility of that protein.
Recognizing this, food manufacturers and supplement companies formulate some of their products with the most — and often least expensive — protein possible so they can proudly display the amount on their packaging in large bold font.
However, because some protein sources are less digestible and provide fewer of the amino acids your body needs in the appropriate quantities, you may be getting less protein than the label claims.
This article breaks down why you need to consider the quality of the protein in comparison to the stated amount of the food products and supplements you buy.
What is Protein?
Protein supports immune health, drives metabolic reactions, maintains fluid balance, and provides the building blocks for muscle repair and growth (1).
Protein is made up of chains of amino acids — similar to beads strung on a necklace.
There are hundreds of these amino acids in nature, but only 20 make up the proteins in your body.
Of these 20, nine are essential, meaning you must get them from your diet since your body cannot produce them.
Your body can make the remaining 11 amino acids — called nonessential amino acids — from the essential amino acids.
Some of these nonessential amino acids, however, become essential when your body cannot produce enough of them, such as during pregnancy, in certain disease states, or when recovering from illness or physical trauma (1).
What is the protein digestibility-corrected amino acid score (PDCAAS)?
Protein quality refers to how well your body can digest, absorb, and use it to make it into other proteins.
There are various methods that food and supplement manufacturers can use to determine protein quality.
Though it has limitations, the protein digestibility-corrected amino acids score (PDCAAS) tends to be the most widely used method for determining protein quality and is the official method used in the United States (2).
It compares the essential amino acid composition of the food product or supplement with the requirements of a preschool-aged child to provide an amino acid score, which is then adjusted according to its digestibility.
The PDCAAS ranges from 0.0 (poor quality) to 1.0 (high quality).
Compared with plant protein, animal protein is generally of higher quality since the body can more easily digest and absorb it, and because animal protein contains more of the essential amino acids in the proportions that your body needs.
For these reasons, plants have a lower PDCAAS, typically ranging between 0.4 and 0.9, meaning that 40% to 90% of the essential amino acids you consume from plants are available to your body after digestion.
However, certain plant-based proteins like soy protein isolate can have a PDCAAS of 1.0, meaning 100% of the essential amino acids are available to your body after digestion.
Because plants vary in their essential amino acid content and digestibility, combining several plant-based protein sources can also increase the PDCAAS.
For example, because rice protein is low in the essential amino acid lysine, but rich in cysteine and methionine, it pairs well with pea protein, which is low in cysteine and methionine, but high in lysine.
PEScience Select Vegan Protein uses both pea and brown rice protein concentrate to achieve an amino acid profile similar to high-quality animal sources like milk or egg protein.
Here’s a look at common protein sources and their PDCAAS (3):
Milk protein concentrate
Soy protein isolate
Pea protein concentrate
Navigating protein content claims
Food and supplement companies can claim that their product is a “good” or “excellent” source of protein.
To qualify as a “good source,” the product needs to offer a minimum of five grams of protein, equivalent to 10% of the daily value (DV) set at 50 grams. Alternatively, it should provide at least 10 grams to be classified as an “excellent source (2).”
Manufacturers can also include a statement on the packaging about the amount of protein contained in the product.
In either case, they must substantiate these claims based on the protein’s quality and digestibility using the PDCAAS method (2).
Unfortunately, many food and supplement products that make claims about protein content don’t include the %DV or fail to adjust the total protein content based on the PDCAAS.
Due to differences in protein quality and digestibility, failing to adjust the total protein content according to its PDCAAS can be deceiving, and overestimates the stated protein content available to your body by 15-20%, and sometimes much higher (2).
For example, a product that provides 10 grams of wheat gluten might list the total protein as 10 grams.
However, because wheat gluten has a PDCAAS of 0.25, your body can only use 25% of the amino acids, so for labeling purposes, the product should list the total protein as containing 3 grams.
In contrast, because casein has a PDCAAS of 1.0, meaning your body can use all the essential amino acids it provides, a product that provides 10 grams of casein protein is correct in listing the total protein content at 10 grams.
This example is especially common among food and supplement products that use plant proteins, and relatively inexpensive sources like wheat since they have a lower PDCAAS compared with animal proteins.
How to determine whether protein content has been adjusted
Many companies don’t adjust the total protein amount on the label for amino acid profile or digestibility based on its PDCAAS.
Thus, it’s useful to know how to determine how much protein you’re actually getting from the products you buy, especially those that are plant-based.
Recall that food and supplement manufacturers must list the %DV of protein — which is set at 50 grams — if the product makes a statement on the packaging label about its health effects or the amount of protein it provides.
Here is the calculation for %DV: [(Protein grams / 50) x 100].
Using the example from earlier, a product that provides 10 grams of casein protein will provide 20% of the DV for protein. In this case, because 10 divided by 50 is 0.20, you know that the PDCAAS is 1.0 since it matches with the stated %DV.
However, the product with the same amount of protein from wheat gluten will provide only 5% of the DV for protein since its PDCAAS is 0.25.
In this case, because the stated %DV is 5% and not 20%, you know that the PDCAAS is much lower than 1.0 and that the protein content is overstated since it was not adjusted for amino acid composition or digestibility.
PEScience adjusts the protein content of all their products according to the PDCAAS so that you can be confident that the stated protein content is what your body can utilize fully.
Take PEScience’s Select Vegan Protein for example.
Although it provides high-quality complementary pea and rice proteins, it would provide more than 24 grams of protein per serving if unadjusted for its PDCAAS.
Instead, it’s honestly labeled as containing 20 grams of protein per serving to provide 40% of the DV (20 / 50 = 0.4).
PEScience also adjusts total protein content based on the PDCAAS for its popular Homestyle Buttermilk Protein Waffle & Pancake Mix, something other popular high-protein pancake and waffle mixes knowingly skip to unethically showcase a higher protein amount.
Without adjusting for the PDCAAS, PEScience’s Waffle & Pancake Mix would have 19 grams of protein instead of the labeled 15 grams.
How much protein do you need?
The current recommended dietary allowance (RDA) for protein is 0.36 grams per pound (0.8 grams per kg) of body weight (4).
This translates to 54 grams of protein for a 150-pound (68-kg) person.
While most people meet or exceed this recommendation — including those that follow a predominantly plant-based or vegan diet — the RDA is based on the minimum amount you need to function — it tells you nothing about what is optimal for you health or fitness goals.
The current evidence is clear that many people can benefit from more protein than the current RDA to support overall health, muscle growth and recovery, immune health, or promote weight loss.
However, the optimal amount for you depends on various factors related to body composition, gender, age, health status, fitness level or experience, and physical activity level.
- Athletes: 0.63–0.9 grams per pound (1.4–2 grams per kg) of body weight
- Weight loss: 1–1.4 grams per pound (2.3–3.1 grams per kg) of body weight
- Blood sugar and blood pressure support: 0.45–0.55 grams per pound (1.0–1.2 grams per kg) of body weight
- Older adults: 0.45–0.55 grams per pound (1.0–1.2 grams per kg) of body weight
It’s best to evenly distribute your protein intake throughout the day, especially if your goal is to gain muscle or lose weight.
You can achieve your protein target primarily with food like meats, seafood, poultry, dairy, beans, and peas, but protein supplements and other protein-fortified foods like bars, oatmeal, or waffle or pancake mixes can also be an efficient and relatively cost-effective way to get more protein.
If you follow a predominantly plant-based or vegan diet, you can still meet your protein needs by consuming a higher quantity of protein.
The bottom line
The PDCAAS is a widely used method for assessing protein quality based on the body’s essential amino acid requirements and ability to digest them.
Manufacturers must use this method to adjust the %DV for protein if they make a claim about protein’s health effects or the protein content on the product’s label.
Many high-protein food products and supplements often display the total protein content without accounting for its PDCAAS. This oversight — whether intentional or not — means that the product might actually contain fewer usable grams of protein than claimed.
You can determine what the true available protein content is by dividing the stated protein content by 50 to see if it equals the stated %DV. If it’s lower, you know that the PDCAAS score is less than 1.0 and that not all the protein is available to your body after digestion.
Alternatively, you can choose reputable and honest companies like PEScience that do adjust the total protein content according to its PDCAAS.
The amount of protein you need daily depends on various factors, but you can meet your needs with both foods and supplements.