PDCAAS & Protein Digestibility

In an attempt to be educated consumers, there are key spots we tend to check on nutrition labels. One of the first stops on our gaze’s trip down the label is the amount of protein. While protein is an essential building block for tissue and an integral part of nearly every physiological reaction in our body, we sometimes get carried away with our protein intake. Excess calories are still excess calories, whether they come from sugar, fat, or even – yes, our friend -protein. Extra calories ➡️ excess energy ➡️ excess fat. Protein is also a nitrogen containing food molecule. Because nitrogen must be excreted through the urine, a severe overconsumption of protein can possibly cause dehydration and a put a strain on the kidneys due to the increased demand to dump all of the excess nitrogen (This should not be a serious health concern unless this behavior of protein overconsumption is prolonged and severe, you do not need to worry if you accidentally / occasionally overeat the recommended amount of protein).

It is important to know the recommended daily protein intake to ensure you are consuming enough for bodily processes, but not so much that you are putting unnecessary strain on your system. Protein should make up approximately 15% of your total daily calories (1 gram of protein = 4 calories, or you can use helpful food tracking apps such at MyFitnessPal).

How to calculate actual protein needs:

  • Protein needs differ depending on age, gender, and activity level

  • General RDA (recommended dietary allowance) is 46g/day for women and 56g/day for men

  • For a more accurate number, use this calculation (convert pounds to kilograms by dividing it by 2.2)

  • Take your body weight in kilograms and multiply it by an activity factor:

  • 0.8 for sedentary adults

  • 1.0 for moderately active adults

  • 1.2-1.4 for highly active athletes

  • Example: Susie, female, 25 years old, runs several times a week and does light resistance training occasionally. She weighs 145 pounds.

  1. 145 pounds / 2.2 = 65.9 kg

  2. Moderately active = 1.0 activity factor

  3. Susie should aim to eat ~66g of protein a day

  4. ADDITIONAL MATH (who doesn’t love that?) 66g of protein x 4 calories / gram = 264 calories

  5. If protein makes up 15% of her calories, her total daily caloric intake will be somewhere around 1,760 calories

Different proteins are digested differently. Bioavailability = the amount of that specific food component is actually absorbed and used by the body. Does not always equate to the exact amount consumed.

Protein Digestibility Corrected Amino Acid Score (PDCAAS) is a system for measuring the quality of a protein. You may remember from biology class that amino acids are the building blocks of proteins. These amino acids are assembled in the body to create functioning proteins, and although there are 22 different amino acids, 9 of them cannot be made from scratch by the body so they are considered “Essential Amino Acids” and must be obtained through the diet. The method for determining the quality of these amino acids is a bit technical and mind numbing to try and process (and also involves “fecal digestibility” so it may be best to steer clear of this topic for now…), so luckily a chart has been developed to compare and rank the digestibility of different protein sources.

(NCBI Article on PDCAAS)

Milk protein (whey protein) is often considered the gold standard of protein as it is nearly 100% digestible and absorbable. Although, with many people who have sensitivities to the other components of milk, there are other options for high quality protein sources. Egg whites are also almost 100% digestible, as is soy (although, again, these present sensitivity issues in some populations).

There are certain protein sources such as the peas, rice, and wheat that you see on the chart that may not seem as impressive, but by combining several different of these protein sources you can provide yourself with a complete array of all essential amino acids. These combinations of proteins are called Complementary Proteins. An example of a complementary protein combination is rice and corn. On their own, both are missing at least some of those 9 essential acids, but when combined they fill the gaps for each other and provide a complete set of all essential amino acids. These plant based sources may have less digestible protein overall but offer added benefits of vitamins, minerals, and fiber and should not be overlooked as excellent protein sources.

Here is a more comprehensive list from Pro Portion Foods website.


Note: DIASS stands for digestible indispensable amino acid score and is not what we are focusing on for the sake of simplicity, to learn more about this please visit this website

Tip: a health claim that is made on the front of food packaging must be backed up by scientific evidence and proven to the FDA, and protein claims made on the front must go by the PDCAAS score. For instance, a protein bar may have 18 total grams of protein on the back panel nutritional label, but on the front only claim “15g of Protein!” This is because only 15g of that protein is digestible according to its PDCAAS score.

Additional sources:


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s