Whey Bioavailability - Explained in Detail

Bioavailability of Protein Powder

Whey Protein Bioavailability

Bioavailability, in simplest terms, is a metric signifying effective nutrient content. When assessing the nutritional value of a protein source, the most critical factor is rooted in the body's ability to digest and recognize individual amino acids for future utility.

The bioavailability score of protein serves as an indicator of nutritional potential in terms of the amino acid profile value and the digestive absorption rate of the active nitrogen-based components. The greater the protein's bioavailability score, the more beneficial the protein is from the body's ability to utilize its composition for raw materials. 

Rate: Capacity of absorption as a function of time. How much and how long does it take for the body to utilize the protein.

Spectrum: Of the Essential Amino Acids, how many are present in the proportions required to nurture the human body.

For all practical purposes, the takeaways to consider from this article include -

  • Assessing a whey protein product for quality will always encompass the source of origin and the processing.
  • Bioavailability scores assigned to protein sources are indirect measurements. The scoring projections onto human digestive systems stem from experiments performed on pigs and rats.
  • Be wary of any brand pushing "Bioavailability" as a marketing claim. The value of a protein supplement may be different for everyone regardless of the nitrogen content found in the feces of a pig that made it onto scientific publication.

Bioavailable Whey Protein Isolate

When discussing the "Bioavailability" of whey, we cannot stress the importance of high-quality food paired with a functional & healthy digestive tract.

When it comes to bioavailability, it's not just about the quality of the protein but also your body's ability to break down and absorb the protein in the small intestine efficiently [1].

It's important to consider that regardless of how bioavailability is measured, the metric itself hinges on two independent factors -

  1. Quality of Food
  2. Gut Health Robustness

When considering the quality of food or the inherent worth of any particular supplement, determining nutritional value is a trust game.

Suppose you are as skeptical as we are about the regulatory governance of our food and consumable products in general. In that case, there is a good chance you have made yourself and your family aware of food labels and their significance.

Synonymous with trust is accreditation, as the saying goes, "Trust, but verify." Understanding the relevance of food labels, their meaning, along the food's source of origin is the only way to capitalize on what can be controlled in terms of the bioavailability potential of your protein product selection.

Nutrient Integrity & Food Labels: Is the food what it says it is (i.e., Organic, Grass-Fed, Non-GMO, Gluten-Free, Undenatured, Cold Processed, Natural, Hormone Free, Pesticide Free, rBGH Free, Lactose-Free, Amino Acid Profile)

Efforts exerted upfront researching a brand will significantly advantage your decision quality and selection of protein. Food labels and verified claims together may be the only inputs you have to determine protein quality. Behind these labels is a culmination of physiochemical properties that significantly impact a protein's digestibility (Dissociation, Solubility, Hydration & Swelling Capacity, Foam Stability, Emulsifying Effects).

Learn More: Food Label Guide .PDF
Learn More: Undenatured Whey Protein
Learn more: What is Cold Processed Whey Protein?

Most Bioavailable Whey Protein

The "bioavailability potential" when referring to a whey protein product is the only data point a consumer needs to make an informed decision. The fact is that "bioavailability" depends on just as many factors that have nothing to do with the product as factors that do, however, are equally important. To hit this point home, we offer the following examples.

High Bioavailability Potential - Two Individuals consume the same whey protein powder in similar circumstances. 

Person A absorbs 80% of the amino acids. 

Person B absorbs a mere 10%.

Low Bioavailability Potential - Two Individuals consume the same whey protein powder in similar circumstances. 

Person A absorbs 16% of the amino acids. 

Person B absorbs a mere 2%.

Conclusions: The variance in absorption capacity in these examples has a lot to do with the inherent characteristics of the individual, as observed in the difference between person A & person B in both instances. 

However, the bioavailability potential of the whey protein in the first example is very high. At the same time, the product quality in the second example is not very good, so even if the consumer has exceptional gut health, there isn't much bioavailability potential there. 

Whey Protein Bioavailability Marketing Points

These two cases exemplify why the "bioavailable" claim is a bit of a scam when referencing the product alone. Bioavailability is a success measure requiring both interfaces to be known (Protein Quality + Gut Health).

The bioavailability potential of any protein reflects the inherent protein quality alone, leaving gut-health factors uncharacterized and out of the equation. Without both pieces of the puzzle, nutritional benefits go unrealized.


Learn More: Digestive Enzymes & Whey Protein Isolate
Learn More: Side Effects of WPI

How to Assess Bioavailability Potential?

Source of origin and quality assurance continue to dominate chat forums as consumers don't have a clear path to supplement transparency. Without accreditation, it is next to impossible to trust marketing content. The only way to make an educated assessment of the bioavailability potential of any given whey protein powder is to understand the sourcing and processing practice of the brand.

Pairing the lack of natural transparency in the sports nutrition space with the rise of factory farming and GMO food concerns brings valid skepticism to any discussions of bioavailability and nutritional value.

> 99% of ALL whey protein sold in the United States is sourced from factory farms and processed without regard to nutrition preservation.

After ensuring the product provides the best bioavailability potential, the focus must be inward, looking at our gut health, working to understand better what works, and how intelligently feeding our body can serve us as the fountain of health and longevity.

Whey Isolate bioavailability after consumption is impacted by a myriad of factors that include but are not limited to the following - 

  • Digestive Capabilities (Intraindividual & Interindividual Variability)
  • Physiological Well Being of the Consumer
  • Biorhythms

How to Determine Whey Protein Bioavailability

There are two primary methods used to determine the bioavailability of whey protein isolate and most proteins. Not all protein is considered equal, and consideration should be given to the wide range of bioavailability variance between each protein type and even within the same type
depending on the quality of the protein and the individual.

Each protein category has a baseline nutritional value range, and by relying on standard methods of bioavailability measurement, large organizations have successfully mapped out the differences. Bioavailability charts will contain various food items and a paired scoring for bioavailability.

The two metrics that Indicate "bioavailability" on paper most widely used in the space of sports nutrition include - 
  2. DIAAS

PDCAAS Method Explained

PDCAAS is an abbreviation for "Protein Digestibility Corrected Amino Acid Score." For the last 25 years, the PDCAAS method has been the globally recognized standard for determining bioavailability scores for protein. This method put grass-fed dairy protein on the map and is partly responsible for the popularity of dairy protein powders worldwide.

It is a fundamental concept that focuses on food composition, particularly the essential amino acids (EAA - amino acids the body does not produce). The method compares the EAA composition to what the body needs to support the growth and development of a two to five your old child. The protein is tested before consumption then again from fecal matter. The assumption is that the difference in amino acid concentration from the samples determines what the body effectively absorbed.

Protein Bioavailability Chart 

 Protein Type

Protein Digestibility Corrected Amino Acid Score (PDCAAS)

*Untruncated PDCAAS Values

Digestible Indispensable Amino Acid Score (DIAAS)

Whey Protein Isolate (WPI) 1.00 1.25 1.22
Whey Protein Concentrate (WPC) 1.00 1.34 1.33
Casein Protein Concentrate (CPC) 1.00 1.23 1.21
Pea Protein Concentrate (PPC) 0.75 0.84 0.73

*Actual score prior to truncating to a value of 1.0 if PDCAAS > 1.0 [6] [9]

Is Whey Protein Bioavailable?

Yes, Whey Protein tops the charts based on PDCAAS resulting in a perfect score amongst many other protein sources. Unfortunately, there isn't much resolution at the top; a 1.0 represents the best PDCAAS (bioavailability value) a protein source can obtain. The 1.0 means that compared to the amino acids measured before consumption, the 2nd measurement of the EAAs concentration from the feces is drastically less.

The PDCAAS served nutritionists and the public very well for a long time. However, the limitations of PDCAAS are now understood to impact the scoring system's integrity significantly. These flaws greatly affect the value proposition for various protein sources.

The flaws include -

  • Inadequate resolution among the highest quality protein sources
  • Overestimation of protein quality due to products containing antinutritional factors (Components such as lectins, trypsin inhibitors, and tannins that are common within pea protein are known to increase protein losses at the end of the small intestine thus producing a false digestibility score) [7]
  • Discounting the impact of the large intestine (colon) breaking down EAAs via bacteria for disposal thus attributing this nitrogen depletion to a false bioavailability score
  • Overestimation of the quality of poorly digestible proteins supplemented with limiting amino acids, known in the supplement industry as "amino spiking."

The solution or following method that fills most of these gaps and provides more excellent resolution at the top of the PDCAAS scale came to light about ten years after the advent of the PDCAAS. In 2013 the updated method (DIAAS) was given preference over the PDCAAS by The Food and Agricultural Organization [9].

The latest and most applicable process of estimating bioavailability via dietary quality evaluation is called DIAAS [2]

DIAAS Method Explained

DIAAS is an abbreviation for "Digestible Indispensable Amino Acid Score."

The evolution of the DIASS scoring methodology addresses the shortcomings of the traditional PDCAAS. The premise of the DIAAS stems from the concept that the ability to break down protein and utilize its nitrogen-based macro-nutrients does not always reflect the digestibility of individual dietary indispensable amino acids. For true digestibility, using a method that produces a score based on dietary vital amino acids individually is preferred and more accurate.

Unlike the PDCAAS, the DIAAS model extracts the second sample before the food enters the large intestine, then exposed to fermentation. The fermentation in the large intestine is believed to be a significant culprit of false attribution towards bioavailability scores due to the nitrogen depletion that occurs. General terms to help speak to the differences between the two methods.

Ileal digestibility: measured by the difference between the number of amino acids ingested and the number of amino acids recovered from the digested food in the ileum. The DIAAS measures ileal digestibility.

Fecal digestibility: represents the difference between the amount of a food item ingested and the number of feces produced. The PDCAAS measures fecal digestibility however attempts to rectify with another coefficient.

Large Intestine: The large intestine, or colon, is responsible for processing waste and further metabolizing nutrients via bacteria breakdown (resulting in gas).

Small Intestine: The small intestine is responsible for absorbing nutrients into the bloodstream. The small intestine metabolizes food using enzymes released by the pancreas and bile produced by the liver.

A DIAAS is the ratio of the digestible amino acid content in the food (mg/g of protein) to the same amino acid in a reference pattern taken from age-specific amino acid requirements. The lowest value across the essential amino acids converted to a percentage represents the DIAAS metric of the food. 

The DIAAS metric has potential to become a more mainstream protein quality claim.  There is likely to be published and universal protein categories based on the following bracket recommendations based on the DIAAS scale.  

  • A Score of <75% will have no claim associated
  • A Score equal to or >75% & < 99% is "Good Protein Quality" 
  • 100% on the DIASS or more is considered "Excellent Protein Quality"

Low-quality proteins that would otherwise not be utilized by the small intestine may easily get broken down in the large intestine at the point where fecal matter is produced. This fact clarifies the importance of sampling at the small intestine's end [3].

Bioavailability of Protein Powders

Its important to understand that bioavailability scores serve only as an indirect quality indicator against the best possible models. Bioavailability scores of brand specific protein do not exist. In fact, the models used to develop a score come from various non-ruminant animal studies thus also provide a relationship that may have it's gaps.

Bioavailability of Whey?

To make the most informed decision, follow these steps to compare brands with the understanding that information is power. Asking for the data and coming to your own conclusion is the best advice we can offer.

  1. Amino Acid Profile - Look for BCAAs count per 25 grams protein
  2. Processing Method Details - Stay away from Native Whey
  3. Source of Origin - Stay away from CAFOs
  4. Accreditations - Verify Claims
  5. Rule out Amino Spiking - Look at all ingredients

Learn More: BCAAs & Source of Origin (Grass-Fed Matters)
Learn More: What is a CAFO (Factory Farming in the USA & Milk Quality)?

Please feel free to ask us to take a look at a brand you are considering and we would be happy to give you some tangible take always. 

[1] Vraníková, Barbora, and Jan Gajdziok. “Biologická dostupnost léčiva a možnosti jejího ovlivňování” [Bioavailability and factors influencing its rate]. Ceska a Slovenska farmacie : casopis Ceske farmaceuticke spolecnosti a Slovenske farmaceuticke spolecnosti vol. 64,1-2 (2015): 7-13.
 [2] United Nations, Food and Agriculture Organization. Dietary Protein Quality Evaluation in Human Nutrition: Report of an FAO Expert Consultation on Protein Quality Evaluation in Human Nutrition, 31 March - 2 April, 2011 Auckland, New Zealand. Illistrated ed., 66 Pages, Food and Agriculture Organization of the United Nations, 2013.
[3] Hendriks, Wouter H et al. “Ileal and faecal protein digestibility measurement in humans and other non-ruminants - a comparative species view.” The British journal of nutrition vol. 108 Suppl 2 (2012): S247-57. doi:10.1017/S0007114512002395
[4] Marinangeli, Christopher P F, and James D House. “Potential impact of the digestible indispensable amino acid score as a measure of protein quality on dietary regulations and health.” Nutrition reviews vol. 75,8 (2017): 658-667. doi:10.1093/nutrit/nux025
[5] Hassanien, Mohamed. (2012). Physico-chemical Properties of Proteins. 10.13140/RG.2.2.18310.93768. 
[6] Hoffman, Jay R, and Michael J Falvo. “Protein - Which is Best?.” Journal of sports science & medicine vol. 3,3 118-30. 1 Sep. 2004
[7] Salgado, Paulo et al. “Legume grains enhance ileal losses of specific endogenous serine-protease proteins in weaned pigs.” The Journal of nutrition vol. 132,7 (2002): 1913-20. doi:10.1093/jn/132.7.1913
 [8] Sarwar, G. “The protein digestibility-corrected amino acid score method overestimates quality of proteins containing antinutritional factors and of poorly digestible proteins supplemented with limiting amino acids in rats.” The Journal of nutrition vol. 127,5 (1997): 758-64. doi:10.1093/jn/127.5.758
[9] Rutherfurd, Shane M et al. “Protein digestibility-corrected amino acid scores and digestible indispensable amino acid scores differentially describe protein quality in growing male rats.” The Journal of nutrition vol. 145,2 (2015): 372-9. doi:10.3945/jn.114.195438
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