Making Protein Digestibility Testing Easier to Swallow

Protein is an essential nutrient vital for producing enzymes, hormones, and cells; repairing damaged tissue; building strong muscles and bones; and maintaining healthy skin and blood. Understanding how our bodies digest protein from different sources is crucial for optimizing nutrition and product development.

The Journey of Protein Digestion

Proteins begin to break down in the stomach upon contact with pepsin, the primary digestive enzyme. These broken-down proteins become peptides, which travel to the small intestine. With the help of enzymes, peptides are further broken down into individual amino acids and absorbed into the bloodstream. Once absorbed, the body delivers these amino acids to various parts, reconstructing them as needed to maintain health and strength.

Unlike fats and carbohydrates, our bodies do not store protein, making consistent intake essential. Athletes and fitness enthusiasts often consume protein shakes before or after workouts to aid muscle repair, as exercise can cause small tears in muscle fibers.

What is Protein Digestibility Testing?

Protein digestibility tests determine a protein source's ability to be digested and the ratio of essential amino acids it provides for human consumption.

Why is Protein Digestibility Testing Important?

Proteins consist of complex amino acid chains. While our bodies can synthesize some amino acids, essential amino acids must be obtained through diet, primarily from animal proteins, dairy products, nuts, and beans.

Modern farming and food manufacturing practices can impact the quality of protein sources, making digestibility testing crucial. Not all proteins are created equal, and digestibility varies from source to source. Testing ensures proper nutrition and helps refine product formulations.

How to Test for Protein Digestibility

There are multiple protein digestibility testing methods, but the most common method is the Protein Digestibility Corrected Amino Acid Score (PDCAAS) method, which became the preferred industry method in 1993 at the recommendation of the Food and Agriculture Organization of the United Nations (FAO) and the Food and Drug Administration (FDA).

Protein Digestibility Corrected Amino Acid Score (PDCAAS) method

The PDCAAS method works by comparing the amino acid profile of a specific protein source against the standard amino acid profile of casein. The highest possible score is a 1.0, which means that after the protein is digested it provides 100% of the essential amino acids required for human nutrition.

Drawbacks of the PDCAAS Method:

• Long turnaround time for results.
• Relatively high cost per test.
• Reliance on rats as test subjects, raising ethical concerns and questions about the accuracy of reflecting human digestion.

Medallion’s ASAP Quality Score method

The ASAP Quality Score, developed at Medallion Labs, uses the same casein standard as the traditional PDCAAS method but achieves similar results in vitro (in a test tube) rather than in vivo (inside a living subject).

Advantages of the ASAP Method:

• Results are available within 15 days.
• Significantly lower cost.
• Does not rely on or require animal testing.
• Excellent correlation to in vivo rat values (correlations greater than 0.97 over a wide range of scores).

¹Based on published literature values
²Based on direct analysis of the same sample by both methods

Regulation, Standardization, and Labeling

The Food and Drug Administration (FDA) regulates food labeling but does not specify a daily value for protein unless the product claims to be "high in protein" or is intended for children under the age of 4.

Lack of Standardization Across Industries

Disagreements persist over a standardized method for testing protein digestibility because different proteins respond differently to various tests. This means one test might provide a more favorable digestibility score than another.

For example, the FAO has shifted their allegiance to a new method called the Digestible Indispensable Amino Acid Score (DIAAS). The dairy industry favors the DIAAS method because “high-quality proteins, such as the proteins from milk, whey, and other dairy products, may score 30% higher than when using the older method for assessing quality.”

Something to Chew On

Selecting the appropriate protein digestibility testing method depends on your specific needs, providing the most accurate results to refine your product, meet regulatory standards, and inform your customers. While current regulations recognize the rat PDCAAS method for finished products, the ASAP method is a valuable tool for R&D and pilot plant studies, saving significant time and money. For organizations with animal testing moratoriums, the ASAP method is an ideal alternative.