Have you ever wondered how much protein your body can actually use depending on the source? PDCAAS, which stands for protein digestibility corrected amino acid score seeks to give you an answer on the amount of protein your body can actually utilise depending on the different amounts of amino acid the protein consumed is composed of.

What Is PDCAAS And Why Does It Matter?

Protein is a popular macronutrient for improving satiety, recovering from training and increasing muscle mass. However, we know that certain proteins can be used more readily by the body than other proteins. When the body uses proteins, it breaks them down into their individual amino acids before resynthesizing the proteins it actually requires.

Whilst some measurements of protein quality look at bioavailability and others look at amino acid profile, PDCAAS looks at both of these properties.

PDCAAS has also been adopted by the FAO (Food and Agricultural Organisation of the United Nations) and the WHO (World Health Organisation) as the preferred method of measuring the protein value in human nutrition.

Amino Acid Profiling

PDCAAS works by assessing protein quality by looking at the first limiting essential amino acid of the test protein as a percentage of the same amino acid in a reference pattern of essential amino acids.

A PDCAAS score of 1 means all the amino acids required for protein synthesis in the right quantities are present within the food source. The closer a PDCAAS score is to 1, the more effectively the human body can utilise the protein.

Some dietary sources of protein may have a value greater than 1. These should be reduced to 1 as this is the theoretical maximum value. Scores greater than 1 do demonstrate that the source of protein is extremely rich in all the essential amino acids the human body needs for protein synthesis.

However, it was decided that the increased amino acid value provided by foods with PDCAAS scores above 1 would not contribute additional benefit to human health, so they were reduced to 1.

The human body can synthesise certain amino acids. However, there are other amino acids which cannot be synthesised known as essential amino acids (EAAs) or indispensable amino acids (IAAs).

If a dietary source of protein is missing even one essential amino acid, its PDCAAS score will be 0.

PDCAAS Scores For Different Foods

Based on their amino acid profiles and bioavailability, different foods will have different PDCAAS scores. Here are the PDCAAS scores of some common protein supplements:

  • Milk protein concentrate (1)
  • Whey protein isolate (1)
  • Whey protein concentrate (1)
  • Soy protein isolate (0.99)
  • Pea protein concentrate  (0.893)
  • Rice protein concentrate (0.419)

Here are the PDCAAS scores of some commonly consumed foods:

  • Egg (1)
  • Cow’s milk (1)
  • Beef (0.92)
  • Soy (0.91)
  • Chickpeas (0.78)
  • Black beans (0.75)
  • Vegetables in general (0.73)
  • Legumes (0.7)
  • Cereals and derivatives (0.59)
  • Peanuts (0.52)
  • Wheat (0.42)

What Is Protein Synthesis Used For?

Protein synthesis is important for many biological processes. Protein is perhaps the most important macronutrient that we consume. It is used within every cell in the body and most of your nails and hair are made out of protein (not just muscles)!

Protein is used in the synthesis of hormones, enzymes, bones, muscles, cartilage, skin and more. It really is essential for optimal health which is why it’s important to not just make sure you consume enough protein, but you’re able to utilise the protein you eat for the metabolic processes carried out by your body daily.

Issues With PDCAAS

Because PDCAAS is used to measure how efficiently we can utilise protein from one food source, that means it doesn’t take into account the potential PDCAAS score if you were to mix two different protein sources e.g. beans and rice. For example a mix of peas and rice will have a similar amino acid profile to whey (although it will contain more calories for the same amount of protein). However, we consume lots of different foods and lots of different sources of protein so it’s hard to apply PDCAAS to reality. It is still a good measure of identifying how effectively we can use protein from individual sources though.

Another issue is that the PDCAAS score is based on the essential amino acid requirements of preschool children. Adults may have individual essential amino acid requirements.

The third issue is that PDCAAS is measured using fecal digestibility rather than ileal digestibility. Fecal digestibility overestimates the nutritional value of a protein because nitrogen is lost for protein synthesis in the body and is partly excreted in urine as ammonia.

Notes On PDCAAS

PDCAAS is a useful measure for assessing how effectively we can utilise protein from individual food sources, but its everyday application is limited due to how we mix and match many of our food sources which contain proteins. It is a good way of finding out which food sources will provide us with more protein nutrition we can actually use compared to other food sources. This information may prove beneficial for those seeking to improve body composition, lose weight or enhance athletic performance.


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Further Reading:

Are Protein Supplements Good Value?

Maximising Muscle Protein Synthesis