Whey Protein Versus Soy Protein Part 2

Whey Protein Versus Soy Protein Part 2.

In my previous article in this series we set up an imaginary competition between these two popular protein supplements, using the same methods used by scientists to determine a protein source’s bioavailability.  In the first few rounds, whey dominated all events.  Let’s see if soy can stage a comeback.

Soy Versus Whey – Which has a Better Amino Acid Score?

The amino acid score (AAS) is fast, consistent, and inexpensive. It measures essential amino acids in a protein compared to a reference protein. The AAS rates the protein on the most limiting amino acid found in the protein under consideration.

One limitation of the AAS is that it does not consider the digestibility of the protein.

A value greater than 1 indicates that the protein being considered contains a greater amount of essential amino acids than humans require.

How do the AAS values compare in the soy versus whey protein debate?

Round 4 – Soy vs. Whey Protein

Soy Vs. Whey Protein
AAS

Soy Protein Concentrate
0.99

Whey Protein
1.14

Round 4 of the Soy Protein versus Whey Protein debate goes to…

Whey Protein.

Soy Versus Whey – Which has a Better Protein Digestibility Corrected Amino Acid Score?

The protein digestibility corrected amino acid score (PDCAAS) makes a correction for the limitation of the simple amino acid score described above.

Like the AAS, the PDCAAS measures the It measures essential amino acids in a protein compared to a reference protein. The reference protein meets the essential amino acid requirements of humans, and is given a PDCAAS of 1.0.

The Food and Agriculture Organization of the United Nations (FAO) set out to address the concerns about some of the measurements above with the PDCAAS measurement. As a result, many health experts recognize PDCAAS as the standard measure of protein quality.

This method is not without flaws, however. In particular, in 1990, the FAO/WHO decided that proteins having a PDCAAS higher than 1.0 would be rounded down to 1.0 to indicate that it meets or exceeds the requirements of the average human.

These essential amino acid needs of the average human may be significantly lower than the needs of bodybuilders, weight lifters, and other highly active individuals.

Because of the rounding down of proteins that have scores greater than 1.0, there is no way to discern differences between proteins with a PDCAAS score of 1.0 other than to refer back to the other measures that PDCAAS hoped to eliminate.

As indicated below, this lack of clarity is of particular concern in the soy versus whey protein debate.

How do the PDCAAS values compare in the soy versus whey protein debate?

Round 5 – Soy vs. Whey Protein

Soy Vs. Whey Protein
PDCAAS

Soy Protein Concentrate
1.00

Whey Protein
1.00

Round 5 of the Soy Protein versus Whey Protein debate goes to…

Push.

 

So, in today’s events, though soy made a strong showing in the second event, whey still maintains the lead.

Next time, in the final events, we will see if soy can continue to build on the momentum from the last event.

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