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The Prof Blog: Does Protein Quality Really Effect Muscle Growth?

Protein Quality has always been a hot topic amongst weight trainers, but now with a flood of new proteins entering the market, protein quality is really starting to become a key issue.

So with all the marketing hype about plant proteins like pea, rice and hemp, insect proteins, fish proteins and collagens, what is the truth? How do they compare with good old whey?

Let’s take a quick step back and first of all cover why take a protein supplement at all? Well most of us know that following a regular strength training program of progressive resistance leads to increases in muscular strength and size, known as muscle hypertrophy. Adding supplemental protein has also been shown to enhance this response. A 2016 review by Dr Stuart Phillips of McMaster University in Canada, and published in Nutrition & Metabolism looked at the affect of protein quality on post exercise protein synthesis.

Traditionally protein quality can be measured or estimated using measure called the Protein Digestibility Corrected Amino Acid Score or PDCAAS. While this gives a relative measure of protein effectiveness, it has recently been replaced with a new measure of called the Digestible Indispensable Amino Acid Score or DIAAS.

The DIAAS looks at the ratios of amino acids in a given protein source, especially the essential amino acids (the ones your body can’t make). It considers how well a given protein is digested, absorbed and interacts right throughout your intestinal tract, and also places a higher value on Leucine content because of Leucine’s ability to turn on muscle protein synthesis. Quite simply, if a protein source doesn’t contain enough Leucine, it won’t stimulate protein synthesis to any great degree.

So how do the different proteins measure up? The table below shows the PDCAAS and available DIAAS for a number of proteins:

table_prof_blog

The DIAAS are not available yet for all protein sources however a review of the data clearly shows Whey Protein Isolate, Whey Protein Concentrate and potentially Casein and Whole Egg are excellent quality proteins. This means you will need to consume less of these proteins to gain the same muscle building benefits as lesser proteins in the table.

When we start looking at some of the more popular ‘new’ proteins on the market, including pea and rice, or other protein sources, the quality and therefore muscle building ability start dropping away quickly. For example, based on the DIAAS, you would need to consume 3 times more rice protein (with the extra associated carbs) than pure WPI.

A recent popular protein choice is hydrolysed collagen, more commonly known as gelatin. Collagen proteins are made from animal connective tissue but lack specific essential amino acids, most notably tryptophan, which results in a PDCAAS of zero. This mean your body can use hydrolysed collagen for repairing hair, nails and connective tissue, but they are very poor choices for muscle building, even if they are fortified with other amino acids.

Other newer protein sources like insect proteins or fish proteins are also likely to have lower PDCAAS than dairy or egg, based on what is known about their physical characteristics according to the review.

Now many companies will try to blind you with fancy marketing and pseudo-science of half truths about why their amazing new protein is the best thing to come onto the market is years. But who should you trust – an acknowledged scientific expert (Dr Phillips), or some commercial marketing department.

The take-home message is pretty clear – dairy and egg are still the kings of protein supplements, and unless you have a food allergy or other significant health, dietary or philosophical reasons to choose otherwise, they are your best bet for building maximum muscle.

References: Phillips, Nutrition & Metabolism (2016) 13:64, DOI 10.1186/s12986-016-0124-8

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