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"Understanding which role proteins can play in our diets is an excellent way to improve health and body composition. With a priority on consuming complete proteins, and utilizing specific protein sources for specific goals, the road to a healthy lifestyle can be made significantly more attainable."
-Article written by Ethan Wood, CPT & Registered Nutritionist
What is a Complete Protein?
Every protein is composed of some combination of amino acids. In total, there are twenty amino acids, however, only nine of these are considered essential because, as humans, we are unable to produce these and must intake through diet or supplementation.
When a protein consists of all nine essential amino acids, it can then be considered complete. These are typically animal-derived proteins with some plant options existing as well.
While it's important to primarily consume complete proteins, this doesn't mean incomplete proteins are inherently bad. As long as an individual is consuming an adequate amount of protein from varied sources, chances are they're meeting their amino acid requirements.
How is Protein Quality Determined?
The FDA has been using a system called PDCAAS (Protein Digestibility-Corrected Amino Acid Score) to classify proteins based on their effectiveness in humans.
This system looks at not only a protein source's amino acid make-up and how it compares to the requirements of the human body, but also our ability to actually absorb and digest these proteins.
The score operates on a scale of 0 to 1, where 0 would be the worst, and 1 would be the best.
We will be referring to this score as PQ, or Protein Quality, later in the article.
Which Proteins are Considered Complete?
Now that we understand what qualifies a protein as complete, and how to categorize these based on effectiveness, let's look a little more into the specifics of complete proteins.
Whey
Whey protein has long been considered one of the most ideal sources for muscle growth and recovery.
Whey is the liquid portion of milk that has separated during cheese production.
When isolated, whey can be a very dense source of complete protein and is used in a wide variety of protein powders.
Whey's effectiveness as a protein is partly due to its amino acid profile. It is particularly high in BCAAs (Branched-Chain Amino Acids) which are the three amino acids that are considered most important for muscle growth.
Whey's effectiveness can also be attributed to its absorption rate. Whey is the fastest-digesting protein we know of, with the average body able to absorb ~10g per hour. This means it's an excellent choice for post-workout as the proteins get to work repairing muscles as quickly as possible.
Whey has been given a score of 1 on the PQ scale, which is the highest possible rating.
Casein
Casein is similar to whey in the fact that they're both complete proteins derived from milk.
In terms of effectiveness and amino acid make-up, casein is also very similar to whey. However, the similarities end here.
Casein is considered a "time-release" or slow-digesting protein. This is because casein turns into a gel-like substance in the digestive tract and is absorbed much more slowly. Around 6g of casein protein can be absorbed per hour.
This makes casein a better choice as a meal replacement or before bed as the amino acids are released and sustained in our system over a much longer period of time.
Casein has also been given a score of 1 on the PQ scale, making it an equally powerful alternative to whey.
Egg
The amino acid make-up of egg protein is understood to be the most similar to the requirements of the human body. This makes it an excellent benchmark for all other proteins.
Egg protein is considered medium-digesting. While it's difficult to estimate exactly how quickly this protein is absorbed, it will generally fall somewhere in-between whey (fast) and casein (slow).
Egg protein is also highly-nutritious. Beyond the protein content, a high-quality egg protein will offer additional vitamins & minerals - nutrients that keep the body healthy.
Egg protein has been given a score of 1 on the PQ scale, and is used as the benchmark for all other proteins.
Beef
Beef protein is considered highly-nutritious and an excellent source of essential amino acids, but is digested slowly and absorbed less efficiently than other sources.
The amino acid profile of beef protein is very similar to the make-up of human muscles. This allows it to be easily used by the body.
Beef protein also contains a large amount of vitamins & minerals, which makes it a generally healthy choice. However, certain powders may or may not contain these additional nutrients.
While beef is an excellent source of complete protein, it's much more complex than other sources and therefore is difficult to absorb in the digestive tract.
Beef protein has been given a score of 0.92 on the PQ scale, mainly due to its low absorption rate.
Pea
Pea protein is one of the few plant proteins that can be considered complete. With a solid amino acid profile and decent absorption, pea protein can be an excellent choice for vegans, vegetarians, and individuals with limiting dietary restrictions.
For a plant protein, pea is excellent source of BCAAs and iron, but is relatively low in the essential amino acid methionine.
Pea protein is one of the most easily-absorbed of the plant proteins, however, animals proteins are typically more easily digested and absorbed.
Pea protein has been given a score of 0.893 on the PQ scale, which is one of the highest plant-based protein scores.
Complete Proteins Chart
| Protein | Source | PQ | Digestion Rate | Ideal For |
| Whey | Milk | 1 | Fastest | Post-Workout |
| Casein | Milk | 1 | Slowest | Before Bed/Meal Replacement |
| Egg | Animal | 1 | Medium | Anytime |
| Beef | Animal | 0.92 | Slower | Meal Replacement |
| Pea | Plant | 0.893 | Faster | Anytime |
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