Protein Digestibility

You’ve probably heard the popular tip, “Eat enough protein every day.” There is nothing wrong with the statement, but optimizing your protein intake depends on more than sheer quantity.


Protein quality and digestibility are also important metrics to consider. 


With that in mind, let’s take a closer look at protein, its digestibility, and what that means for you.


What Is Protein?


Proteins are organic molecules made of amino acids - the building blocks of life. Once we consume some protein, the body breaks it down and absorbs the amino acids. These then travel into the bloodstream and contribute to the plasma amino acid pool. The storage of amino acids travels around the body, lending building blocks where needed.


Protein is mainly known for its roles in muscle repair, growth, and overall development (1). But amino acids are essential for much more than that. For example, amino acids are vital for producing hormones, enzymes, neurotransmitters, and antibodies (2). 


What Does Protein Digestibility Mean?


Protein digestibility is a measure of how well your body can use a particular type of protein. Digestibility determines how many of the amino acids your body can use productively.


A component of digestibility is the overall protein profile, which also influences how beneficial a specific protein is for you. The human body needs 20 amino acids to function normally, 11 of which it can synthesize on its own. The remaining nine are the essential amino acids, which we need to consume through food. A complete protein has an adequate amount of all nine essential amino acids (3).


The protein source also impacts its rating of digestibility. Animal proteins tend to digest more quickly than those from plants (4). One reason is that specific plant proteins contain inhibitors that prevent enzymes in the small intestine from breaking them down. Because of that, some experts recommend consuming slightly more plant-based protein to make up for the poorer digestibility rating. 


Processes such as hydrolysis and cooking can also influence our ability to break down specific proteins (4). Hydrolysis is a process where long protein chains get broken down into shorter peptides, making it easier for us to break them down entirely. Whey hydrolysate is one such example because it has shorter chains, allowing us to digest it more quickly and absorb its amino acids (5).


What Does It All Mean For You?


Well, it means that you should pay attention to your protein sources aside from your overall daily intake. Sure, getting your 1.6 to two grams of protein per kilogram is essential (1). But the source of that protein will also impact muscle protein synthesis.


Whey protein is one of the best options because it:

  • Digests relatively quickly, flooding your body with large amounts of amino acids
  • It offers large amounts of all nine essential amino acids 
  • It has an excellent digestibility rating, meaning that your body makes use of nearly all the amino acids inside


Vegan protein is also beneficial, but you should go for whey unless you have a solid reason. Plant-based proteins are often incomplete (lacking one or more essential amino acids), and their digestibility rating is up to 30 percent less than that of whey.