Bioavailability of Protein


A key step to understanding and measuring how useful a source of protein is understanding a protein's bioavailability. Not all proteins are created equal, and some proteins are more beneficial to you than others.

The bioavailability of protein is how useful and effective it is to your body. There are 3 main types of amino acids, while some amino acids can be created by your body, there are others which cannot. Good protein sources should contain all 3:

  • Indespensable amino acids (IAAs) - These are also known as essential amino acids. These amino acids must be obtained from foods since the body cannot manufacture them. Foodstuffs such as red meat like beef and white meat like poultry, fish dairy and soy all contain all 8 IAAs. These foods rank highly on the bioavailability charts and are therefore known as complete proteins, since they contain the full range of IAAs. On the other hand, proteins from vegetables and grain contain large amounts of some IAAs and low amounts of others. Since they are incomplete sources of IAAs, they rank lower on the bioavailability charts.
  • Dispensable amino acids (DAAs) - These are also known as non-essential amino acids. The reason why they are "non-essential" is that they don't necessarily have to be taken from foodstuffs since they can be manufactured by the body.
  • Branched chain amino acids (BCCAs) - These are a special type of essential amino acids which unlike other amino acids, are metabolised in the muscle instead of the liver. They are important in determining a protein source's bioavailability.

The ratio of IAAs to DAAs and BCAAs is what determines the bioavailability of a protein source and how effective it is in repairing and building muscle tissue.

The main measure of the bioavailability of a certain protein is the biological value (BV). This indicates how close the amino acids present in the protein source match the amino acids required by the body. The more closely matched they are, the more protein can be used to repair and build muscle tissue. So BV measures the percentage of protein that is actually used by the body effectively.

Being complete proteins, meat and dairy products rank the highest on the BV scale. The following is a top 3 list of the BV of common protein sources for bodybuilders.

  1. Whey Protein (BV 100+)
  2. Eggs (BV 100)
  3. Dairy, meat, fish, poultry (BV 70 - 100)

Unfortunately, grains, vegetables and nuts, being incomplete proteins, all have a BV under 70. While they will still contribute some useful protein to the body, a protein source with a low BV will not be used as effectively by the body to build muscle.