Protein Quality: Not All Proteins Are Created Equal

white-eggsNot all proteins are created equal. Complete proteins supply all of the essential amino acids the body needs for growth and repair, while incomplete lack one or more of these essential amino acids. Animal proteins are usually complete proteins, while plant proteins are deficient in one or more essential amino acids the body requires. That’s why vegetarians need to diversify their plant-based protein sources, so they can get all of the essential amino acids their bodies need for health.

Higher quality proteins have another characteristic. They’re more easily digested and absorbed. This means the body has an easier time using them to build muscle and carry out other important bodily functions. Bodybuilders and athletes can benefit from consuming a source of high-quality protein that’s easily digested and absorbed after a strength training workout to supply their muscles with the protein they need for growth and repair.

Protein Quality Can Be Measured

The quality of a protein can be measured in several ways. One way is to feed a standardized amount of a particular protein to a person and see how much nitrogen they excrete in their feces and urine. Unlike carbohydrates and fat, protein contains nitrogen, so the amount of nitrogen excreted after consuming a standard amount of a protein under controlled conditions gives a rough indication of a protein’s quality. Higher quality proteins will be better absorbed and used by the body, so less nitrogen will be excreted.

Based on these results, researchers have assigned biological values to protein foods. These values can be used to compare one protein to another in terms of how well the body can absorb and use them. Biological value is a rough indication of a protein’s quality relative to another protein.

Which Protein Sources Are Highest in Quality

Whey protein, a protein isolated from milk, tops the list of protein sources with the highest biological values. Bodybuilders love whey protein because it’s quickly absorbed and rapidly reaches their muscles to start building lean body mass. Taking whey protein after a workout also speeds up muscle recovery and repair.

To get whey protein, you need to take a whey protein supplement or drink a shake with added whey. Whey isn’t found naturally in food since it’s a product of the conversion of cow’s milk to cheese.

The natural food source with the highest biological value for protein is the humble egg. It’s an underappreciated source of high-quality protein. Egg whites also contain egg protein but without the cholesterol. Eggs are an inexpensive source of protein, and they top the list of high-quality protein sources.

Other protein foods with high biological values are fish, beef and cow’s milk. Surprisingly, fish with a biological value of 83 outranks beef with a biological value of 80 on the quality scale. Chicken has a biological value of 79 and a milk value of 80.

In the plant protein arena, soybeans rank high with a biological value of 67. Rice, whole- grain wheat, peanuts are lower since they don’t have the full spectrum of essential amino acids the body needs.

The biological value of a protein is a simple and fairly accurate way to compare the quality of one protein to another. If you’re trying to build lean body mass, higher quality protein foods are the easiest for the body to digest and use, but plant-based protein sources also have benefits. Many such as beans, nuts and whole wheat contain vitamins and phytochemicals that meat-based protein sources don’t have. That’s a good thing when it comes to health.



Exercise Physiology. Fifth edition. McArdle, Katch, and Katch. 2001.


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