Protein quality and biological value

Protein quality and biological value

Depending on the quality of the dietary protein supplied, the amino acids are present in a different ratio. This ratio is crucial to how much of the protein the body can actually use. It is expressed by the so-called “biological value” and depends on the content of essential amino acids. In order for the body to be able to utilize the food protein, it must first be broken down into its individual amino acids. They are then added together and into amino acid compounds, so-called peptide chains. If a specific amino acid is not sufficiently present in this chain, or perhaps not represented at all, the eaten protein cannot be fully utilized and absorbed. In this respect, the least abundant amino acid is the limiting factor in biological value.

Egg protein (egg white + yolk combined) serves as a reference point and is set at a biological value of 100. Therefore, protein mixtures that are higher in their biological value provide the body with the same total protein intake, but with more usable and absorbable amino acids. Up until now, values greater than 100 are possible, because it is not specified how much protein the human body will exactly use in absolute terms, but how much protein is absorbed in comparison to egg protein.

Animal protein sources such as meat, eggs, dairy products or fish generally have a higher value than vegetable protein sources such as legumes, cereal or vegetables due to the higher content of essential amino acids. However, animal sources of protein also have the disadvantage that their intake often comes along with larger amounts of fat, cholesterol and purine, which in some cases can put more pollution and stress to the body (more specifically the liver). Many of these negative side effects are not present in most vegetable protein sources. In turn vegetable protein sources may seem to be the better option, but they are very low in protein content (and sometimes even have a low biological value), so that with larger quantities of vegetables many carbohydrates are consumed.

In short: protein comes with adverse effects. Animal protein is higher in fat and cholesterol, but the ratio of protein is a lot higher per 100g of product. Vegetable protein lower in fat and cholesterol, but the ratio is lower and you are forced to consume a lot more carbohydrates.

Fig.1: Protein sources and their biological value
Food item Biological value
Whole Egg 100
Potatoes 98
Beef 91
Fish 87
Tofu 86
Cheese 84
Brown rice 81
Whole Wheat 76
Green beans 73
Corn 72
Wheat 57

 

However, the biological value can be increased by mixing different sources of protein, since this will result in a different ratio of amino acids. Beans for example are usually quite low in value, but by combining them with corn, a value that is equivalent to that of whole egg is achieved.

Fig.2: Combinations of protein sources
Food combination Ratio Biological value
Potato/Whole egg 10/1 136
Tofu/Whole egg 10/3 123
Milk/Whole egg 2/5 122
Wheat/Whole egg 1/3 118
Beef/Potatoes 3/1 114
Wheat/Yogurt 4/3 110
Rice/Whole egg 2/3 106
Green beans/Corn 7/6 100

 

 

Due to the above negative side effects of natural protein sources, protein concentrates (e.g. whey protein shake) can make a good and convenient alternative, but are of course, never essential or necessary. Of course, these supplements should not replace a balanced diet for protein supply and intake, but should serve, as the name suggests, as a supplement to an already fundamentally profound and strong, balanced diet. Protein supplements are very well suited to provide the body with a good amino acid balance in a quick and convenient way. Key here is, as so often in bodybuilding and fitness, in the variety. Many health experts and physicians recommend to consume as many different types of protein sources (and food in general, not only protein) as possible. Different sources of food and protein will provide the body with a much better and more balanced amino acid profile than if you were limited to just one or two sources of protein.

 

Protein requirements of the individual