PROTEIN- BIOLOGICAL VALUE

Most of you often wonder why there is a significant price difference when it comes to protein supplements- Some of them are cheaper and others are way more expensive, even though the protein concentration is the same as in the cheaper ones.

The answer here hides behind the parameters of the supplements, namely, their biological value. In order to clear out the proteins’ properties, we will first need to take a look at those parameters.

What Does ‘Biological Value’ Mean?

This is simply an indicator that defines the level of effectiveness during the digestion of the given protein (Simply- The proteins highest in biological value are digested and metabolized to a bigger extent)

This effectiveness however is characterized with two indicators:

  1. The level of protein retention in the organism
  2. The balance of the organism’s essential amino acids

So far, there are no absolute values that express the biological value of proteins, which is why a standard value is used instead.

In sports nutrition, the equivalent of this value is protein from eggs, meaning that every other protein, whether it comes from food or supplements, is compared to egg protein.

On the flipside however, it is well known that the average nitric content in proteins is about 15%, which is the leverage for all methods used to determine the biological value of a given type of protein.

There are two commonly used methods to determine that- Biological and chemical.

Biological Protein Rating Methods

These methods are based on using test animals or microorganisms and are the most accurate ones when it comes to rating protein quality.

Nitric Balance

The basics of determining this balance have been laid with the term ‘biological value’ of proteins. The nitric balance is expressed with BV=B/A, where B is the retained nitrogen in the organism and A is the nitrogen absorbed from food, via the digestive system.

An additional characteristic to the nitric balance is the “Net protein utilization” index, which is the ratio of retained nitrogen (B) to the total amount of nitrogen in the food ingested (I). Another indicator used to rate proteins is the digestibility (D) of the given protein.

To determine the level of nitric retention in the organism, there are a couple of methods used. One of them is based on the change of body mass during the ingestion of protein, this is the so-called “Protein Efficiency Ratio- PER”

PER=(W-Wk)/P, where P is the total amount of protein, in the food that has been ingested during the past 24 hours, while W and Wk is the weight of the organism in the beginning and end of the 24-hour cycle.

This is a standard method in bodybuilding, as it is simple and easily applicable for fast-gaining professional bodybuilders.

However, can we say that the PER of a certain protein is a constant value for every organism?

To get the PER values of a protein, the tests are done on lab rats, meaning that the amino acid content of the protein tested is related to the protein requirements of rats and not humans.

And there is a difference between the amino acid requirements of rats and humans.

For example, mice need more sulfur-containing amino acids, compared to people.

Using lab mice to determine PER of a given animal/plant protein might lead to an overestimation/underestimation of their qualities, respectively.

Keep this in mind next time you check out the PER value on a protein tub.

Protein Evaluation- Biochemical Methods

These methods are based on the quality and quantity of certain substances, like free amino acids, in the bodily fluids.

To rate the nutritional properties of proteins, the most common method used is determining the ratio of essential to non-essential amino acids in the blood plasma. This is the so-called “Plasma-amino acids ratio” (PAA-r).

PAA-r=(B-A)/R, where B is the concentration of a certain amino acid in the blood plasma, after eating, A- The concentration of the same amino acid on an empty stomach and R- The organism’s requirements and needs of this amino acid.

Amino Acid Needs In Humans

The normal, non-training organism needs 8 essential amino acids: Methionine, threonine, tryptophan, leucine, isoleucine, lysine, phenylalanine and valine.

However, young and/or physically active organisms are often in a deficit of non-essential amino acids- Arginine and glutamine.

This is simply caused by the quick growth of the musculature, which requires an increased amount of amino acid intake.

Depending on the duration of this amino acid deficit, it is possible to develop the so-called “cachexic syndrome”, which is expressed in the loss of weight and muscle mass.

If, however, the organism is in a deficit of a certain essential amino acid, the observed effects are loss of appetite, exhaustion, irritation and negative values of the organism’s nitric balance, caused by the lowered food intake.

Another interesting thing is the fact that in order to maintain the nitric balance in an organism, that consumes a balanced mixture of amino acids, high energy (food) intake is required.

Through researches, scientists determined that when the nitric source for the organism is a balanced mixture of essential and non-essential amino acids, the body uses 45 calories per 1 kilogram of bodyweight to maintain the nitric balance.

However, if we use raw protein like casein, instead of that mixture, the nitric balance is maintained with just 35 calories per 1 kilogram of bodyweight.

This phenomenon is explained with the fact that different proteins elapse different times to get sucked in to the intestinal tract.

Free amino acids get sucked in faster than protein, simply because protein needs to get broken down into amino acids first, while the free amino acids have passed that phase.

As we already mentioned early on in the article, egg protein from whole eggs is considered the standard for biological value of proteins, as eggs have a Biological value (BV) of 100 (BV=100).

Later on, however, as science and the supplement market advanced, protein isolates came to the market. These supplements showed the highest BVs of over 150 (BV=150+).

There is no measuring unit for the BV of protein supplements, but the numbers are rather accepted as coefficients and can be compared to foods, to determine which food it is closest to when it comes to biological value.

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