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Biological value of a protein: what is it?
Biological value of a protein: what is it?

Biological value of a protein: what is it?

Author:
Date: July 20, 2021

Biological value is a measure of the proportion of protein absorbed from a food and its incorporation into the body's own Protein. It easily indicates how the digested protein can be used in protein synthesis in the body's cells. Protein is the main source of nitrogen in food. BV measures the proportion of this nitrogen absorbed by the body and that excreted. The absorbed part is incorporated into the body Protein that form the organism. The ratio of nitrogen incorporated in the body and nitrogen absorbed gives the measure of the "usability" of Protein: The BV.

Unlike other methods for determining the usability of a protein source, the BV Biological Value does not take into account how a protein can be digested and absorbed. The biological value uses two similar scales: 1- true use of the percentage (usually indicated with a percentage symbol) 2- percentage use related to an easily usable protein source, often eggs These two values ​​will be similar but not identical The BV is a parameter commonly used in nutrition science. [1] Often popular in the bodybuilding world for choosing protein sources. [2] [3]

Determination of the BV

Per the exact determination of the BV biological value : [4]


1- The test organism must consume only protein or a mixture of Protein of interest (test diet)

2- The test diet must contain non-protein sources of nitrogen

3- The test diet must be of appropriate contents and quantities in order to avoid the use of Protein as a source of energy

These test conditions are typically carried out over the course of more than a week with strict dietary controls. Furthermore, fasting before the test helps to obtain more consistent and reliable data.

There are two scales on which the biological value BV is measured: percentage of utilization and relative utilization. In the utilization percentage the BV has a percentage sign (%), and in the relative utilization the BV has no units.

Percentage of use

The biological value is determined by this basic formula [4] [5]

BV = ( N r / N a ) * 100

Dove:

N a = absorbed nitrogen of the Protein present in the test diet

N r = nitrogen incorporated in the body in the test diet

However, the direct measurement of N r is essentially impossible. It will typically be measured indirectly and accounted for urinary nitrogen excretion [6] and fecal nitrogen excretion. This part of ingested protein is not absorbed by the body and therefore is not included in the BV calculation.

BV = (( N i - N e (f) - N e (u) ) / ( N i - N e (f) )) * 100

Dove:

N i = intake of nitrogen in Protein in the test diet

N e (f) = (nitrogen excreted with faeces, on test diet) - (nitrogen excreted with faeces not from ingested nitrogen)

N e (u) = (nitrogen excreted in urine, on test diet) - (nitrogen excreted in urine not from ingested nitrogen)

Note:

N r = N i - N e (f) - N e (u)
N a = N i - N e (f)

This can take any value from 0 to 100. A BV of 100% indicates full use of a protein. that is, 100% of the Protein taken in and absorbed are incorporated into the Protein of the body. The 100% value is an absolute maximum, no more than 100% of the Protein taken can be used (in the equation above N e (u) and N and (f) cannot go negative, setting 100% as maximum BV.

Relative use

Due to experimental limitations, the BV Biological Value is often measured against an easily usable protein. Egg protein is normally considered the most readily usable protein and given a BV of 100. Per example:

Two BV tests are performed on the same person; one with the test protein source and one with the reference protein (egg protein)

relativo BV = ( BV(test) / BV(egg) ) * 100

Dove:

BV (test) = BV percentage of the test diet for that individual

BV (egg) = percentage BV of the reference diet (egg) for that individual

This is not limited to values ​​below 100. Egg protein BV percentage is only 93.7% which allows other Protein with BV percentage between 93.7% and 100% to take a relative BV of over 100 Per example whey protein takes a relative BV of 104, while its BV percentage is less than 100%.

Properties of protein sources

Three major properties of a protein source affect its BV:

1- Amino acid composition, and the limiting amino acid, which is usually lysine

2- Preparation (cooking)

3- Vitamin and mineral content

The amino acid composition is the main effect. All Protein are made up of combinations of the 21 biological amino acids. Some of these can be synthesized or converted in the body, while others can and should be ingested with the diet. These are known as essential amino acids (EAAs), of which there are 9 in humans. Missing EAAs in the diet prevents protein synthesis. If a protein source lacks critical EAAs, then its BV will be evaluated from the missing EAAs that form a bottleneck for protein synthesis. Per example, if a muscle protein requires phenylalanine (an essential amino acid), then it must be supplied with the diet to synthesize muscle protein. If the protein source in the diet does not have phenylalanine, the muscle protein cannot be produced,

Food preparation methods have an impact on the availability of amino acids in a food source. Some preparations and cooking can damage or destroy some EAAs, reducing the BV of a protein source.

Many vitamins and minerals are essential for the proper functioning of cells in the body. If minerals or vitamins are critically present in the protein source, the BV can be massively lowered. Many BV tests artificially add vitamins and minerals (e.g. in yeast extract) to avoid this.

Comparison with other methods

There are several other important methods for determining the usability of a protein source, including:

Net protein Utilization (NPU)
Protein Efficiency Ratio (PER)
Nitrogen Balance (NB)
Protein digestibility (PD)
Protein Digestibility Corrected Amino Acid Score (PDCAAS)

Typical values

Common foods and their values: (Note: this scale uses 100 as 100% of the incorporated nitrogen)

Whey protein: 96 [11]

Soybeans: 96 [12]

Human milk: 95 [13]

Chicken egg: 94 [13]

Soy milk: 91 [12]

Buckwheat: 90 [14]

Cow's milk: 90 [13]

Cheese: 84 [15]

Quinoa: 83 [16]

Rice: 83 [15]

Soybean meal: 81 [12]

Fish: 76 [17]

Meat: 74 [17]

Bean: 65 [12]

Common foods and their values: [18] (Note: these values ​​use egg as a reference value (100). So foods that provide even more nitrogen than whole eggs can have a value of more than 100. This does not mean that 100% of the nitrogen in food is incorporated into the body, and not excreted)

Concentrated whey protein: 104

Whole egg: 100

Cow's milk: 91

Manzo: 80

Casein: 77

Soybeans: 74

Wheat gluten: 64

  1. Thomas, K. On the biological value of nitrogen substances in various foods in 1909. Arch. Physiol., 219.
  2. Optimum Sports Nutrition: Your Competitive Edge, A Complete Nutritional Guide Per Optimizing Athletic Performance; Chapter 12. by Dr. Michael Colgan
  3. The Great Animal Versus Vegetable Protein Debate What Is The Best Protein Per Muscle Growth?
  4. ^ Jump up to: a b Mitchell, H.H. (1923). "A Method of Determining the Biological Value of Protein". Journal of Biol. Chem. 58 (3): 873.
  5. Chick H., Roscoe, M.H. (1930). "The biological values of Protein: A method for measuring the nitrogenous exchange of rats for the purpose of determining the biological value of Protein". Biochem J. 24 (6): 1780-2.
  6. Fixsen, M.A.B. "The biological value of purified caseinogen and the influence of vitamin B2 upon biological values, determined by the balance sheet method". Biochem J. 1930; 24(6): 1794–1804.
  7. S.G. Srikantia (August 1981). "The Use Of Biological Value Of A Protein In Evaluating Its Quality Per Human Requirements". Joint FAO/WHO/UNU Expert Consultation on Energy and Protein Requirements Rome, 5 to 17 October 1981. Food and Agriculture Organization of the United Nations.
  8. Mitchell, H.H. A method for determining the biological value of protein. 1924 J. Biol. Chem., 58, 873. http://www.jbc.org/cgi/reprint/58/3/873.pdf
  9. Mitchell, H.H. and G.G. Carman. The biological value of the nitrogen of mixtures 1926 of patent white flour and animal foods. J. Biol. Chem., 68, 183.
  10. Recent developments in protein quality evaluation by Dr E. Boutrif.
  11. Hoffman, Jay R.; Falvo, Michael J. (2004). "Protein – Which is Best" (PDF). Journal of Sports Science and Medicine 3 (3): 118–30.
  12. [Soybeans: Chemistry and Technology (copyright 1972) (b) Synder HE, Kwon TW. Soybean Utilization. Van Nostrand Reinhold Company, New York, 1987]
  13. http://www.medbio.info/Horn/Time%206/protei4.gif
  14. Eggum BO, Kreft I, Javornik B (1980). "Chemical-Composition and Protein-Quality of Buckwheat (Fagopyrum esculentum Moench)". Qualitas Plantarum Plant Foods for Human Nutrition 30 (3–4): 175–9. doi:10.1007/BF01094020.
  15. Jolliet, P. "Enteral nutrition in intensive care patients: a practical approach." Intensive Care Medicine (1998).
  16. Ruales J, Nair BM. "Nutritional quality of the protein in quinoa (Chenopodium quinoa, Willd) seeds." Plant Foods Hum Nutr. 1992 Jan;42(1):1-11.[1]
  17. Microsoft PowerPoint - The Nutritious Egg
  18. Protein, Which Is Best." (PDF). JSSM. Retrieved 2007-10-31.



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