Biological value
The biological value of the proteins in a food is a measure of the efficiency with which these food proteins can be converted into the body's own proteins, and thus one of the options for determining the value of proteins . The more similar the dietary proteins are to the body proteins in terms of their amino acid composition, the less effort the body has to put into implementation . The content of essential amino acids is of particular importance . Whole egg is used as the reference value , the biological value of which was defined as 100 or 1 (100%), as it was the protein source with the highest known biological value at the time the definition was found.
The concept of biological value was developed by the German nutritionist Karl Thomas (1883–1969) at the suggestion of Max Rubner .
definition
The method of biological value from Thomas was completed by Mitchell in 1924 and, in order to avoid confusion with other methods for determining biological value, has also become known as the classical biological value. The definition for calculating the classic biological value is given in a simplified form by the following formula:
Biological value = retained nitrogen / absorbed nitrogen x 100
If a food protein is used better by the body than egg protein, it has a biological value with a value of over 100. If, on the other hand, a protein is used more poorly by the body than egg protein, the biological value of this protein is below 100. The higher the biological value of a food protein is, the lower the amount required. To meet the protein requirement with proteins from whole eggs, z. B. a daily minimum of 0.5 g per kilogram of lean body weight required. With increasing biological value, the intake required for the protein balance decreases; z. B. at 136 for 65% potato (protein) with 35% egg (protein) to less than 0.4 g / kg.
Through a clever combination, foods with a relatively low biological value can become a high-quality biological meal, as the amino acid compositions of the respective proteins complement each other and thus increase in value. Many traditional food combinations lead to a complementary effect (see combination examples). Animal protein is usually easier to use than vegetable protein, as its amino acid composition is more similar to that of the body's own protein.
Higher quality is not automatically to be equated with “more valuable” or “more valuable”, since the health value of a food is determined by numerous other factors, e.g. B. the content of vitamins , minerals , the type and amount of fats , carbohydrates , fiber , secondary plant substances, exposure to anthropogenic toxins (e.g. pesticides, see organic agriculture ) and the like. a. m. The adjective “high quality” is used to express that less protein is needed to meet the body's protein needs.
Examples
| Food | Biological value |
|---|---|
| Whey protein | 104 |
| Full egg (reference value) | 100 |
| soy | 96 |
| tuna | 92 |
| soy milk | 91 |
| Buckwheat | 90+ |
| Cow's milk | 88 |
| Edam cheese | 85 |
| Quinoa | 83 |
| rice | 83 |
| Potatoes | 76 |
| Rye flour (82% grinding) | 76-83 |
| beef | 80 |
| Casein | 77 |
| Beans | 72 |
| Corn | 72 |
| oats | 60 |
| lenses | 60 |
| Wheat flour (83% grinding) | 56-59 |
Combination examples
| Food combination | Value |
|---|---|
| 65% potatoes and 35% whole eggs | 136 |
| 75% milk and 25% wheat flour | 123 |
| 60% chicken eggs and 40% soy | 122 |
| 71% chicken eggs and 29% milk | 122 |
| 85% rice and 15% yeast | 118 |
| 68% chicken eggs and 32% wheat | 118 |
| 77% beef and 23% potatoes | 114 |
| 55% soy and 45% rice | 111 |
| 75% milk and 25% wheat | 105 |
| 55% potato and 45% soy | 103 |
| 52% beans and 48% corn | 101 |
The mixing ratio refers to the protein contained in the food, not to the total weight of the food. The combination of beans and corn in particular plays an important role in optimizing the mostly low-protein diet in developing countries.
Incomplete proteins
Protein sources that do not contain all of the essential amino acids are referred to as “incomplete protein” and have a biological value of 0. However, through suitable combination with other protein sources, the value can be increased significantly - as already described above.
Similar effects
Even outside the context of proteins, effects come into play that are logically related to biological value. The law of the minimum states that the growth of plants is restricted by the relatively scarce resource (nutrients, water, light, etc.). In the economic theory of production , the importance of the scarcest resource is described by the Leontief production function.
criticism
The biological valence method only measures the amount of protein that is retained in the body. Therefore, critics have pointed out that, for example, whey protein is digested so quickly that it enters the bloodstream and is converted into carbohydrates much faster than previously thought through a process known as gluconeogenesis . It was discovered that rates of oxidation also increased , creating steady state metabolism , a process that does not change the overall protein balance. Thus, the critics claim that when the human body consumes whey protein, it is absorbed so quickly that most of it goes to the liver for oxidation and thus is used for energy production rather than protein synthesis. This would call into question whether the method defines which proteins are best biologically usable.
As a result, organizations such as the Food and Agriculture Organization of the United Nations (FAO / WHO) or the Food and Drug Administration (FDA) no longer judge the quality of proteins in humans by their biological value, but by the Protein Digestibility Corrected Amino Acid Score (PDCAAS) .
See also
swell
- Löffler, Petrides: Biochemistry & Pathobiochemistry . 7th edition. Springer-Verlag, 2003, ISBN 3-540-42295-1 , pp. 685ff
Individual evidence
- ↑ Classical biological value - definition, calculation and meaning: biological value
- ↑ a b c Jay R. Hoffman, Michael J. Falvo: Protein - Which is Best . In: Journal of Sports Science and Medicine . 3, No. 3, 2004, pp. 118-30.
- ↑ a b [Soybeans: Chemistry and Technology (copyright 1972) (b) Synder HE, Kwon TW. Soybean Utilization. Van Nostrand Reinhold Company, New York, 1987]
- ↑ Eggum BO, Kreft I, Javornik B: Chemical-Composition and Protein-Quality of Buckwheat (Fagopyrum esculentum Moench) . In: Qualitas Plantarum Plant Foods for Human Nutrition . 30, No. 3-4, 1980, pp. 175-9. doi : 10.1007 / BF01094020 .
- ^ J. Ruales, BM Nair: Nutritional quality of the protein in quinoa (Chenopodium quinoa, Willd) seeds. In: Plant Foods for Human Nutrition Volume 42, Number 1, January 1992, pp. 1-11, ISSN 0921-9668 . PMID 1546052 .
- ↑ Jolliet, P. "Enteral nutrition in intensive care patients: a practical approach." Intensive Care Medicine (1998).
- ^ Gesundheit.gv.at - Lexicon of medical terms: Biological value
- ↑ akademie-sport-gesundheit.de: Biological value
- ↑ Joint FAO / WHO / UNU Expert Consultation on Energy and Protein Requirements, The use of biological value of protein in evaluating its quality for human requirements , SG Srikantia, University of Mysore .
- ↑ FAO / WHO (1991) Protein Quality Evaluation Report of Joint FAO / WHO Expert Consultation, Food and Agriculture Organization of the United Nations, FAO Food and Nutrition Paper No. 51, Rome.
- ^ Schaafsma, G. (2000) 'The protein digestibility-corrected amino acid score. Journal of Nutrition 130, 1865S-1867S