Sūkalu olbaltumvielu nozīme uzturā

Importance of whey protein in nutrition

Whey protein is a heterogeneous mixture of proteins. Whey proteins are made up of different protein fractions. Cow (Bos taurus) milk contains 3.5% protein, of which 80% is casein and 20% whey protein. Whey protein has a biological value (BV) of 104, while casein has a biological value (BV) of 77. On the other hand, BV of total milk protein - 91[33]. BV is a coefficient that shows how much of the protein absorbed in the body's intestinal tract is consumed for the creation of new proteins, but not for energy needs [34].
Most whey proteins are compactly coiled globular molecules that are mainly hydrophobic and linked by peptide bonds [30].

Properties of whey proteins:

  • helps stimulate appetite suppression and satiety [8,9,10, 11];
  • is a high-quality protein source rich in all essential amino acids and other biologically active substances that help reduce fat mass and preserve muscle mass as part of a well-balanced diet and physical activity [13,14,15,16] ;
  • helps maintain a positive glutathione level by providing the necessary amino acids (glutamic acid, cysteine, glycine) in the diet, also by modeling their synthesis [17,18];
  • facilitates the absorption of minerals, vitamins and fatty acids taken with food [17,20,21];
  • Helps improve mood and concentration [17,20,21];
  • Helps preserve and reduce loss of body protein (muscle) due to sacropenia in the elderly [12,22,23,24];
  • are more easily digested and absorbed compared to other protein sources [17,21,21].
  • whey proteins have 10-30% more "value" than barley, rice, soy and pea proteins, according to the Digestible Indispensable Amino Acid Score (DIAAS) of the International Food and Agriculture Organization (FAO). ) methods [25]
β-lactoglobulin:
  • is a globular protein of 162 amino acid residues [30];
  • is very rich in branched chain amino acids (Figure 25).1%), especially leucine (13.5%) [35];
  • is synthesized in the mammary gland of the cow [35];
  • contains two –S-S- bonds and one free thionyl group [30];
  • constitutes 50-60% of whey protein and 10% of total milk protein (2-4 g/l) [35].
The biological role of β-lactoglobulin has not been fully elucidated. It is known that it performs a transport function - the molecule contains a hydrophobic part that can bind vitamins A and D, Ca2+ and fatty acids, as a result of which their reabsorption in the body is facilitated [21]. β-lactoglobulin participates in the regulation of phosphorus metabolism in the cow's mammary gland [21]. β-lactoglobulin can also bind mutagenic heterocyclic amines, thus providing a kind of protection against their carcinogenic nature [20]. β-lactoglobulin is the only allergen in whey protein. Milk allergy is a clinical immunological reaction to one or more milk proteins [35]. Milk allergy is observed in 2-3% of children, most of them disappear when they reach 3 years of age [21]. In hypoallergenic infant formulas containing whey proteins, β-lactoglobulin is either separated or available in a hydrolyzed form [28]. In addition to biological activity, it also contains peptide chains encoded in its structure, which can be released in the gastrointestinal tract during enzymatic hydrolysis [35, 21]. Biologically active peptides are specific sequences of amino acids that cause positive effects on body functions and conditions that can affect human health [21]. The biologically active peptides of β-lactoglobulin are attributed: antihypertensive, antithrombotic, antimicrobial and immunomodulating properties [21].
α-lactoalbumin:
  • α-lactoalbumin is a monomeric globular calcium-containing protein composed of 123 amino acid residues, including lysine, leucine, threonine, tryptophan, and cysteine ​​[36];
  • contains four –S-S- bonds [30];
  • is synthesized in cow mammary gland cells and acts as a regulatory component in the enzymatic system and is responsible for the biosynthesis of lactose [36];
  • makes up 20% of whey protein and 3.4% of total milk protein (0.6-1.7 g/l) [36];
The ratio of α-lactoalbumin to β-lactoglobulin in whey proteins is 1:3 [20].
In contrast to β-lactoglobulin, α-lactoalbumin has a very low immunogenicity, thus a low allergy-inducing potential, which makes it a suitable nutrient for children with milk allergy [21].The health-promoting effects of
α-lactoalbumin are divided into three categories:
  • effect of whole intact protein;
  • effects of individual amino acids from digested protein;
    • Effects of
  • formed by peptides in the gastrointestinal tract by hydrolyzing proteins.
One of the biologically active functions of α-lactoalbumin is facilitated by its high tryptophan content (Fig.9 g/100 g), is an increase in serotonin levels and a decrease in cortisol concentration, resulting in improved concentration, mood and reduced susceptibility to stress [22]. α-lactoalbumin can bind not only Ca but also Mg and Zn. Relatedly, absorption of these minerals in the small intestine is facilitated [37]. Biologically active peptides of α-lactoalbumin have been attributed antimicrobial, immunomodulatory and anticancer properties[37]. Due to its similarity to human albumin, its high nutritional value and biologically active properties, α-lactoalbumin is widely used in infant formulas [36]. Purified α-lactoalbumin is added to the diet of athletes as a good source of essential amino acids [28].
Lactoferrin:
  • is a monomeric, globular Fe3+-binding glycoprotein of 689 amino acid residues [39];
  • enters milk from blood plasma [39];
  • belongs to the group of transferrins, which are blood plasma metal-binding and transport proteins [39];
  • Lactoferrin constitutes 1% of whey protein [39];
  • lactoferrin has two Fe3+ binding sites. Each of them can bind 1.4 mg Fe3+ /g [40].
Lactoferrin has various health-promoting properties. It has antibacterial, anti-inflammatory, anti-cancer, immunomodulatory and bone-promoting properties, as well as the ability to influence cell proliferation and differentiation [21]. The antibacterial effect of lactoferrin is most effective against bacteria that require iron to reproduce. Lactoferrin forms chelates with iron ions present in microorganisms [21]. Antioxidative activity is also attributed to lactoferrin. Lactoferrin attracts free Fe+3 ions, which catalyze the formation of free radicals (superoxide, hydroxyl-) [28]. Lactoferrin used in artificial milk formulas for infants. Lactoferrin supplements the formula, making it more similar to breast milk, which contains 20 times more lactoferrin compared to cow's milk. Iron-saturated lactoferrin is used in iron supplements to facilitate iron absorption [28].
Lactoferrin is also used in toothpastes and mouthwashes, where it performs an antibacterial function in a complex with lactoperoxidase and lysozyme [28].
Blood serum albumin:
  • accounts for 3% of whey protein [38];
  • is a globular protein of 583 amino acid residues [38];
  • it is not synthesized in the mammary gland, but enters the milk from the blood plasma [38];
  • contains 17 -S-S- bonds [30].
  • similar to β-lactoglobulin binds hydrophobic molecules t.see fatty acids [38];
  • blood serum albumin contains all essential amino acids [38].
Immunoglobulins (IgG, IgA, IgM, IgA):
  • also called "antibodies", make up 9-10% of whey proteins [20];
  • are glycoproteins composed of four peptide chains linked by disulfide bonds [41];
  • is nutritionally a good source of the essential amino acid, cysteine ​​[41].
The main function of immunoglobulins is to provide passive immunity to newborns. Immunoglobulins contain antibodies that are directly involved in the defense against microbial pathogens and promotion of the phagocytosis process, as a result of which adhesion of microorganisms is prevented, viruses and toxins are neutralized [21]
                            Importance of whey proteins in nutrition
Amino acids in whey proteins are found in the composition of the fractions described above and, minimally, also in the form of free amino acids. The amino acid content of whey proteins can vary and can be influenced by various factors [38]. Whey proteins contain all essential amino acids, they make up 60% of the total amino acids in them [30].
Whey proteins are an excellent source of sulfur-containing (methionine, cysteine) amino acids. The ability of sulfur-containing amino acids to promote immune function and the body's antioxidative capacity by modeling glutathione synthesis is of great importance in the body [28]. Glutathione is an endogenous antioxidant present in every cell of the human body. Especially in the liver, where it provides detoxification of cells and the lymphatic system. A positive amount of glutathione stimulates the functioning of the immune system, it is directly related to the aging processes of the body. Glutathione biosynthesis in the body requires glutamic acid, cysteine ​​and glycine [42].
Whey proteins are also a dietary source of branched chain amino acids (isoleucine, leucine, valine). Branched chain amino acids play an important role in skeletal muscle protein synthesis, and they can also be involved in the energetic metabolism of muscle tissue [28].
After whey OBV is digested in the gastrointestinal tract, not all amino acids participate in the energy metabolism of the human body and the formation of plastic material. Some of the proteins are enzymatically cleaved to peptides of different lengths, in which the number of monomers can vary from 2 to 20 amino acids. These discrete amino acid sequences are inactive in the protein from which they came. In their free form, they have a wide range of biological activity, including antimicrobial, antihypertensive, and immunomodulating activity[43].
Basic information taken from Anša Sauer 2015. of the literature description of the bachelor thesis. SIA Valens Nutri product OBVProt is a source of native whey proteins (there is no by-product of cheese or curd production - whey). 
                                              References
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9. Anderson, H., Moore, S. Dietary proteins in the regulation of food intake and body weight in humans. Journal of Nutrition, 2004, Vol. 134, Iss. 4, p. 974-979.
10. Hall, W. L, Millward, D. J, Long, S. J, Morgan, L. M Casein and whey exert different effects on plasma amino acid profiles, gastrointestinal hormone secretion and appetite. British Journal of Nutrition, 2003, Vol. 89, Iss. 2, p. 239-248.
11. Sebely Pal, Simone Radavelli-Bagatini, Suleen Ho, Jenny-Lee McKay, Martin Hagger, Monica Jane. Dairy Whey Proteins and Obesity. In: John F. Trepanowski, Krista A. Varady. Nutrition in the Prevention and Treatment of Abdominal Obesity. Elsevier, 2014, c. 32, p. 351–361.
12. Ha, E., Zemel, M. Functional properties of whey, whey components and essential amino acids: mechanism underlying health benefits for active people. Journal of Nutritional Biochemistry, 2003, Vol. 14, Iss. 5, p. 251-258.
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14. Layman, D. K, Boileau, R. A, Erickson, D. J, Painter, J. E, Shiue, H ., Sather, C ., Christou, D. D A reduced ratio of dietary carbohydrate to protein improves body composition and blood lipid profiles during weight loss in adult women. Journal of Nutrition, 2003, Vol. 133, Iss. 2, p. 411-417.
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2 comments

Paldies par jūsu jautājumu par “Ķīnas pētījuma” apgalvojumiem attiecībā uz kazeīnu un vēža augšanu. Tas ir ļoti svarīgs temats, un es saprotu jūsu bažas. Atļaujiet man sniegt plašāku skaidrojumu, balstoties uz jaunākajiem zinātniskajiem pētījumiem.

Pirmkārt, jāatzīmē, ka “Ķīnas pētījuma” eksperimenti tika veikti galvenokārt ar grauzējiem. Cilvēku un grauzēju fizioloģija būtiski atšķiras, īpaši attiecībā uz gremošanas sistēmu un vielmaiņu. Tas nozīmē, ka šos rezultātus nevar tieši attiecināt uz cilvēkiem1.
Otrkārt, pētījumi koncentrējās uz izolētu kazeīnu, nevis veseliem piena produktiem. Reālajā dzīvē mēs patērējam pilnvērtīgu pārtiku, kur uzturvielas mijiedarbojas sarežģītos veidos2.
Treškārt, kazeīna daudzums, ko izmantoja šajos pētījumos, bieži bija daudz lielāks nekā tas, ko cilvēki parasti uzņem ar sabalansētu uzturu3.
Ceturtkārt, plaša mēroga pētījumi ar cilvēkiem nav konsekventi parādījuši saistību starp piena produktu patēriņu un paaugstinātu vēža risku. Dažos pētījumos pat novērota iespējama aizsargājoša ietekme pret noteiktiem vēža veidiem4.
Piektkārt, piena produkti ir vērtīgs avots daudzām svarīgām uzturvielām, tostarp kalcijam, D vitamīnam un augstas kvalitātes olbaltumvielām5.
Visbeidzot, vadošās veselības organizācijas, balstoties uz pieejamajiem pierādījumiem, pašlaik neiesaka izvairīties no piena produktiem vai kazeīna vēža profilakses nolūkos6.

Interesants fakts: Šveice, valsts ar vienu no augstākajiem siera (un līdz ar to kazeīna) patēriņa līmeņiem pasaulē, uzrāda ļoti labus veselības rādītājus, tostarp relatīvi zemu vēža mirstības līmeni78. Tas liek apšaubīt tiešu cēloņsakarību starp kazeīna patēriņu un vēža risku cilvēkiem reālās dzīves apstākļos.
Kaut arī “Ķīnas pētījums” uzdeva interesantus jautājumus, ir svarīgi tā secinājumus interpretēt piesardzīgi. Uztura zinātne ir sarežģīta, un reti ir ieteicams veikt plašas izmaiņas uzturā, balstoties uz vienu pētījumu vai grāmatu.
Ja jums ir konkrētas bažas par savu uzturu, es iesaku konsultēties ar dietologu vai uztura speciālistu. Viņi var sniegt personalizētus ieteikumus, ņemot vērā jūsu individuālās veselības vajadzības un jaunākos zinātniskos pierādījumus.
Atsauces:
1 Nguyen, T. L. A., et al. (2015). How informative is the mouse for human gut microbiota research? Disease Models & Mechanisms, 8(1), 1-16. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4283646/
2 Jacobs, D. R., & Tapsell, L. C. (2013). Food synergy: the key to a healthy diet. Proceedings of the Nutrition Society, 72(2), 200-206. https://www.cambridge.org/core/journals/proceedings-of-the-nutrition-society/article/food-synergy-the-key-to-a-healthy-diet/8F3B7D577D9FD214642C439544D91329
3 Thorning, T. K., et al. (2016). Milk and dairy products: good or bad for human health? An assessment of the totality of scientific evidence. Food & Nutrition Research, 60(1), 32527. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5122229/
4 Aune, D., et al. (2012). Dairy products and colorectal cancer risk: a systematic review and meta-analysis of cohort studies. Annals of Oncology, 23(1), 37-45. https://www.annalsofoncology.org/article/S0923-7534(19)37221-3/fulltext
5 Rozenberg, S., et al. (2016). Effects of Dairy Products Consumption on Health: Benefits and Beliefs—A Commentary from the Belgian Bone Club and the European Society for Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases. Calcified Tissue International, 98(1), 1-17. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4703621/
6 World Cancer Research Fund/American Institute for Cancer Research. (2018). Diet, Nutrition, Physical Activity and Cancer: a Global Perspective. Continuous Update Project Expert Report. https://www.wcrf.org/diet-and-cancer/
7 Swiss Federal Statistical Office. (2021). Food balance sheets. https://www.bfs.admin.ch/bfs/en/home/statistics/agriculture-forestry/food.html
8 World Health Organization. (2020). Switzerland: Country Health Profile 2019, State of Health in the EU, OECD Publishing, Paris/European Observatory on Health Systems and Policies, Brussels. https://www.euro.who.int/__data/assets/pdf_file/0009/419463/Country-Health-Profile-2019-Switzerland.pdf

Ansis Zauers

Labdien. Kādas ir jūsu domas par to, ka kazeīns veicina vēža augšanu (no grāmatas “lielais Ķīnas pētījums”. Īsumā – veica petijumus, kur pelēm un žurkām deva kancorogenas vielas un žurkām/pelēm, kuram uztura nebija kazeins vēzis neveidojas , bet kur bija kazeins vēzis veidojas. Paldies

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