In the context of protein consumption, the quality of protein, its amino acid spectrum and the division into complete and incomplete proteins are often mentioned. But how are these parameters evaluated and which proteins can we use best? Aren't the different types of protein in the diet "equal"?
For a better understanding, recall that the basic building blocks of proteins are amino acids. There are 21 different amino acids in the human body, from which our body is able to form proteins - we are talking about the so-called proteinogenic amino acids. Eight of them are essential, i.e. our body cannot synthesize them and we must therefore take them in sufficient quantities through food. And it is the content and ratio of essential and non-essential amino acids that are the basic parameters for assessing the quality of protein. Simply put, the more the amino acid spectrum corresponds to the physiological needs of the organism, the better the "quality" of the protein from a given source.
There are a number of indicators that assess protein quality. Among the basic ones are indicators based on the measurement of nitrogen, the main source of which is protein. These include Biological Value (BV), Net Protein Utilisation (NPU) or nitrogen balance. Over time, the Amino Acid Score (AAS) and the Essential Amino Acid Index (EAAI) have proven to be more accurate in providing information on the representation of individual amino acids.
However, the most widely used indicators at the moment are primarily PDCAAS (Protein Digestibility-Corrected Amino Acid Score), which, unlike those mentioned above, also takes into account the absorbability of a particular protein source. Nevertheless, it has its shortcomings - e.g. it neglects the presence of antinutrients, underestimates full-fat protein sources and overestimates non-full-fat sources. For this reason, the FAO has for many years advocated the Digestible Indispensable Amino Acid Score (DIAAS) to correct these deficiencies. The DIAAS is determined on the basis of the so-called actual (ileal) digestibility.
This appears to be more accurate than the apparent (faecal) one, as it is not affected by the ability of the microbiome (gut bacteria) to use amino acids and peptides that do not come from the ingested source.
Several studies have been published in recent years comparing these two indicators. These show that DIAAS appears to be more accurate, especially in the case of certain dairy and vegetable protein sources, and gives more accurate information with regard to digestibility. Thus, PDCAAS, but especially DIAAS, can currently be considered as the most reliable indicators. However, we must be aware that there are a number of factors that influence protein availability, namely age, gender, weight, health status and nutrition. Physical activity also plays an important role, with an increase in amino acid absorption in the gut in athletes.
Whatever the indicator, it is abundantly clear that animal protein is biologically more valuable than plant protein. They usually have a complete amino acid spectrum, contain almost no antinutritional substances and can thus be better absorbed by the body. So let's keep in mind that even if a diet based purely on plant sources would suit someone, applying such an approach to specific groups of people - e.g. children, pregnant women, the elderly or athletes - may not always be ideal.
Recent studies show that protein quality also plays a significant role in the anabolic response of the body, or in the stimulation of muscle protein synthesis, which is particularly important for strength athletes. They also discuss the consumption of high quality protein sources in combination with exercise as an effective tool to alleviate sarcopenia (loss of muscle mass and strength in older individuals).
Proteins are therefore not equal in terms of availability and anabolic response! But there is certainly no need to be concerned with their quality at every meal. Just get a rough idea, but more importantly, eat a balanced, varied diet and avoid any extremes! We should try to ensure that our diet contains multiple sources of protein, both complete (animal) and non-complete (plant), which contain many health benefits including antioxidants, flavonoids, etc. Only in such a case do we have the best chance that our physiological needs will be met and our organism will not suffer in any way.
Literature
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MATHAI, John k., Yanhong LIU a Hans h. STEIN. Values for digestible indispensable amino acid scores (DIAAS) for some dairy and plant proteins may better describe protein quality than values calculated using the concept for protein digestibility-corrected amino acid scores (PDCAAS). BRITISH JOURNAL OF NUTRITION [online]. 2017, 117(4), 490-499 [cit. 2019-07-11]. DOI: 10.1017/S0007114517000125. ISSN 00071145.
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