1. Recognize proteins and peptides
(1) Composition of proteins
Protein is a long chain composed of 20 kinds of amino acids, in a certain order of arrangement, that is, polypeptide chains, these amino acids in the polypeptide chain "hand in hand", combined together by dehydration and condensation, and then folded to form a substance with a certain spatial structure. Peptides are compound fragments between amino acids and proteins, two or more amino acids dehydrated and condensed to form several peptide bonds to form a peptide, multiple peptides multi-stage folding to form a protein molecule. Peptides composed of 2 to 10 amino acids are called oligopeptides.
(2) The function of proteins
Protein is the material basis of all life, and without protein there is no life. Protein is an indispensable structural component of the human body, and any organ, tissue, cell and many antibodies and enzymes of our human body are inseparable from protein. Protein is the most basic living substance, and all cells, organs, and tissues are inseparable from proteins, and the immune system is no exception.
Schematic diagram of peptide bond formation structure
2. Protein - the main force of the immune system
(1) What is the immune system?
The immune system is composed of immune organs (bone marrow, thymus, spleen, lymph nodes, tonsils, small intestinal collection lymph nodes, appendixes, etc.), immune cells (lymphocytes, mononuclear phagocytes, neutrophils, basophils, eosinophils, mast cells, platelets, etc.), and immune molecules (complement, immunoglobulins, cytokines, etc.). Modern medical research shows that the vast majority of diseases are related to immune system disorders. Man's best weapon against disease is not drugs, but the body's own sound immune system. A healthy immune system protects the body from viruses, bacteria, and pollutants. Balanced nutrition plays a pivotal role in strengthening the body's immune system, and the basic nutrient that makes up immunity is protein.
(2) What is the relationship between the immune response and protein?
The immune response is a series of responses produced by the immune system to antigen (substance) stimulation, divided into innate immunity and specific immunity. Innate immunity is the gradual formation of organisms in long-term evolution, is the body's first line of defense against pathogen invasion (including skin and mucous membranes belonging to the physical barrier), which is characterized by non-specificity, the first contact with antigens can play an effect, but there is no memory; and specific immunity is also known as acquired immunity, this immunity is for specific pathogens, it is the body's acquired infection (cured or asymptomatic infection) or artificial vaccination (bacteria, vaccines, toxoids, immunoglobulins, etc.) and the body's ability to resist infection. Specific immune responses can be divided into sensitized T cell-mediated cellular immune responses and antibody-mediated humoral immune responses. Sufficient protein is to ensure the maturity of T cells and into cytotoxic T lymphocytes to kill pathogenic substances; and humoral immunity in B lymphocytes mature can not be separated from proteins, while the antibodies produced in humoral immunity are themselves proteins, antibodies are active in the blood of a "commando team", but also for the human body to resist the invasion of bacteria and viruses, improve the body's resistance has played an important role.
3. Oligopeptides - immunomodulatory small sharp soldiers
(1) A new understanding of oligopeptides
Traditional theory holds that proteins must be broken down into free amino acids in the body in order to be absorbed by the mucosa of the gastrointestinal tract. Modern nutrition studies have found that proteins can be directly absorbed and utilized by the intestinal mucosa after being decomposed into small molecular weight oligopeptides. Studies in recent years have proved that small molecule oligopeptides can play a special function that the overall structure of the protein does not have or is not obvious, and is not limited to the nutritional role of the protein.
Oligopeptides are divided into functional oligopeptides and nutritional oligopeptides, wherein the nutritional oligopeptides play a nutritional function similar to proteins and amino acids, while functional oligopeptides are in the nervous system, exocrine and endocrine processes to play a specific messenger role, antioxidant, improve immunity and other functions, so functional oligopeptides are collectively referred to as biologically active peptides.
(2) Oligopeptides and immune effects
In recent years, studies have found that many food protein hydrolysis of oligopeptides have immunomodulatory effects, such as studies have shown that wheat oligopeptides can promote the proliferation of T lymphocytes, improve cellular immunity; improve the level of antibodies in body fluids, enhance humoral immune function; enhance macrophage function; enhance the activity of natural killer cells, thereby enhancing the effect of the immune system, improve the body's immunity. In addition, such as soybean oligopeptide, collagen oligopeptide, corn oligopeptide, etc. have been reported to enhance immunity. It should be noted that at present, the role of peptides and human health is mostly animal testing studies, and more human studies need to be carried out to confirm. At present, there are already oligopeptide products on the market for sale.
4. Intake of proteins and peptides
Good eating habits can not only help food digestion and absorption, but also help the body improve immunity and reduce the risk of infection and disease. Therefore, it is necessary to consume sufficient protein in the diet, otherwise it will affect the function of the immune system and reduce the body's resistance. Foods containing high-quality protein play an important role in the body's fight against infectious diseases. In the recent COVID-19 outbreak, the most seriously ill patients are the elderly and people with underlying diseases, which are related to their weak immunity, because these people are prone to protein and other nutrient deficiencies due to insufficient dietary intake due to disease or aging (such as poor teeth affecting eating, etc.). It is recommended to consume according to the standard of 1.16 g/kg.d, for adult men, 65 grams of protein per day, and adult women 55 grams per day.
So, how do we supplement with high-quality protein?
(1) First of all, from the perspective of quantity, how much protein should we supplement?
The human body loses some protein every day, so we have to eat protein every day to make up for these losses. According to the recommendations of the World Health Organization (WHO), the minimum protein intake should be able to balance the loss of nitrogen in the human body and ensure that people maintain protein balance during moderate physical activity. However, defining protein requirements only in terms of nitrogen balance does not necessarily determine optimal intake. In fact, everyone's protein needs are different, and are related to many factors, such as age, weight, and amount of exercise.
(2) Secondly, we also have to consider the quality of the protein.
In general, grain cereals have lower levels of lysine, threonine, cysteine and methionine. Second, compared to plant protein, animal protein is more bioavailable, easier to digest, and has good protein quality, but is also rich in saturated fatty acids and cholesterol. Soybeans have a high protein content and high lysine content, which can play a protein complementary role with grain cereals and improve the nutritional value of protein. What we usually call high-quality protein refers to animal protein and soy protein.
(3) Finally, how should we match our diets and consume the right protein?
In order to consume sufficient protein, we should first follow the recommended principles of the "Diet for Chinese Residents (2016)" to achieve a reasonable diet and nutritional balance. According to the dietary guidelines, the amount of animal food should be moderate, eat fish, poultry, eggs, lean meat in moderation, eat 280-525g of fish per week, livestock and poultry meat 280-525g, eggs 280-350g, all kinds of alternate consumption, the average daily intake of 120-200g. In addition, eat a variety of dairy products, equivalent to 300g of liquid milk per day, often eat soy products, and eat nuts in moderation.
Precautions: If the diet cannot meet enough protein for various reasons (such as disease affecting eating, chewing difficulties, loss of appetite, etc.), you can supplement protein appropriately under the guidance of a dietitian or professional, such as protein powder and peptide preparations. At the same time, do not consume excessive protein, protein in the process of decomposition will produce a lot of acidic substances, but also increase the burden of the liver and kidneys, but also lead to dehydration, decalcification in the body.
In short, protein is the foundation of life, and a reasonable dietary intake of adequate protein is also the fundamental guarantee of normal immunity.