Improving our own resistance has become a topic we cannot avoid. Infants and young children are susceptible to infectious viruses. One of the reasons is that their immune systems are immature and their ability to resist external pathogenic microorganisms is weak. As we all know, the nutritional status of the human body is the basis for the immune system to exert resistance to external pathogens, and children often have more nutritional problems. Among them, the nutrient that is most closely related to the body's resistance is protein. According to the WHO report, infections caused by protein malnutrition account for more than 40% of the mortality rate of children under 5 years of age. Protein is the material basis for the construction of the human immune system and the guardian of the human immune response. This article will discuss how to ensure that the protein nutrition of infants and children is in good condition to deal with the challenges brought by pathogenic microorganism infection.

Ⅰ. Protein nutrition

Protein is one of the most amazing organic macromolecular substances in nature. Before the discovery of the double helix structure of biological genetic material DNA, the protein was the most used word to express life. In layman's terms, protein is an important component that builds all cells, tissues, and organs of all organisms, especially the human body. It can be said that DNA carries the information of life, and protein is the expression of life.

Human life needs protein to express and present, and the process of human life activities also needs protein to participate in to complete. Imagine a fertilized egg cell that grows into a 3.2kg newborn after 270 days of gestation in the uterus. After breastfeeding and supplementation, the weight reaches 12kg at the age of 2 years. The essence of this process is the continuous increase of cells in the body. The process of continuous accumulation of, protein, etc. If the human body wants to synthesize its own protein to meet the needs of growth and development, it must continuously obtain more than 20 kinds of amino acid raw materials that constitute human protein. So where do these raw materials come from? The answer is food, which is the relatively familiar protein nutrition.

Protein is a nitrogen-containing organic compound. Humans have no ability to use the nitrogen in the air to synthesize protein. But legumes seem to be able to use root rhizobia to fix nitrogen in the air to synthesize protein or turn inorganic nitrogen in the soil into protein. As the top of the food chain, humans can use protein from animal and plant foods as raw materials to synthesize their own protein.

Whether it is eating plant foods or animal foods, the amino acids after protein digestion can be absorbed into the human body and used by the human body. It is worth noting that among the more than 20 kinds of amino acids synthesized by the human body, 8 kinds of amino acids cannot be synthesized by the human body and must be eaten from food. These amino acids are called "essential amino acids". If you are interested, you can remember the names of these 8 amino acids, lysine, tryptophan, phenylalanine, methionine, threonine, isoleucine, leucine, and valine. In addition, the liver of immature infants has limited synthesis capacity, and histidine cannot be synthesized either. There are 9 kinds of amino acids are necessary.

The human body needs amino acids to synthesize its own protein, not only in sufficient quantities, but also in a complete range of essential amino acids and appropriate ratios to meet the needs of synthesizing different proteins. Therefore, if food can provide a complete range of essential amino acids, the closer its mutual ratio is to the requirement of synthesizing human protein, the higher the nutritional value of the food protein will be. Compared with plant foods, the types and mutual ratio of essential amino acids in animal foods are closer to the human body, and their protein quality is usually higher than that of plant foods.

"Protein nutrition" basically means to provide the human body with raw materials to synthesize its own "live" protein, which is essentially food protein. As a human food protein, it is originally active, but it is active against animals and plants. In addition, as a raw material to provide human protein, it needs to undergo various cooking processes (physical or chemical). Even if "live" fresh food is eaten directly, gastric acid will denature (inactivate) these "live" proteins.
Therefore, food protein can be considered "dead" protein. Of course, no matter whether we eat "live" or "dead" protein, these protein macromolecules cannot enter our bodies. The gastrointestinal tract will digest them into short peptides or amino acids, which are then absorbed into the bloodstream, taken up by tissue cells, and used to synthesize various proteins of our body.

Ⅱ. Protein is the first element to maintain the efficient vitality of the immune system

From food intake, digested amino acids and short peptides are absorbed by tissues and cells to synthesize the body's own protein. Protein plays many roles in the human body. Good protein nutrition is the basic raw material to participate in the synthesis of various cells. For children, it is growth and development; for adults, it is the renewal and functional maintenance of tissues and organ cells; For the patient, it means restoring health; for the bodybuilder, it means increasing muscle. For the immune system, good protein nutrition is the resistance to pathogenic microorganism infection.

As mentioned earlier, good protein nutrition, as a basic raw material, participates in the synthesis of various cells, and the tissues, organs and cells of the immune system are no exception. As we all know, the human immune system includes immune organs, immune tissues, immune cells, and immune factors. Good protein nutrition is the material basis for building immune organs, immune tissues, immune cells, and immune factors. As the immune response to pathogens, there are two sets of defense systems, innate immunity, and adaptive (specific) immunity. Although they have different mechanisms to resist pathogen invasion, they all require good protein nutrition, and immune cells are fast in the immune response. The material basis for the production of value-added and immune factors is even more inseparable from protein.

1. The dependence of innate immunity on protein

Innate immunity is composed of multiple layers of defense, including barriers formed by skin, epithelium, and mucous membranes. Among them, the barriers constructed by the respiratory tract, digestive tract, and urinary tract mucosa are the most important, because this is the window through which the human body opens (including the mouth and eyes). Is also the most vulnerable place for pathogenic microorganisms. The barrier constructed by mucosal cells and the mucus and secretions attached to the surface can effectively block most pathogens from the body. For children, the barrier constructed by the intestinal mucosa, secretions (containing lysozyme, lactoferrin, ribonuclease, etc.), and probiotics covered on the surface, plus the immune cells under the mucosa is considered to be the largest in children Immune tissues and intestines are also considered to be the largest immune organs in children. The mucosa and its submucosal immune cells (macrophages and neutrophils) not only mature, but also constantly renew. Mucosal cells are the fastest renewal cells in the body. They are renewed every 6 days to maintain their vitality and proliferation ability, which can get rid of all the pathogens and foreign objects that you encounter. All of the above require good protein nutrition as a basis. Of course, various micronutrients such as vitamin A, zinc, and vitamin C are also involved and play a vital role.

2. The dependence of acquired immunity on protein

Acquired immunity is also called adaptive immunity or specific immunity. The functions of this system are mainly performed by T cells and B cells, forming two subsystems of cellular immunity and humoral immunity. When the body encounters a specific pathogen invasion, the immune system will identify its characteristics (antigens), and then activate the production mechanism, allowing the prepared immune cells to rapidly increase in value and carry out targeted training. Attack the" cells, and then put on identification tags, to find specific pathogens (targets) to destroy them, to resist or kill the invaders, or to secrete and release a large number of targeted antibodies into the blood, tissue fluid, and secretions, and surround, eliminate specific pathogens. Acquired immunity continuously learns in dealing with pathogens, forming a smart immune system with a high IQ.

Please note that in order to deal with invaders at any time, the human body must maintain a high degree of vigilance against invaders. This requires maintaining the activity of the body’s immune system at all times, like all cells in the body, immune cells need to be constantly renewed. They also need to consume a lot of protein, as well as various nutrients that help protein synthesis and turnover.

Ⅲ. Diet tips to maintain a good resistance: high-quality protein is in charge, a diversified and balanced diet

Finally, let me talk about how to achieve high-quality protein in the diet of infants and children.

1. Breast milk: For infants and young children, breast milk protein is definitely the best quality, and the protein level in breast milk is very suitable, no more, no less, just right.

2. Meat and fish food: Animal food is basically a source of high-quality protein. Children's supplementary food should include adequate amounts of lean meat of livestock and poultry, fish, and shrimp. Livestock and poultry lean meat not only provides high-quality protein, but also contains iron, zinc, vitamins and other micronutrient-dense foods. In addition to providing high-quality protein, fish also provides important polyunsaturated fatty acids. Parents should pay attention to those children who prefer not to eat meat. Children who cannot keep up with their growth and development, have poor immunity, and are often sick, must eat enough fish, shrimp, and lean meat every day.

3. Eggs: Egg protein is generally used as a benchmark for high-quality protein. The amino acid ratio of its protein is very suitable for human physiological needs, is easily absorbed by the body, and the utilization rate can reach more than 98%, and it is convenient to eat. Children after 1 year old must eat one egg a day.

4. Animal milk: Milk has complete nutrients and is easy to digest and absorb. The protein content in milk is about 3%, and the proportion of essential amino acids meets human needs. Like eggs, milk protein is also considered the benchmark of high-quality protein. After breastfeeding, children over 1 year old should have about 500ml of milk per day. Breast milk is the best. When breastfeeding is not possible or lack of breast milk, you can choose appropriate infant formula milk, or mix the appropriate amount of fresh milk, yogurt, etc. as a supplement for infants. Children after 2 years of age should drink 300ml~400ml fresh milk or an equivalent amount of milk products every day.

It is important to note here that the nutritional value of protein in plant foods is relatively poor, and the best of them is soybean protein, and legumes and cereal protein can make up for each other's shortcomings and improve each other's performance. However, please note that for infants and children, if there are conditions to get animal foods such as meat, eggs, fish milk, etc., it is best not to rely too much on soy foods to provide protein.