Children and adolescents are in a period of vigorous physical and mental development, so it is very important to provide adequate and high-quality nutrition reasonably to ensure their normal physical and mental development. Reasonable arrangement of nutrition is helpful to improve work ability and academic performance, promote good development and reduce diseases, while malnutrition will lead to physical and mental retardation, leading to a significant decline in learning efficiency. Chronic malnutrition will reduce the resistance of children and adolescents to infectious diseases, cause specific immune dysfunction, and lead to an increase in the incidence of infectious diseases.
Nutritional characteristics of children and adolescents
1. Children and adolescents grow rapidly and have strong metabolism. In order to meet the needs of growth and development, the amount of calories and various nutrients required is higher than that of adults.
2. The digestive metabolism of children and adolescents is obviously different from that of adults, and they gradually transition to the adult state with their growth and development.
3. There are great individual differences in the development speed of children and adolescents, so there are also great individual differences in nutritional needs.
4. The younger children and adolescents are, the more likely they are to suffer from nutritional deficiency diseases.
Children and adolescents' needs for various nutrients
The demand of children and adolescents for heat energy is directly proportional to the growth and development speed. The daily demand for heat energy is calculated according to per kilogram of body weight, and the younger the age, the greater the demand. The sources of heat energy are three thermogenic nutrients in food, namely protein, fat and carbohydrate. For children and adolescents, the proportion of calories in protein should be appropriately increased to meet the needs of growth and development.
1, protein: protein is the foundation of life, and it is an important nutrient for composing body components, renewing and repairing tissues, regulating physiological functions and supplying calories. Protein supply for children and adolescents must maintain a positive nitrogen balance (that is, the amount of nitrogen ingested from food and stored in the body is greater than the amount of nitrogen excreted), so as to ensure adequate protein for the growth and development of the body.
2. Fat: Fat is an important nutrient for supplying heat, maintaining body temperature, forming sphingomyelin in tissues and cells, especially in brain and peripheral nerve tissues, and promoting the absorption of fat-soluble vitamins.
3. Carbohydrate: Carbohydrate, also known as sugar, is the most economical and main source of heat energy for human beings. In addition to providing heat energy, carbohydrates have many important physiological functions: sugar can form glycoprotein with protein, which is the basic component of many hormones, enzymes and antibodies; Mucin in glycoprotein is an important component of cartilage, bone and cornea. Glycolipid formed by the combination of sugar and lipid is the main component of nerve tissue; Sugar is also involved in the composition of genetic material nucleic acid.
4. Inorganic salts and trace elements: Human tissues contain almost all kinds of elements existing in nature. Among these elements, except for carbon, hydrogen, oxygen and nitrogen, which mainly exist in the form of organic compounds, the rest exist in the form of inorganic salts, which are collectively called inorganic salts (also known as minerals). Inorganic salts and trace elements are indispensable substances for maintaining physiological functions and forming tissues and cells.
5, vitamins: vitamins naturally exist in food, the human body can not be synthesized, must be obtained from food. Their function is mainly to regulate and maintain various biochemical reaction processes in human life activities.
6, water: water is the source of life, it maintains the normal operation of various physiological functions in the body, all organs and tissues in the body contain water. Water in human body accounts for about 60%-70% of body weight. Water is the material basis of human metabolism; Water is also the main component of blood, which transports nutrients to all parts of the body. Water in the body can take metabolites out of the body through exhalation, sweating and defecation. Water can also help the human body to dissipate heat, keep body temperature constant, make skin and muscles flexible, lubricate joints and maintain motor function.
7. Dietary fiber: Dietary fiber refers to crude cellulose in various foods. Cellulose cannot be decomposed and absorbed by human body, but it helps to remove many harmful metabolites, help intestinal peristalsis and normal defecation, and reduce the accumulation of harmful substances in intestinal tract. Therefore, people call cellulose the seventh nutrient and it is an indispensable substance for human body.
Nutritional deficiency diseases that children and adolescents are prone to.
1, calcium deficiency rickets. Calcium is the most abundant mineral in human body, accounting for about 1 of body weight. 5%-2。 0%, of which 99% are concentrated in bones and teeth. The function of calcium in human body is to form bones and teeth, maintain the normal activity of neuromuscular, promote the activity of some enzymes, participate in the process of blood coagulation and maintain the stability of intracellular colloid. Calcium deficiency in infants will affect the development of bones and teeth, which is manifested as rickets.
The best sources of calcium in food are milk and dairy products, which are not only rich in calcium, but also have high absorption rate. In addition, beans, green vegetables and various melon seeds are also good sources of calcium.
2. Zinc deficiency and short stature. Zinc is a component or activator of many enzymes, which plays an important role in maintaining normal metabolism of human body. Zinc is related to the biosynthesis of DNA, RNA and protein, which is necessary for human growth and wound healing. Zinc can maintain normal taste, promote appetite and participate in the immune function of the body.
When the human body is deficient in zinc, it may lead to growth retardation. Therefore, zinc deficiency may lead to short stature, decreased taste or pica, loss of appetite, delayed sexual maturity, difficult wound healing, decreased immune function and easy infection.
Animal food is the main source of zinc.
3. Vitamin A deficiency and night blindness. Vitamin A, also known as retinol, not only maintains the health of epithelial cells, but also promotes their growth and development. Its main physiological function is as a component of photosensitive substances in visual cells, which is related to people's visual dark adaptation. Dark adaptation refers to the speed at which people can see objects in dark places from bright places. If vitamin A is sufficient, the dark adaptation time will be short; When vitamin A is deficient, the dark adaptation ability decreases, which can lead to night blindness in severe cases.
Various animal livers, cod liver oils and egg yolks are rich in vitamin A, and colored vegetables such as spinach, alfalfa, pea seedlings and carrots are rich in carotene. Carotene can be converted into vitamin A in the body, which has the same effect on the human body.
Long-term excessive intake of vitamin A can cause poisoning. The main symptoms of poisoning are anorexia, overexcitation, muscle stiffness, hepatomegaly and itchy skin.
4. Vitamin B2 deficiency and angular stomatitis. Vitamin B2, also known as riboflavin, is orange. Vitamin B2 is a component of many important coenzymes in the body and an indispensable substance in the process of biological oxidation. Vitamin B2 deficiency can lead to many diseases, such as angular stomatitis, milky white mouth and cracking. Panniculitis, swelling of lower lip, desquamation and pigmentation; Glossitis, erythema in the middle of the tongue, clear edge and swelling of the tongue body. In addition, it can also cause scrotal dermatitis, seborrheic dermatitis, blepharitis and other diseases.
Vitamin B2 is one of the most easily deficient vitamins in China's diet. If you don't pay attention to the choice of food, it is easy to have insufficient intake of vitamin B2. Only a small amount of vitamin B2 is stored in the liver and kidneys and needs to be supplemented from food every day. Animal foods, such as viscera (liver, kidney and heart), eggs and milk, are rich in vitamin B2, followed by beans and fresh green leafy vegetables.
Basic requirements of balanced diet for children and adolescents
A balanced diet means that the variety, quantity and quality of various foods are in harmony with the physical needs of children and adolescents.
1. Reasonable collocation of various foods: The more kinds of foods, the more complete the nutrition provided, so the diet should be diversified and reasonably collocated. The combination of coarse and fine grain can make various protein in grain complement each other, improve the nutritional value of protein and provide fiber for human body; The combination of meat and vegetable is not only beneficial to the protein complementarity of food, but also can adjust the acid-base balance of the body.
2, reasonable cooking, reduce nutrient loss: cooking should reduce the damage and loss of water-soluble inorganic salts and vitamins. The main purpose of food cooking: (1) to make food mature and increase the digestibility; (2) increase the color and fragrance of food, improve the sensory characteristics of food and stimulate appetite; (3) Kill harmful microorganisms in food and ensure food hygiene.
3. Pay attention to the color, smell and taste of food: the sensory characteristics of food are very important to children. The diet is good in color, smell and taste, which can promote the secretion of digestive juice and stimulate appetite.
4. Food hygiene: ensure that food is non-toxic, harmless, pollution-free and non-corrupt.
5, cultivate good eating habits: eat regularly and quantitatively, not picky eaters, not partial eclipse, not eating too much polysaccharide, eating salt in moderation, chewing slowly.
6. Reasonable dietary system: students adopt a three-meal system with an interval of 4-6 hours; Each meal lasts for 20-30 minutes; Calorie distribution for each meal: 30% for breakfast, 40% for lunch and 30% for dinner.