According to the human body's demand for nutrients and their contents in the body, it can be divided into macro nutrients and micro nutrients. Macronutrients refer to protein, lipids and carbohydrates (sugars), while micronutrients refer to minerals (inorganic salts) and vitamins. In addition, protein, lipids and carbohydrates can release energy through oxidation in the body. These three nutrients are also called productivity (calorie) nutrients.
Protein is the foundation of all life, accounting for 65,438+06% ~ 65,438+09% of human body weight. About 3% of protein in human body is updated every day, and the intestine and bone marrow are the fastest. Protein's main function in the body is to form and repair human tissues; Physiologically active substances such as enzymes, hormones and antibodies participate in regulating physiological functions; Provide energy, and each gram of protein is oxidized in the body to generate 16.74 kJ energy. Its main food sources are meat, fish, eggs, milk and soybeans.
Lipids include neutral fats and lipids. Neutral fat is commonly known as oil, including animal oil and vegetable oil. Its main function is to store and supply energy, form biofilm, increase satiety and delicious food, supply essential fatty acids and promote the absorption of fat-soluble vitamins. There are two kinds of fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are often added to health food because they can promote the development of brain and retina and reduce blood lipid.
Carbohydrate, also known as sugar, is the main component of rice and wheat. Its main function is to provide human energy, help the liver detoxify, preserve protein and promote ketone oxidation. Dietary fiber is a kind of carbohydrate that the human body can't digest and absorb, mainly from vegetables and fruits. Its physiological functions are: ① enhancing gastrointestinal peristalsis and promoting fecal excretion. Middle-aged and elderly people should increase their intake of dietary fiber. 2 control weight and lose weight. Dietary fiber can not be digested and absorbed, but it can produce satiety, reduce energy intake, and achieve the effect of weight control and weight loss. ③ Lowering blood sugar and blood cholesterol, dietary fiber reduces the absorption of sugar by small intestine, and absorbs bile acid and fat, thus reducing its absorption and achieving the effect of lowering blood fat.
Minerals, also known as inorganic salts, are the general names of other chemical elements except carbon (C), hydrogen (H), oxygen (O) and nitrogen (N) in human body. According to the content in the body, it is divided into macro elements and trace elements. The weight of a large number of elements in the body is greater than 0.0 1% of the body weight, including seven elements: potassium, sodium, calcium, magnesium, phosphorus, sulfur and chlorine. Others such as zinc, iodine and iron are trace elements. The minerals most closely related to the growth and development of children and adolescents are mainly calcium, iron, iodine and zinc.
Calcium is the most abundant mineral in human body. Calcium deficiency can lead to rickets, osteoporosis, osteomalacia and muscle spasm. China Nutrition Society recommends that the daily intake of calcium for adults is 800 mg. The best food sources of calcium are milk and dairy products. In addition, beans, shrimp skin, kelp, oilseeds and vegetables are also rich in calcium.
Iron is the most abundant trace element in human body, which is mainly involved in the composition of red blood cells and the utilization of oxygen. Iron deficiency leads to iron deficiency anemia, mainly manifested as loss of appetite, irritability and fatigue, pallor, palpitation and shortness of breath, dizziness and decreased immunity. Iron deficiency affects children's intellectual development and behavior. The human body only absorbs bivalent iron, not trivalent iron. Some plant foods have high iron content, but the absorption rate is too low to achieve the effect of iron supplementation. Good foods for iron supplementation include animal liver, whole blood, lean meat and fish. It should be pointed out that the content of iron in dairy products is low, so iron cannot be supplemented.
The content of zinc in human body is 2 ~ 3 grams, which is one of the important trace elements in human body and closely related to the growth and development of children and adolescents. Zinc deficiency is characterized by slow growth or even stagnation, hypoplasia of sexual organs, inhibition of sexual maturity, hypoplasia of secondary sexual characteristics and sexual infantilism; Loss of taste and smell, loss of appetite, and even pica; Low resistance, easy infection and slow wound healing; It can also be manifested as dry and rough skin, facial acne and recurrent oral ulcer. Animal food is a good source of zinc, especially seafood, red meat and animal liver. Plant food contains less zinc and has low absorption rate.
Vitamins are a kind of low molecular weight organic compounds necessary to maintain normal metabolism and physiological functions of the body, which can be divided into fat-soluble vitamins and water-soluble vitamins. Fat-soluble vitamins include vitamin A, vitamin D, vitamin E and vitamin K, while water-soluble vitamins include vitamin B 1, vitamin B2, vitamin B6, vitamin B 12, vitamin C, nicotinic acid, pantothenic acid, folic acid and biotin.
Vitamin A deficiency will lead to decreased adaptability and, in severe cases, night blindness. Dry keratosis of conjunctiva can form dry eye, which can cause blindness in severe cases; Dry skin; Children's growth and development are slow, susceptible to infection, impaired hemoglobin synthesis and metabolism, and low immunity. High-dose intake of vitamin A can cause acute, chronic poisoning and teratogenic toxicity. Foods rich in vitamin A include animal liver, cod liver oil, fish eggs, whole milk and poultry eggs. Dark vegetables are rich in β -carotene and can also provide a certain amount of vitamin A.
The main function of vitamin D is to regulate the metabolism of calcium and phosphorus in the body, which is beneficial to the normal growth and development of bones and teeth. Foods rich in vitamin D include cod liver oil, cream, chicken liver and eggs. And vitamin d can also be obtained by sunbathing. High-dose intake of vitamin D can lead to poisoning.
Vitamin C deficiency can lead to scurvy, which is characterized by gingival swelling and bleeding, conjunctival bleeding, hair follicle keratinization, subcutaneous ecchymosis, purpura and joint pain. Vitamin C mainly comes from vegetables and fruits, including a variety of spicy (sweet) peppers, tomatoes, cauliflower and dark leafy vegetables, as well as a variety of fruits such as citrus, lemon, jujube, hawthorn, kiwi fruit and Rosa roxburghii.
Vitamin B 1 deficiency leads to beriberi. Foods rich in vitamin B 1 include cereals, beans, dried yeast, nuts, animal offal, eggs and lean pork.
Vitamin B2 is one of the nutrients easily lacking in our traditional diet. Vitamin B2 deficiency can cause angular stomatitis, blepharitis, scrotum (labia) dermatitis, seborrheic dermatitis on both sides of nose, etc. Because vitamin B2 deficiency can cause inflammation of oral cavity and scrotum at the same time, it is called "oral-reproductive syndrome". Foods rich in vitamin B2 include animal liver, kidney, heart, egg yolk and milk. The content of green vegetables and beans in plant food is high, but there are few grains.
Folic acid deficiency can lead to megaloblastic anemia, glossitis and gastrointestinal dysfunction. In recent years, folic acid deficiency is related to neural tube defects in newborns (including anencephaly and spina bifida). Foods rich in folic acid include liver, kidney, eggs, fish, green leafy vegetables, nuts and soybeans.
Water is the most basic substance to sustain life activities. The water content of adults accounts for 50% ~ 60% of body weight, about 60% for men and 50% for women. Water has the functions of regulating body temperature, lubricating joints, intestines and respiratory tract, promoting substance metabolism and maintaining tissue morphology. The human body needs about 2500 ml of water every day, which can be obtained from food (about 1000 ml of water), drinking water or beverage (about 1200 ml) and metabolic water (about 300 ml).