Nutrition refers to the process of digestion, absorption, and utilization of food or nutrients by the human body. It is also a process in which humans obtain food from the outside world to meet their physiological needs, including ingestion, digestion, absorption, and utilization in the body. The following is the content of nutrition knowledge organized by Xiaobian. I hope everyone likes it!
Nutrients
Nutrition is the process of digesting, absorbing, and utilizing nutrients needed for the growth, development, and maintenance of life. Nutrients are chemical substances that can nourish the body.
In general, nutrients can be divided into two major categories, macronutrients and micronutrients. Large nutrients include protein, fats, carbohydrates and some minerals. The daily needs are large. They constitute the vast majority of food and provide the energy and substances needed for growth, metabolism and exercise. Micronutrient requirements are minimal, ranging from a few mg (1/1000 g) to several μg (1/1000 mg), including vitamins and trace elements, which catalyze the utilization of macronutrients.
Large nutrients
Organic macronutrients include carbohydrates, fats, and proteins, which account for 90% of the dry weight of foods, providing 100% of energy. They are digested in the intestines and broken down into basic units: carbohydrates break down into monosaccharides, fats break down into fatty acids and glycerol, and proteins break down into amino acids. The energy they generate is 1g of protein or sugar to produce 4kcal of heat, and 1g of fat produces 9kcal of calories. As a source of energy, carbohydrates, proteins, and fats can be converted to each other in proportion to their energy content.
The energy needs vary, depending on age, gender, and physical activity, ranging from about 1000 to more than 4000 kcal per day. In general, women, children and the elderly with low activity need about 1600 kcal per day. Older children, active teenagers, adult women and less active men need about 2000 kcal per day. Lively adolescents need about 2400 kcal a day. Usually about 55% of the calories come from carbohydrates, 30% from fat, and 15% from protein. If the intake of energy does not meet the body's needs, weight will fall. The body stores fat and a small amount of protein to supplement these needed energy. Hunger for 8 to 12 weeks will lead to death.
Essential fatty acids account for only 7% of fat consumption (3% or about 8g of total calories) in common diets and are major nutrients. They include linoleic, linolenic, arachidonic, and eicosapentaenoic acids. And docosahexaenoic acid. Linoleic acid and linolenic acid are derived from vegetable oils; eicosapentaenoic acid and docosahexaenoic acid are essential for brain development and are derived from fish oil. In the body, arachidonic acid can be converted from linoleic acid. Eicosapentaenoic acid and docosahexaenoic acid can be converted from linolenic acid, and fish oil is also an important source.
Minerals include calcium, phosphorus, chlorine, potassium, and magnesium (see Section 135) and are large nutrients. Because of the relatively large number of daily needs (about 1 ~ 2g per day). Water is also a large nutrient, requiring 1 ml of water per kcal of calories consumed, which is equivalent to 2500 ml of water per day.
Micronutrients
Vitamins and trace elements are micronutrients. Vitamins are classified as water soluble (vitamin C and 8 B vitamins) and fat soluble (vitamin D, E, and K) (see Section 135).
The essential trace elements include iron, zinc, copper, manganese, platinum, selenium, iodide, and fluoride. With the exception of fluoride, all other minerals are required for activating enzymes in metabolism.
Fluoride and calcium form stable complexes that help stabilize the content of trace elements in bone and teeth and also help prevent dental caries. Trace elements such as chromium, arsenic, cobalt, nickel, silicon, and vanadium may be necessary for animal nutrition, but it is not certain whether human nutrition is necessary or not. All trace elements are toxic at high doses, and some (arsenic, nickel, and chromium) may also be carcinogenic. Nutritional requirements A reasonable diet is necessary to form and maintain a healthy body and meet the enormous energy needed for physical and mental work. The amount of essential nutrients a person needs each day is determined by age, sex, height, weight, metabolism, and activity. Through research data analysis has assessed the need for 45 essential nutrients in food, the National Academy of Sciences Food Nutrition Committee and the agricultural sector regularly publish the recommended daily dietary nutritional supply (RDA), used to calculate the dietary needs of healthy people .
The U.S. agricultural sector has proposed that a balanced diet consists of four basic types of food. They are: dairy products, meat and vegetable protein, bread and cereals, and fruits and vegetables. A new, optimized pyramid dietary advice was proposed to help people choose to supplement essential nutrients while reducing the incidence of many diseases such as cancer, hypertension, coronary heart disease, stroke, etc. . This proposal varies according to the amount of energy consumed by each person (from 1600 to 2400 kcal or more). For example, a person with a requirement of 1600 kcal should consume 6 portions of cereals and 3 portions of protein food each day, while a person with a requirement of 2400 kcal should consume 10 portions of cereal and 5 portions of protein. In general, fat intake should be reduced to 30% of total calories, while intake of fruits, vegetables, and cereals should be increased. Principles of nutrition and health From the consideration of safety in peacetime, many people began to pay attention to nutritional supplements, but experts pointed out that nutritional supplements should not be too blind and need to be supplemented according to their own needs. For example, children and adolescents, pregnant women, and middle-aged and elderly people in the growth and development period all have different nutritional requirements.
Nutrition and health care is actually a process. In this process, food and nutrients should complement each other and cannot rely solely on one aspect. In the “Balanced Diet Pagodas for Chinese Residentsâ€, Taki (lowest layer) is cereals, potatoes and mixed beans and water; the fourth layer is vegetables and fruits; the third layer is livestock and poultry meat, fish and shrimp, and eggs. The second layer is milk and dairy products, soybeans and nuts; the spire (the highest layer) is oil and salt, and the weight is reduced layer by layer. Of course, different groups of people should consult their dietitians to formulate their own daily diet. In short, it is necessary to absorb various nutrients in a balanced manner.
Taking calcium as an example, simply taking calcium from food, many people think that this is enough, but the body absorbs calcium, but also needs vitamin D to assist, therefore, not to drink enough milk every day, eat enough calcium Food is enough. Reasonable nutrition Reasonable nutrition refers to the balance between the calorie provided by the athletes eating three meals a day and the energy and nutrients needed by the athletes to complete the daily exercise. From the aspect of nutrients, there must be sufficient heat energy, and the content and ratio of protein, fat, and carbohydrate should be appropriate, and there should be sufficient inorganic salts, vitamins, trace elements, and moisture, that is, the kinds of various foods on a daily basis. The number of choices should be adequate and sufficient.
Nutrition refers to the process by which the body ingests food from outside and uses the nutrients it contains to sustain life activities. Nutrients are the active ingredients in foods. The body through the ingestion of food and the external environment, and through the effective use of nutrients to maintain its own structural integrity and internal environment stability.
There are many kinds of foods available to humans in nature, and their functions vary. However, the types of nutrients needed to maintain the daily needs of the human body are only: proteins, sugars, fats, minerals (also known as inorganic salts, which can be further divided into two types: macroelements and trace elements), vitamins, food cellulose and water. About 40 kinds. Each of them has its own special physiological functions and participates in the metabolic activities of the human body. No single natural food of any kind in the natural world can provide all the nutrients that the human body needs. A variety of foods must be matched with each other in a certain proportion in order to meet the reasonable nutritional needs of the human body. Therefore, reasonable nutrition emphasizes that: The nutrients contained in foods for human consumption should be complete in variety, moderate in content and appropriate in proportion.
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