The English word Nutrition in nutrition is interpreted as: 1, an organic process in which organisms absorb and use food and liquids to maintain normal functions, grow and maintain themselves. 2. Research on the relationship between food and health and disease. 3, a pursuit of the best combination of nutrients and all foods to achieve the best health of the body.
Essential nutrients include vitamins, inorganic salts, amino acids, fatty acids and some carbohydrates as energy sources.
Non-essential nutrients refer to nutrients that the body can synthesize from other chemicals, although they can also be obtained from diet.
Nutrients refer to the basic elements in food that can be absorbed and used to improve health. Some nutrients are necessary because they cannot be synthesized by the body, so they must be obtained from food. Nutrients can be divided into macronutrients and micronutrients. It constitutes the main part of diet, providing energy and basic nutrition for growth and life-sustaining activities.
Carbohydrate, fat (including essential fatty acids), protein, inorganic salts and water are macro nutrients. Carbohydrates are broken down into glucose and other monosaccharides; Fat is broken down into triglycerides; Protein is broken down into amino acid series.
These macronutrients are mutually convertible energy sources; Fat produces 9 kcal/g of heat; The average heat production of protein/carbohydrate is 4 kilocalories/gram, and ethanol is usually not used as a nutrient, and 7 kilocalories are produced per gram of heat. Carbohydrates and fats can preserve tissue proteins. Essential amino acids (EAA) are an integral part of protein and must be provided through diet. Of the 20 amino acids that make up protein, 9 are essential, that is, they are obtained from diet, because they cannot be synthesized by the body. There are 8 kinds of amino acids that are necessary for all people.
The recommended daily dietary allowance (RDA) in protein decreased from 2.2g/kg for three-month-old infants to 65,438+0.2g/kg for five-year-old children and 0.8g/kg for adults.
The requirement of dietary protein is positively correlated with the growth rate, but the growth rate is different at different stages of life. EAA demand reflects different demands on protein. The total EAA demand of infants (765,438+0.5 mg/kg/day) accounts for 32% of the total EAA demand in protein. 10~ 12 years old children need 23 1mg/kg every day, accounting for 20%; Adults need 86mg/kg daily, accounting for 1 1%.
The amino acid composition of different protein is very different. The biological value (BV) of protein is determined by its amino acid composition and similarity between animal tissues. The amino acid composition of egg protein is exactly the same as that of animal tissue, and its BV is 100. The biological value of animal protein in milk and meat is higher (about 90), while the protein BV in cereals and vegetables is lower (about 40). Some protein, such as gelatin protein, lack tryptophan and valine, and their biological potency is zero. The complementarity of different protein in the diet determines the total BV of the diet. The RDA of protein assumes that the average BV of compound diet is 70. Bio-price is just a simple viewpoint to evaluate the utilization of protein. Some scholars put forward the protein/carbohydrate proportional coefficient method, which is objective.
The requirement of essential fatty acid (EFA) is equivalent to 6%~ 10% of fat intake (equivalent to 5~ 10g/d). They include omega-6 fatty acids-linoleic acid (cis-octadecacarbon -9, 12- dienoic acid), arachidonic acid (cis-eicosacarbon-5,8,1,14- tetraenoic acid) and omega-3 fatty acids. Must be supplied by diet: vegetable oil provides linoleic acid and linolenic acid, and marine fish oil also provides EPA and DHA raw materials. However, some efas can be synthesized from other efas. For example, the body can synthesize arachidonic acid from linolenic acid. Linoleic acid can partially synthesize EPA and DHA. The formation of many eicosapentaenoic acids, including prostaglandins, thromboxanes, prostacyclins and leukotrienes, requires EFA. Omega-3 fatty acids seem to play a role in reducing the risk of coronary heart disease. All national education is polyunsaturated fatty acids (PUFA), but not all PUFA are national education.
Dietary fiber belongs to nonabsorbable carbohydrates and exists in many forms (such as cellulose, hemicellulose, pectin and gum). Different dietary fiber components act in different ways, depending on their structure and solubility. Fiber can improve the movement of gastrointestinal tract and help prevent constipation and treat diverticulosis. Foods with high soluble fiber content can reduce the increase of postprandial blood sugar, which is sometimes part of diabetes control measures. Vegetables and fruits rich in guar gum and pectin can reduce the plasma cholesterol level by promoting the conversion of liver cholesterol into cholic acid. Some people think that fiber can promote the excretion of carcinogens produced by bacteria in the large intestine. Epidemiological evidence strongly supports the relationship between colon cancer and low fiber intake and the beneficial role of dietary fiber in functional bowel disease, acute appendicitis, obesity, varicose veins and hemorrhoids, but its mechanism is still unclear. The typical western dietary fiber content is low (about 12g per day), which is due to the intake of highly refined flour and low intake of fruits and vegetables. It is generally recommended to eat more cereals, vegetables and fruits, and increase the fiber intake to 30g per day.
Macroelements: sodium, chlorine, potassium, calcium, phosphorus, magnesium and sulfur. The daily needs of human beings are measured in grams.
Water is also considered as a macro-nutrient, because every energy consumption of 1kcal requires 1ml of water, about 2500 ml/d, vitamins and trace elements are micronutrients, and vitamins are divided into water-soluble and fat-soluble. The water-soluble vitamins are vitamin C (ascorbic acid) and eight B vitamins-thiamine (vitamin B 1), riboflavin (vitamin B2), nicotinic acid, pyridoxine (vitamin B6), folic acid, cobalamin (vitamin B 12), biotin and pantothenic acid. Fat-soluble vitamins include retinol (vitamin A), cholecalciferol and ergocalciferol (vitamin D), α -tocopherol (vitamin E), chlorophyllin and menaquinone (vitamin K). Only the storage of vitamins A, E and B 12 in the body is meaningful.
The essential trace elements include iron, iodine, fluorine, zinc, chromium, selenium, magnesium, molybdenum and copper. Except for fluorine and chromium, these trace elements are combined with enzymes or hormones needed for metabolism. Fluorine and calcium form a compound (CaF2), which can stabilize the mineral matrix in bones and teeth and prevent dental caries. Except for iron and zinc, trace element deficiency is less common in clinical practice in industrialized countries. Other trace elements involved in animal nutrition (namely, aluminum, arsenic, boron, cobalt, nickel, silicon and alum) have not been determined, and they are also necessary for human body. All trace elements are toxic at high concentrations, and some elements (arsenic, nickel and chromium) have been considered as the cause of cancer. In the body, lead, cadmium, barium and strontium are toxic, but gold and silver are inert as components of teeth. The goal of a reasonable diet is to achieve and maintain an ideal body composition and give full play to the potential of physical and intellectual work. The daily dietary requirements of essential nutrients (including energy sources) depend on age, sex, height, weight, metabolism and physical activity. The Food and Nutrition Committee of the National Academy of Sciences/National Research Council and the United States Department of Agriculture regularly review the scientific literature on human needs of 45 essential nutrients. Because we know little about vitamins and minerals, we can only estimate the safe and appropriate daily dietary intake. In order to be healthy, body composition must be kept within a reasonable range. This requires a balance between energy intake and consumption. If energy intake exceeds consumption or consumption decreases, weight will increase, leading to obesity. On the contrary, if the energy intake is lower than the consumption, the weight will be reduced. Standard height, weight and body mass index are often used to evaluate the ideal composition of the body. Body mass index is equal to weight (kg) divided by the square of height (m). In order to get enough nutrition, human body consumes a lot of food every day. The whole process in which the human body continuously ingests food from the outside, digests, absorbs, metabolizes and utilizes substances (nutrients or nutrients) needed by the human body in food to maintain life activities.
●RDA= recommended daily nutrient intake
●SDA= maximum safe intake per day.
● Free radicals: harmful compounds produced by the body in the oxidation reaction, which are highly oxidizing and can damage the tissues and cells of the body, thus causing chronic diseases and aging effects.
● Antioxidant: It is a substance that can help capture and neutralize free radicals, thus eliminating the harm of free radicals to human body. Such as vitamins a, c, e, selenium, zinc, copper and manganese.