(nutrition) the nutrients contained in food; Absorbing nutrients and nourishing the body has the function that organisms absorb nutrients from the outside to maintain life. Nutrition is a science that studies the effects of food on living things. Nutritionists interpret nutrition as the interaction and balance between nutrients and other substances in food and health and diseases, as well as the process of ingestion, digestion, absorption, transportation, utilization and excretion of substances. In its development process, nutrition not only includes the changes of food entering the body, such as participating in biochemical reactions and combining with tissues and cells; It also includes instructing people how to choose food to ensure the normal growth, development and reproduction of the body. Therefore, nutrition has not only biological significance, but also social and economic significance.
From low to high, from single-celled organisms to higher animals and plants, from living in water to living on land, the living environment is different and the ecology is different. In this way, the required nutrients and the way of taking nutrients are also different. Nutrients needed by living things are composed of many elements, including hydrogen, oxygen, nitrogen and carbon. These are the main elements that make up the protein of organisms and store energy. In addition, there are a small amount of sulfur, phosphorus, calcium, magnesium, potassium, sodium, chlorine and various trace elements. Some trace elements are only trace elements in organisms.
Plants and microorganisms containing chlorophyll and purple pigment can directly absorb these inorganic compounds from the outside through roots, leaves or cell membranes, and use the energy of sunlight to synthesize organic substances needed for their own growth and other life activities, such as protein, lipids and carbohydrates (sugars). Organisms with this way of nutrition are called autotrophs or inorganic vegetative organisms. Other organisms (such as animals) cannot directly use external inorganic substances to synthesize organic substances needed for their own lives, and must obtain nutrition from autotrophs or other similar organisms. Through the metabolic process, the ingested substances are transformed into organic substances such as protein, lipids and carbohydrates. The creature with this way of nutrition is called heterotrophs.
Nutrients are essential food ingredients to maintain normal life activities. The study of nutrients in modern nutrition is mainly aimed at the nutritional needs of people and livestock. Nutrients are divided into seven categories: protein, lipids, carbohydrates, vitamins and minerals, water and cellulose.
[Edit this paragraph] protein
Protein is the main component of tissues and cells, and protein is also contained in body fluids. The nutritional function of protein lies in its various amino acids. There are more than 20 kinds of amino acids that make up food protein, some of which cannot be synthesized by humans and animals and must be obtained from food. These amino acids are called "essential amino acids", namely methionine, lysine, tryptophan, threonine, valine, phenylalanine, leucine and isoleucine. In addition, the growth of young children needs histidine, and birds such as chickens also need arginine and glycine. Amino acids other than these essential amino acids are called "nonessential amino acids" because they can be synthesized in vivo.
The types and contents of amino acids in protein are different. Some protein lacks certain essential amino acids, such as gelatin protein without tryptophan and corn gluten without lysine. Therefore, evaluating the nutritional value of a food protein mainly depends on whether the amount of various essential amino acids it contains can meet the needs of the body. When it is insufficient, the body cannot effectively synthesize protein, and other amino acids can only produce sugar (glycogen heterogenesis) through deamination metabolism and provide heat energy as fuel. Therefore, the amino acid pattern of food protein is the key to determine its quality. At present, the nutritional value of food in protein is evaluated based on the whole egg essential amino acid model, or the essential amino acid model in human milk, or the hypothetical model based on the amount of essential amino acids in human body. This is the so-called chemical evaluation method of nutritional value in protein. In addition, there is a biological evaluation method, which evaluates the nutrition according to the utilization rate of food protein in the body. Commonly used are "protein Physiological Value" (abbreviated as BV, that is, the percentage of nitrogen retained and absorbed in the body), "Net Protein Utilization Rate" (abbreviated as NPu, that is, the percentage of nitrogen retained and absorbed in the body, that is, BV× protein digestibility), or "protein Efficiency Ratio" (abbreviated as PER, that is, the weight gain per gram of protein intake).
[Edit this paragraph] Lipid-fat
Include neutral fats and lipids. The former mainly supplies energy, while the latter has important physiological functions. The basic composition of lipids is fatty acids, which can be divided into essential fatty acids and non-essential fatty acids. There are three kinds of essential fatty acids, namely linoleic acid, linolenic acid and arachidonic acid. The biological activities of these three essential fatty acids are different, among which arachidonic acid is the largest, linoleic acid is the second, and linolenic acid is the most. What's your problem? Long-chain fatty acids with 0 carbon and 22 carbon play a special role in the development and function of brain and retina. When animals lack essential fatty acids, they grow slowly and have skin symptoms (depilation, eczema and dermatitis, scaly skin, etc.). It is reported that children will have the same symptoms when they are short of essential fatty acids. However, it is difficult for adult animals and people to have symptoms of deficiency because a large amount of linoleic acid is stored in the body. Lack of essential fatty acids can change the composition of phospholipid fatty acids in cell membrane, thus affecting the function of membrane; It can also reduce the synthesis of prostaglandin. The precursors of prostaglandin are 18 carbon and 20 carbon polyunsaturated fatty acids. It is suggested that the ratio of trienoic acid to tetraenoic acid in blood should be used as an indicator of whether essential fatty acids are lacking. This is due to the competition of enzyme system in fatty acid metabolism. When linoleic acid is deficient, the amount of arachidonic acid produced by the extension and desaturation of linoleic acid carbon chain decreases, and the metabolism of oleic acid, another group of fatty acids, increases, producing a large amount of eicosatrienoic acid, so the ratio of trienoic acid to tetraenoic acid in blood increases. The requirement of essential fatty acids for human body is about 1 ~ 2% of the daily thermal energy requirement according to its calorimeter.
[Edit this paragraph] Sugar
Sugar is also called carbohydrate, because their general formula is cn (H2O) m. With the development of science, it is found that the number ratio of hydrogen atoms to oxygen atoms in sugar is not necessarily 2: 1, nor does it exist in the form of water molecules, and some substances that meet the general formula are not sugar, so the name carbohydrate has lost its original meaning and is rarely used.
(sugar) the main nutrient that provides bioenergy. The carbohydrates in food are polysaccharide (starch) and cellulose. Monosaccharide, the degradation product of polysaccharide, can be utilized by most organisms, while cellulose can only be degraded and utilized in organisms with cellulase. When the dietary calorie intake is insufficient, human adipose tissue and protein will decompose to supplement the calorie deficiency. It is characterized by growth stagnation and weight loss. In severe cases, it will lead to death. People's eating habits are different, and the calories provided by dietary carbohydrates generally account for 45 ~ 80% of the total calorie consumption. In economically underdeveloped areas, it can reach more than 90%, because carbohydrates are the cheapest source of heat energy. If the calorie of dietary carbohydrate is too low and the calorie of fat is too high, ketosis will occur. People who lose weight often limit carbohydrates to limit calorie intake and increase labor to consume body fat. In this case, ketosis will also occur. Therefore, the heat energy from carbohydrates should not be less than 45% of the total heat energy.
Fiber cannot be digested and utilized by humans and most animals. Dietary fiber includes cellulose, hemicellulose, pectin, seaweed polysaccharide and lignin. When fiber was determined in the early years, plant tissues were digested with acid and alkali, and the residue was crude fiber, and most of the other fiber components suffered losses during the determination. Now the new method can determine the various components of fiber separately. Dietary fiber is fermented by bacterial cellulase in gastrointestinal tract, and most of it can be hydrolyzed into short-chain fatty acids. Herbivores use this as energy.
Epidemiology and laboratory work have proved that dietary fiber can reduce the occurrence of tumors, such as colon cancer. The reason lies in their hydrophilicity and gel-forming ability, which increases the volume of feces and facilitates excretion, thus accelerating the excretion of sterol metabolites with tumor activity and reducing the contact time with colon. Dietary fiber is also good for other diseases, such as coronary heart disease? ⒏? ⑻ á á á á á á á á á á á á? Can titanium core be sued? Small?
Protein, lipids and carbohydrates are nutrients that generate heat energy. All biological reactions must have enough heat energy. The heat energy provided by dietary protein, lipids and carbohydrates, after deducting the undigested part, is called physiological heat energy value. The physiological caloric values of protein, fat and carbohydrate per gram are 4.0, 9.0 and 4.0 kcal respectively. This is the data commonly used to calculate dietary calories.
Under normal circumstances, calorie intake and consumption should be in a state of balance, that is, intake and consumption are equal, which is an energy balance. In the growth stage of organisms, substances in the body are increasing, especially protein and lipids, so there is energy storage. But when the intake exceeds the need, it is stored in the body in the form of lipid. On the contrary, when the intake is lower than necessary, it will consume its own substances, leading to emaciation.
[Edit this paragraph] Minerals
/kloc-In the mid-9th century, it was found that feeding animals only with protein, fat and carbohydrates could not sustain their lives, so it was considered that the ashes after burning food must have physiological functions. However, animals still die after being replenished with ashes. It was not until vitamins were discovered in the early 20th century and the important role of minerals was gradually clarified that we had a more comprehensive understanding of nutrients. There are dozens of mineral elements in the human body, which are widely distributed throughout the body. At present, it has not been proved that these elements have physiological functions. Among them, a few elements have physiological functions and are called essential elements. According to its content in the body, it can be divided into macronutrients and micronutrients. The former includes calcium, phosphorus, magnesium, potassium, sodium, chlorine and sulfur. The latter includes iron, copper, zinc, manganese, molybdenum, chromium, cobalt, nickel, vanadium, tin, iodine, selenium, silicon and fluorine.
Calcium, phosphorus and magnesium are the main components of bones and teeth. Magnesium is also an important component of plant chlorophyll. The physiological functions of calcium, phosphorus and magnesium are as follows: calcium and magnesium play an extremely important role in muscle fiber contraction, nerve conduction and activation of biochemical reactions, and calcium also plays an extremely important role in blood coagulation. Phosphorus is related to energy metabolism. Adenosine triphosphate (ATP) is an important compound for storing and releasing energy. Magnesium is an activating substance that produces adenosine triphosphate. Magnesium, potassium, sodium and chlorine are all important electrolytes to maintain acid-base balance and appropriate osmotic pressure of body fluids. Sulfur is an essential amino acid containing sulfur-methionine and cystine, as well as the components of thiamine, pantothenic acid, biotin and other vitamins. Sulfhydryl groups composed of sulfur and hydrogen play an important role in biological reactions.
Among micronutrients, iron is an important component of hemoglobin and a carrier of oxygen. Copper and iron have synergistic effect in hemoglobin synthesis. Iodine is the main component of thyroxine. Chromium is a component of glucose tolerance factor. Cobalt is a component of vitamin B 12. It is known that zinc is an auxiliary group of more than 40 enzymes, and zinc deficiency will lead to growth stagnation and immature sexual development. Manganese, molybdenum and selenium are also components of the enzyme. Fluorine is also an essential element because it can prevent dental caries. Other elements, such as nickel, vanadium, tin and silicon, have been found not to exist in animal experiments, but their mechanisms have not been clarified. Excessive intake of essential elements can also have adverse effects on the body.
[Edit this paragraph] Vitamins
Adequate vitamins are enough, not the more the better.
Because vitamins are essential nutrients and have important physiological functions, some people think that it is good to eat more vitamins, which is not only wrong, but also very dangerous! Vitamins can be divided into water soluble and fat soluble. When vitamin A, vitamin D and other fat-soluble vitamins are ingested too much, they cannot be excreted directly through urine, which is easy to accumulate in the body and cause poisoning. If you take a large amount of vitamin A orally for a long time, there will be poisoning symptoms such as decalcification of bones, joint pain, dry skin, loss of appetite and hepatosplenomegaly. Long-term oral administration of vitamin D can lead to hypercalcemia, anorexia, nausea, vomiting, diffuse muscle weakness and muscle pain. As for water-soluble vitamins, although they can be excreted from the urine after eating too much, they are less toxic, but a large amount of intake will still damage human organs. If you take a large dose of vitamin C, it may stimulate the gastric mucosa to bleed together. In addition, long-term overdose of vitamins will reduce the absorption rate of vitamins in food, and once it is stopped, it will lead to symptoms of vitamin deficiency. Therefore, long-term overdose of vitamins is not a scientific practice. The dose taken by normal people, including vitamins in food, can reach the amount stipulated by China's dietary standards.
Six nutrients necessary for human body:
Carbohydrate (accounting for 50% ~ 60% of intake calories), fat (accounting for 20% ~ 30% of intake calories), protein (accounting for 10% ~ 15% of intake calories), vitamins, minerals and fiber are six essential nutrients for human body.
Carbohydrate is the main energy source in the world, and cells can convert carbohydrate into glucose. It should be noted that when we eat fruit, we are getting the vitamins, minerals, fiber and water we need every day. Carbohydrates are found in fruits, vegetables, sugar, flour, milk, wheat, corn, oats and rice, as well as nuts and grains.
Fat can provide us with a lot of energy, including fatty acids needed to coordinate physical activities, and it can also transport some fat-soluble vitamins to various parts of the body. Saturated fat exists in beef, pork, chicken, fish, dairy products, eggs and tropical cocoa butter, while unsaturated fat can be obtained from pure olive oil, vegetable oil, peanuts and avocados.
Some scientists in protein have suggested that foods rich in animal protein are easy to cause coronary heart disease, because they contain a lot of toxins and wastes excreted by animals' own cells. But modern nutritionists believe that foods containing animal protein are more beneficial to health. The main animal protein comes from poultry and fish.
Foods containing protein include livestock meat, poultry and fish, dairy products, eggs, wheat, rye, corn, oats, barley, millet, edible fungi, beans and nuts.
Vitamins are important ingredients needed by human body. All foods contain certain vitamins, but fruits and vegetables have the highest content.
Vitamins are essential for regulating body functions. Unlike the nutrients mentioned above, vitamins do not provide calories, but they play an important role in the metabolic process. Vitamins can be obtained from the following foods: carrots, spinach, mushrooms, eggs, milk, yeast, malt, lemon, orange, pineapple, melon, guava, cod liver oil and egg yolk.
Minerals All foods contain a small amount of minerals, but fruits and vegetables have the highest content. The most important minerals for human body are iron, calcium, phosphorus, copper, iodine and potassium. Minerals mainly exist in milk, cheese, cream, fish, tomatoes, spinach and butter.
Fiber exists in beans, grains, fruits, vegetables, wheat bran and whole wheat bread. Although fiber is not considered as the most important nutrient, it is highly valued by doctors and nutritionists. It can promote digestion, especially in removing garbage from the body. The latest research shows that fiber helps to reduce the cholesterol content in the blood. Most doctors recommend taking a certain amount of fiber every day. The initial intake should be less, and then gradually increase to avoid adverse reactions caused by poor adaptability.
Siyang
Thinking and nurturing is a new concept corresponding to nutrition. Nutrition is the organic and inorganic substances that must be ingested into the human body every day, and it is meaningful to form the outside of the human body.
Thinking and nurturing are the stimulation of the individual by the internal or external environment that the human body contacts every day. Its function, like nutrition, is one of the indispensable conditions for human body. However, the function of spiritual cultivation is to influence the intelligent process of human body; Nutrition affects the life process of human body.
Thinking nutrients are: according to natural attributes, they are divided into sensible substances, trace substances, structures and conjectures. Perceptual things are all things in nature that can be directly recognized by people, such as water. Trace substances are substances that are invisible to human beings but can be known with the help of various instruments invented by people, such as H2O. Structure refers to the characteristics of matter, which is a metaphor for the connection characteristics of H (hydrogen) and O (oxygen). Inference is all kinds of things that humans can't understand but may exist, such as the types of electronic partitions in hydrogen.
Taking organism as reference, it can be divided into inner original block and outer original block. The original block of human body is called the inner original block, and vice versa, which is called the outer original block because of the change of human life or life process caused by the stimulation from the body. For example, abdominal pain is an internal mass.
Many places are like "stimulation", but stimulation is passive and spiritual cultivation is active. The human body can control the generation process of its own wisdom through choice. When you are young, it is the choice of parents and environment. When you grow up, you decide the formation of intelligence through your own choices. China's "Meng Mu lives next door" more than 2,000 years ago is the best example of the profound influence of thinking and education on people's intelligent process.
If you want your children to get ahead, you must give them a good "upbringing". Just as you supplement them with "calcium" and "zinc", you can't be careless. You make up his Dojo, he is a Taoist, you make up his "killing pigs", he is a butcher. Only when you supplement his knowledge can he become Mencius.
Chinese, mathematics and history are children's best thoughts, but the most important thing is the living environment.
[Edit this paragraph] Female nutrition
Here are eight nutrients that women need:
1, folic acid 400 μ g/day
Best source: asparagus, beet, broccoli, fortified cereals.
2. Vitamin B61.5mg/day
Best sources: flounder, herring, tuna, lean meat, chicken breast, banana, potato.
3. Vitamin C 100 mg/day
Best sources: cantaloupe, broccoli, grape juice, orange juice, strawberry and pepper.
4. Vitamin E 23 international unit,15mg/day.
Best sources: peanut butter, sunflower oil, safflower oil, hazelnut and sunflower seeds.
5, calcium 1000 mg/day, over 50 years old 1200 mg/day.
Best sources: cabbage, skim milk, yogurt, sardines.
6, iron 20 mg/day, over 50 years old 15 mg/day.
Best sources: lean steak, shrimp, fortified breakfast cheese, wheat, lentils, preserved apricots, tofu and oysters.
7, magnesium 320 mg/day
Best sources: buckwheat, tofu, almonds and sunflower seeds.
8. Zinc15mg/day.
Best sources: steak, pork chops, veal, tofu, oysters.