Nutrition has the function that organisms obtain nutrition from the outside world 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 five categories: protein, lipids, carbohydrates, vitamins and minerals.
Protein human tissues and cells are mainly composed of protein, and body fluids also contain protein. 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).
Lipids 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. Long-chain fatty acids of carbon 0 and carbon 22 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.
Carbohydrate (sugar) is the main nutrient of 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 rest 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哐 I ⑻ ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 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.
Minerals/KLOC-It was found in the middle of the 0/9th century that feeding animals with protein, fat and carbohydrate alone 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.
Vitamins are essential trace organic compounds for human body. Every vitamin has its own physiological function. Lack will lead to special diseases, and serious lack will lead to death. Divided into fat-soluble and water-soluble. Now known fat-soluble vitamins include A, D, E and Ko, while water-soluble vitamins include ascorbic acid, thiamine, riboflavin, nicotinic acid, vitamin B6, folic acid, cobalamin, biotin, pantothenic acid, choline and inositol.
What anti-nutritional factors are there in beans?
Protease inhibitor, beany smell, flatulence factor, phytic acid, saponin, isoflavone, phytohemagglutinin.
How to remove its influence on the nutritional value of bean food?
Protease inhibitor-can be destroyed by steam heating for 30 minutes or pressure heating for 1kg 10-25 minutes.
Beany smell-after being treated with ethanol, it is heated above 95 degrees Celsius or evaporated under reduced pressure.
Flatulence factor-Processing into bean products can remove flatulence factor.
Phytic acid-35%-75% phytic acid can be dissolved at pH4.5-5.5.
Saponins and isoflavones-beneficial to human body
Plant erythrocyte agglutinin-can be destroyed by heating.
What are the nutritional values of dairy products?
Protein, with an average content of 3% and a biological value of 85, is a high-quality protein.
Fat, the content of which is about 3%, is distributed in the milk slurry in the form of granular fat balls, and the absorption rate reaches 97%.
Carbohydrate, mainly lactose, 1/6 is as sweet as sucrose, which can regulate gastric acid, promote gastrointestinal peristalsis, promote calcium absorption and promote the growth of intestinal lactic acid bacteria.
Mineral, rich in calcium, phosphorus and potassium.
Vitamin, vitamin A, vitamin D, carotene.
What are the characteristics of yogurt compared with fresh milk?
Yogurt is fermented by lactic acid bacteria, lactose is converted into lactic acid, protein is solidified, and fat is hydrolyzed to varying degrees, forming a unique flavor. Lactobacillus and Bifidobacterium in lactic acid bacteria are intestinal probiotics. Yogurt is also suitable for infants with digestive dysfunction, the elderly and lactose intolerant people with primary lactose deficiency.
What are the dietary guidelines for China residents?
1, the food is diverse, mainly cereals; 2. Eat more vegetables, fruits and potatoes; 3, often eat milk, beans or their products; 4, often eat the right amount of fish, poultry, eggs, lean meat, eat less fat and meat oil; 5, diet, physical activity should be balanced, maintain a suitable weight; 6. The diet is light and salt-free; 7. If drinking alcohol should be restricted; 8. Eat clean, hygienic and non-perishable food.
What is the pagoda of China residents' balanced diet?
China Residents' Balanced Diet Pagoda is a food quantitative guidance scheme designed according to China residents' dietary guidelines and China residents' dietary structure characteristics. It transforms the principle of balanced diet into the weight of various foods, and displays it in the form of an intuitive pagoda, intuitively telling residents the classification concept of bookstores and the reasonable intake range of various foods every day, which is convenient for people to understand and implement in their daily lives.
What problems should be paid attention to in application?
1. There is no need to eat everything according to the recommended amount of "pagoda" every day in daily life. The recommended intake of various foods is an average proportion, so the types of daily foods should include all kinds of foods in the pagoda, and the proportion of all kinds of foods should be basically the same as that of the dietary pagoda.
2, similar exchange, deployment of colorful meals, grain for grain, beans for beans, meat for meat.
3. The amount of food for three meals should be reasonably distributed. The amount and time interval of three meals should match the working hours and working conditions, 30% in the morning, 30% in the evening and 40% for lunch. Special circumstances can be adjusted appropriately.
4. Make full use of local resources according to local conditions.
5, to develop habits, long-term adherence.
What is the nutritional value of cereal? Does it affect its nutritional value during processing and cooking?
Protein is mainly composed of glutenin, gliadin, albumin and globulin. Because of the low lysine content, the nutritional value of cereals in protein is lower than that of animal foods. Amino acid fortification and protein complementation are often used to improve the nutritional value of cereal protein.
Carbohydrate, mainly starch, is concentrated in the starch cells of endosperm, and its content is above 70%, which is the most ideal and economical energy source for human beings.
Fat, the content is very low, the content of rice and wheat is about 1%-2%, mainly concentrated in aleurone layer and germ. It is easy to become a by-product during processing. Rice bran can extract rice bran oil, oryzanol and sitosterol which are closely related to human health. Germ oil extracted from corn and wheat germ can reduce serum cholesterol and prevent atherosclerosis.
The mineral content is about 1.5%-3%, which mainly exists in chaff and aleurone layer, mainly calcium and phosphorus, and mostly exists in the form of phytate, which is not easily absorbed.
Vitamins are an important source of B vitamins. Thiamine, riboflavin, nicotinic acid, pantothenic acid and pyridoxal are mainly distributed in aleurone layer and germ. The higher the precision of grain processing, the more vitamin loss.
What is the nutritional value of food?
The nutritional value of food refers to the degree to which the nutrients and energy contained in a certain food meet the same needs of the human body.
How to evaluate?
Types and contents of nutrients Generally speaking, the closer the types and contents of nutrients provided in food are to human needs, the higher the nutritional value of food.
The protein of nutritional quality is reflected in the composition of amino acids and the degree to which they can be digested and utilized; The advantages and disadvantages of fat are reflected in the composition of fatty acids and the content of fat-soluble vitamins.
The strength of human immunity depends on two aspects, one is congenital factor and the other is acquired factor.
Congenital factors refer to genes, not heredity; It also includes whether there are congenital infections and congenital genetic diseases.
There are many acquired factors that can be artificially controlled; Let me tell you what I know.
How to improve immunity?
1 prevention of infection: all kinds of infections can lead to low immunity, from a small point of view, colds; Scientific research has found that frequent colds can lead to decreased immunity; Generally speaking, HIV infection leads to the complete collapse of human immune system, and the result is fatal; Therefore, it is very important to prevent virus infection, understand the transmission routes and harmfulness of various viruses, and vaccinate all vaccines, such as hepatitis B vaccine.
2 Strengthen nutrition and suggest eating more meat. Many people say that eating vegetables is good, but in terms of nutritional value, meat food can enhance immunity; I'm not talking about being fat.
3 Healthy living habits, quitting smoking and drinking, sleeping no less than 6 hours a day, overwork will damage immunity.
4 mentality must maintain a happy attitude, smile more, sometimes daydream, mental stress, low immunity.
Moderate exercise helps to improve immunity, don't overdo it, because immunity is very low when you are tired.
6 Prevention of diseases Many non-communicable diseases can cause anemia patients with low immunity to catch a cold easily.
Drugs (not recommended) unless the patient, such as thymosin, some Chinese herbal medicines, such as Ganoderma lucidum.
How to enhance resistance?
Have a good sleep. Poor sleep is related to the decline of immune system function. The body's resistance will decrease and the incidence will increase. But do you have to sleep for eight hours? Not necessarily, as long as you wake up in the morning and feel refreshed.
Exercise for 30 minutes every day. Studies have shown that the number of immune cells will increase and the resistance will be relatively enhanced for 30 to 40 minutes a day, 5 days a week and 12 weeks. As long as the heart beats faster, walking after meals is very suitable. If it is too intense or lasts for more than 1 hour, the body will produce some hormones and inhibit the activity of the immune system.
Massage can relax the body and relieve stress. It was found that after massage for 45 minutes every day for 1 month, the number of immune cells would increase and the immune function would be obviously improved.
Vitamin C is 200 grams a day, and taking 200 to 500 mg of vitamin C every day helps to enhance the body's resistance.
Vitamin E As long as you eat 200 international units of vitamin E every day, you can strengthen your ability to fight infectious pathogens.
Don't abuse antibiotics. Abuse of antibiotics will reduce the hormones responsible for coordinating the immune system in some patients.
People with more friends are less likely to catch a cold, and their immune function is 2% stronger than that of introverts. Researchers believe that good social relations help to fight stress, reduce stress hormones and affect immune cell function. However, too much contact will also become a kind of pressure, don't force yourself. Three or five intimate friends are more important than a bunch of casual acquaintances.
Laughter can reduce stress hormones. In addition, the study pointed out that laughter significantly increased interferon, stimulated immune function, and immune cells became more active. If you feel that you lack humor, you can watch more comedies and funny animations, think about the plot when you are nervous, and learn to be optimistic about the status quo.
Daydreaming for 5 minutes every day and deep breathing for 5 minutes every day can increase the number of immune cells and even enhance the activity of cells.
I believe that your optimism can keep your immune system at its best. A study by students of the University of California Law School found that optimistic students have more T cells to expand the immune response than pessimistic students, and the cells responsible for eliminating the virus are also more active.
Spending 20 minutes in a diary every day to write out your unhappiness can make your body more resistant to bacteria and viruses. According to research, people who spend 20 minutes a day and write three to five times a week see a doctor half as often as those who don't write. Researchers at new york University also pointed out that writing can make people see the problem clearly, and the stress will be reduced, so that the body will not produce stress hormones.