Protein Encyclopedia ②

Consumption

Protein food is an important nutrient for the human body. Ensuring the supply of high-quality protein is an important issue related to health. How to choose protein is economical and nutritious?

First of all, we must ensure that there is sufficient quantity and quality of protein food. According to research by nutritionists, an adult needs to update more than 300g of protein every day through metabolism, of which 3/4 are derived from amino acids produced in the body's metabolism. The reuse of these amino acids greatly reduces the amount of protein that needs to be supplemented. Generally speaking, an adult's daily intake of 60g～80g protein can basically meet the needs.

Secondly, a reasonable combination of various foods is an effective method that is economical and can effectively improve the nutritional value of protein. It is best to have one-third of the protein consumed daily from animal protein, and two-thirds from plant protein. The people of our country have the habit of eating mixed foods. Mixing several kinds of proteins with low nutritional value. The amino acids in them complement each other, which can significantly increase the nutritional value. For example, cereal protein contains less lysine and more methionine. Bean protein contains more lysine and less methionine. When these two types of protein are mixed, the essential amino acids complement each other, which is close to the needs of the human body, and the nutritional value is greatly improved.

Third, every meal must have a certain quality and quantity of protein. The human body does not set up a storage warehouse for protein. If you eat too much protein at a time, it will inevitably cause waste. On the contrary, when there is insufficient protein in food, young people will be stunted, and adults will feel fatigue, weight loss, and disease resistance weakened.

Fourth, eating protein must be based on sufficient calorie supply. If the calorie supply is insufficient, the body will consume protein in food for energy. Each gram of protein provides 18kJ of calories when oxidized in the body, which is equivalent to glucose. Using protein as an energy source is a waste, and it is an overkill.

The protein intake may be excessive, and the amount of protein required to maintain health varies from person to person.

The average healthy adult male or female needs approximately 0.8 grams of protein per kilogram (2.2 pounds) of body weight.

Related research

extend your life

According to foreign media reports on the 11th, a groundbreaking study may become the key to longevity and health of the elderly. American researchers have discovered a protein called SIRT1. It can not only prolong the life of mice, but also postpone the age of onset related to health. In addition, it also improves the overall health of mice, lowers cholesterol levels, and even prevents diabetes. The researchers said that although this study was conducted on mice, it will eventually be applied to humans one day.

The research team led by Dr. Raphael De Cabo of the National Institute of Aging of the National Institutes of Health tested the effect of SIRT1720, a small molecule that activates SIRT1, on the health and lifespan of mice. Decab said: "We have verified for the first time that the artificial SIRT1 activator not only prolongs the lifespan of rats fed on standard food, but also improves their health span. This shows that we may develop to reduce the burden of age-related metabolic diseases and chronic diseases. The molecules.” These researchers also found that SRT1720 prolonged the average life span of mice by 8.8%.

SRT1720 supplements also reduce body weight and body fat percentage, and improve the muscle function and exercise coordination ability of mice throughout the life.

Scientists have discovered that SRT1720 supplements lower total cholesterol and low-density lipoprotein cholesterol levels that help fight heart disease, and improve insulin sensitivity that may help prevent diabetes.

It is known to scientists that SIRT1 and its sister protein SIRT2 play an important role in the metabolism of a large number of species. They are also involved in DNA repair and gene regulation, and may help prevent diabetes, heart disease and cancer. Mice are provided with this supplement and standard diet at 6 months of age and other life stages. But experts warn that this research is still in a very early stage, and no relevant experiments have been conducted on humans.

Related Disciplines

1982 American S. B. Prusiner discovered the protein factor Prion, updated the concept of medical infection, and won the Nobel Prize in Physiology and Medicine in 1997.

One of the most amazing discoveries of the 20th century is that the active state and inactive state of many proteins can be converted into each other. Under a precisely controlled solution condition (for example, by dialysis to remove the chemical substance that causes inactivation), the inactivated protein can be transformed into Active form. How to restore proteins to their active state is a major research area of biochemistry called protein folding.

The synthesis of protein is to transcribe the information hidden in DNA into mRNA through the action of enzymes in the cell, and then the corresponding amino acids are transported to the ribosome by tRNA according to the principle of codon-anticodon pairing, according to the encoding of mRNA They are arranged in strings in order to form a polypeptide chain, which is then folded and twisted into a protein. Protein is the basic macromolecule of life. It can be regarded as a brick of a living body.

Through genetic engineering, researchers can change the sequence and thereby change the structure of the protein, target substance, regulatory sensitivity and other properties. The gene sequences of different proteins can be spliced together to produce "absurd" proteins with two protein properties. This form of patching has become a major tool for cell biologists to change or probe cell functions. In addition, another attempt in the field of protein research is to create a protein with brand-new properties or functions. This field is called protein engineering.

Food content

protein

Foods with a lot of protein include: livestock milk, such as milk, goat milk, horse milk, etc.; livestock meat, such as cattle, sheep, pork, etc.; poultry meat, such as chicken, duck, goose, quail, etc.; eggs, such as eggs, Duck eggs, quail eggs, fish, shrimps, crabs, etc. There are also soybeans, including soybeans, green beans, and black beans. Among them, soybeans have the highest nutritional value. It is a high-quality source of protein in infant food; in addition, like sesame, The protein content of dried fruits such as melon seeds, walnuts, almonds, and pine nuts is relatively high. Since the content of amino acids in various foods, the types of amino acids contained are different, and the content of other nutrients (fat, sugar, minerals, vitamins, etc.) are also different, the above foods are all available when adding complementary foods to babies If you choose, you can also provide children with high-protein foods according to local conditions.

protein

Protein foods are expensive. Parents can use several cheap foods to mix together to increase the utilization rate of protein in the body. For example, the biological value of simply eating corn is 60%, wheat is 67%, and soybeans is 64%. If these three foods are mixed in proportion and eaten, the utilization rate of protein can reach 77%. A ubiquitous biological macromolecule mainly composed of amino acids. It is the most basic substance of living organisms as well as nucleic acid, and it is responsible for various extremely important functions in the process of life activities. The basic structural unit of protein is amino acid, and there are 20 kinds of amino acids appearing in protein. Amino acids are connected to each other by peptide bonds to form a peptide chain.

A brief history In 1820, H. Bracono discovered glycine and leucine, which were the amino acids that were initially identified as protein components, and other amino acids were discovered later. By the end of the 19th century, it was clear that protein was mainly composed of a class of fairly simple organic molecules-amino acids. In 1902, E. Fischer and F. Hofmeister independently clarified that the chemical bonds that connect amino acids in protein molecules are peptide bonds; in 1907, E. Fischer succeeded in chemically connecting 18 amino acids synthesized peptides for the first time, thus establishing the peptide theory as the basis of protein chemical structure. The knowledge of the precise three-dimensional structure of proteins mainly comes from the X-ray diffraction analysis of protein crystals. In 1960, JC Kendrew used X-ray diffraction analysis technology to determine the crystal structure of myoglobin for the first time. This was the first three-dimensional structure to be elucidated. Protein. Chinese scientists completely synthesized crystalline bovine insulin by chemical synthesis in 1965, realizing the artificial synthesis of protein for the first time; from 1969 to 1973, the crystal structure of porcine insulin was determined at 2.5 angstroms and 1.8 angstroms resolution. , This is the first three-dimensional structure of a protein clarified by China.

active

After the protein molecule is affected by some external physical and chemical factors, although the peptide chain of the molecule is not cracked, its natural three-dimensional structure is changed and destroyed, which leads to the loss of protein biological activity and other physical and chemical properties. Change, this phenomenon is called protein denaturation. As early as 1931, Chinese biochemist Wu Xian put forward the correct theory of denaturation for the first time. The main factors that cause protein denaturation are: ①Temperature. ② pH. ③Organic solvents. ④Urea and guanidine hydrochloride. This is the most widely used protein denaturation reagent. ⑤ Detergents and aromatic ring compounds.

Protein denaturation is often accompanied by the following phenomena: ① Loss of biological activity. This is the most important feature of protein denaturation. ② Changes in chemical properties. ③ Changes in physical properties. After the denaturation factor is removed, the denatured protein molecule can revert to the natural conformation before denaturation. This phenomenon is called protein renaturation. The renaturation of protein includes complete renaturation, basic renaturation or partial renaturation. Only a few proteins can fully renature after severe denaturation. The study of protein denaturation and renaturation is very important to understand the folding process of protein molecules in vivo and in vitro. Mainly through the study of protein denaturation and renaturation, the spontaneity of protein folding has been affirmed, and the characteristic three-dimensional structure of protein molecules is only determined by its amino acid sequence. When the active protein molecule is just synthesized in the organism, it often does not show activity, that is, it does not have the specific biological function of this protein. In order for a protein to exhibit its biological activity, a very common phenomenon is that the peptide chain of a protein molecule must be broken in a specific way during some biochemical processes.

The activation of protein is a way of biological regulation, and this kind of phenomenon is widespread in various important life activities.

Many proteins are composed of subunits. When this type of protein completes its biological functions, its efficiency and reaction speed are regulated to a large extent on the relationship between subunits. It is a fairly common phenomenon that subunits participate in the regulation of protein functions, especially in regulating the catalytic function of enzymes. Some enzymes have allosteric sites that do not overlap with the active site. The combination of the allosteric site and the allosteric ligand causes changes in the three-dimensional structure of the enzyme molecule, resulting in changes in the three-dimensional structure of the active site. This change may increase or may Inactivate the catalytic ability of the enzyme. Such enzymes are called allosteric enzymes. Known allosteric enzymes have two or more subunits in structure.

Features

Proteins have multiple functions in organisms.

Catalytic function A protein with a catalytic function is called an enzyme, and all the chemical reactions in the metabolism of an organism are catalyzed by enzymes.

Motor function from the lowest bacterial flagella to the muscle contraction of higher animals is achieved through protein. Muscle relaxation and contraction are mainly accomplished by the sliding of thick filaments with myosin as the main component and fine filaments with actin as the main component.

Transport function In the process of life activities, the transport of many small molecules and ions is completed by a variety of specialized proteins. For example, plasma albumin transports small molecules in the blood, and hemoglobin in red blood cells transports oxygen and carbon dioxide.

Mechanical support and protection The tissues with mechanical support functions of higher animals, such as bones, connective tissues, and hair, skin, nails and other tissues with covering and protection functions, are mainly composed of collagen, keratin, and elastin.

Immune and defense function organisms have a variety of defense methods in order to maintain their own survival, many of which are executed by proteins. For example, antibodies are a class of highly specific proteins that can recognize and bind foreign substances that invade organisms, such as foreign proteins, viruses, and bacteria, and cancel their harmful effects.

Regulatory function In maintaining the normal life activities of organisms, in various processes such as the regulation of metabolic functions, the control of growth and differentiation, the regulation of reproductive functions, and the continuation of species, peptides and protein hormones play an extremely important role. In addition, there are proteins that receive and transmit regulatory information, such as receptor proteins for various hormones.

development of

As a biological macromolecule that plays an important role in life activities, protein is closely related to all major research topics that uncover the mysteries of life. Protein is the main food ingredient for humans and other animals, and a high-protein diet is one of the important signs of the improvement of people's living standards. Many pure protein preparations are also effective drugs, such as insulin, human gamma globulin and some enzyme preparations. In clinical testing, the determination of the activity of related enzymes and the changes of certain proteins can be used as indicators for the clinical diagnosis of some diseases. For example, the identification of lactate dehydrogenase isoenzymes can be used as indicators of myocardial infarction, and the increase in alpha-fetoprotein can be used as an indicator of myocardial infarction. As an indicator of early liver cancer lesions, etc. In industrial production, certain proteins are important raw materials for the food industry and light industry. For example, wool and silk are both proteins, and leather is processed collagen. After applying various enzyme preparations in industrial sectors such as tanning, pharmacy, and silk reeling, production efficiency and product quality can be improved. The importance of protein in agriculture, animal husbandry, and aquaculture is also obvious.

The protein can be used as a reagent for screening compounds or salts thereof that can promote or inhibit the activity of the protein of the present invention. Furthermore, the compound or its salt and the neutralizing antibody that inhibits the activity of the protein of the present invention can be used as a medicine for the treatment or prevention of bronchial asthma, chronic obstructive pulmonary disease, and the like.

Protein plays a very important role in the life activities of cells and organisms. The structure and shape of living things are related to proteins. Protein is also involved in the regulation of gene expression, as well as many life activities such as redox, electron transfer, neurotransmission, learning and memory in cells. The enzymes that catalyze various biochemical reactions in cells and organisms are mainly proteins. Many important hormones, such as insulin and thymus hormone, are also proteins. In addition, a variety of proteins, such as the protein in plant seeds (beans, peanuts, wheat, etc.), animal protein, cheese, etc., are proteins for the nutritional growth of organisms. Some proteins, such as snake venom and bee venom, are weapons of animal attack and defense.

Protein accounts for 20% of the human body, the largest proportion of the body. Bile, except urine, are all protein synthesis. Only when protein is sufficient can the metabolism be normal. Just like building a house, the main raw material for building the body is protein.

1. Protein is the basic material for the construction of new tissues, and is the raw material for enzyme and hormone synthesis; it maintains the balance of potassium and sodium; and eliminates edema.

2. It is the components of synthetic antibodies: white blood cells, T lymphocytes, interferons, etc., which improve immunity.

3. Provide some energy.

4. Lower blood pressure, buffer anemia, it is the carrier of red blood cells.

5. Form the human body's collagen. The vitreous of the eyeball and rhodopsin have collagen.

7. The power source of brain cell division is protein; cerebrospinal fluid is synthesized by protein; memory is reduced

8. Sexual dysfunction

9. Liver: hematopoietic function; synthetic hormones, enzymes; detoxification. Lack of protein and unhealthy liver cells. With a good liver, one’s health is guaranteed.

10. Heart-pump organ. Lack of protein will cause cold hands and feet; hypoxia; myocardial hypoxia can cause heart failure-death.

11. Spleen and stomach: digest food every day, digestive enzymes are synthesized by protein. Lack will cause insufficient gastric motility, indigestion, and hiccups. Stomach ulcer, gastritis; excessive gastric acid, irritating the ulcer surface, you will feel pain, protein only has the function of repairing regenerated cells. There are ligaments on the digestive wall, the lack of protein will loosen, the internal organs will droop, and the uterine organs will shift.

12. Limbs: old legs, lack of protein, muscle atrophy; reduced bone toughness, easy to fracture

13. Antibodies will decrease, making you easy to catch colds and fever.

main research

history

In the 18th century, Antonio François (Antoine Fourcroy) and other researchers discovered that proteins are a unique class of biological molecules. They discovered that treating some molecules with acid can cause them to coagulate or flocculate. The examples they noticed at the time were protein from egg white, blood, serum albumin, cellulose and wheat gluten. Dutch chemist Gerhardus Johannes Mulder conducted elemental analysis on general proteins and found that almost all proteins have the same experimental formula. The use of the term "protein" to describe this type of molecule was proposed in 1838 by Mulder's collaborator Jons Bezelius. Mulder then identified the degradation product of the protein and found that it contained leucine, which is an amino acid, and got its (very close to the correct value) molecular weight of 131 Da.

For early biochemists, the difficulty of studying proteins is that it is difficult to purify large amounts of proteins for research. Therefore, early research work focused on proteins that can be easily purified, such as blood, egg white, proteins in various toxins, and digestive and metabolic enzymes (obtained from slaughterhouses). In the late 1950s, Armour Hot Dog Co. purified ribonuclease A from one kilogram of pure bovine pancreas and provided it to scientists all over the world for free. Scientists can buy more and more types of pure proteins from biological companies.

The famous chemist Linus Pauling successfully predicted the regular protein secondary structure based on hydrogen bonds, and this idea was first proposed by William Astbury in 1933. Subsequently, Walter Kauzman summarized his research results on denaturation and the previous research work of Kaj Linderstrom-Lang, and proposed that protein folding is mediated by hydrophobic interactions. In 1949, Frederick Sanger correctly determined the amino acid sequence of insulin for the first time and verified that the protein is a linear (no bifurcation or other form) polymer formed by amino acids. Atomic resolution protein structure was first analyzed by X-ray crystallography in the 1960s; in the 1980s, NMR was also applied to the analysis of protein structure, and cryo-electron microscopy was widely used to analyze the structure of super-large molecular complexes. . As of February 2008, there are close to 50,000 atomic resolution coordinates of the three-dimensional structure of proteins and related complexes in the protein database.

research method

Proteins are the most studied type of biomolecules, and their research includes "in vivo" and "in vitro". In vitro studies are mostly applied to purified proteins, placing them in a controllable environment in order to obtain their functional information; for example, studies related to enzyme kinetics can reveal the chemical mechanism of enzyme-catalyzed reactions and their interaction with different substrate molecules. Relative affinity between. In vivo research experiments focus on the active role of proteins in cells or entire tissues, so as to understand where proteins function and the corresponding regulatory mechanisms.

Anticancer effect

When cancer cells proliferate rapidly, they need the help of a protein called survivin. This protein is encoded and synthesized by the apoptosis-suppressing gene Survivin. It is abundant in cancer cells, but it is almost absent in normal cells. The dependence of cancer cells on survivin protein makes survivin a natural target for the manufacture of new anticancer drugs, but there are still some unsolved mysteries on how to deal with survivin protein.

Survivin protein belongs to a class of proteins that prevent cells from destroying themselves (ie, apoptosis). Such proteins mainly inhibit the action of apoptotic enzymes (caspases) to prevent them from sending cells on the road to suicide. No scientist has ever observed the interaction between survivin protein and apoptotic enzyme. There are also other signs that the survivin protein plays a different role-helping to pull the cell apart after cell division.

Biochemist Guy Salvesen grasped the structure of survivin protein "and did not clarify the doubt about how it prevents cell suicide." The fact that these proteins pair up is indeed surprising, and it is almost difficult to find unimportant dimerization regions. The interface between the two proteins will be a good target for anti-cancer drugs to intensively deal with.

Genomics

When I mentioned Proteomics before 1996, I am afraid that very few people know it, but some people are still skeptical about knowing a little about the two. However, the 2001 Science magazine has listed proteomics as one of the six research hotspots, and its popularity is second only to stem cell research. The level of interest in proteomics is now impressive.

1. Research significance and background of proteomics research

With the implementation and advancement of the Human Genome Project, life science research has entered the post-genome era. In this era, the main research object of life sciences is functional genomics, including structural genomics research and proteomic research. Although the genomes of multiple species have been sequenced, the function of more than half of the genes in these genomes is usually unknown. The strategies used in functional genomics, such as gene chip, serial analysis of gene expression (SAGE), etc., are all considered from the perspective of mRNA in the cell, and the premise is that the level of mRNA in the cell reflects the protein The level of expression. But the fact is not exactly the case. From DNA mRNA protein, there are three levels of regulation, namely transcriptional control, translational control, and post-translational control. From the perspective of mRNA, it actually only includes the regulation of transcription level, and does not fully represent the level of protein expression. Experiments have also proved that the correlation between mRNA abundance and protein abundance in tissues is not good, especially for low-abundance proteins, the correlation is even worse. More importantly, complex post-translational modifications of proteins, subcellular localization or migration of proteins, and protein-protein interactions are almost impossible to judge from the mRNA level. Undoubtedly, protein is the executor of physiological functions and the direct manifestation of life phenomena. The study of protein structure and function will directly clarify the change mechanism of life under physiological or pathological conditions. The existence of the protein itself and the laws of its activities, such as post-translational modification, protein-protein interaction and protein conformation, still rely on direct protein research to solve. Although the variability and diversity of proteins and other special properties make protein research technology far more complicated and difficult than nucleic acid technology, it is these characteristics that participate in and affect the entire life process.

2. Strategy and scope of proteomics research

Once proteomics appeared, there were two research strategies. One can be called the "exhaustion method", that is, the use of high-throughput proteomics research techniques to analyze as many as possible or even close to all proteins in the organism. This view looks at proteomics from a large-scale and systematic perspective. It is also more in line with the essence of proteomics. However, because protein expression changes continuously with space and time, it is an elusive goal to analyze all the proteins in the organism. Another strategy can be called "functional method", that is, to study the changes in cell protein composition at different periods, such as the differential expression of proteins in different environments, with the main goal of discovering different protein types. This view is more inclined to use proteomics as a means and method to study life phenomena.

The research scope of early proteomics mainly refers to the expression profile of proteins. With the development of the discipline, the research scope of proteomics is constantly improving and expanding. The study of protein post-translational modification has become an important part and a huge challenge in the research of proteomics. The study of protein-protein interaction has also been included in the research category of proteomics. The analysis of protein high-level structure is traditional structural biology. Although some people try to include it in the scope of proteomics research, it is still unique.

3. Proteomics Research Technology

It can be said that the development of proteomics is both driven by technology and limited by technology. The success of proteomics research depends largely on the level of its technical methods. Protein research technology is far more complicated and difficult than gene technology. Not only are the types of amino acid residues far more than nucleotide residues (20/4), but also proteins have complex post-translational modifications, such as phosphorylation and glycosylation, which bring many difficulties to the separation and analysis of proteins. In addition, it is not easy to perform in vitro amplification and purification of proteins through expression vectors, making it difficult to prepare large amounts of proteins. The rise of proteomics has brought new demands and challenges to technology. The research of proteomics is essentially the large-scale parallel separation and analysis of proteins at the cellular level, often processing thousands of proteins at the same time. Therefore, the development of high-throughput and high-sensitivity

A high-degree, high-accuracy research technology platform is the main task in proteomics research for quite some time. The technical foundation and development trend of the international proteomics research technology platform are as follows:

3.2 Sample separation and analysis in proteomics research

Using the isoelectric point and molecular weight of the protein to distinguish various proteins by two-dimensional gel electrophoresis is a very effective means. It plays a key role in proteomic separation technology. How to improve the separation capacity, sensitivity and resolution of two-dimensional gel electrophoresis and the accurate detection of differential expression of proteins are key issues in the development of two-dimensional gel electrophoresis technology. The main trends abroad are the use of narrow pH gradient gel separation in first-dimensional electrophoresis and the development of high-sensitivity protein staining techniques combined with two-dimensional gel electrophoresis, such as new fluorescent staining techniques.

Mass spectrometry technology is the fastest growing, most dynamic and potential technology in proteomics research. It determines the type of protein by measuring the quality of the protein. The core technology of current proteomics research is two-dimensional gel electrophoresis-mass spectrometry technology, which separates proteins by two-dimensional gel electrophoresis, and then uses mass spectrometry to identify the proteins one by one. For protein identification, high throughput, high sensitivity and high precision are the three key indicators. The general mass spectrometry technology is difficult to integrate the three, and the developed mass spectrometry technology can meet the above three requirements at the same time, so as to realize the accurate and large-scale identification of proteins.

The nitrogen content of protein is relatively constant, about 16% on average.

Relationship with height

According to reports, during World War II, the supply of animal food in Japan was insufficient. Each person only supplied 2 kg of meat, 12.5 kg of milk and dairy products, and 2.5 kg of eggs each year. At that time, the average height of 12-year-old students was only 137.8 cm. After the war, Japan's economy developed rapidly, people's lives improved, and animal foods increased. Each person consumed 13 kilograms of meat, 25 kilograms of milk and dairy products, and 15 kilograms of eggs each year. According to a survey in 1970, the height of a 12-year-old teenager (Juvenile Food) has reached 147.1 cm, an average height increase of 9.3 cm. From this example, we can see the effect of protein food (protein food) on the increase of children (children's food).

Protein is the main compound that constitutes all life, the material basis and the first element of life, and it occupies the primary position in nutrients. Children and infants cannot increase their height without protein. The bones and other tissues of the human body are composed of protein. In all the chemical reactions of metabolism in the body, the catalysis of enzymes is inseparable, and all enzymes are made of protein. The various hormones that play a role in the growth of adolescents are also proteins and their derivatives. In addition, bone mineralization binder, osteocalcin, alkaline phosphatase, human bone-specific growth factor and other substances involved in the processes of bone cell differentiation, bone formation, bone reconstruction and renewal are also composed of proteins. Therefore, protein is the most important compound in human growth and development, and an important raw material for growth.

Fat-soluble vitamins (vitamin foods), iron (iron foods), calcium, phosphorus and other inorganic salts and some trace elements (trace element foods) necessary for the growth and development of infants and young children (food for infants and young children), and also in protein foods At the same time. Therefore, some children and adolescents only like to eat vegetarian food (vegetarian food) and are afraid of eating meat dishes such as chicken, fish, meat, eggs, or reluctantly eat a little under the supervision of their parents. This practice is undesirable and will inevitably lead to The height is affected by lack of protein.

The correct dietary principle is to have a variety of foods, match the thickness, adhere to grain, beans, and vegetables, and increase the amount of meat, fish, eggs, and milk appropriately to supplement adequate nutrition for body development, ensure raw materials for height increase, and promote Taller.

Supplementary Notes

Protein food sources of protein can be divided into two categories: plant protein and animal protein. Among plant proteins, cereals contain about 10% protein, which is not high, but because it is the staple food of people, it is still the main source of dietary protein. Beans are rich in protein, especially soybeans which contain 36%-40% of protein. The amino acid composition is also reasonable, and the utilization rate in the body is high. It is a very good source of protein in plant proteins.

Eggs contain 11% to 14% protein and are an important source of high-quality protein. Milk (milk) generally contains 3.0%~3.5% protein, which is the best source of protein for infants and young children. Protein is composed of amino acids. Among the 22 essential amino acids for the human body, 9 kinds of amino acids (amino acid food) cannot be synthesized by the human body or in insufficient synthesis, and they must be obtained through diet.

Meat includes the muscles of poultry, livestock and fish. Fresh muscle contains 15%~22% protein. The nutritional value of muscle protein is better than that of plant protein. It is an important source of human protein.

The main source of protein is divided into animal protein and plant protein. Generally speaking, the nutritional value of animal protein is higher than that of plant protein. Based on the protein content per 500 grams, the protein-rich foods include:

①Meat products: 84.5 grams of pork, 100.5 grams of beef, 100.5 grams of pork liver;

②Eggs: 63.5 grams of eggs, 63 grams of duck eggs;

③Fish and shrimp: 88 grams of carp, 83 grams of grass carp, and 80 grams of sea shrimp;

④Rice noodles: 60.5 grams of wheat flour, 50 grams of barley, 42.5 grams of corn;

⑤Beans: 11 grams of mung beans, 108.5 grams of red beans, 249 grams of black beans;

⑥Vegetables: 70 grams of day lily, 41 grams of kelp. Soy protein has better nutrition, and it is high-quality protein with animal protein.

Calculate the requirement

The protein requirement varies depending on various factors such as health status, age, weight, etc. People who are taller and older or younger require more protein.

The following figures are the index of protein required by people of different ages:

Age 1—3 4—6 7—10 11—14 15—18 19 and above

Index 1.80 1.49 1.21 0.990.880.79

The calculation method is:

First find out your own age group index; then multiply this index by your own weight (kg); the answer is the number of grams of protein you need in a day.

For example: weight 50 kg, age 33 years old, its index is 0.79.

0.79×50=39.5 grams. This is the amount of protein needed in a day.

The average protein requirement in a day is at least about 45 grams, which is about 15 grams for a meal. Note that breakfast must be adequate protein intake.

Suitable for all people who need protein supplementation. Pregnant and breastfeeding women, urban white-collar workers with high work pressure, often staying up late to work, elderly parents, young children in the growth and development period, people recovering from surgery, high blood pressure.

Supplement after childbirth

There are three points to pay attention to the intake of protein after childbirth:

First, the intake of protein should be sufficient, because new mothers need to take in enough protein to breastfeed.

Second, protein should be high-quality. Generally speaking, fish and shrimp protein is better than meat, and white meat is better than red meat. Try not to eat meat that may have hormones artificially fed animals, but eat natural foods

Third, protein intake should be balanced, and don't just choose one food to eat.

A small number of people do not have enough milk and milk is slower. In order to help milk, you can drink some soups with Chinese medicine ingredients. This helps the mother's body to recover and regulate (uterine contractions, lochia discharge), smooth milk delivery, and nutritional supplements.

Fitness crowd supplement

During fitness exercise, the body's demand for protein is much stronger than in other stages. Cereal protein contains less lysine. If it is eaten with foods containing more lysine, such as soybeans, meat, eggs, etc., it will increase the nutritional value of each other. For another example, soybean contains very low methionine, while corn contains high methionine. If the two are combined, they will complement each other and increase nutritional value.

Through the above examples, during fitness exercises, we can adjust our past diet structure to achieve food diversification, a balanced combination of coarse and fine grains, a reasonable distribution of animal protein to each meal, and appropriate intake of soy products, which can greatly improve our meal Nutritional value. Under this circumstance, performing fitness exercises will eventually show that the fitness effect is significantly improved.