Protein and exercise ①: the importance of protein

"Many athletes believe that protein is the key to sports success It's hard to find strength athletes who refuse protein supplements, most of whom are convinced that their success is due, at least in part, to extra protein In fact, most athletes ingest too much protein, which reduces the ingestion of other essential nutrients that are essential for success in sports Simply put, if one nutrient is too much, it will reduce the intake of other equally important nutrients "
Athletes who especially need more protein (as a percentage of total energy intake) usually consume less protein Endurance athletes look thinner than strength athletes and are not as strong Because they need to burn a certain level of protein in normal endurance training, they need almost as much protein quality (per unit weight) as strength athletes On the contrary, power athletes usually take more protein than they need, and even worse, many athletes take protein powder or amino acid supplements to further improve their protein intake Since 30 grams of meat provides about 7000 mg of fatty acids, while a typical fatty acid supplement only supplies 500-1000 mg, the protein intake strategy followed by many athletes is unreasonable 1 Function of protein "Proteins are digested into amino acids after entering the body, which combine with other amino acids decomposed in the body to form an amino acid pool Tissues take amino acids from the pool and synthesize specific proteins (muscles, hair, fingers / toenails, hormones, enzymes, etc.) that the body needs If other fuels (carbohydrates and fats) do not meet the energy requirements, this amino acid pool can also provide the energy for combustion (through a deamination process) "
The main functions of protein are as follows: 1 Protein provides the carbon source needed for energy generation reaction Some amino acids can be converted into glucose, metabolized to provide ATP, while other amino acids can be stored as fat, then metabolized to provide ATPo 2 Protein is a very important compound in controlling the liquid volume and osmotic pressure of blood and organism This function is an important regulatory factor to maintain water balance 3 Protein is an amphoteric compound, which can buffer in acidic and alkaline environment to maintain the optimal pH value of blood 4 Protein is the main component of antibody, which is very important to maintain health 5 Protein can produce enzymes, which are involved in the cell process of digestion and other chemical end products 6 Protein is one of the most important components of tissues, heart, liver, pancreas, muscle and bone 7 Protein is the "smart" material carrier in the blood, which can accurately transport the material to the position of the receptor For example, ferritin is a protein that transports iron 8 Proteins can synthesize specific hormones (such as insulin) and neurotransmitters that control the function of the body
2 Protein metabolism Proteins are made up of carbon, hydrogen, oxygen, nitrogen and, in some cases, sulfur Protein is the only nutrient with nitrogen, which makes it both necessary and potentially toxic Amino acid structural units make up proteins with larger molecular structure Some of these amino acids can be synthesized from other amino acids, which are called nonessential amino acids, while some of them must be obtained from our food, which is called essential amino acids Since the word "nonessential" implies that although they exist, they are not really needed, it is easy to confuse the words "essential amino acids" with "nonessential amino acids" However, the reality is that essential amino acids and nonessential amino acids are equally important (and therefore necessary) in human metabolism
Amino acids combine to form larger proteins, and the sequence of amino acids and the secondary and tertiary structures of proteins determine its function When ingesting dietary protein, the protein is digested into multiple skin (small protein molecules) and finally broken down into independent amino acids Amino acids are absorbed by the blood, transported to different tissues through the blood, and processed into proteins needed by the body In order to ensure that tissues can produce the required proteins, essential amino acids are essential Some people think that if you want to have healthy looking hair and nails, you should take the same protein (gel) with the main components of your hair and nails Gel is a low quality protein, and the content of essential amino acids is very small, so it will not promote the best protein synthesis Simply put, eating hair and nails does not promote the best synthesis of hair and nails The best way to ensure the synthesis of required proteins is to provide all necessary amino acids to cells to generate various proteins needed by the body The best way is to get as much amino acid supply as possible from the diet, so that the tissues can synthesize the amino acids they need and optimize their body functions
Liver is an important processing place for protein synthesis, which constantly regulates the protein demand of the body, and synthesizes amino acids and proteins to meet various needs of the body Protein synthesis is realized by transamination and deamination In transamination, the nitrogen in the amino acid is used to produce another amino acid; in deamination, the amino acid is removed from the amino acid and converted to ammonia The remaining carbon shelves are either reconstituted for fat storage, or converted to glucose (alanine and glutamate), or burned to release energy Ammonia produced in deamination is toxic to the body, but enzymes in the liver can convert ammonia into urea Urea is excreted from the body through urine Therefore, the more additional protein you eat, the more ammonia (urea) you need to excrete from the body, and most of the remaining amino free carbon chains are stored in the form of fat 3 Protein demand "Each gram of protein produces about 4 kcal of heat, with the same energy density as carbohydrates The recommended amount of protein intake for ordinary people is 12%} 15% of the total calories Therefore, people who consume 2000 kcal per day need 240300 kcal (60-75 g) of energy protein per day Most non athletes consume 0.8g protein per kg body weight to meet their daily needs According to this principle, a 165 pound (75 kg) non athlete needs 60 grams of protein per day If the protein requirement of kg body weight is taken as the unit, the protein requirement of athletes is higher because of the high demand of the fat free body weight and the protein of tissue repair and the need to burn a small amount of protein in sports activities This makes athletes need about twice as much protein as non athletes (1.21.7g / kg) As a result, a 165 pound (75 kg) athlete needs 120 grams (480 kcal) of protein per day Although the protein intake of 120 grams per day seems to be a lot, it only accounts for a relatively small proportion of the total energy consumption per day, i.e it can and should mainly meet the demand of nutrients through the intake of food Compared with protein, the minimum recommended intake of carbohydrates is 30 kcal per kilogram of body weight, so the 165 pound (75 kg) person's demand for carbohydrates alone is equivalent to 2250 kcal of heat energy " Athletes need to ingest more protein than non athletes for the following reasons: 1 In the process of training, the energy supply of amino acids (from protein) accounts for 5% - 15% of the combustion fuel When muscle glycogen is reduced, the protein used to provide energy is increased It is generally believed that endurance training consumes more glycogen than strength training, so endurance exercise is easy to cause a high proportion of protein consumption 2 Exercise will cause muscle damage, and tissue repair will increase the demand of protein 3 Endurance training may cause a small amount of protein to be lost in the urine (when there is no training, there is usually no protein or almost no protein in the urine) Although athletes' demand for protein has increased, most athletes take in much more protein (only from food) than they actually need This is evidenced by the protein content of some foods that are often ingested Although most athletes have no difficulty in getting enough protein, the protein intake of the following types of athletes should be carefully monitored, because it may be difficult for them to get enough protein: Young athletes with dual needs of training and growth athletes who diet for ideal weight and body size Vegetarian athletes who do not eat meat, fish, eggs or dairy products Athletes who limit food intake for religious or cultural reasons As mentioned above, we can get energy (kcal) from protein But burning protein as a fuel is like decorating breakfast food with family diamonds Although you think it improves the quality of breakfast, it is a waste of resources Protein is very important for the production and maintenance of tissues and the production of hormones and enzymes It is a waste to burn it as fuel Moreover, when protein is used as fuel for combustion, nitrogen must be removed from the amino acid chain and excreted When it is necessary to increase the excretion of nitrogenous waste, the water lost from urine must be replenished In this way, it will lead to two kinds of bad results: the waste of protein due to combustion; and the increase of water loss in the process of nitrogen-containing waste discharge, thus increasing the risk of dehydration In addition, a high protein diet increases the excretion of calcium in the urine (a significant issue for older women at risk of bone disease) Another potential problem is that the fat content of high protein diet will also be high, which may increase the risk of cardiovascular disease Therefore, the best way to ensure that the body's protein needs are met is to eat adequate, carbohydrate rich foods, as well as a small amount of dairy products and meat (in the case of vegetarians, adequate soy foods) "In a single food, meat and dairy products can provide all the necessary amino acids, but protein from plants cannot Therefore, vegetarians should pay attention to the diversification of food to optimize the availability of essential amino acids The general rule to ensure a reasonable proportion of essential amino acids is to mix grains and beans in the same meal Cereals and legumes are good sources of tau, threonine, phenylalanine and leucine Corn and other grains contain less isoleucine and lysine, while tryptophan and methionine are abundant In contrast, beans are rich in isoleucine and lysine, while tryptophan and methionine are rare By taking in grains and beans at the same time, the amino acids in the two kinds of food complement each other, so as to provide high-quality protein "