Protein is a magical life substance in the body. In the energy-yielding nutrient , the main function of sugar and fat is to provide energy to the body, while protein has dual functions: it can produce energy. At the same time, it can also provide raw materials for the organization of the body, and the growth and development of the body can be regarded as the continuous accumulation process of the protein. Therefore, it can be said that there is no life without protein. Proteins are composed of amino acids. In the body's protein metabolism, amino acids are mainly used for synthesis and catabolism. When the body is starved, the storage of carbohydrates is rapidly reduced, while fat and protein are used as energy sources for long-term energy consumption.
First, the dietary reference intake of protein
Protein intake includes two concepts of physiological requirements and supply. Physiological requirements refer to the amount of protein needed to sustain life and ensure growth and development. The supply is based on a 50% to 200% safety factor in order to eliminate individual differences and the quality of nutrients in food, maintaining a high level of health and ability to work. In 2000 , the recommended nutrient intakes recommended by the Chinese Nutrition Society were recommended for protein intake (RNIs) , which were 75 g / d and 60 g / d for adults and men, and 80 g / d for physical activity. 70g / d; heavy physical activity were 90g / d and 80g / d respectively .
Whether exercise increases the amount of protein required, the conclusions of the study are not completely consistent. For the fitness population, protein intake should be 12-15% of total calories, about 1.2-2.0g/kg body weight. And not only must meet the requirements in quantity, at least one-third of the quality of the essential amino acids, including animal protein. Among them, soy protein is also a high quality protein. Some people think that eating more protein will promote muscle growth, but it turns out that under the premise of progressive strength training, the right amount of protein can make muscles grow. Excessive protein intake cannot synthesize too much muscle. And excess protein is harmful from a medical point of view. It will increase the burden on the liver and kidneys ; lead to increased fat storage ; cause dehydration and acidification of body fluids, causing fatigue to occur early.
Second, a reasonable choice of dietary protein
After clarifying the amount of protein our body needs to consume every day, what we need to do is to rationally choose food to match the diet and meet the protein needs of the body. Foods that provide protein are multifaceted, such as casein in milk, lactalbumin, egg albumin in eggs, egg phosphoprotein, albumin in meat, muscle protein, soy protein in soybean , wheat Gluten, gluten, etc. in corn. Therefore, in addition to meat and other meat products such as beef and mutton, eggs and dairy products, including rice, wheat and other grains, are our way to obtain protein. Because the amino acid composition of each food is not the same, in order to make the body's essential amino acid species and quantity ratio suitable, we advocate a mixed intake of a variety of protein-containing foods, so that the protein in the food complement each other and improve the protein in the diet. value.
The quality of the protein in the food is also one of the basis for our choice to supplement the protein. The ease with which proteins in food can be digested by the body varies from food to food. For example, the protein in oats is harder to digest than in eggs. In general, because the amino acid composition of the protein is close to that of the human body, the amino acids in the animal protein are most easily digested and absorbed, and the utilization rate can reach more than 90% , followed by the legume protein ( about 80% ) , cereals and The absorption efficiency of other plant proteins is low. For men, animal protein, such as meat, fish, eggs, and milk, is the best source of protein in the diet, whether it is to maintain health and maintain body energy or to meet the needs of bodybuilding and muscle growth.
Third, high protein content of food
meat
The protein of meat is mainly found in lean meat, which is mostly fat. Each 100 grams of lean pork contains 20.3 grams of protein and 6.2 grams of fat. Each 100 grams of chicken contains 19.3 grams of protein and 9.4 grams of fat. The protein content of lean beef is comparable to that of pork, containing 20.2 grams of protein per 100 grams, but with a fat content of only 2.3 grams. The protein and fat content per 100 grams of lean lamb is 20.5 grams and 3.9 grams, respectively. Therefore, from the perspective of limiting fat intake, lean beef and mutton should be selected as the main meat supplementing protein. Arranging more than seven or so lean beef in three meals a day can satisfy the day's protein needs of male white-collar workers who often sit in the office. Of course, if you are still doing bodybuilding exercises, then the amount of protein you need per day is higher. It is recommended that you use protein and other nutritious foods such as protein powder to increase the protein content of your muscles, while avoiding protein intake and avoiding intake. Too much fat that is bad for the body.
After slaughtering livestock and poultry, a series of biochemical reactions occur in the meat tissue under the action of enzymes, which makes the meat more elastic, and the food value is the highest at this time. Some people think that "eat meat is not as good as soup," and this understanding is not comprehensive. In the cooking process, in addition to some water-soluble nutrients, some of the nitrogenous substances in the meat are dissolved in the soup, so that the soup tastes delicious, but after boiling, the protein of the meat will coagulate with heat, so most of the protein remains in the meat. Among them, the protein dissolved in the soup is only a small part.
Egg
All kinds of eggs are basically the same in nutrients, and eggs are more commonly eaten. Eggs are the most absorbing foods in the human body. The proteins in egg whites and egg yolks are high-quality proteins, which contain 8 kinds of essential amino acids, and the utilization rate can reach 99.7% . It contains 13.3 grams of protein per 100 grams of egg. In addition, eggs also contain a large amount of lecithin and calcium, phosphorus, iron and other elements and vitamins, so eggs have a higher nutritional value.
When eating eggs, be careful not to eat raw, because the egg whites of raw eggs contain some substances that affect the activity of B vitamins in eggs. In addition, the anti-trypsin present in the protein of raw eggs also affects the absorption of protein in the gastrointestinal tract and reduces the edible value of eggs. There are usually a large number of harmful bacteria on the surface of the eggshell, and egg yolk egg white and the like are easily contaminated by these harmful bacteria after the eggshell is broken. Therefore, be sure to cook, cook and eat when eating eggs. Generally, it is advisable to eat 1 or 2 eggs per day. Excessive consumption will consume too much cholesterol and protein, increasing the burden on organs such as liver and kidney.
Milk
The protein content of milk is also very rich. The protein content in milk is higher than that of human milk. 25 kinds of amino acids including 8 essential amino acids are mainly tyrosine, and the physiological value is second only to eggs. The milk supplied on the market includes raw milk, pasteurized milk, sterilized milk, etc., wherein the raw milk has a short shelf life but is nutritious and retains most of the active ingredients in the milk.
In dairy products, the protein of yoghurt is more easily digested and absorbed by the fermentation of lactic acid bacteria, and has a positive effect of promoting secretion of gastric juice and lowering blood cholesterol concentration. White-collar workers who operate computers in the office, men who regularly smoke alcohol, bones and patients with cardiovascular disease are advised to drink more yogurt.
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