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When it comes to protein, it's not too familiar to people who love meat and build muscle.
Protein is the material basis of all life; and all manifestations of life are essentially the embodiment of protein function.
It can be said that there is no life without protein!
As one of the essential nutrients of human beings, protein plays an important role in maintaining the stability of muscles, bones and nerves, enhancing immune system function, and promoting metabolism.
Although protein is good, don't be greedy
If you don't eat enough protein, it will cause various health problems. Like what:
- When energy intake is sufficient, and protein intake is severely insufficient: patients may present with abdominal and leg edema, weakness, apathy, slow growth, discoloration of hair, fragile and easy loss of hair, susceptibility to infection and other diseases.
- When both protein and energy intake are severely inadequate: patients may experience wasting weakness, decreased physical strength, decreased resistance, decreased appetite, dry skin and poor elasticity, thinning and yellow hair, and dryness.
Therefore, eating adequate protein is essential for maintaining a normal and healthy life.
However, this does not mean that meat lovers can open their bellies and enjoy the big fish and meat to the fullest.
Eating too much protein is also harmful to the human body, especially animal protein:
- Eating too much animal protein will inevitably eat more animal fat and cholesterol at the same time, which will not only invisibly increase energy intake, but also may lead to abnormal metabolism of blood lipids in the body.
- Eating too much protein itself can also have harmful effects on health. Because the process of protein metabolism (protein deamination is decomposed, nitrogen is excreted from the urine) requires a lot of water, which increases the burden on the kidneys, if the function of the kidneys themselves has been damaged, the harm will be greater.
- Eating too much animal protein will lead to excessive intake of sulfur-containing amino acids, which will accelerate the loss of calcium in the bones, which is prone to osteoporosis.
- Eating too much protein may lead to excessive intake of homocysteine, and excessive intake of homocysteine may be a risk factor for heart disease. The study found that men who consumed too much homocysteine had a 3-fold increased risk of developing heart disease compared to those who consumed normal protein.
- If too much protein is consumed and too little carbohydrate is consumed (such as a ketogenic diet, etc.), the risk of metabolic acidosis may increase, which can lead to coma and death.
- In addition, eating too much protein may be associated with some cancers, such as colon cancer, breast cancer, kidney cancer, pancreatic cancer and prostate cancer.
You see, although protein is so important, you can't eat too much, you can't eat too little.
So how much protein should I eat?
To promote good health, the amount of protein that needs to be consumed varies for people of different ages, genders, and physical activity. The specific intake recommended in the "Reference Intake of Dietary Nutrients for Chinese Residents" is shown in the following figure:
▲Reference intake of dietary protein for Chinese residents. AI: appropriate intake; EAR: average requirement; RNI: reference intake. (Image source: References[1])
According to the textbook "Food Nutrition and Hygiene (8th Edition)", the recommended daily intake of protein for Chinese adults is 1.16 g per kilogram of body weight.
That is, for a woman who is healthy and weighs 50 kilograms, the recommended daily protein intake is: 50 * 1.16 = 58 grams.
However, if there is a specific disease or situation, it is recommended to consult a clinical dietitian or doctor. A study published in the Journal of Sports Science & Medicine noted that for patients with kidney disease, it is recommended to limit protein intake to 0.8 g/kg of body weight.
Usually, if the daily protein intake is 1.2 g/kg of body weight ~ 2 g/kg of body weight, it can be called a high-protein diet.
The negative effects of high-protein diets on the human body have been briefly introduced at the beginning of the article. If you want to try a high-protein diet, be sure to consult a professional nutritionist or dietitian first.
So you see, protein is not to eat as much as you want, only a scientific and reasonable diet can be alive in the new year!
So in daily life, how to eat high-quality protein?
High-quality protein is eaten like this
While protein is available in a variety of foods, not every food contains high-quality protein.
In some foods, the type and quantity of amino acids of protein are very close to the protein pattern of the human body, so it is conducive to our absorption and metabolism, and the nutritional value is higher.
We call this kind of food that is close to the body's amino acid pattern as high-quality protein (complete protein). High-quality protein not only maintains the health of adults, but also promotes the growth and development of children.
The high-quality proteins in the daily diet are: eggs, milk, meat, fish and other animal proteins, as well as soy protein in soybeans.
It should be noted that the protein in eggs is closest to the amino acid pattern of human proteins, which can be called the best quality protein, and is also commonly used as a reference protein (standard protein).
Typically, an egg contains at least about 6 grams of protein. For people who don't like to eat meat or are vegetarians, it is a good choice to supplement high-quality protein by eating eggs.
In addition to protein, eggs are also a good source of vitamins and minerals. Among them, vitamins are mainly concentrated in egg yolks, including vitamin A, vitamin E, vitamin B2, B5, B6 and B12, folic acid and so on.
There are so many types of eggs, is there a difference in nutritional value?
The Dietary Guidelines for Chinese Residents (2016) point out that although the nutrient content in eggs is affected by the variety, season and feed, the nutrient content in various eggs such as white eggs, yellow eggs, and native eggs does not vary greatly.
But if the eggshell of the egg is not clean enough (chicken manure), it needs to be paid attention to. Because Salmonella easily contaminates eggs through the pores of the eggshell.
If you eat contaminated eggs, you may cause Salmonella infection, which can cause nausea, vomiting, abdominal pain, watery diarrhea, fever and other symptoms.
In addition, animal foods such as beef, pork, chicken, turkey, and fish are also one of the excellent sources of protein.
If you want to supplement your protein with meat, it is best to eat lean meats, white meats (such as skinless chicken breasts and fish), and avoid processed and fried meats such as ham, bacon, hot dogs and sausages.
When supplementing protein, in addition to paying attention to which foods to eat, you should also pay attention to the way of processing, try to choose the way of steaming and cooking, and avoid frying or roasting.
Since there is a high-quality protein (complete protein), is there a non-high-quality protein (semi-complete protein)?
In fact, most plant-derived proteins are semi-complete proteins. Because the type or quantity of amino acids in the protein of these foods is not close to that of the human body, the digestion and absorption of protein will be affected after eating alone.
as:
- Although nuts are rich in protein, some nuts have relatively low amino acid content, and walnut protein is not enough in methionine and lysine.
- Staple foods such as rice, flour, and corn lack lysine.
In order to improve the nutritional value of plant proteins, it is recommended to eat two or more foods together and eat together with different foods, which is conducive to protein amino acid complementarity (protein complementarity) between different foods.
For example, protein in meat and legumes can compensate for the lack of lysine in rice, corn and pasta.
Therefore, the "Dietary Guidelines for Chinese Residents" recommends that the variety and diversity of food be improved in the daily diet: it is required that 5 major types of foods should be included in the daily diet, with an average of more than 12 kinds of foods eaten per day and more than 25 kinds of foods per week, paying attention to balanced diet and meat and vegetarian combinations.
Resources
Nutritional intake of Chinese residents. Retrieved Dec 7 ,2021,from http://www.gxcdc.com/uploadfile/2018/0709/20180709041508867.pdf
[2] 7 Top Healthy Protein-Rich Foods. Retrieved Dec 7,2021,fromhttps://health.usnews.com/wellness/food/slideshows/top-healthy-protein-rich-foods
[3] Plant protein vs. animal protein: Which has the greatestimpact bone health? . Retrieved Dec 7 ,2021,fromhttps://nutrition.org/plant-protein-vs-animal-protein-which-has-the-greatest-impact-bone-health/
[4] Hoffman, J. R., & Falvo, M. J.(2004). Protein–which is best?. Journal of sports science &medicine, 3(3), 118.
[5] Sun Changhao.et al., (2017) Food Nutrition and Hygiene (8th Edition). People's Medical Publishing House
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