The importance of protein in nutritional health is indisputable. Especially in the current COVID-19 battle, it has been recognized that adequate protein is important for maintaining normal immune function and strengthening resistance.
From the source, protein can be divided into plant protein and animal protein.
Proteins from different sources vary greatly in many ways. Understanding these differences can help us choose protein rationally and maintain and improve our health better (soybean protein is the most productive plant protein, and soy and its products are also an important part of our traditional diet. Therefore, the following introduction mainly refers to soy protein).
植物蛋白和动物蛋白的主要区别包括：Key differences between plant and animal proteins include:
结构和存在方式不同 Different structures and modes of existence
From the protein molecule, the protein is a peptide chain of amino acids (the first class structure), the peptide chain forms a spiral or fold (secondary structure), further winding formation group (tertiary structure), various groups are grouped together in a certain pattern (class 4).
The secondary structure of plant protein is dominated by the “β-folding”, and animal protein is dominated by the “α-spiral”. From the presence of protein in food, plant protein is often combined with carbohydrates (non-starch polysaccharide and dietary fiber), and animal proteins mainly coexists with fat.
All these factors will bring about the difference in nutritional value between plant protein and animal protein. Animal protein, for example, is often accompanied by a high intake of saturated fats. Edible soybean includes both soybean protein and functional components such as dietary fiber, isoflavone and soybean phospholipid.
The human body’s demand for protein, first of all, needs to have enough amount (adults need 1 gram per kilogram of body weight every day). Second, the protein quality should be ensured that can fully satisfy human body nutrition health demand.
We need dietary protein to provide 20 amino acids; If there are not enough of these amino acids, some can be “borrowed”(the body synthesizes non-essential amino acids or indirectly from other nutrients), and some must be obtained from food (the nine essential amino acids cannot be borrowed).
消化率不同 Different digestibility
Digestibility refers to the degree of decomposition of protein by digestive enzymes and the degree of absorption of amino acids and peptides after digestion. The more food is absorbed by the body, the higher its nutritional value. General egg protein is often used as a reference protein with a digestibility of 100%. The accepted measure of protein quality is the “Protein Digestibility Corrected Amino Acid Score”（PDCAAS）,with a score of 1.
The four players currently tied to the first one are: whey protein, casein, egg protein, and soy protein. The PDCAAS 1 means that the protein contains all the nine necessary amino acids that the body needs, and every one reaches the amount required (there should be a wooden bucket in your head, with nine boards, and any one of them is short of the water). In other words, if you’re capricious and want to eat just one protein and still be healthy, the only way you can do that is by choosing a protein with PDCAAS 1.
Plant proteins often coexist with phytic acid, protease inhibitors, phytohemagglutinin, tannic acid and other antinutritional factors that affect digestion. Coupled with structural differences, plant proteins tend to have a lower digestibility than animal proteins. Therefore, food processing is particularly important for improving the digestibility of plant protein. Just by cooking food, you can increase protein digestibility by 18%. Soybean meal has a protein digestibility of only 80%, while soy protein isolate can reach 98%.
健康作用不同 Different health effects
Compared with animal proteins, plant proteins have many health benefits, including a reduced risk of cardiovascular disease, type 2 diabetes and some cancers.
For example, milk protein has the function of controlling body weight and lowering triglycerides, while isolated soy protein has a more obvious effect on lowering blood lipids (triglycerides, total cholesterol and LDL-C can all be reduced) than milk protein. Soy protein can also lower blood pressure, improve insulin sensitivity, and reduce the level of inflammation in the body.
Regulatory authorities in 13 countries and territories, including the U.S. FDA, have certified 25 grams of soy protein a day to reduce the risk of heart disease.
对环境影响和可持续性不同 Different environmental impact and sustainability
Compared with animal protein, plant protein has obvious advantages in environmental protection and sustainability. For example, producing 1kg of isolated soy protein releases 2.4kg of carbon dioxide into the environment, while producing the same amount of beef protein is 178kg.
Other animal proteins such as chicken and pork, also have much higher greenhouse gas emissions than soy. It takes 8 square meters of farmland a year to produce 1 kilogram of isolated soy protein, and 1311 square meters of beef protein.
In the past few years, the burning of the Amazon rainforest, the fires in Australia, the high summer temperatures in Europe, the melting of the glaciers in both the North and the South etc. have made more and more people realize the urgency of reducing greenhouse gas emissions.
How can we get enough protein from our diet? Here are some specific recommendations for protein intake:
足量 Adequate intake
Different populations have different protein requirements. In general, adults need 1 gram of protein per kilogram of body weight per day, while the elderly need a modest increase to 1.2 grams or more. Protein needs vary by age: 30 grams per day for 3-5 year olds, 35 grams per day for 6-year olds, 40 grams per day for 7-8 year olds, 45 grams per day for 9-year olds, and 50 grams per day for 10-year olds. The peak protein needs are 14 to 18 year olds, 75 grams per day for boys and 60 grams per day for girls. Who gets sick depends on the circumstances. Human body is right protein demand, not be in the light of some kind of protein setting, accordingly, no matter give priority to with animal protein or plant protein, should absorb sufficient amount of protein.
Diversity of protein sources helps ensure that the body gets all the amino acids it needs through complementation. For example, grain protein is relatively low in lysine, soy protein is low in sulfur amino acids, whey protein is high in leucine etc. Emphasizing the diversity of protein sources is actually the application and embodiment of dietary diversity in protein. For example, the combination of plant protein and animal protein; combination of plant proteins (such as beans) or animal proteins (livestock, poultry and fish), etc.
In the implementation of the “Dietary Guidelines for Chinese Residents” recommended to eat 12 kinds of different foods a day, 25 kinds a week, pay attention to the collocation of food rich in protein, which is conducive to the balance of protein nutrition. In some cases, choosing the right sources of protein and mixing them together is better for your health. For example, patients with chronic renal insufficiency need to reduce protein intake appropriately, and soy protein isolate may be more suitable for them as a protein source because of its advantages in lowering blood lipids, lowering blood pressure, anti-oxidation and regulating calcium and phosphorus metabolism. For muscle synthesis and recovery after exercise, the mixture of isolated soy protein and milk protein in proper proportion is better.
Dietary factors play a very important role in health. For chronic diseases such as cardiovascular disease, type 2 diabetes and tumor, dietary factors are the biggest risk factors. But unfortunately, there are still many people who do not form good eating habits. For example, children and teenagers are becoming more and more picky about food. And old people, often because the increase of age and physiological function are reduced, the necessary dietary adjustment fails to be made actively and bring about protein intake to wait for inadequacy “recessive malnutrition”.
Therefore, it is necessary to supplement some protein when balanced and adequate nutrition is not achieved through the diet.
Soy protein isolate or soy protein isolate mixed with milk protein products can be selected for protein supplement. Soy protein isolate has incomparable advantages in heart health, lowering blood lipids, lowering blood pressure, delaying kidney function decline, and environmental protection. How much supplement is appropriate, should consult a doctor or dietitian, depending on their own situation. For most protein powder products on the market today, the recommended amount of supplement is between 10 and 20 grams per day.
In a word, plant protein is an important source of dietary protein. At present, the majority of protein consumed by humans comes from plant sources, especially in Asia and Africa. Although the animal protein in the diet of Euramerican developed country is more than plant protein, but in recent years, plant protein gets more and more favour, a strong meal “plant wind” already blown all over the world. As a country with a long history of plant-based diet and an excellent dietary tradition, it is of great significance for us to study and use plant protein.