Is the relationship between protein and immunity what you think?

Let’s first learn about immunity

The main function of the human immune system is to reject foreign bodies and eliminate mutated or aged cells in the body. The basis for these functions is immune organs, immune cells and various immune molecules. Immune organs include the chest, spleen, tonsils and lymph nodes. The immune system is usually divided into innate immunity and specific immunity, and can also be divided into cellular immunity and humoral immunity. The body's immune system is a metabolically active system. A large number of immune cells and immune molecules are generated and consumed every day. Therefore, the function of the immune system is closely related to the body's nutritional status.

What is the relationship between protein and immunity?

The immune system is complex and affected by many factors. Dietary nutrition plays an important role in the growth, development and normal function of the immune system. The relationship between the immune system, immune function and dietary nutrition is mainly reflected in the fact that dietary nutrition is the material basis of systemic health, that is, the material basis of the immune system and immune function. It can be said that various nutrients are indispensable for maintaining normal immune function. Of course, the specific relationship between various nutrients and immunity is different. Protein, as one of the three major macronutrients, is particularly important. Immune cells, antibodies, complement and other various immune molecules are mainly composed of proteins.

However, with adequate nutrition, the immune system is already able to maintain normal function, and protein supplementation cannot further improve immunity. Therefore, searching major databases, there are few research results on improving immunity in normal people by supplementing protein.

The impact of dietary nutrition on immune system function is mainly manifested in impaired immune system function in malnutrition. The relationship between various nutrient deficiencies and immunity depends on the role of this nutrient in immune function, the degree of deficiency, and the state of the body. The immune function declines in protein malnutrition (deficiency). The first is humoral immunity; as nutritional status deteriorates, cellular immunity is further affected. Relevant research results are mainly that in people with protein malnutrition (deficiency), the response to vaccination is reduced, and the incidence of infectious diseases is increased. Correspondingly, after protein supplementation for people with protein deficiency, it can be seen that the immune system function returns to normal.

Soy protein deserves special attention

We generally believe that the main source of protein for the human body is animal protein. In fact, in general, the protein intake of the Chinese population is still greater in the form of plant protein than in the form of animal protein. This is especially true in economically underdeveloped areas. Soy protein is currently the plant protein with the largest output, and soybeans and their products are also an extremely important component of my country's traditional diet. Therefore, we will briefly introduce soy protein.

Depending on the protein content, soy protein is generally divided into soy protein concentrate (protein content above 70%) and soy protein isolate (protein content above 90%).

The human body's demand for protein is actually a demand for various amino acids. Of the 20 amino acids needed by the human body, 9 must be taken from food (histidine is also an essential amino acid for infants and young children). Therefore, a good protein must contain all these 9 amino acids. In addition, the human body's demand for various amino acids varies, so a good protein is one that meets the human body's needs for various essential amino acids. People of different ages have different needs for amino acids. For example, in the recommendations of the Food and Agriculture Organization of the United Nations/World Health Organization, we can see that the demand for leucine is relatively high, while that for tryptophan is relatively low. Compared with older children or adults, children aged 2-5 have the highest demand for amino acids. Soy protein isolate not only contains the 9 essential amino acids required for normal growth and development of the human body, but also the content of these amino acids can well meet the needs of people of all ages, so soy protein isolate is a high-quality complete protein. Such a protein, if used according to the currently recognized protein evaluation standard, namely PDCAAS (Protein Digestibility Corrected Amino Acid Score), is a high-quality protein with a PDCAAS of 1. Soy protein isolate is the only plant-based protein with a PDCAAS of 1. Like milk protein and egg protein, as the only source of protein, it can fully meet the human body's needs for protein and amino acids.

The body's need for protein is also reflected in quantity. According to the "Dietary Reference Intake of Chinese Residents 2013" (DRIs) released by the Chinese Nutrition Society, the daily protein intake of adult women should reach 55 grams, and that of men should reach 65 grams, which is equivalent to 1 gram of protein per kilogram of body weight per day. The Dietary Reference Intake of Chinese Residents (DRIs) also gives recommended values ​​for protein intake for different groups of people.

Of course, different proteins have different advantages for certain special needs. For example, soy protein isolate has special advantages in heart health, while whey protein has a relatively high leucine content and is more widely used in muscle building and fitness. In foods developed for lactose-intolerant patients, soy protein isolate has a natural advantage because it does not contain lactose. Vegans who give up milk protein and egg protein can also get enough high-quality protein through soy protein isolate. The production of the same amount of soy protein isolate requires less water and arable land than beef protein, and emits less greenhouse gases, etc.

In general, sufficient high-quality protein is essential for our health. For people who cannot get enough protein from their diet for various reasons (such as people with poor eating habits or picky eaters), and people who have increased protein requirements due to special circumstances (such as athletes and the elderly), it is necessary to supplement protein in moderation. They should try to choose high-quality protein with a high PDCAAS score, such as soy protein isolate.

What is the conclusion?

In the population, due to unbalanced diet or some special circumstances, the protein intake is insufficient or the demand increases, which is an objective problem. For these people, it is necessary to supplement protein in moderation. In order to improve efficiency, the protein used for supplementation should be complete high-quality protein. At present, soy protein isolate, egg protein and milk protein can be called high-quality proteins.

Insufficient protein intake may cause a decline in immune function. Therefore, it is reasonable to improve immunity by supplementing protein for people who have insufficient protein intake and weakened immunity.

For people who have adequate dietary protein intake, or people who have certain conditions that require limiting protein intake (such as patients with renal insufficiency), there is no need for additional protein supplementation, and blindly supplementing may even be harmful to the body.

Therefore, if you need to supplement protein, it is best to consult the hospital nutrition clinic or a qualified professional before making a decision.

In summary:

1. Protein is the material basis for maintaining normal immune function. Protein malnutrition (lack) will damage immune function.
2. Soy protein isolate, milk protein and egg white are complete high-quality proteins suitable for protein supplementation;
3. Protein supplementation has the effect of enhancing immunity for people with protein malnutrition (deficiency).

References:

1. Dietary Guidelines for Chinese Residents (2016). Compiled by Chinese Nutrition Society. Beijing: People's Medical Publishing House, 2016.

2. Dietary Reference Intakes of Nutrients for Chinese Residents (2013 Edition). Edited by Chinese Nutrition Society. Beijing: Science Press, 2014.

3. Modern Clinical Nutrition (Second Edition). Edited by Gu Jingfan et al. Beijing: Science Press, 2009.

4. Soybean Protein Science and Materials. Edited by Chen Yun et al. Beijing: Chemical Industry Press, 2014.

5, Cordle CT et al. Immune status of infants fed soy-based formulas with or without added nucleotides for 1 year: part 2: immune cell populations. Journal of Pediatric Gastroenterology and Nutrition. 2002;34:145–153.

6, Childs CE et al. Diet and immune function. Nutrients 2019, 11, 1933; doi:10.3390/nu11081933.

7, Nicholson LB et al. The immune system. Essays in Biochemistry. 2016;60: 275–301.