Proper nutrition is an important condition for maintaining normal immune function, and malnourished people usually have poor immunity, increased risk of infection, and higher case fatality rate. Vitamins are a class of organic compounds necessary in the process of human life activities and play a vital role in all stages of the immune response. Vitamins exist in natural foods, the human body generally can not synthesize, must be supplied by food, can be divided into fat-soluble (vitamin A, D, K, E) and water-soluble (B vitamins, vitamin C) two categories.
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Vitamin A - the "patron saint" of the first line of defense of immunity
Vitamin A is a general term for a class of compounds containing the biological activity of retinol, which have the functions of maintaining normal vision, promoting epithelial tissue proliferation and differentiation, and promoting growth and development in children. It participates in the whole process of maturation of the human immune system, can improve the stability of cell membranes, maintain the integrity of the mucosal barrier, and is the "guardian saint" of the first line of defense of immunity.
The recommended intake of vitamin A for adults in mainland China is 800 mcg RAE per day for men and 700 μg RAE per day for women. The foods that contain the most vitamin A in daily life are liver and eggs. A healthy adult can meet the need for vitamin A by consuming pork liver 1 to 2 times a month, about 1 to 2 taels each time. The carotenoids contained in vegetables and fruits can be converted into vitamin A in the body, especially dark green and reddish vegetables, such as broccoli, carrots, spinach, etc., can also play a role in supplementing vitamin A.
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B vitamins - "assist" the normal functioning of the immune system. B vitamins are a "big family" that includes vitamins B1, B2, niacin, pantothenic acid, folic acid, B12, and more. B vitamins are important coenzymes involved in the metabolism of the three major nutrients in the human body, and are indispensable water-soluble vitamins for maintaining the normal functions of the human body. B vitamins can mediate immune regulation, assist the normal functioning of the immune system, such as participating in the proliferation, differentiation, maturation and activation of lymphocytes, and regulate the production of cytokines; Vitamin B12 is an immunomodulator of cellular immunity; Folic acid supports immune response, etc.
B1 and B6 are abundant in meat, vegetables, grains and legumes. B2 is widely distributed in food, and the content in animal foods is relatively high, especially liver, eggs, milk, etc. Most of vitamin B12 comes from meat, such as fish, animal offal, eggs, milk, etc.
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Vitamin C - the "number one helper" for boosting immune function
Vitamin C promotes collagen synthesis, promotes wound healing, whitens the skin, and aids immune defenses by supporting various cellular functions in nonspecific immunity and specific immune responses.
The recommended intake of vitamin C for adult residents of China is 100 mg/day. The main food source of vitamin C is fresh vegetables and fruits, such as broccoli, peppers, cabbage and prickly pears, kiwi fruit, strawberries, etc., one pound of vegetables and half a kilogram of fruits per day is enough to provide the daily vitamin C needs, and the general population does not need additional supplements.
It should be noted that vegetables and fruits should be eaten fresh through daily diet, because the content of vitamin C will be greatly reduced over time. In addition, vitamin C is easily decomposed by high temperature, and for vegetables, it is recommended not to overcook if it can be eaten raw.
Vitamin D – a regulator of immunity
In the 20th century, researchers experimentally proved that vitamin D is the component of cod liver oil to treat rickets. Because it is the fourth named vitamin, it is called vitamin D. Vitamin D, also known as anti-rickets vitamins, its main role is to regulate calcium and phosphorus metabolism, promote intestinal calcium and phosphorus absorption and bone calcification, and maintain the balance of blood calcium and blood phosphorus. When the body is deficient in vitamin D, rickets, osteomalacia, etc. will occur. Vitamin D receptors are widely present in immune cells, so they can participate in the proliferation and differentiation of a variety of immune cells. In addition, vitamin D can both enhance the innate immune response and suppress the acquired immune system, thereby regulating the immune response.
The recommended intake of vitamin D for adult residents of China is 10 mcg/day. Vitamin D is abundant in animal foods such as liver, eggs, dairy products, etc., of which fatty fish is a good source of vitamin D. Sun exposure is also the most important, natural and economical source of vitamin D, hence the name "sunshine vitamin."
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Vitamin E's first line of defense against lipid peroxidation
Vitamin E protects cells and internal structures from being destroyed, preventing the destruction of certain enzymes and internal cellular components. Vitamin E is an important fat-soluble antioxidant in cell tissue, which is the body's defense against lipid peroxidation, thereby protecting cell membranes from free radical damage, and is important for maintaining the normal function of immune cells.
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The appropriate intake of vitamin E for adult residents in China is 14 mcg/day. Vitamin E-rich foods are widely distributed, and cooking oils are often the main source of vitamin E that people get from their diets. In addition, there is a certain amount of vitamin E in beans, nuts, and vegetables. On average, eat a handful of nuts every day, stir-fry with 20~25 grams of vegetable oil can meet the needs of the human body.
There is no better doctor in the world than our own immune system. Vitamins are essential for maintaining the body's normal immune function, and providing the various vitamins needed by the human body through a healthy and balanced daily diet can build an indestructible line of defense for the body.