Reasonable diet is the material basis for ensuring good immunity. Mineral elements have important physiological functions in the human body, most of them maintain the integrity of immune cells by participating in the formation of nucleic acids and enzymes and energy metabolism in the body, and have a certain impact on both specific and non-specific immunity of the body.

On the one hand, elements of iron, selenium, zinc and copper not only contribute to the formation of antibodies, but also promote the proliferation and activation of lymphocytes, which play a role in maintaining immunity.

On the other hand, free radicals are generated during the immune response, and iron, zinc, selenium, and copper, as components of enzymes, exert antioxidant effects through enzymatic reactions.

Mineral deficiencies produce certain diseases, and a person’s appetite is affected in a state of illness, which in turn affects food digestion, absorption, metabolism, and growth and development, which in turn can indirectly affect the immune system [1-4].

Iron

Iron is an important trace element in the human body that maintains normal hematopoietic function and participates in the transportation of oxygen. Iron deficiency can cause fatigue, panic and shortness of breath, dizziness, and pallor; iron deficiency in children can affect growth and intellectual development, and irritability; iron deficiency in infants can impair cognitive ability and irreversible neurodevelopmental damage; long-term iron deficiency impairs oxidative metabolism in muscles, reducing physical endurance and athletic ability; iron deficiency also affects cell-mediated immunity, reducing the body’s resistance to infection; iron deficiency in pregnant women is associated with preterm birth and low birth weight; and iron deficiency is associated with premature birth and low birth weight, which can indirectly affect the immune system [1-4]. Iron deficiency is associated with preterm labor, low birth weight and fetal death [2-4].

The average daily iron intake of urban and rural residents in China is 21.4 mg, and the recommended daily amount of iron for men aged 18 to 50 years is 12 mg and for women is 20 mg, with 66.7% of the total number of people reaching the RNI recommendation [5, 6]. However, the prevalence of iron deficiency anemia is 20% in women and up to 35% in pregnant women in China. The overall intake of iron is not low, yet iron deficiency remains common, which is related to iron absorption.

Iron absorption is closely related to the body’s iron nutritional status, physiopathologic changes, dietary iron content and presence of forms. Iron exists in two forms in food: heme iron and non-heme iron. Heme iron exists in animal food hemoglobin and myoglobin, accounting for less than 10% of the total dietary iron, absorption rate of 10 to 40%, absorption by dietary factors is very small, but too much calcium in the diet can reduce the absorption of heme iron.

Non-heme iron mainly exists in plant foods and dairy products, accounting for more than 90% of the total dietary iron, non-heme iron needs to be separated from organic matter first, be reduced to heme iron to be absorbed, the absorption rate is less than 10%, the absorption of dietary factors have a greater impact.

Dietary factors to promote the absorption of non-heme iron are vitamin C, organic acids, vitamin B2, vitamin A, meat factor, the body needs to increase. Dietary factors that inhibit non-heme iron absorption are phytic acid, oxalic acid, ellagic acid, polyphenols, excessive dietary fiber intake, calcium, zinc, soy protein, and yolk high-phosphate protein. It is important to maximize the facilitating effect and avoid the inhibiting effect in the diet.

Calcium

Calcium is the element that makes up bones and teeth and is involved in regulating the release of many hormones and neurotransmitters. Calcium deficiency can lead to symptoms such as bone softening and osteoporosis. Calcium is closely related to the human immune system, and calcium deficiency in the human body decreases the activity of immune cells and the secretion of antibodies, which makes children susceptible to recurrent infections, and the elderly fall ill due to decreased resistance [7].

The recommended daily amount of calcium for people aged 18-50 years in China is 800 mg, and the recommended daily amount of calcium for people over 50 years old is 1000 mg, while the average intake of calcium in China is 364.3 mg/d, which is less than half of the recommended amount [5, 6].

Milk and milk products are the best source of calcium for those who tolerate cow’s milk, with an average calcium content of 100 mg in 100 g of fresh milk, 118 mg in 100 g of yogurt, and even more calcium in skim milk powder. The lactose in milk promotes the absorption of minerals such as calcium, iron and zinc.

For lactose intolerant people, you can consume yogurt, cheese, lactose hydrolyzed milk. Soybeans and their products are a good source of calcium. Tofu contains 110 to 140mg/100g of calcium.

Zinc

Zinc is essential for the normal development and function of cells that mediate innate and adaptive immunity, and has the ability to promote sexual development and maintain sexual function. Fetal growth and development, and children’s bone growth are closely related to the level of zinc in the body, and zinc combines with salivary proteins to form gustatory hormones, which can enhance appetite, and zinc affects the activity of digestive enzymes, which alters digestive function. Zinc can maintain skin health, control the secretion and production of immunomodulatory factors, and affect the development of lymphoid organs and antibody synthesis.

In addition, zinc is involved in nucleic acid and protein metabolism, which also indirectly affects the immune system [8]. In China, the daily recommended amount of zinc for men aged 18-50 years is 12.5 mg, and that for women aged 18-50 years is 7.5 mg, and the average daily zinc intake of urban and rural residents in China is 10.7 mg [5, 6].

Shellfish, red meat, and animal offal are excellent sources of zinc, and dried fruits, cereal germ, and wheat bran are rich sources of zinc.100g of oysters contains 71.2mg of zinc, 85g of cooked oysters contains 67mg of zinc, 100g of wheat germ flour contains 23.4mg of zinc, 100g of pecans contains 12.6mg of zinc, 85g of lean steak contains 4.9mg of zinc, 250ml of plain yogurt contains 2.2mg of zinc, and 85g of pecans contains 12.6mg of zinc. 2.2mg, 85g boiled shrimp contains 1.5mg of zinc, 85g pork chop contains 2.8mg of zinc.

Iodine

Iodine is involved in the synthesis of thyroxine. Thyroxine is a very important hormone in the human body that promotes physical and brain development. Iodine deficiency during fetal life can cause stillbirth, congenital malformations, high postnatal mortality, fetal hypothyroidism, affecting physical and brain development, and cretinism.

Iodine deficiency in childhood causes goiter, mental and physical developmental disorders. Iodine deficiency in adulthood causes goiter and hypothyroidism.The recommended daily amount of iodine for adults over 18 years of age is 120 μg, the daily requirement of iodine for pregnant women is 230 μg, and for lactating mothers is 240 μg [5].

People in low iodine areas can consume iodized salt for iodine supplementation, and people in plain areas consume iodized salt appropriately. The iodine requirement during pregnancy has nearly doubled compared to pre-pregnancy, and a daily intake of 6g of iodized salt, which can be obtained from salt, is about 120 μg of iodine, which can satisfy the iodine needs of women in general, but can only satisfy half of the iodine requirement of pregnant women, and it is recommended that pregnant women consume seafood 1 to 2 times a week to satisfy the iodine requirement of pregnant women. Seafood is rich in iodine, 100g of fresh kelp, 2.5g of dried seaweed, 0.7g of dried wakame, and 40g of marine fish can all provide 110μg of iodine.

Mineral elements are involved in important physiological functions of the human body, and the intake of appropriate amounts of mineral elements is the basis for ensuring good immunity. A balanced diet is an effective way to obtain the right amount of minerals. To improve immunity, start with a balanced diet.