Micronutrients deficiencies: impact on infants’ immune system

There is no “miracle food” that can prevent diseases. However, micronutrients play an essential role in strengthening immune defenses. Inadequate intakes can lead to a deficiency of the immune system, predisposing children to infections and exacerbating undernutrition.

Vitamin A

Vitamin A helps the immune system of infants fight infections. Indeed, it plays a very important role in regulating immune responses and in the generation of antibodies¹.   Vitamin  A deficiency causes increased sensitivity to various pathogens in the respiratory and gastrointestinal tract. Children deficient in vitamin A have an increased risk of developing respiratory and diarrheal diseases and an excessive inflammatory response¹.  A good intake of vitamin A restores the generation of antibodies, reduces the incidence of respiratory tract infections and reduces mortality associated with diarrhea².

Food sources of vitamin A³:  

• Dairy products (cheeses, milks and yoghurts)
• Eggs
• Oily fish (mackerel, salmon…)
• Enriched margarine
• Enriched cereals

Vitamin C

Ascorbic acid (or vitamin C) is an essential component of every living cell.  It intervenes in the defense against viral and bacterial infections and strongly promotes the absorption of iron⁴. Highly concentrated in leukocytes, it is used quickly during an infection to prevent oxidative damage from reactive oxygen species (ROS)^1.2. Reduced concentrations of this vitamin in leukocytes are associated with reduced immune functions resulting in anergia in almost all components of the immune system². A balanced intake of vitamin C improves several components of the immune response and improves the absorption of iron, an important modulator of the immune system¹.

Food sources of vitamin C³:

• Bell peppers
• Broccoli and sprouts
• Red fruits (strawberries, blackcurrant, raspberries…)
• Lemons, oranges, kiwis, guava
• Enriched cereals

Vitamin D

In addition to its effects on calcium and bone metabolism, vitamin D acts as a powerful immuno-regulator¹. Its concentration impacts, in particular, the differentiation and activity of cells of the immune system. Vitamin D stimulates the expression of anti-microbial peptides, found in innate immunity cells (neutrophils, monocytes…) and in the epithelial cells lining the respiratory tract¹. Thus, vitamin D deficiency predisposes children to respiratory infections¹. Newborns, infants and pregnant women are most at risk of vitamin D deficiency⁵.  Sun exposure is the most natural way to get enough vitamin D (15 minutes per day) but the intakes may also be increased through diet or supplements⁵.

Food sources of vitamin D³:  

• Oily fish (salmon, sardines, mackerel…)
• Eggs
• Enriched margarine
• Enriched cereals

Iron

Iron occurs at all levels of the immune system modulation. It is essential for oxygen transport as well as for cell growth and differentiation, including that ofT lymphocytes^1,2. It also plays an important role in regulating cytokines production and in the process of bacteria destruction by neutrophils¹. Thus, iron deficiency affects the ability to have an adequate immune response (maturation, differentiation and proliferation of immune cells)⁶. A balanced intake of well-absorbed iron and coupled with vitamin C helps prevent iron deficiency.

Food sources of iron^3.7:

• Meat (especially red meat)
• Fish
• Fortified infants formulas and growing-up milks
• Enriched cereals             
  
  

Zinc

Zinc is a dietary trace element that, beyond its essential functions in growth and development, plays an crucial role for high-proliferation immune cells and influences innate and adaptative immune functions¹. Zinc deficiency hinders hostdefense process, increasing the child’s susceptibility to various pathogens². Thus, ensuring adequate zinc intakes is essential for optimal immune function and protection against infectious pathogens².

Food sources of zinc³:

• Cereals products, such as wheat germ
• Meat
• Seafood
• Dairy products (milk, cheese)
• Bread

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