The First 1000 Days: Nutrients for the Immune System
Infant immunity is directly influenced by growth and development in the womb, despite the protections afforded to them by the maternal immune system. Characteristic of a strong immune system is the ability to overcome illness and a reduction in susceptibility to infection, and this is a development of both excellent nutrition during pregnancy, and exposure to micro-organisms during infancy.
What is the immune system?
The immune system contains many different types of cells, proteins, metabolic pathways, and organs, each with specialized functions. Together they form immune responses that fight off pathogens (i.e., bacteria, viruses, fungi, parasites).
What is the role of the immune system?
As an infant grows, the developing immune system is challenged via exposure to such pathogens – this is an important process, as it allows the immune system to strengthen itself and develop “memory”, or a system of recognition of previously identified threats. In addition, tolerance must also be established, to allow for the distinction between harmful foreign material (such as viruses) from non-harmful foreign material (such as food). Insufficient immune memory development is detrimental to children over time, as it may impede their ability to avoid re-infection by previously encountered pathogens; conversely, poor immune tolerance can lead to allergies and autoimmune diseases.
Nutrients for the immune system
The production and differentiation of immune cells, proteins and structures relies on adequate nutrition, which can be achieved through consumption of sufficient quantities of vitamins A, B6, B9, B12, C, D & E; trace elements such as zinc, copper, selenium, and iron; and omega-3 fatty acids such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA).
The Best Nutrients for Immune Protection
Vitamins for immune system health
Vitamins A, B(-group), C, D & E are essential parts of the growing immune system, as well as in overall health & well-being. Collectively found within almost all cereal grains, red meat, fruit and (green, leafy) vegetables, a balanced diet ensures that their intake is sufficient to imbibe the body with all their benefits. Table 1 below summarises the effects of each of these vitamins, with respect to immune function.
Table 1: Summary of vitamins for immune system health.
|Vitamin A||Maintains cell integrity and plays a key role in allowing immune cells (i.e., macrophages, lymphocytes, natural killer cells, and neutrophils) to maintain their normal function.|||
|Pyridoxine (B6)||Required to produce antibodies; deficiency in B6 decreases lymphocyte population and specific immune cell effectiveness, but this can be corrected with B6 supplementation.||[1-3]|
|Folate (B9)||Required for DNA/RNA synthesis and cell division; Deficiency (megaloblastic anaemia) leads to improper responses to stimuli by immune cells involved in allergy and viral infections (can be corrected with folate supplementation).||[1-2, 4-5]|
|Cobalamins (B12)||Key vitamin in DNA synthesis and cell replication; Deficiency leads to decreased immune cell populations and improper responses by immune cells involved in allergy and viral infections – can be reversed with more B12.||[1-2, 6]|
|Vitamin C||Antioxidant protection for the immune system; supplementation improves neutrophil function in nasal conditions.||[1, 7]|
|Vitamin D||Heavily influences immune system activity during common respiratory infections; supplementation (particularly in deficient individuals) protects against acute respiratory infections.||[8-9]|
|Vitamin E||Antioxidant protection; enhancement of the immune system; while deficiencies are rare in humans, supplementation has been shown to improve immune function in elderly patients.||[1, 10-11]|
Minerals for immune system health
Trace elements found in food are critical to many aspects of immunity, though are often under-considered within the diet. Nutrients such as zinc, copper, selenium, and iron are normally found in high amounts in most red meats, nuts, fruit, vegetables, and dairy, as well as commonly being added to supplements and infant formulae for nutritional purposes. Table 2 below summarises the effects upon the immune system of each of these minerals.
Table 2: Summary of minerals for immune system health.
|Zinc||Critical factor in normal immune cell function (particularly neutrophils and natural killer cells); Deficiency leads to improper macrophage and lymphocyte function, decreasing immune system power.|||
|Copper||Key element involved in immune system development and function, as part of cuproenzymes; Supplementation of copper in malnourished infants shown to protect against severe infections of the lower respiratory tract.||[1, 13]|
|Selenium||Essential factor in “selenoproteins” that are important in immune system function; deficiency decreases capability to fight (poliovirus) infection, but this can be reversed with selenium supplementation.||[1, 14]|
|Iron||Required to fight off invaders, as it is involved in lymphocyte cycling and pathogen removal; deficiency reduces this capability. Excessive iron can be detrimental to the body, as it may decrease effectiveness in fighting infections such as malaria.||[1, 15-16]|
Long chain fatty acids
Omega-3 fatty acids such as DHA and EPA are a vital component of a balanced diet, when considering growth and development. Following consumption from dietary sources such as fish and plant oils or seeds and nuts, long chain fatty acids are embedded in the membrane of human immune cells, where they modulate immune functions such as cell signalling and phagocytosis  and exert potent anti-inflammatory effects . EPA also provides antioxidant protection , and so may play an important role in maintaining maternal health. Due to these roles, supplementation during pregnancy and breastfeeding could potentially allow for a more rapid maturation of the immune system  and protection against respiratory illnesses commonly found in infants . However, as with all nutrient consumption, excessive intake of DHA and (in particular) EPA may have negative effects upon immune function and pathogen clearance [1, 21]. Hence, following RDI guidelines is important in acquiring all benefits that these nutrients have to offer.
|Immune health||Vitamins A, B6, B9, B12, C, D, E; Zinc, Copper, Selenium & Iron; DHA & EPA.|
- Drake et al. [Internet]. Oregon (USA): Linus Pauling Institute Micronutrient Information Center (Oregon State University). Immunity In Depth; 2016 July [cited 2021 April 21]. Available from https://lpi.oregonstate.edu/mic/health-disease/immunity.
- Calder et al. Scientific Review: The Role of Nutrients in Immune Function of Infants and Young Children. Mead Johnson & Company; Glenview, IL, USA: 2007. Emerging Evidence for Long-Chain Polyunsaturated Fatty Acids.
- Rall et al. Nutr Rev. 1993 Aug;51(8):217-25.
- Gross et al. Am J Clin Nutr. 1975 Mar;28(3):225-32.
- Wagner (1995). Bailey, L.B. eds. Folate in Health and Disease :23–42 Marcel Dekker New York, NY.
- Erkurt et al. Med Princ Pract. 2008;17(2):131-5.
- Levy et al. J Infect Dis. 1996 Jun;173(6):1502-5.
- Olliver et al. J Infect Dis. 2013 Nov 1;208(9):1474-81.
- Martineau et al. BMJ. 2017 Feb 15;356:i6583.
- Traber et al. Free Radic Biol Med. 2007;43(1):4-15.
- De la Fuente et al. Free Radic Res. 2008 Mar;42(3):272-80.
- Mol Med. 2008 May-Jun;14(5-6):353-7.
- Castillo-Durán et al. Am J Clin Nutr. 1983 Jun;37(6):898-903.
- Broome et al. Am J Clin Nutr. 2004 Jul;80(1):154-62.
- J Nutr. 2001 Feb;131(2S-2):568S-579S; discussion 580S.
- Sazawal et al. Lancet. 2006 Jan 14;367(9505):133-43.
- Prostaglandins Leukot Essent Fatty Acids. 2006;75(3):197-202.
- Mason et al. Biochim Biophys Acta. 2015 Feb;1848(2):502-9.
- Damsgaard et al. J Nutr. 2007 Apr;137(4):1031-6.
- Lapillonne et al. BMC Pediatr. 2014 Jul 2;14:168.
- Fenton et al. Prostaglandins Leukot Essent Fatty Acids. 2013;89(6):379-390.