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Our immune system is an amazing, complex team of cells and molecules that work in tandem and around the clock to defend our bodies from infections. The immune system protects the body from infection through a multi-layered defense system. The first line of defense is the innate, or non-specific, immune system which creates a barrier that stops bacteria and viruses from entering the body and destroys those that have entered. Our skin, for example, wraps our entire body and secretes antibacterial substances that quickly kill bacteria and spores that land on it¹³. Without it, we see mold grow on our skin, just like how unwrapped food gets moldy.

The second line of defense is the adaptive, or specific, immune system which is composed of a type of white blood cell called lymphocytes. The adaptive system differs from the innate system by "remembering" its encounter with invading organisms and providing us protection from being re-exposed to them¹⁴. For example, when children are vaccinated, a weakened form of a disease is introduced into their bodies. The body's immune system then recognizes it and is able to immediately deal with the real form of the disease when it encounters it.

Newborn children do not have fully developed immune systems^2-3. A child's respiratory and digestive systems are particularly prone to infections because organisms are easily able to enter through the nose and mouth. Here, proper nutrition plays an essential role in providing nutrients for the development and growth of the innate and adaptive immune systems that help support 3 aspects:
• Respiratory Health
• Gut Health
• Body Resistance to Common Infections

DHA (docosahexaenoic acid), a type of polyunsaturated fatty acid and an important building block for brain and eye development is incorporated in immune system cells and decreases their ability to promote inflammation^1,4,5. As such, it appears to have beneficial effect in helping combat asthma and other respiratory and inflammatory diseases^1,5,6.

Prebiotics help foster the growth of "good" bacteria in the intestines¹². These bacteria promote the growth of good bacteria and suppress the growth of pathogenic, or bad bacteria in the intestinal lining, thereby allowing the intestinal immune system to function at optimal levels and maintaining good gut health.

Micronutrients also help support growth and development. For example, Vitamin A promotes healthy skin, respiratory and digestive systems functions^7,8 and supports the growth of immune cells^1,7. Vitamin C deficiency is known to impair the proper function of the innate immune system^{1, 9,} while poor iron intake may result in reduced number of immune cells¹⁰. Zinc is essential for the growth of cells and tissues and maintaining the function of all types of white blood cells¹¹.

1. Field, C.J., I.R. Johnson and P.D. Schley. (2002). Nutrients and their role in host resistance to infection. J. Leuk. Biol., 71:16-32.
2. Kelly, D., and A.G. Coutts. (2000). Early nutrition and the development of immune function in the neonate. Proc. Nutr. Soc., 59:177-185.
3. Calder, P. C., S. Krauss-Etschmann, E. C. De Jong, C. Dupont, J.-S. Frick, H. Frokiaer, J. Heinrich, H. Garn, S. Koletzko, G. Lack, G. Mattelio, H. Renz, P. T. Sangild, J. Schrezenmeier, T. M. Stulnig, T. Thymann, A. E. Wold, and B. Koletzko. (2006). Early nutrition and immunity – progress and perspectives. Br. J. Nutr., 96:774-790.
4. Blok, W.L., M.B. Katan, and J.W.M. van der Meer. (1996). Modulation of inflammation and cytokine production by dietary (n-3) fatty acids. J. Nutr., 126:1515-1533.
5. Calder, P.C. (2003). n3-polyunsaturated fatty acids and inflammation: from molecular biology to the clinic. Lipids, 38:343-352.
6. Ergas, D., E. Eilat, S. Mendlovic and Z.M. Sthoeger. (2002). n-3 fatty acids and the immune system in autoimmunity. Israeli Med. Assoc. J., 4:34-38.
7. Stephensen, C.B. (2001). Vitamin A, infection and immune function. Annu. Rev. Nutr., 21:167-192.
8. Thurnham, D.I., C.A. Northop-Clewes, F.S.W. McCullough, B.S. Das and P.G. Lunn. (2000). Innate immunity, gut integrity and vitamin A in Gambian and Indian infants. J. Infect. Dis., 182:S 23-S 28.
9. Hatch, G.E. (1995). Asthma, inhaled oxidants, and dietary antioxidants. Amer. J. Clin. Nutr., 61:S 625-S 630.
10. Beard, J.L. (2001). Iron biology in immune function, muscle metabolism and neuronal functioning. J Nutr., 131:568S-579S.
11. Fraker, P.J., L.E. King, T. Laakko and T.L. Vollmer. (2000). The dynamic link between the integrity of the immune system and zinc status. J. Nutr., 130:1399S-1406S.
12. Ouwehand, A., E. Isolauri and S. Salminen. (2002). The role of the intestinal microflora for the development of the immune system in early childhood. Eur. J. Nutr., 41 (Suppl 1): I32-I37. (38)
13. http://health.howstuffworks.com/immune-system13.htm
14. http://pathmicro.med.sc.edu/ghaffar/innate.htm

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