A healthy, varied diet, together with other factors, can contribute to the proper functioning of the immune system. In this article, you will read about the functioning of the immune system and the various internal and external factors that can influence the immune system. We will also discuss the possible impact of certain nutrients and food components on the immune system.
The immune system is made up of two parts: the innate immune system, or the immune system you are born with, and the adaptive immune system, or the immune system your body ‘learns’ as you go through life.1 The epithelium, for example the oral cavity, the lungs or the intestines, is the first point of contact in the body for potential pathogens. When this contact occurs, the innate immune system responds rapidly.1 In many cases, this reaction is enough to clear away the disease agents. If not, then the adaptive immune system comes into play. This system can work much more specifically to destroy a pathogen, but it takes longer to accomplish this.1
A properly functioning immune system maintains a good balance between the responses against both internal and external factors that influence the immune system.1 Examples of these factors include diet, the composition of the intestinal flora, hereditary factors, smoking and (air) pollution.1 An imbalance in the coordination of these immunological responses may lead to a reduced immune response or even to an immune response that is too strong.1 The first case leads to an increased risk of (chronic) infections, and in the second case, there is a risk of developing allergies and auto-immune disorders.1
During certain phases of life, the immune system can function less than optimally. This is primarily true during the period immediately following birth and as a person ages.1 In young children, the immune system is not yet fully developed. As a result, young children are more susceptible to infection and may develop problems with the development of oral tolerance for ‘safe’ proteins in their diets or in their environments.1 In the elderly, the innate as well as the adaptive immune responses are less efficient and less specific due to the ageing of the cells and tissues.2,3 A healthy lifestyle can help to delay this decline. A well-varied diet, exercise and sufficient sleep all have a positive effect on the functioning of the immune system.2,3
How is nutrition linked to the immune system? Research has shown that various dietary components can have an effect on the immune system.4-10 Examples of these components include non-digestible sugars, vitamins, minerals and bioactive proteins and fats.4-10 In the tonsils at the back of the throat, these active components – before they are digested in the stomach and intestines – come into contact with the mucosal immune system. Upper respiratory pathogens and allergens also enter the body through the throat and tonsils, so they may also have an effect on the immune response in the (upper) respiratory tract. If they are taken up in the blood, they may even have an impact on the systemic immune response.11
Some foods, e.g. milk, naturally contain bioactive proteins. Bioactive proteins are proteins that have been shown to have specific biological activity.13-15 Examples of these proteins include lactoferrin, cytokines, such as IL-10 and TGF-β, and immunoglobulin G (IgG).13-15 The occurrence of this type of bioactive protein is unique to animal products; in other words, they are not present in vegetable-based drinks. However, the processing of milk by heating results in the reduction in the functional activity of bioactive proteins in pasteurized milk. In milk processed at ultra-high temperatures, these proteins are still present as a food source, but they no longer function as bioactive proteins.
In raw, unprocessed milk*, the bioactive proteins are still intact and functional. A great deal of research has been done into the possible effects of these proteins in raw milk.12,13,16,17 This research is particularly relevant to vulnerable populations. However, no consensus has yet been reached about the possible effects of bioactive proteins.
Many internal and external factors, including, for example, certain dietary components, can influence the immune system. A healthy lifestyle has a positive effect on the functioning of the immune system. Healthy dietary habits and sufficient exercise and sleep are particularly important aspects of a healthy lifestyle.
* The consumption of raw, unprocessed milk is not safe and is not recommended due to the risk of pathogens which are rendered harmless during the normal heat-processing of the milk.
- Abbas, A. K., Lichtman, A. H., & Pillai, S. (2019). Basic Immunology: Functions and Disorders of the Immune System. Elsevier Health Sciences.
- Montecino-Rodriguez, E., Berent-Maoz, B., & Dorshkind, K. (2013). Causes, consequences, and reversal of immune system aging. The Journal of Clinical Investigation, 123(3), 958-965.
- Weyh, C., Krüger, K., & Strasser, B. (2020). Physical activity and diet shape the immune system during aging. Nutrients, 12(3), 622.
- Walther, B., & Sieber, R. (2011). Bioactive proteins and peptides in foods. International Journal for Vitamin and Nutrition Research, 81(2), 181.
- Calder, P. C. (2013). Feeding the immune system. Proceedings of the Nutrition Society, 72(3), 299-309.
- Lomax, A. R., & Calder, P. C. (2008). Prebiotics, immune function, infection and inflammation: a review of the evidence. British Journal of Nutrition, 101(5), 633-658.
- Triantis, V., Bode, L., & Van Neerven, R. J. (2018). Immunological effects of human milk oligosaccharides. Frontiers in Pediatrics, 6, 190.
- Doherty, A. M., Lodge, C. J., Dharmage, S. C., Dai, X., Bode, L., & Lowe, A. J. (2018). Human milk oligosaccharides and associations with immune-mediated disease and infection in childhood: A systematic review. Frontiers in Pediatrics, 6, 91.
- German, J. B., & Dillard, C. J. (2006). Composition, structure and absorption of milk lipids: a source of energy, fat-soluble nutrients and bioactive molecules. Critical reviews in food science and nutrition, 46(1), 57-92.
- Spencer, S. P., & Belkaid, Y. (2012). Dietary and commensal derived nutrients: shaping mucosal and systemic immunity. Current Opinion in Immunology, 24(4), 379-384.
- van Neerven, R. J. J. (2014). Mucosal immunity : barriers, bugs, and balance. Wageningen: Wageningen University, Wageningen UR.
- Loss, G., Depner, M., Ulfman, L. H., Van Neerven, R. J., Hose, A. J., Genuneit, J., … & Weber, J. (2015). Consumption of unprocessed cow’s milk protects infants from common respiratory infections. Journal of Allergy and Clinical Immunology, 135(1), 56-62.
- Abbring, S., Hols, G., Garssen, J., & van Esch, B. C. (2019). Raw cow’s milk consumption and allergic diseases–the potential role of bioactive whey proteins. European Journal of Pharmacology, 843, 55-65.
- Ulfman, L. H., Leusen, J. H., Savelkoul, H. F., Warner, J. O., & van Neerven, R. J. (2018). Effects of bovine immunoglobulins on immune function, allergy, and infection. Frontiers in Nutrition, 5, 52.
- van Neerven, R. J., Knol, E. F., Heck, J. M., & Savelkoul, H. F. (2012). Which factors in raw cow’s milk contribute to protection against allergies?. Journal of Allergy and Clinical Immunology, 130(4), 853-858.
- Brick, T., Hettinga, K., Kirchner, B., Pfaffl, M. W., & Ege, M. J. (2019). The beneficial effect of farm milk consumption on asthma, allergies, and infections: from meta-analysis of evidence to clinical trial. The Journal of Allergy and Clinical Immunology: In Practice, 8(3), 890-891.
- Riedler, J., Braun-Fahrländer, C., Eder, W., Schreuer, M., Waser, M., Maisch, S., … & von Mutius, E. (2001). Exposure to farming in early life and development of asthma and allergy: a cross-sectional survey. The Lancet, 358(9288), 1129-1133.