The immune system protects your child from:
-Infection (such as bacteria, viruses, and fungi)
-Toxins (chemicals made by microbes)
-Cell changes
It is made up of different organs, tissues, cells, structures, and proteins that work together. There are two subsystems within the immune system, known as the innate (non-specific) immune system and the adaptive (specific) immune system. Both work together whenever a germ or harmful substance triggers an immune response (1). The bowel is one of the organs that is crucial in defending the body against germs: more than half of all the body's cells that produce antibodies are in the bowel wall (2).
The immune system is complex, with many key nutrients required in supporting the organs, cells, structures, and proteins that are part of the immune system. This post will not cover every nutrient, but I will highlight some key nutrients and functional components of foods that are important in supporting the immune system in children.
Breastmilk
Breastmilk helps to build and support a child's immune system from the moment a child is born through to their last breast-feed. Factors present in breast milk offer active or passive immunoprotection such as:
Immunoglobulin A, the most abundant antibody in breast milk, is made and excreted in response to maternal exposure to specific bacteria and viruses and protects against pathogens in the infant’s local environment.
Immunoglobulin g and immunoglobulin m – protection against specific pathogens.
Breast milk also contains a range of other protective factors that work to support immune system develop, inhibit and/or destroy bacteria and viruses, and promote the growth of healthy bacteria (3)
Fat: Omega-3 and Omega-6
A variety of foods high in fat are important to support the immune system. Specifically polyunsaturated fats of omega 6 and omega 3 (4). These fats are important in the immune system for functional and structural roles and are also vital for absorption of fat-soluble vitamins A, E, D, and K (5,6).
Include a variety of foods high in omega 3 and omega 6 in your child's diet.
Foods high in omega 3:
Oily fish such as salmon and sardines, hemp seeds, chia seeds, ground flaxseeds, walnuts, avocado, and oatmeal.
Foods high in omega 6:
Walnuts, tofu, hemp seeds, sunflower seeds, peanut butter, avocado, eggs.
Vitamin A
Vitamin A is crucial to a number of physiological functions of the immune system (7, 8)
Two forms of vitamin A are available in the human diet: preformed vitamin A (retinol) and provitamin A (carotenoids).
Vitamin A1 (preformed) is only found in animal-sourced foods, such as oily fish like salmon, herrings and sardines, liver, cheese and butter, cod liver oil, and eggs.
Your body can produce vitamin A from carotenoids found in plants. These carotenoids include beta-carotene and alpha-carotene, which are collectively known as provitamin A. Choose brightly coloured vegetables and fruits like, sweet potato, pumpkin, kale, carrot, capsicum, mango, rockmelon, watermelon.
Vitamin D
Vitamin D has numerous effects on cells within the immune system, and mulitple studies have associated lower levels of vitamin D with increased infection and autoimmunity (9). Vitamin D can be obtained in small amounts from the diet, however it is mostly synthesized in the skin with exposure to sunlight.
Vitamin D can be found naturally in a small number of foods, including oily fish, cod liver oils, animal liver, eggs and butter. However, it's hard to get an adequate amount of vitamin D from food alone, and in Australia we do not routinely supplement vitamin D in children like other countries do (like the UK). With sunscreen use, skin covering (especially in summer), and more indoor lifestyles, even Australian children can easiy become deficient in vitamin D.
*Cod liver oil is a supplement that can provide omega 3, vitamin D and vitamin A to children especially when intake of these foods are low. Follow the recommended amount as specified on the product label.
Vitamin C
Vitamin C is a potent antioxidant and supports various cellular functions of both the innate and the adaptive immune system. Vitamin C deficiency results in impaired immunity and higher susceptibility to infections (10).
There are a number of foods that are high in vitamin C including;
Oranges
Strawberries
Tomato
Brussel sprouts
Broccoli
Blueberries
Lemon
Iron
Iron is a fundamental element for normal development of the immune system, and iron deficiency affects the body's capacity to have an adequate immune response (11, 12).
Haem sources of iron include: liver, beef, lamb, pork, chicken, turkey and fish
Non Haem sources of iron include: chia seeds, legumes, tofu, eggs, green leafy vegetables and sesame seed paste.
It is best to include a variety of iron foods from Haem and Non-Haem sources.
Zinc
Zinc is an essential micronutrient vital to support the immune system. Diets that are deficient in zinc can lead to impaired immunity, delayed recovery from and worse outcomes following infection. Sustained insufficient zinc intake leads to dysregulation of the innate immune response and increases susceptibility to infection (13) There is also emerging evidence to show that zinc may act during acute infection and help to 'boost' the body's immune response (14). The body doesn’t store zinc, so regular intake of foods high in zinc is required.
Foods to include that are high in zinc include: Meat (including red meat, pork, turkey), shellfish, legumes like chickpeas and lentils, hemp seeds, pumpkin seeds, sesame seeds, peanuts, tree-nuts, eggs and wholegrains like wheat, quinoa and oats.
Pre-biotics
The healthy bacteria in a child's intestine can be beneficially influenced by diet. Fibers, the non-digestible parts of fruits, vegetables, and whole grains are an important energy source for healthy bacteria. Healthy bacteria ferment the fiber in the gastrointestinal tract which leads to the production of short-chain fatty acids (SCFA) which support immune function (15). In numerous studies using different fiber interventions, fibers have been attributed to maintaining intestinal health by enhancing barrier function, inhibiting cell damage from infection, and preventing colonization with pathogenic bacteria (16).
Include a variety of high fiber foods and foods high in resistant starch; a variety of fruits and vegetables, whole grains like quinoa, rice, and wheat, seeds like chia seeds, pumpkin seeds, hemp seeds, flaxseed meal, and a variety of nuts.
Pro-biotics
Pro-biotics are 'live micro-organisms that provide a health benefit' and make up a child's microbiome (17). A child's microbiome plays a critical role in the training and development of and communication to components of the innate and adaptive immune system. The amount and type of healthy bacteria within the gastrointestinal tract can directly impact overall health and susceptibility to infection (18). Research shows that pro-biotics are safe and well tolerated in healthy infants and children (19)
Foods high in probiotics are foods that are fermented or made with live cultures, such as: Yoghurt (made with live cultures), Kefir (fermented milk drink), Sauerkraut (fermented cabbage), Beetroot Kvass (fermented beetroot drink), Kimchi (fermented spicy cabbage).
The sodium content of some fermented foods can be quite high, so use small amounts in children less than 12 months and you can also rinse under water, and include as part of varied diet (otherwise low in added salt).
Immune Support Smoothie
1 x serving of cod liver oil (suitable for your child's age/weight as specified on the product)
2 x teaspoon of chia seeds or hemp seeds
1 x teaspoon of flaxseed meal
1/2 cup of frozen blueberries
1/2 a banana
1/3 cup of full-fat greek yoghurt (made with live cultures)
1/2 cup of water
Blitz and serve.
X Anna
References:
Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. How does the immune system work? [Updated 2020 Apr 23]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK279364/
Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. What are the organs of the immune system? [Updated 2020 Jul 30]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK279395/
NHMRC (2012) Infant feeding guidelines: information for health workers.
Prentice, A. M., & van der Merwe, L. (2011). Impact of fatty acid status on immune function of children in low-income countries. Maternal & Child Nutrition, 7 Suppl 2, 89-98. doi:http://dx.doi.org/10.1111/j.1740-8709.2011.00313.x
Calder P.C. (2008) The relationship between the fatty acid composition of immune cells and their function. Prostaglandins, Leukotrienes, and Essential Fatty Acids79, 101–108.
Calder P.C. (2010) Does early exposure to long chain polyunsaturated fatty acids provide immune benefits?Journal of Pediatrics156, 869–871.
Villamor E, Fawzi WW. Effects of vitamin A supplementation on immune responses and correlation with clinical outcomes. Clin Microbiol Rev. 2005;18(3):446-464. doi:10.1128/CMR.18.3.446-464.2005
Semba RD. Vitamin A and immunity to viral, bacterial and protozoan infections. Proc Nutr Soc. 1999 Aug;58(3):719-27. doi: 10.1017/s0029665199000944. PMID: 10604208.
Aranow C. Vitamin D and the immune system. J Investig Med. 2011;59(6):881-886. doi:10.2310/JIM.0b013e31821b8755
Carr AC, Maggini S. Vitamin C and Immune Function. Nutrients. 2017;9(11):1211. Published 2017 Nov 3. doi:10.3390/nu9111211
Mascotti DP, Rup D, Thach RE. Regulation of iron metabolism: translational effects mediated by iron, heme and cytokines. Annu Rev Nutr 1995;15:239–61.
Hassan, Tamer Hasan MD et.al; Impact of iron deficiency anemia on the function of the immune system in children, Medicine: November 2016 - Volume 95 - Issue 47 - p e5395 doi: 10.1097/MD.
Sapkota, M., & Knoell, D. L. (2018). Essential role of zinc and zinc transporters in myeloid cell function and host defense against infection. Journal of Immunology Research, 2018, 8. doi:http://dx.doi.org/10.1155/2018/4315140
Brooks WA, Yunus M, Santosham M, Wahed MA, Nahar K, Yeasmin S, Black RE. Zinc for severe pneumonia in very young children: double-blind placebo-controlled trial. Lancet. 2004 May 22;363(9422):1683-8. doi: 10.1016/S0140-6736(04)16252-1. PMID: 15158629.
G.R. Gibson, R. Hutkins, M.E. Sanders, S.L. Prescott, R.A. Reimer, S.J. Salminen, et al.Expert consensus document: the International scientific association for probiotics and prebiotics (ISAPP) consensus statement on the definition and scope of prebiotics Nat. Rev. Gastroenterol. Hepatol., 14 (8) (2017), p. 491
Tolulope Joshua Ashaolu, Immune boosting functional foods and their mechanisms: A critical evaluation of probiotics and prebiotics, Biomedicine & Pharmacotherapy,Volume 130, 2020,
ValdesA M, WalterJ, SegalE, SpectorT D. Role of the gut microbiota in nutrition and healthBMJ 2018; 361 :k2179 doi:10.1136/bmj.k2179
1. Zheng, D., Liwinski, T. & Elinav, E. Interaction between microbiota and immunity in health and disease. Cell Res30, 492–506 (2020). https://doi.org/10.1038/s41422-020-0332-7
Royal Childrens Hospital Melbourne 'Probiotics for infants and children' fact sheet. Available: https://www.rch.org.au/uploadedfiles/main/content/ccch/cpr_vol22_no1_factsheet.pdf
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