It’s that time of year again. Winter’s here — and so is the never-ending carousel of bugs your little one seems to collect (you too, if you’re lucky). The immune system is incredibly complex — especially in babies — which might leave you wondering: can we do anything to support it?
First, can we actually "boost" the immune system?
Technically speaking, no. We can’t “supercharge” a baby’s immune system in the same way you’d boost a battery. Babies are born with an immature immune system and must gradually build their immunity over time. This means some sickness is not only expected, but a normal part of their development. Exposure to foreign substances, such as viruses and bacteria, activates and helps build the immune response for the next time they are exposed to those substances.
What we can do is support the natural development of their immune system by creating the right conditions for it to thrive. Nutrition plays a key role—exposing your little one to a variety of nutrient-rich foods helps lay the foundation for a strong, healthy immune system so it can initiate an effective response against pathogens when they do get in.
1. Key Nutrients for Immune Support
Here are five key nutrients to focus on — and how to make them work for your little one.
Iron
Iron is one of the most important nutrients in the first two years of life — essential for growth, brain development, and immune function. It helps immune cells develop and function properly, so is essential for building and maintaining a strong immune system. Studies have found that iron deficiency is associated with a weakened immune response, increasing the frequency of respiratory infections, gastroenteritis, and ear infections (Jayamanna & Jayaweera, 2022; Golz et al., 2001).
Babies need around 11mg/day from 7–12 months (that’s more than an adult male!).
Toddlers need 9mg/day
Iron is found in:
- Animal-based iron sources (heme iron) include red meat, poultry, and fish.
- Plant-based sources (non-heme iron) include legumes, tofu, leafy greens, whole grains such as quinoa, nuts, and seeds such as hemp seeds.
Iron absorption can be affected by several factors:
- The form of iron matters—heme iron from animal foods is absorbed more easily than non-heme iron from plant sources.
- High doses of calcium and zinc can impair absorption. Avoid any high doses of these nutrients close to an iron-rich meal (for example: a glass of milk after dinner).
- Phytates, which are found in plant-based foods such as whole grains and legumes reduce absorption. Soaking, souring or fermenting grains and legumes prior to eating can help break these down, improving iron availability.
- Vitamin C enhances iron absorption from plant sources, so pairing the two together is an easy strategy to improve iron availability. For example, lentil and spinach puree (iron) with finger food strawberries (vitamin C).
Vitamin A
Supports skin and mucosal barriers (your body's first line of defence, known as “innate immunity”) and helps develop immune cells (NIH, 2025).
It can be found in orange and yellow veggies such as carrots, sweet potato, pumpkin, as well as leafy greens, dairy, eggs and organ meats such as liver (however if offering liver, ensure it is from a high quality, organic source and you only offer in small amounts, as vitamin A is toxic at high levels).
Vitamin C
Vitamin C is a powerful antioxidant that supports both our innate immunity (our body’s physical barriers, the first line of defence) and adaptive immunity (the part of our immunity that builds up over time after exposure to different pathogens). It supports proliferation of important immune system cells, reduces the inflammatory response, and helps kill off any “bad” cells in the body (NIH, 2025).
Vitamin C deficiency is uncommon but is linked to increase susceptibility for infection. Luckily it is readily available in some of your little one’s favourite foods, such as strawberries, oranges, kiwifruit, and tomatoes, so unlikely that you will need additional supplementation if they are consuming a range of fruit and vegetables each day.
Vitamin D
Vitamin D is best known for its role in bone health, however there is strong evidence for its role in regulating the immune system. Deficiency has been linked to increased risk of respiratory infections in infants and children, and studies have found that supplementing with vitamin D helps to prevent recurrent infections, such as influenza A and acute ear infections (Mailhot & White, 2020; Urashima et al., 2010; Marchisio et al., 2013).
The best way to obtain vitamin D is through daily safe sun exposure directly onto the skin (around 15-20mins). If your little one is deficient in vitamin D (diagnosed via blood test), then supplementation is recommended, as food sources are limited in vitamin D. However, my absolute favourite hack is to sunbake your mushrooms for 15mins up to 2 hours, which has been found to generate up to 100% of your daily vitamin D requirements (Cardwell et al., 2018).
Zinc
Zinc plays a key role in supporting both the innate and adaptive immune responses, helping immune cells function properly. It also acts as an antioxidant and may have antiviral properties, so even a mild deficiency can weaken the body’s ability to fight off infections (Hechtman et al., 2019). Zinc is essential for gut health, specifically the renewal of important cells in the intestinal wall and for supporting tight junctions between these cells to prevent unwanted substances passing through and triggering an immune response.
Zinc is found in red meat, poultry, seafood, dairy, legumes, nuts, and seeds. However, like iron, its absorption can be reduced by certain compounds—such as phytates and fibre in plant foods—as well as by high-calcium and iron-rich foods, so follow the strategies mentioned above to improve absorption.
2. Support Their Gut = Support Their Immunity
About 70-80% of the immune system is located in the gut, so nurturing a healthy microbiome is one of the most effective ways to support immune development.
Here are some simple strategies to support the gut:
- Offer a variety of fibre-rich foods (which help with gut motility and blood glucose regulation): fruits, veggies, oats, legumes.
- Include prebiotic foods (which feed the healthy gut bacteria): garlic, onions, oats, bananas, apples, leeks, asparagus, pears
- Include fermented foods (when age appropriate): sauerkraut, kefir*, yoghurt*, miso*, tempeh*. Start small and build slowly — even just a few drops of sauerkraut brine is a great start.
- Limit ultra-processed foods and excessive sugar (which can contribute to dysbiosis and gut inflammation).
- Use antibiotics only when necessary, under medical advice — and when you do, consider a probiotic concurrently to support healthy bacteria (as recommended by a healthcare professional).
- Minimise stress: ensure your little one has lots of connection time, play, and exposure to the outdoors which can all help reduce stress and regulate the nervous system.
- Exposure to dirt and nature: Research has shown that exposure to nature improves microbial diversity of the gut and therefore support immune system pathways (Andersen et al., 2021; Roslund et al., 2020).
*contains a top allergen, so introduce mindfully.
4. Breastfeeding (When Possible)
Breastmilk plays a foundational role in shaping your baby’s immune system by supporting the growth of beneficial gut bacteria and providing important immunological compounds. Together this support gut integrity and reduce the risk of infections during early life (Pirker and Vogl, 2024).
If breastfeeding isn’t part of your journey — you’re not alone, and your baby can absolutely thrive with a nourishing, diverse diet and the strategies shared here.
The Bottom Line?
Immune health isn’t about “boosting” — it’s about building.
Your child’s immune system is still learning — and your role is to provide a calm, nourishing environment that supports that development.
There’s no magic superfood — but there’s a lot of power in the everyday. Whole foods. Rest. Play. Connection. It all adds up.
And if you’re feeling unsure about whether your baby or toddler is getting what they need — you’re not alone. That’s exactly what I’m here for.
If you’d like help reviewing your baby’s diet, managing picky eating, or supporting their immunity through food, I’d love to help. Book a 15-minute discovery call here, or explore my 1:1 consults and group workshops for calm, evidence-based support.
With you every messy, nourishing step of the way,
Kelly xx
Nutritionist | Feeding the Bump
References:
Andersen L, Corazon SS, Stigsdotter UK. Nature Exposure and Its Effects on Immune System Functioning: A Systematic Review. International Journal of Environmental Research and Public Health. 2021; 18(4):1416. https://doi.org/10.3390/ijerph18041416
Cardwell G, Bornman JF, James AP, Black LJ. A Review of Mushrooms as a Potential Source of Dietary Vitamin D. Nutrients. 2018 Oct 13;10(10):1498. https://doi.org/10.3390/nu10101498
Golz A, Netzer A, Goldenberg D, Westerman ST, Westerman LM, Joachims HZ. The association between iron-deficiency anemia and recurrent acute otitis media. Am J Otolaryngol. 2001 Nov-Dec;22(6):391-4. https://doi.org/10.1053/ajot.2001.28075
Hechtman, L., Schloss, J., Harris, K., Bridgman, K. (2019). The immune system, in Clinical Naturopathic Medicine. Second edition, Elsevier.
Jayamanna, Ushani & Jayaweera, J A A. (2022). Childhood Anemia and Risk for Acute Respiratory Infection, Gastroenteritis, and Urinary Tract Infection: A Systematic Review. Journal of Pediatric Infectious Diseases. 18. http://dx.doi.org/10.1055/s-0042-1760237
Mailhot G, White JH. Vitamin D and Immunity in Infants and Children. Nutrients. 2020; 12(5):1233. https://doi.org/10.3390/nu12051233
Marchisio P, Consonni D, Baggi E, Zampiero A, Bianchini S, Terranova L, Tirelli S, Esposito S, Principi N. Vitamin D supplementation reduces the risk of acute otitis media in otitis-prone children. Pediatr Infect Dis J. 2013 Oct;32(10):1055-60. https://doi.org/10.1097/inf.0b013e31829be0b0
National Institutes of Health (2025). Dietary supplements for immune function and infectious diseases. https://ods.od.nih.gov/factsheets/ImmuneFunction-HealthProfessional/#h11
Pirker AL, Vogl T. Development of systemic and mucosal immune responses against gut microbiota in early life and implications for the onset of allergies. Front Allergy. 2024 Jul 17;5:1439303. https://pmc.ncbi.nlm.nih.gov/articles/PMC11288972/
Roslund MI, Puhakka R, Grönroos M, Nurminen N, Oikarinen S, Gazali AM, Cinek O, Kramná L, Siter N, Vari HK, Soininen L, Parajuli A, Rajaniemi J, Kinnunen T, Laitinen OH, Hyöty H, Sinkkonen A; ADELE research group. Biodiversity intervention enhances immune regulation and health-associated commensal microbiota among daycare children. Sci Adv. 2020 Oct 14;6(42):eaba2578. https://pubmed.ncbi.nlm.nih.gov/33055153/
Urashima M, Segawa T, Okazaki M, Kurihara M, Wada Y, Ida H. Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. Am J Clin Nutr. 2010 May;91(5):1255-60. https://doi.org/10.3945/ajcn.2009.29094
Boosting Your Baby’s Immune System: What Actually Helps (and What Doesn’t)