Gut Microbiota Maturation and Immune Development in Toddlerhood

The gut plays a central role in toddler resilience through its involvement in digestion, nutrient absorption, immune signalling and barrier function. During early life, the gut microbiota undergoes rapid development and interacts closely with the maturing immune system. These early microbiota–immune interactions may influence immune development and later susceptibility to allergic and atopic disease. ⁶

Early-life nutrition is one of the key factors shaping microbial maturation. Zhou et al. describe the relationship between food nutrition, microbiota development and immune maturation as an interconnected process that may influence lifelong health trajectories.⁷ This supports the importance of dietary diversity, adequate fibre intake and safe, nutrient-dense foods during toddlerhood.

Fermented foods, including fermented dairy such as yoghurt or maas/amasi, may form part of a gut-supportive dietary pattern, depending on processing methods and whether live microorganisms remain in the final product. The Codex Standard for Fermented Milks provides a framework for understanding how fermented dairy products are produced and classified.⁴ However, gut health should be approached holistically and not attributed to one food alone.

A resilient toddler gut is supported by diverse foods, fibre-containing fruits, vegetables, legumes and whole grains, safe food handling, continued breastfeeding where applicable, and appropriate use of antibiotics under healthcare guidance. These strategies align with WHO and PAHO/WHO recommendations for safe, varied and nutritionally adequate feeding during early childhood.^1,2

References:

1. World Health Organisation. WHO Guideline for Complementary Feeding of Infants and Young Children 6–23 Months of Age. Geneva: World Health Organisation; 2023.
2. Pan American Health Organisation; World Health Organisation. Guiding Principles for Complementary Feeding of the Breastfed Child. Washington, DC: PAHO/WHO; 2003.
3. World Health Organisation. Infant and Young Child Feeding [Fact sheet]. Geneva: World Health Organisation; 2023.
4. Codex Alimentarius Commission. Codex Standard for Fermented Milks (CXS 243-2003). Rome: FAO/WHO; adopted 2003, revised 2008, 2010.
5. European Food Safety Authority Panel on Dietetic Products, Nutrition and Allergies. Dietary reference values for vitamin D. EFSA Journal. 2016;14(10):4547.
6. Donald K, Finlay BB. Early-life interactions between the microbiota and immune system: impact on immune system development and atopic disease. Nature Reviews Immunology. 2023;23:735–748.
7. Zhou X, Du L, Shi R, Chen Z, Zhou Y, Li Z. Early-life food nutrition, microbiota maturation and immune development shape life-long health. Critical Reviews in Food Science and Nutrition. 2019;59(sup1):S30–S38.