By Dr. Ismael Perdomo

Pediatrician – Epidemiologist

Introduction: A Critical Stage for Lifelong Health

Between 12 and 24 months of age, children go through a period of rapid physical and neurological growth. This is also a stage of high biological plasticity, in which nutrition not only meets energy requirements, but also modulates gene expression (epigenetics), influences the development of the intestinal microbiota, and establishes patterns of health or disease that can persist throughout life.

This stage is part of what scientific evidence defines as the first 1000 days of life, a decisive period for the prevention of chronic diseases, immune maturation, and cognitive development.

Breastfeeding and Complementary Feeding

Breastfeeding should continue until 2 years of age or beyond, as recommended by the World Health Organization (WHO). After the first year, breast milk remains an important source of energy, healthy fats, immunoglobulins, and bioactive compounds.

At the same time, children should gradually receive a variety of natural, nutrient-dense solid foods, including:

Iron: meat, liver, legumes, eggs, spinach.
Zinc: fish, whole grains, meat.
Vitamin D: fatty fish, egg yolk, and moderate sun exposure.
Polyunsaturated fatty acids (DHA): fish, ground nuts, and seeds such as flaxseed and chia.

Evidence confirms that many children in this age group experience iron and vitamin D deficiencies; therefore, their intake should be prioritized, with supplementation considered in at-risk cases.

Which Foods to Offer: Density, Color, and Texture
Avoid soups, broths, and thin porridges as the primary source of calories.
Prioritize solid foods appropriate for the child’s dentition.
Use colorful foods and attractive textures to encourage acceptance.
Offer fresh fruits with properly washed peel whenever possible (avoid storing peeled fruit).
Include whole and natural dairy products such as unsweetened yogurt and fresh cheese.
Incorporate whole grains, legumes, vegetables, and animal proteins.
Preferred cooking methods: steamed, baked, or boiled, with minimal salt and without artificial seasonings.
What to Avoid: Ultra-Processed Foods, Salt, Sugars, and Dysbiosis
Completely avoid candies, juices, sodas, and sugary beverages.
Do not add salt or sugar to meals.
Avoid industrialized porridges and processed cereal mixes.
Limit refined flours, packaged snacks, fried foods, and sugary cereals.

These types of products can alter the intestinal microbiota, promote gut dysbiosis, and increase the risk of obesity, allergies, inflammatory diseases, and even conditions such as ADHD and autism spectrum disorders, as supported by recent scientific evidence.

Epigenetic Nutrition: Programming Future Health

During the first 1000 days, diet influences the expression of key genes through epigenetic processes such as DNA methylation and histone modification. Malnutrition, excessive sugar intake, or deficiencies in essential micronutrients may leave lasting biological marks that increase the risk of metabolic, cardiovascular, immunological, and neuropsychiatric diseases later in life.

Gut Microbiota: The Developing Second Brain

A child’s microbiota is mainly shaped by:

Breastfeeding (favoring bifidobacteria dominance).
Proper introduction of fiber-rich solid foods.
Avoidance of unnecessary antibiotics and ultra-processed foods.

A healthy microbiota produces metabolites such as short-chain fatty acids, which regulate inflammation, immune tolerance, and the gut-brain axis, influencing behavior, sleep, and cognition.

Probiotics and Prebiotics: Valuable Allies with Caution
Natural prebiotics: fruit fibers, oats, legumes, and root vegetables.
Probiotics: may be beneficial in children born by cesarean section, those exposed to antibiotics, or premature infants.

In healthy children, adverse effects are rare and generally mild, including gas or loose stools. In immunocompromised children or extremely premature infants, probiotics should only be used under medical supervision.

Healthy Habits: Education and Guidance
Offer 3 main meals and 2 healthy snacks per day.
Encourage children to feed themselves with active supervision.
Avoid forcing children to eat; respect hunger and fullness cues.
Do not allow screen time during meals.
Establish regular meal schedules and avoid constant snacking between meals.
Involve children in food preparation and food selection whenever possible.
Teach handwashing and oral hygiene habits early.

The approach of “the adult provides, the child decides” promotes self-regulation, improves the child’s relationship with food, and helps prevent overeating and family conflicts around meals.

Conclusion

Nutrition between 12 and 24 months of life is far more than a matter of calories; it is a preventive, educational, and deeply biological act. Proper nutrition during this stage lays the foundation for lifelong health, intelligence, immunity, and well-being.

As parents, caregivers, and healthcare professionals, we have the responsibility to protect this epigenetic and metabolic window of opportunity through a varied, natural, loving, and respectful approach to nutrition.

References
Gallegos D. Effects of Food and Nutrition Insecurity on Global Health. The New England Journal of Medicine. 2025;392(7):686-697.
Heymsfield SB, Shapses SA. Guidance on Energy and Macronutrients across the Life Span. The New England Journal of Medicine. 2024;390(14):1299-1310.
Riley LK, Rupert J, Boucher O. Nutrition in Toddlers. American Family Physician. 2018;98(4):227-233.
Schwarzenberg SJ, Georgieff MK. Advocacy for Improving Nutrition in the First 1000 Days to Support Childhood Development and Adult Health. Pediatrics. 2018;141(2).
Moumin NA, Netting MJ, Golley RK, et al. Usual Nutrient Intake Distribution and Prevalence of Inadequacy Among Australian Children 0-24 Months. Nutrients. 2022;14(7):1381.

Additional references available upon request.