Breast Milk and Formula: What is the main source of nutrition for babies during most of the first year?

January 10, 2026 •

2 min read

According to the World Health Organization, fewer than half of infants under six months are exclusively breastfed, but health experts agree that what is the main source of nutrition for babies is breast milk or infant formula throughout the first year. These milk-based feeds provide the bulk of essential nutrients and energy needed for rapid growth and development, even after solid foods are introduced around six months.

Quick Summary

For a baby's first year, breast milk or infant formula is the primary source of nutrients and energy. While solids are introduced around six months, milk remains the most important part of their diet for sustained growth and development.

Key Points

Milk is Primary: For the majority of a baby's first year, breast milk or infant formula is the main source of energy and nutrients.
Exclusive for Six Months: Health experts recommend exclusive feeding with breast milk or formula for the first six months of life.
Solids Complement, Don't Replace: After six months, solid foods are introduced to complement milk, which still provides most of the nutritional needs.
Wait for Readiness Cues: Introduce solids only when your baby shows developmental signs of readiness, such as being able to sit up and having good head control.
Breast Milk Benefits: Breast milk is biologically optimized for infants, containing vital antibodies and easier-to-digest nutrients.
Formula is a Safe Alternative: For parents who cannot or choose not to breastfeed, infant formula is a healthy alternative that provides all necessary nutrients.

The First Six Months: Exclusive Feeding

For the first six months, health organizations like the AAP and WHO recommend exclusively feeding infants breast milk or formula. During this time, a baby's digestive system is still developing, making milk the ideal and easily digestible food source. Breast milk offers tailored nutrition and immune-boosting antibodies, while formula is a regulated, healthy alternative providing necessary nutrients.

Why Only Milk is Needed Initially

Perfectly Balanced Nutrition: Provides essential carbohydrates, proteins, and fats.
Immune System Support: Breast milk offers protective antibodies.
Developmental Readiness: Infants lack the skills for solid foods.
Digestive Comfort: Easier to digest, particularly breast milk.

The Introduction of Complementary Foods (6-12 Months)

Around six months, babies may be ready for solid foods to complement milk. Solids provide extra energy and nutrients like iron, but milk remains the most nutrient-dense part of their diet. This period is for exploring tastes and textures.

Signs of Readiness for Solid Foods

Sits up with support and has good head control.
Coordinates eyes, hands, and mouth.
Shows interest in food.
Loses the tongue thrust reflex.

Comparison: Breast Milk vs. Infant Formula

Breast milk is optimal, but formula is a healthy choice based on individual circumstances.


Feature	Breast Milk	Infant Formula
Composition	Dynamic and adapts to needs.	Standardized and regulated.
Nutrients	Easily absorbed with bioactive components.	Provides essential nutrients but less bioactivity/antibodies.
Immune Support	Contains maternal antibodies.	Does not contain antibodies.
Digestion	Easier to digest.	May be less easily digested.
Convenience	Always available; no prep.	Requires preparation.
Cost	More affordable long-term.	Can be a significant expense.

The Role of Milk During the Transition to Solids

Milk is crucial from 6-12 months. Breast milk can provide half or more of energy needs, and formula remains a vital nutrient source. Solids should complement, not replace milk, allowing gradual increase in food variety. By 12 months, babies eat family foods but benefit from continued milk feeds.

Conclusion: The First Year is All About Milk

Breast milk or formula is the main source of nutrition for babies during most of the first year. Exclusive milk feeding is recommended for the first six months, followed by the introduction of complementary solids alongside milk from six to twelve months. This approach ensures proper nutrient intake for growth and development. Learn more from the Centers for Disease Control and Prevention's guidance on infant nutrition.

Frequently Asked Questions

The right time to introduce solid foods is around six months of age, when your baby shows signs of developmental readiness, such as being able to sit up with support and showing interest in food.

It is not recommended to start solids before four months, and typically not before six months, as a baby's digestive system needs time to mature and they lack the necessary oral motor skills.

During the transition period after six months, it is recommended to offer milk (breast milk or formula) first before introducing solids. This ensures your baby gets the primary nutrients and energy from their milk.

The primary difference is that breast milk's composition dynamically changes to meet a baby's needs and contains maternal antibodies, while formula is a standardized, regulated product that lacks these protective immune factors.

Yes, the AAP recommends that all breastfed babies receive a vitamin D supplement soon after birth, as breast milk may not provide enough to prevent deficiency.

Signs of readiness include sitting up with minimal support, holding their head steady, showing interest in food, and losing the 'tongue thrust' reflex.

No, whole cow's milk is not recommended as a main drink for infants under 12 months. Infant formula or breast milk should be the primary source of nutrients.

Solid foods in the first year are for taste, texture exploration, and supplementing nutrients like iron. Milk still provides the majority of the calories and essential nutrients needed for rapid infant growth.