IBCLC Practice Exam 2026 – Complete Preparation Guide

The component that supplies the main energy source in human milk is fat. Fat in breast milk is crucial for providing the necessary calories that infants need for growth and energy. It not only serves as a concentrated source of energy but also plays an essential role in the absorption of fat-soluble vitamins (A, D, E, and K) and supports brain development due to its high level of essential fatty acids.

Although protein and lactose also contribute to a newborn's nutrition, they serve different primary functions. Protein is vital for growth and development but does not provide as high an energy content as fat. Lactose, the primary carbohydrate in human milk, helps in calcium absorption and provides energy as well, but its energy content is still lower than that of fats.

Vitamins, while important for various bodily functions and development, do not serve as an energy source in the same way that fats, proteins, and carbohydrates do. Therefore, fat remains the predominant source of energy in human milk, making it essential for supporting an infant's rapid growth and energy needs.