What is the osmolality of hydrolyzed protein and free amino acid–containing infant formulas?

• A. 200-300 mOsm/kg
• B. 360-420 mOsm/kg
• C. 310-350 mOsm/kg
• D. 330-370 mOsm/kg

Answer: (D)

Osmolality is the concentration of osmotically active particles in a kilogram of water, which reflects the solute load a baby’s gut and kidneys must handle. Hydrolyzed protein and free amino acid–containing formulas have many small solute molecules—peptides and free amino acids—that increase the number of particles per volume. This raises osmolality compared with intact-protein formulas. The typical osmolality for these specialized formulas falls in the mid to high range, about 330–370 mOsm/kg. That’s higher than standard formulas (which are lower) but still within a range commonly seen for hydrolyzed or amino acid–based formulas. The other ranges are either too low or exceed the usual values for these formulas.