Effect of a lactase preparation on lactose content and osmolality of preterm and term infant formulas

Lactose intolerance due to lactase deficiency often follows acute gastroenteritis. In such situations, a lactose-free formula may be indicated for preterm infants. Therefore, the effect of addition of lactase on the lactose content and osmolality of preterm and term infant formulas was studied. Lactose content of formulas at room temperature was decreased by approximately 50% 1 hour after addition of lactase. Concentration of lactose was reduced by 70% or more after 2 hours in all formulas. Because of the higher initial lactose concentration in term formulas, it took 24 hours to reach the same absolute lactose concentration (10 g/kg formula) found in preterm formulas after 2 hours. There was a moderate increase in osmolality in preterm formulas. The increase was greater in term formulas because of the greater initial concentration of lactose. The addition of lactase appears to be a suitable method for reduction of lactose content of preterm and term formulas, although the increase in osmolality of term formulas may preclude their clinical use.