Abstract 1657

Background: Pediatricians recommended that the osmolality of infant feedings be limited to less than 400 mosm/kg. The purposes of this study were fourfold: 1) to measure the osmolality of breast milk with added powdered formulas in incremental amounts, 2) to investigate the osmolar stability of breast milk with and without added lactose free formula powder, 3) to determine whether there is a difference in the osmolality of fore and hind breast milk, and 4) to evaluate the consistency of kitchen measuring spoons for measuring infant formula.

Methods: Frozen milk was collected from 10 mothers who delivered preterm infants. Various amounts of formula powders were selected to provide five concentrations of powder (2,3,4,5 and 6 grams/dl of breast milk) with calculated energy densities up to 94 kcal/dl (i.e. 73, 79, 84, 89 and 94 kcal/dl. The osmolality of breast milk was measured, with and without the addition of a lactose free powder at the time of mixing and 24 hours later. The weight of one teaspoon (5 ml) of formula powder in kitchen measuring spoons was measured.

Results: The osmolality of fore and hind milk were the same. At 94 kcal/dl (28 kcal/oz), the breast milk-formula powder mixtures had the following osmolalities: Enfalac Lactose Free (385 +/- 19 mosm/kg), Prosobee (388 +/- 12.7 mosm/kg), Neocare (396 +/- 7.8 mosm/kg), Isomil (416 +/- 11.6 mosm/kg), Similac Lactose Free (420 +/- 10.0 mosm/kg), Similac (424 +/- 15.1 mosm/kg), Enfalac (424 +/- 9.0 mosm/kg). The results after 24 hour storage of breast milk with a lactose free formula containing glucose polymers showed a small but significant increase in osmolality whether or not the lactose free formula powder was added. The weight of one teaspoon of formula measured in different kitchen measuring spoons averaged 2.3 grams and ranged from 1.8 to 2.8 grams.

Conclusion: The formulas that increased the osmolality the least were those with glucose polymers as the carbohydrate source. The change in osmolality of breast milk with added lactose free formula during storage for 24 hours powders was not altered by the addition of the formula. Teaspoons available in the home for the measurement of infant formula are quite variable.

Funded by Mead Johnson