Purpose: This prospective, open, randomized, parallel, multicenter study compared fat absorption (ABS) & N, Ca, P and Mg absorption and retention (RET) in two cow's milk based term infant formulas, a lactose free (L-) and a marketed lactose containing (L+) formula. Both were identical except for lactose (L+:100%; L-:0%), calcium (L+:420 mg/L; L-:550 mg/L), & phosphorus (L+:280 mg/L; L-:366 mg/L) content. L- protein was slightly more processed to reduce lactose.

Methods: Following a 4-7 day formula feeding equilibration, urine& stool were collected during a 72 hour metabolic balance. These outputs& formula were analyzed for N, Ca, P & Mg. Stools & formula were also analyzed for fat content. No medication, mineral supplements or solid food was permitted during the study. Weight was measured at the start & end of the metabolic balance.

Results: The table below lists the results. Age, baseline anthropometrics & formula intake did not differ significantly between the 20 L- and 21 L+ infants who completed the study. N balance, & RET for all nutrients were unavailable for 7 & 5 infants, respectively. Study events: 1 L- infant had diarrhea & withdrew; 2 L+ infants had vomiting & 1 had dyspepsia, but were not withdrawn.

Table 1
Full size table

Conclusion: Bioavailability of key nutrients in the new L- formula is similar to that of the L+ formula. The higher Ca RET found in the L- group may be valid or due to unavailability of Ca RET data. Lactose did not appear to influence the ABS of Ca or other nutrients. Supported by Wyeth Nutritionals International