Objective: To evaluate the contribution of the type of milk on serum cholesterol ester fatty acids in infants receiving mixed feeding, we analyzed 3-day dietary records and serum cholesterol ester fatty acid composition of 397 seven-month-old infants.

Study design: The infants received, in addition to solid food, only one type of milk: human milk (n = 218), a ready-to-use liquid formula (n = 139), a powdered formula (n = 33), or soy formula (n = 7).

Results: Mean fat intakes were low and varied from 28% to 31% of energy; the milks provided 43% to 64% of the fat. The mean polyunsaturated/saturated fat ratios of solid foods were from 0.52 to 0.63 and of milks from 0.20 to 0.45. Breast-fed infants' relative serum linoleic acid (18:2n-6) concentration was low (51.2%), whereas infants fed liquid formula had low serum oleic acid (18:1n-9) in accordance with low oleic acid content in that formula. The breast-fed infants had markedly higher serum concentrations of arachidonic acid (20:4n-6) and docosahexaenoic acid (22:6n-3) than the infants fed any of the formulas.

Conclusion: The typical fatty acid patterns of breast- or formula-fed infants were still evident in 7-month-old infants who already received 60% to 70% of their energy from solid food. Marked differences were seen also in the relative concentrations of docosahexaenoic acid and arachidonic acid despite their small contribution in cholesterol esters. (J Pediatr 1997;130:110-6)