Background: We have shown previously in infants that type of milk affects FSR. There was a 2.6 fold increase in FSR of infants fed a cow milk based formula (low cholesterl (chol), 1-3 mg/dl) vs. human milk (HUM, high chol, 9-12 mg/dl) (Pediatr Res, 35:135). The effect of chol supplementation of cow milk based formula has not been studied. Hypothesis: 1) FSR in 4 mos. old infants fed modified formula (MF) (with amounts of chol similar to that found in HUM, 13 mg/dl) will be similar to FSR of infants fed HUM, and lower than those fed regular cow milk based formula (RF). 2) There will be “imprinting” effect of lipid intake early in life on FSR later in life. Design and method: Prospective cross over study in 90 infants; recruited in first wk of life, followed until 4 mos. of age (Arm one), or until 1 yr. of age (Arm two). We report arm one data. We followed 27 infants: HUM (n=13), RF (n=7), or MF (n=7). FSR is measured on 3 consecutive days as the rate of incorporation of deuterium oxide into red cell membrane chol (J Lipid Res, 32: 1049). Serum total chol, triglyceride (trig), and high density (HDL-c), and low density lipoprotein-chol (LDL-c) were measured.Results: Data (mean ± SEM) were analyzed using ANOVA.Table Conclusions: FSR was 3.8 fold higher in cow milk based formula (RF and MF) groups vs HUM, but not different between RF and MF infants. Thus, cholesterol supplement of one cow milk based formulation to HUM levels, did not significantly reduce fractional synthesis rate of cholesterol at 4 months of age. (support by Am. Heart Assoc. and Wyeth Labs)

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