Background:Casein has proved to be hypercholesterolemic. According to results of previous studies, the casein-to-whey ratio in infant formula influences plasma lipid profile. This study explored whether different methods of whey deionization also affect levels of plasma lipids.Methods:Two types of a whey-predominant (whey 60%:casein 40%) formula which differed only in the methods used for whey deionization (ultrafiltration or electrodialysis), were fed to healthy newborn infants for 60 days, using a prospective, double-blind, randomized design. Formulas were otherwise identical in composition.Results:Groups were similar in gestational age, gender, birth weight, and growth parameters. Evaluation of fasting plasma levels after 60 days revealed significantly higher values of total cholesterol (p< 0.001) and low-density lipoprotein cholesterol (p< 0.001) in infants fed ultrafiltrated whey compared with the same values in infants fed electrodialyzed whey. Plasma levels in the two groups of very low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and triglycerides revealed no statistically significant differences.Conclusions:Plasma lipid profile in infancy is influenced by dietary protein, not only by the casein-to-whey ratio, but also by the method of whey deionization.