in: Handbook of dietary and nutritional aspects of bottle feeding 1st edition, Preedy VR,Watson RR,Zibadi S, Editor, Wageningen Academic Publishers, Amsterdam, pp.163-176, 2014
Infant formulas have been used as breastmilk substitutes for decades where adequate breastmilk is not available or contraindicated for the infants because of maternal or neonatal conditions. Initially, infant formulas have been manufactured as powdered products. However after many outbreaks of neonatal sepsis or gastroenteritis due to the bacterial contamination of powdered infant formulas during production or reconstitution in hospital or neonatal intensive care formula kitchens, sterile, ready-to-feed liquid infant formulas have been introduced for clinical use. Additionaly, after the recommendation of the usage of ready-to-feed, liquid infant formulas in healthcare centers, most of the neonatal intensive care units have switched to liquid formulas in disposable bottles in developed countries. However, in the literature the clinical and nutritional characteristics of liquid infant formulas have not been investigated entirely. Few authors have found an increased incidence of regurgitation and delayed growth in term newborn infants who were fed with liquid infant formulas. Similarly, in a recent study, increased incidence of feeding intolerance and delayed growth in the first weeks of life have been reported in preterm infants who received liquid infant formula during neonatal intensive care hospitalization. The authors pointed out to the increased gastric fluid pH and possible delayed gastric emptying as the causes of feeding intolerance. For delayed regaining birth weight, increased feeding intolerance and decreased bioavailability of milk proteins due to higher heat damage during autoclave sterilization of the liquid formula have been proposed as possible mechanisms. Further prospective studies in preterm and term newborn infants comparing the clinical and nutritional characteristics of powdered and liquid infant formulas may induce the development of optimal production and sterilization techniques that minimize heat damage of proteins and other microand macronutrients of milk.